THE INFINITE BAFFLE SPEAKER

[Anonymous]

THE INFINITE BAFFLE SPEAKER
A brief introduction
Copyright (c) 2003 Andre Jute/Real McCoy Audio

There are two kinds of sealed enclosures, the infinite baffle and the air suspension speaker. This very basic introduction is about the infinite baffle, which uses a large enclosure in which the compliance of the air is greater than the compliance of the driver suspension.

The advantages of the infinite baffle over all other coned speaker enclosures, given that it is properly designed and built, include excellent transient response, good low frequency power handling, generally smaller box size, lower sensitivity to misaligned parameters than more complicated alignments, and straightforward ease of design and construction. Conversely, the price is lower sensitivity and higher low frequency cutoff.

The infinite baffle (and to a lesser extent the air suspension) enclosure, is the coned speaker enclosure of choice for the serious audiophile, next to true electrostatics and horns, because of its smooth handling of transients, and absence of one-note bass.


SUCK IT AND SEE?
Only if you are unimaginably rich. Speaker design is far more complicated and fraught with difficulties than amplifier design. The chances of stumbling on a good design by chance are infinitesimally small. Better to calculate twice and cut once.

All the infinite baffle enclosure calculations below use the famous Theile-Small parameters. These calculations also hold for air suspension systems, which are also sealed enclosures.


BOX SIZE
First choose a desired final total Q of the assembly at resonant frequency, Qtc, as the intended outcome for the design. Values of Qtc from 0.6 to 1.0 are theoretically possible, but values over 0.7 Qtc defeat the purpose as transient response degrades with increasing Qtc values. Commercial designs often increase the power handling of the speakers by choosing higher values of Qtc, and car audio designers go the whole hog, but that is not hi-fi. Higher values of Qtc than 0.7 rarely work except for true subwoofers with sub-20 cycle resonant frequency.

Calculate:
Qr = Qtc/Qts
Vr = Qr2-1
Vb = Vas/Vr
Fb = QrFs
F3 = Fb((1/Qtc2-2+((1/Qtc2-2)2+4)0.5)/2)0.5

Also dBpeak = 0
Except in the case where Qtc is larger than (1/2).5 when
dBpeak = 20log(Qtc2/(Qtc2-0.25)0.5)

where,
the Theile/Small parameters are:
Vas = Equivalent air compliance (liters)
Qts = total Q of the driver at its resonant frequency
Fs = resonant frequency of the driver (Hz)

and calculated data is:
Vb = net box volume (liters)
Fb = box resonant frequency (Hz)
F3 = -3dB frequency (Hz)
dBpeak = maximum peak or dip in system response

Net box volume is without dividers and braces, whose space must be added on to the value calculated above.


FREQUENCY RESPONSE
Calculate for each frequency of interest over the spectrum:
Fr = (F/Fb)2
dBmag = 10LOG(Fr2/((Fr-1)2+Fr/Qtc2))

where,
the Theile/Small parameters are:
Fb = resonance frequency of the system
Qtc = Final Q of the system at resonance

and calculated data is:
F = frequency (Hz)
dBmag = SPL 1W/1M at frequency F


POWER RESPONSE
To calculate power response of the bass driver/enclosure assembly, first make these intermediate calculations:

Sd = pi(Dia/100)2/4
Vd = SdXmax/1000
n0 = 9.6410(-10)Fs3Vas/Qes
SPL = 112 + 10LOG(n0)
K1 = (4pi3Ro/c)Fb4(Vd1.15)2
K2 = 112+10LOG(K1)
Amax = 1 except in the case where Qtc is larger than (1/2).5 when
Amax = Qtc2/(Qtc2-0.25)0.5
Par = K1/Amax2
Per = Par/n0
PeakSPL = SPL+10LOG(PEmax)

where,
the Theile/Small parameters are:
Vas = equivalent air compliance (liters)
Qes = electrical Q of driver at resonance
Fs = resonance frequency of driver (Hz)
PEmax = maximum input power of driver (W)
Fb = resonance frequency of the speaker (Hz)
Qtc = final Q of the system at resonance
Dia = effective diameter (cm), which is cone plus 0.333 of surround
Xmax = peak linear displacement of cone (mm)

and where,
pi = 3.14159265359
c = speed of sound in air (345 m/s)
Ro = density of air (1.18 kg/m3)
n0 = free-air efficiency
SPL = driver output @1W/1M
Par = maximum linear power output
Per = electrical input required to produce Par
PeakSPL = Thermally-limited SPL in passband

Now calculate for each frequency F,
Fr = (F/Fb)2
dBmag = 10LOG(Fr2/((Fr-1)2+Fr/Qtc2))
SPLd = K2+40log(F/Fb)
Pmax = K1((Fr-1)2+Fr/Qtc2))/n0
SPLt = dBmag+peakSPL

in which:
SPLd = displacement-limited SPL at F (dB)
Pmax = power required to produce SPLd at F (W)
SPLt = thermally-limited SPL at F (dB)


CAN AN IB ENCLOSURE BE SMALLER THAN THIS?
Yes, it can. If you plan to stuff the enclosure with longhair wool, calculate the volume of the enclosure as 0.75Vb. When it is built, continue to add stuffing until the resonance frequency of the assembly stops falling.


SHOULD AN IB ENCLOSURE BE SMALLER THAN THIS?
No, it shouldnt. The best results are achieved by building it fullsize and leaving it unstuffed, as is most often done in France, where audiophiles are particularly refined. A fullsize enclosure also leaves scope for a little judicious stuffing to finetune the enclosure.


CAN THE ENCLOSURE BE ANY SHAPE?
In theory, yes, but in practice non-standard shapes may require so much extra bracing for resonance-control that you may have to build a second set of enclosures to recover the volume lost to bracing. The standard tower shape has the advantage of a small footprint.

The best of the two proven low resonance tower formats is phi or (1+sqrt5)/2 or 1.618033988749895, where the internal measurements stand in the golden section ration of 0.618:1:1.618 to each other, and the bracing is similarly arranged for resonance cancellation. The other common ratio, for slack designers, is 0.8:1:1.25.

Multiple drivers can be arranged in the familiar dApolito configuration. The front baffle should be narrow, barely wider than the driver. This gets more important the higher the quality of the drivers. Tapering of the box is good, and some of the better commercial designs are tapered on all sides and thus appear to be pyramids with the sharp point lopped off.

The best shape for an infinite baffle is a sphere, which can be built out of dense foam or papier mache style from cold molded strips of ply.

Copyright (c) 2003 Andre Jute/Real McCoy Audio

[Nomen Nescio]

Damn, damn, damn. The anonymous mailer I use strips out formatting from the MSWord files I dictate into, including even apostrophes and quotation marks. Out of this file it has stripped all the carets which I used to indicate powers.

John, Ill send you the file by e-mail. Everyone else had better not use it. The material is in any event in every speaker textbook, very basic stuff.

Sorry, folks, but I dont have a netsite. The story of how it was suppressed and by whom is too well-known to reiterate here.

Andre Jute

THE INFINITE BAFFLE SPEAKER
A brief introduction
Copyright (c) 2003 Andre Jute/Real McCoy Audio

There are two kinds of sealed enclosures, the infinite baffle and the air suspension speaker. This very basic introduction is about the infinite baffle, which uses a large enclosure in which the compliance of the air is greater than the compliance of the driver suspension.

The advantages of the infinite baffle over all other coned speaker enclosures, given that it is properly designed and built, include excellent transient response, good low frequency power handling, generally smaller box size, lower sensitivity to misaligned parameters than more complicated alignments, and straightforward ease of design and construction. Conversely, the price is lower sensitivity and higher low frequency cutoff.

The infinite baffle (and to a lesser extent the air suspension) enclosure, is the coned speaker enclosure of choice for the serious audiophile, next to true electrostatics and horns, because of its smooth handling of transients, and absence of one-note bass.


SUCK IT AND SEE?
Only if you are unimaginably rich. Speaker design is far more complicated and fraught with difficulties than amplifier design. The chances of stumbling on a good design by chance are infinitesimally small. Better to calculate twice and cut once.

All the infinite baffle enclosure calculations below use the famous Theile-Small parameters. These calculations also hold for air suspension systems, which are also sealed enclosures.


BOX SIZE
First choose a desired final total Q of the assembly at resonant frequency, Qtc, as the intended outcome for the design. Values of Qtc from 0.6 to 1.0 are theoretically possible, but values over 0.7 Qtc defeat the purpose as transient response degrades with increasing Qtc values. Commercial designs often increase the power handling of the speakers by choosing higher values of Qtc, and car audio designers go the whole hog, but that is not hi-fi. Higher values of Qtc than 0.7 rarely work except for true subwoofers with sub-20 cycle resonant frequency.

Calculate:
Qr = Qtc/Qts
Vr = Qr2-1
Vb = Vas/Vr
Fb = QrFs
F3 = Fb((1/Qtc2-2+((1/Qtc2-2)2+4)0.5)/2)0.5

Also dBpeak = 0
Except in the case where Qtc is larger than (1/2).5 when
dBpeak = 20log(Qtc2/(Qtc2-0.25)0.5)

where,
the Theile/Small parameters are:
Vas = Equivalent air compliance (liters)
Qts = total Q of the driver at its resonant frequency
Fs = resonant frequency of the driver (Hz)

and calculated data is:
Vb = net box volume (liters)
Fb = box resonant frequency (Hz)
F3 = -3dB frequency (Hz)
dBpeak = maximum peak or dip in system response

Net box volume is without dividers and braces, whose space must be added on to the value calculated above.


FREQUENCY RESPONSE
Calculate for each frequency of interest over the spectrum:
Fr = (F/Fb)2
dBmag = 10LOG(Fr2/((Fr-1)2+Fr/Qtc2))

where,
the Theile/Small parameters are:
Fb = resonance frequency of the system
Qtc = Final Q of the system at resonance

and calculated data is:
F = frequency (Hz)
dBmag = SPL 1W/1M at frequency F


POWER RESPONSE
To calculate power response of the bass driver/enclosure assembly, first make these intermediate calculations:

Sd = pi(Dia/100)2/4
Vd = SdXmax/1000
n0 = 9.6410(-10)Fs3Vas/Qes
SPL = 112 + 10LOG(n0)
K1 = (4pi3Ro/c)Fb4(Vd1.15)2
K2 = 112+10LOG(K1)
Amax = 1 except in the case where Qtc is larger than (1/2).5 when
Amax = Qtc2/(Qtc2-0.25)0.5
Par = K1/Amax2
Per = Par/n0
PeakSPL = SPL+10LOG(PEmax)

where,
the Theile/Small parameters are:
Vas = equivalent air compliance (liters)
Qes = electrical Q of driver at resonance
Fs = resonance frequency of driver (Hz)
PEmax = maximum input power of driver (W)
Fb = resonance frequency of the speaker (Hz)
Qtc = final Q of the system at resonance
Dia = effective diameter (cm), which is cone plus 0.333 of surround
Xmax = peak linear displacement of cone (mm)

and where,
pi = 3.14159265359
c = speed of sound in air (345 m/s)
Ro = density of air (1.18 kg/m3)
n0 = free-air efficiency
SPL = driver output @1W/1M
Par = maximum linear power output
Per = electrical input required to produce Par
PeakSPL = Thermally-limited SPL in passband

Now calculate for each frequency F,
Fr = (F/Fb)2
dBmag = 10LOG(Fr2/((Fr-1)2+Fr/Qtc2))
SPLd = K2+40log(F/Fb)
Pmax = K1((Fr-1)2+Fr/Qtc2))/n0
SPLt = dBmag+peakSPL

in which:
SPLd = displacement-limited SPL at F (dB)
Pmax = power required to produce SPLd at F (W)
SPLt = thermally-limited SPL at F (dB)


CAN AN IB ENCLOSURE BE SMALLER THAN THIS?
Yes, it can. If you plan to stuff the enclosure with longhair wool, calculate the volume of the enclosure as 0.75Vb. When it is built, continue to add stuffing until the resonance frequency of the assembly stops falling.


SHOULD AN IB ENCLOSURE BE SMALLER THAN THIS?
No, it shouldnt. The best results are achieved by building it fullsize and leaving it unstuffed, as is most often done in France, where audiophiles are particularly refined. A fullsize enclosure also leaves scope for a little judicious stuffing to finetune the enclosure.


CAN THE ENCLOSURE BE ANY SHAPE?
In theory, yes, but in practice non-standard shapes may require so much extra bracing for resonance-control that you may have to build a second set of enclosures to recover the volume lost to bracing. The standard tower shape has the advantage of a small footprint.

The best of the two proven low resonance tower formats is phi or (1+sqrt5)/2 or 1.618033988749895, where the internal measurements stand in the golden section ration of 0.618:1:1.618 to each other, and the bracing is similarly arranged for resonance cancellation. The other common ratio, for slack designers, is 0.8:1:1.25.

Multiple drivers can be arranged in the familiar dApolito configuration. The front baffle should be narrow, barely wider than the driver. This gets more important the higher the quality of the drivers. Tapering of the box is good, and some of the better commercial designs are tapered on all sides and thus appear to be pyramids with the sharp point lopped off.

The best shape for an infinite baffle is a sphere, which can be built out of dense foam or papier mache style from cold molded strips of ply.

Copyright (c) 2003 Andre Jute/Real McCoy Audio

[Patrick Turner]

Post by Nomen Nescio
Damn, damn, damn. The anonymous mailer I use strips out formatting from the MSWord files I dictate into, including even apostrophes and quotation marks. Out of this file it has stripped all the carets which I used to indicate powers.
John, Ill send you the file by e-mail. Everyone else had better not use it. The material is in any event in every speaker textbook, very basic stuff.
Sorry, folks, but I dont have a netsite. The story of how it was suppressed and by whom is too well-known to reiterate here.
Andre Jute

I don't want to see you oppressed and suppressed, except when you
are in the mood to set out to lampoon ppl, in a manner which
seems unjustafiable.
Sometimes its not what you say, but the way you say it that makes some of us see red.

If I can get a website established on a shoe string budget, why can't you?

At least wouldn't have to post long tomes to the group, repeatedly,
and the group can switch to your site as you direct them to save the
tedious re-explanations. This would leave you with more time to debate questions
about the technical or sonic issues.

Patrick Turner.

[Chris Hornbeck]

On Tue, 9 Dec 2003 04:30:04 +0100 (CET), Nomen Nescio

Post by Nomen Nescio
The anonymous mailer I use strips out formatting from the MSWord files I dictate into, including

Including carriage returns. Usenet is text-based, so
pure text editors work with it. Anything else looks bad
and is impolite. There's already enough of that, methinks.

Keep 'em flyin',

Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk

[John Byrns]

Hi Andre,

Thanks for the emailed version of the "THE INFINITE BAFFLE SPEAKER", it
looks like the punctuation came through correctly in the email text. My
antique computer/software was unable to decode the Microsoft Word version
you attached though. I suspect it may be the email program I am using
that somehow messes up the separation of the attachment from the email, as
I think I have had this problem with Word documents before, and was able
to resolve it by processing the "raw" email file with a separate file
extraction utility, to recover the Word document, but I just remembered
about that, and haven't tried it yet. I'm not sure why it is only Word
documents that seem to get screwed up that way, while pictures and other
binary attachments make it through unscathed.

Unfortunately I misinterpreted what you originally meant by an "IB". I
assumed you were referring to a large open back baffle. I think a number
of years back "Tube Garden" described some smallish versions of open back
baffles that he had built. Many years ago when I was in Junior High
School I built a Hartley sand baffle. That was a long time ago and I
could be wrong about the Hartley part, maybe it was Warfdale, or maybe
those are the same, I forget my British speaker history. This was an open
back floor standing design of medium size that used two speakers, one
somewhere around 8 inches that was slot loaded to disperse the high
frequencies, and one of about 12 inches or so for the bass. Being a
penniless teenager I didn't use the fancy drivers that were recommended in
the construction article, but just used the first 8" and 12" drivers that
feel to hand. I used the speaker system for a year or two and then when
stereo appeared I retired the sand baffle to the attic in favor of a more
manageable pair of speakers for stereo. Being into weird speakers I think
I had a very brief fling with a Karlson enclosure after the sand baffle,
but that Karlson was the world's worst speaker enclosure.

When I saw "IB" I was thinking of something more on the order of that old
sand baffle.


Regards,

John Byrns

Post by Nomen Nescio
Damn, damn, damn. The anonymous mailer I use strips out formatting from

the MSWord files I dictate into, including even apostrophes and quotation
marks. Out of this file it has stripped all the carets which I used to
indicate powers.

Post by Nomen Nescio
John, Ill send you the file by e-mail. Everyone else had better not use

it. The material is in any event in every speaker textbook, very basic
stuff.

Post by Nomen Nescio
Sorry, folks, but I dont have a netsite. The story of how it was

suppressed and by whom is too well-known to reiterate here.

Post by Nomen Nescio
Andre Jute
THE INFINITE BAFFLE SPEAKER
A brief introduction
Copyright (c) 2003 Andre Jute/Real McCoy Audio

[Snip]


Surf my web pages at, http://users.rcn.com/jbyrns/

[Patrick Turner]

Post by Anonymous
THE INFINITE BAFFLE SPEAKER
A brief introduction
Copyright (c) 2003 Andre Jute/Real McCoy Audio
There are two kinds of sealed enclosures, the infinite baffle and the air suspension speaker. This very basic introduction is about the infinite baffle, which uses a large enclosure in which the compliance of the air is greater than the compliance of the driver suspension.
The advantages of the infinite baffle over all other coned speaker enclosures, given that it is properly designed and built, include excellent transient response, good low frequency power handling, generally smaller box size, lower sensitivity to misaligned parameters than more complicated alignments, and straightforward ease of design and construction. Conversely, the price is lower sensitivity and higher low frequency cutoff.
The infinite baffle (and to a lesser extent the air suspension) enclosure, is the coned speaker enclosure of choice for the serious audiophile, next to true electrostatics and horns, because of its smooth handling of transients, and absence of one-note bass.
SUCK IT AND SEE?
Only if you are unimaginably rich. Speaker design is far more complicated and fraught with difficulties than amplifier design. The chances of stumbling on a good design by chance are infinitesimally small. Better to calculate twice and cut once.
All the infinite baffle enclosure calculations below use the famous Theile-Small parameters. These calculations also hold for air suspension systems, which are also sealed enclosures.
BOX SIZE
First choose a desired final total Q of the assembly at resonant frequency, Qtc, as the intended outcome for the design. Values of Qtc from 0.6 to 1.0 are theoretically possible, but values over 0.7 Qtc defeat the purpose as transient response degrades with increasing Qtc values. Commercial designs often increase the power handling of the speakers by choosing higher values of Qtc, and car audio designers go the whole hog, but that is not hi-fi. Higher values of Qtc than 0.7 rarely work except for true subwoofers with sub-20 cycle resonant frequency.
Qr = Qtc/Qts
Vr = Qr2-1
Vb = Vas/Vr
Fb = QrFs
F3 = Fb((1/Qtc2-2+((1/Qtc2-2)2+4)0.5)/2)0.5
Also dBpeak = 0
Except in the case where Qtc is larger than (1/2).5 when
dBpeak = 20log(Qtc2/(Qtc2-0.25)0.5)
where,
Vas = Equivalent air compliance (liters)
Qts = total Q of the driver at its resonant frequency
Fs = resonant frequency of the driver (Hz)
Vb = net box volume (liters)
Fb = box resonant frequency (Hz)
F3 = -3dB frequency (Hz)
dBpeak = maximum peak or dip in system response
Net box volume is without dividers and braces, whose space must be added on to the value calculated above.
FREQUENCY RESPONSE
Fr = (F/Fb)2
dBmag = 10LOG(Fr2/((Fr-1)2+Fr/Qtc2))
where,
Fb = resonance frequency of the system
Qtc = Final Q of the system at resonance
F = frequency (Hz)
dBmag = SPL 1W/1M at frequency F
POWER RESPONSE
Sd = pi(Dia/100)2/4
Vd = SdXmax/1000
n0 = 9.6410(-10)Fs3Vas/Qes
SPL = 112 + 10LOG(n0)
K1 = (4pi3Ro/c)Fb4(Vd1.15)2
K2 = 112+10LOG(K1)
Amax = 1 except in the case where Qtc is larger than (1/2).5 when
Amax = Qtc2/(Qtc2-0.25)0.5
Par = K1/Amax2
Per = Par/n0
PeakSPL = SPL+10LOG(PEmax)
where,
Vas = equivalent air compliance (liters)
Qes = electrical Q of driver at resonance
Fs = resonance frequency of driver (Hz)
PEmax = maximum input power of driver (W)
Fb = resonance frequency of the speaker (Hz)
Qtc = final Q of the system at resonance
Dia = effective diameter (cm), which is cone plus 0.333 of surround
Xmax = peak linear displacement of cone (mm)
and where,
pi = 3.14159265359
c = speed of sound in air (345 m/s)
Ro = density of air (1.18 kg/m3)
n0 = free-air efficiency
Par = maximum linear power output
Per = electrical input required to produce Par
PeakSPL = Thermally-limited SPL in passband
Now calculate for each frequency F,
Fr = (F/Fb)2
dBmag = 10LOG(Fr2/((Fr-1)2+Fr/Qtc2))
SPLd = K2+40log(F/Fb)
Pmax = K1((Fr-1)2+Fr/Qtc2))/n0
SPLt = dBmag+peakSPL
SPLd = displacement-limited SPL at F (dB)
Pmax = power required to produce SPLd at F (W)
SPLt = thermally-limited SPL at F (dB)
CAN AN IB ENCLOSURE BE SMALLER THAN THIS?
Yes, it can. If you plan to stuff the enclosure with longhair wool, calculate the volume of the enclosure as 0.75Vb. When it is built, continue to add stuffing until the resonance frequency of the assembly stops falling.
SHOULD AN IB ENCLOSURE BE SMALLER THAN THIS?
No, it shouldnt. The best results are achieved by building it fullsize and leaving it unstuffed, as is most often done in France, where audiophiles are particularly refined. A fullsize enclosure also leaves scope for a little judicious stuffing to finetune the enclosure.
CAN THE ENCLOSURE BE ANY SHAPE?
In theory, yes, but in practice non-standard shapes may require so much extra bracing for resonance-control that you may have to build a second set of enclosures to recover the volume lost to bracing. The standard tower shape has the advantage of a small footprint.
The best of the two proven low resonance tower formats is phi or (1+sqrt5)/2 or 1.618033988749895, where the internal measurements stand in the golden section ration of 0.618:1:1.618 to each other, and the bracing is similarly arranged for resonance cancellation. The other common ratio, for slack designers, is 0.8:1:1.25.
Multiple drivers can be arranged in the familiar dApolito configuration. The front baffle should be narrow, barely wider than the driver. This gets more important the higher the quality of the drivers. Tapering of the box is good, and some of the better commercial designs are tapered on all sides and thus appear to be pyramids with the sharp point lopped off.
The best shape for an infinite baffle is a sphere, which can be built out of dense foam or papier mache style from cold molded strips of ply.
Copyright (c) 2003 Andre Jute/Real McCoy Audio

I can't argue with much of what is said here about sealed box enclosures,
except to say that box effects are still present, and what can resonate, will resonate.
Therefore building enclosures which won't resonate much is paramount
in getting the best from boxed speakers, and I prefer a stuffed box to an unstuffed one,
because the sound of a resonant chamber behind the speaker comes through
to the listener.
So hence boxes can be made of disimilar density materials,
laminated with a layer/s of some cloth material, all bonded with some glue with
a lot of give, say latex based rubber.

I don't know if the Book by David B Weems disagrees/agrees with the above calcs,
but I do remember using his methods to check what I was doing when
I went through the phase of finding/building speakers good enough
to enable comparisons of amplifiers or recordings to be made.

Down here in Canberra, a local speaker constructor uses concrete
spheres for his speaker range, and some are single wide range drivered, and others are
two way types, and none produce deep low bass because no-one will buy
enclosures with are 3 feet in diameter, and which could kill a child
if the speaker rolled off its stand onto him or her.
Accommodating midrange drivers into sealed and foam filled enclosures is easy
and effective, since the size of enclosure can be quite small.
tweeters need a tiny real enclosure.

But at bass F, the designs becomes a little more difficult to optimise.
I know folks who vehemtly dismiss any vented enclosure, but who solidly
support transmission line bass as the only way to go.
Maybe its a pity I have never heard a TL that is blameless.
One of the most natural sounding spekers I heard was a 15"
in a 6cu.ft sealed box.
It seemed to go low enough.

But most bass performance is determined by wives.

Wives don't much like speakers, big ones standing
erect and menacing in the lounge, are bleedin ugly, to most
wives, and so men have been forced to accept the T&S parameted
designs with their criticalities, in order to avoid divorces.
Modern living is now mostly done in tiny roomed houses and appartments,
so there isn't room for a speaker of a decent size to make realistically low bass.

Wives typically have better hearing than men, and are not so critical of
sound which us men wouldn't like, since they listen to what it was that
Motzart wrote, and not to the way it is delivered.
So hence those appalling Bose Lifestyle systems, with tiny IB ceiling mounted
speakers, heavily eq'd to get down to 200 Hz, and a "sub" woofer
out of sight which barely gets down to 50 Hz.
The control unit which can sit on a kitchen bench is a real winner with the ladies.
Wives don't like the idea of cutting round holes in walls to mount bass speakers.

Then there are the current crop of Nth European ported speakers, Vienna Acoustic
makes some, and the Motzart model has only 22 litres of enclosure,
with SEAS 5" drivers, and they do make remarkably good bass.
Somehow, I suspect they got their number right better than so
many others.
They seem to have realised its very hard to sell large speakers to
married men living in small rooms, who are the majority of their customers.

A friend has some 1969 15" dual concentric speakers mounted in 6 cu ft
boxes using sand filled timber panels, and ported, and driven by SET 300B amps,
and I really like this system.
His wife is understanding.

I just think there are various different ways to get to an outcome with speakers.
And I believe the calculate, measure, and listen approach is one which
the DIY audphile stands to gain the most from.

Patrick Turner

[Chris Hornbeck]

On Mon, 8 Dec 2003 18:12:49 -0800 (PST), Anonymous

Post by Anonymous
THE INFINITE BAFFLE SPEAKER
A brief introduction

Thanks for the ambitious post.

Post by Anonymous
SHOULD AN IB ENCLOSURE BE SMALLER THAN THIS?
No, it shouldnt. The best results are achieved by building it
fullsize and leaving it unstuffed, as is most often done in
France, where audiophiles are particularly refined. A fullsize
enclosure also leaves scope for a little judicious stuffing to
finetune the enclosure.

An interesting alternative can be found in Siegfried Linkwitz's
seminal Speaker Builder articles, vols. 2, 3, and 4 1980. These
update his earlier AES and WW papers with a simple and simple
to use circuit that takes any sealed box's f-sub-C and Q-sub-TC
and converts to any other. I like 8 Hz and Q of 0.5, but try
a few other possibilities.

Post by Anonymous
CAN THE ENCLOSURE BE ANY SHAPE?
In theory, yes, but in practice non-standard shapes may require
so much extra bracing for resonance-control that you may have to
build a second set of enclosures to recover the volume lost to
bracing. The standard tower shape has the advantage of a small footprint.
The best shape for an infinite baffle is a sphere, which can be built
out of dense foam or papier mache style from cold molded strips of ply.

A cylinder with drivers on both ends can be pretty slick, too.
Cardboard concrete pouring forms are classic in the states.

Good fortune,

Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk

[Phil Allison]

Post by Anonymous
Copyright (c) 2003 Andre Jute/Real McCoy Audio
There are two kinds of sealed enclosures, the infinite baffle and the air

suspension speaker. This very basic introduction is about the infinite
baffle, which uses a large enclosure in which the compliance of the air is
greater than the compliance of the driver suspension.


** This is a definition I have not seen elsewhere - the names are pretty
much synonyms in literature on the subject.

However, there are not too many modern bass drivers that have stiff
suspensions and hence small Vas figures - most 10 inch or 12 inch drivers
have Vas numbers around 80 to 200 litres. So, for the condition of the
compliance of the air to be greater than the compliance of the driver
suspension the box volume ends up just a tad on the large side.

I suppose the benefit is the more gradual roll off and hence phase shift
at low frequencies - but the excursion is greater than otherwise and I
fear that IM will be increased.

If used for a sub woofer with a low ( electronic ) x-over point - over
say one octave only - then not to worry too much.



........ Phil

[Nomen Nescio]

Post by Anonymous
Copyright (c) 2003 Andre Jute/Real McCoy Audio
There are two kinds of sealed enclosures, the infinite baffle and the air

suspension speaker. This very basic introduction is about the infinite
baffle, which uses a large enclosure in which the compliance of the air is
greater than the compliance of the driver suspension.


This is a definition I have not seen elsewhere - the names are pretty
much synonyms in literature on the subject.

Just as well you picked it up, Phil, because actually the example I have prepared for posting when Turners irrelevant advertisements for himself in this thread run down a bit, is the other thing, an air suspension speaker, with a Vas of 222. Id hate to give people the opportunity to say I hypocritically preach one thing and do the other. So, with thanks, here is the amended first section for the article THE INFINITE BAFFLE SPEAKER:


THE INFINITE BAFFLE SPEAKER
A brief introduction
Copyright (c) 2003 Andre Jute/Real McCoy Audio

There are two kinds of sealed enclosures, the infinite baffle and the air suspension speaker. The infinite baffle uses a large enclosure in which the compliance of the air is greater than the compliance of the driver suspension. In the air suspension system a small enclosure is used in which the compliance of the air is a third or less of the compliance of the driver suspension.

We shall refer to both as an infinite baffle (IB) because that is the common usage. However, when we say IB what we normally mean is air suspension (AS) because softly suspended bass drivers are pretty rare, so that just about every sealed enclosure is an air suspension system, misnomered IB.

The advantages of the infinite baffle over all other coned speaker enclosures, given that it is properly designed and built, include excellent transient response, good low frequency power handling, generally smaller box size, lower sensitivity to misaligned parameters than more complicated alignments, and straightforward ease of design and construction. Conversely, the price is lower sensitivity and higher low frequency cutoff.

The infinite baffle enclosure is the coned speaker enclosure of choice for the serious audiophile, next to true electrostatics and horns, because of its smooth handling of transients, and absence of one-note bass.


SUCK IT AND SEE?
Only if you are unimaginably rich. Speaker design is far more complicated and fraught with difficulties than amplifier design. The chances of stumbling on a good design by chance are infinitesimally small. Better to calculate twice and cut once.

All sealed enclosures (infinite baffles and air suspension systems) use the famous Theile-Small parameters.

BOX SIZE
First choose a desired final total Q of

etc etc.

Andre Jute

Post by Anonymous
Copyright (c) 2003 Andre Jute/Real McCoy Audio
There are two kinds of sealed enclosures, the infinite baffle and the air

suspension speaker. This very basic introduction is about the infinite
baffle, which uses a large enclosure in which the compliance of the air is
greater than the compliance of the driver suspension.


This is a definition I have not seen elsewhere - the names are pretty
much synonyms in literature on the subject.

However, there are not too many modern bass drivers that have stiff
suspensions and hence small Vas figures - most 10 inch or 12 inch drivers
have Vas numbers around 80 to 200 litres. So, for the condition of the
compliance of the air to be greater than the compliance of the driver
suspension the box volume ends up just a tad on the large side.

I suppose the benefit is the more gradual roll off and hence phase shift
at low frequencies - but the excursion is greater than otherwise and I
fear that IM will be increased.

If used for a sub woofer with a low ( electronic ) x-over point - over
say one octave only - then not to worry too much.



....... Phil

[Jimmy]

Post by Anonymous
THE INFINITE BAFFLE SPEAKER
A brief introduction
Copyright (c) 2003 Andre Jute/Real McCoy Audio
There are two kinds of sealed enclosures, the infinite baffle and the air

suspension speaker. This very basic introduction is about the infinite
baffle, which uses a large enclosure in which the compliance of the air is
greater than the compliance of the driver suspension.

Post by Anonymous
The advantages of the infinite baffle over all other coned speaker

enclosures, given that it is properly designed and built, include excellent
transient response, good low frequency power handling, generally smaller box
size, lower sensitivity to misaligned parameters than more complicated
alignments, and straightforward ease of design and construction. Conversely,
the price is lower sensitivity and higher low frequency cutoff.

Post by Anonymous
The infinite baffle (and to a lesser extent the air suspension) enclosure,

is the coned speaker enclosure of choice for the serious audiophile, next to
true electrostatics and horns, because of its smooth handling of transients,
and absence of one-note bass.

Post by Anonymous
SUCK IT AND SEE?
Only if you are unimaginably rich. Speaker design is far more complicated

and fraught with difficulties than amplifier design. The chances of
stumbling on a good design by chance are infinitesimally small. Better to
calculate twice and cut once.

Post by Anonymous
All the infinite baffle enclosure calculations below use the famous

Theile-Small parameters. These calculations also hold for air suspension
systems, which are also sealed enclosures.

Post by Anonymous
BOX SIZE
First choose a desired final total Q of the assembly at resonant

frequency, Qtc, as the intended outcome for the design. Values of Qtc from
0.6 to 1.0 are theoretically possible, but values over 0.7 Qtc defeat the
purpose as transient response degrades with increasing Qtc values.
Commercial designs often increase the power handling of the speakers by
choosing higher values of Qtc, and car audio designers go the whole hog, but
that is not hi-fi. Higher values of Qtc than 0.7 rarely work except for true
subwoofers with sub-20 cycle resonant frequency.

Post by Anonymous
Qr = Qtc/Qts
Vr = Qr2-1
Vb = Vas/Vr
Fb = QrFs
F3 = Fb((1/Qtc2-2+((1/Qtc2-2)2+4)0.5)/2)0.5
Also dBpeak = 0
Except in the case where Qtc is larger than (1/2).5 when
dBpeak = 20log(Qtc2/(Qtc2-0.25)0.5)
where,
Vas = Equivalent air compliance (liters)
Qts = total Q of the driver at its resonant frequency
Fs = resonant frequency of the driver (Hz)
Vb = net box volume (liters)
Fb = box resonant frequency (Hz)
F3 = -3dB frequency (Hz)
dBpeak = maximum peak or dip in system response
Net box volume is without dividers and braces, whose space must be added

on to the value calculated above.

Post by Anonymous
FREQUENCY RESPONSE
Fr = (F/Fb)2
dBmag = 10LOG(Fr2/((Fr-1)2+Fr/Qtc2))
where,
Fb = resonance frequency of the system
Qtc = Final Q of the system at resonance
F = frequency (Hz)
dBmag = SPL 1W/1M at frequency F
POWER RESPONSE
To calculate power response of the bass driver/enclosure assembly, first
Sd = pi(Dia/100)2/4
Vd = SdXmax/1000
n0 = 9.6410(-10)Fs3Vas/Qes
SPL = 112 + 10LOG(n0)
K1 = (4pi3Ro/c)Fb4(Vd1.15)2
K2 = 112+10LOG(K1)
Amax = 1 except in the case where Qtc is larger than (1/2).5 when
Amax = Qtc2/(Qtc2-0.25)0.5
Par = K1/Amax2
Per = Par/n0
PeakSPL = SPL+10LOG(PEmax)
where,
Vas = equivalent air compliance (liters)
Qes = electrical Q of driver at resonance
Fs = resonance frequency of driver (Hz)
PEmax = maximum input power of driver (W)
Fb = resonance frequency of the speaker (Hz)
Qtc = final Q of the system at resonance
Dia = effective diameter (cm), which is cone plus 0.333 of surround
Xmax = peak linear displacement of cone (mm)
and where,
pi = 3.14159265359
c = speed of sound in air (345 m/s)
Ro = density of air (1.18 kg/m3)
n0 = free-air efficiency
Par = maximum linear power output
Per = electrical input required to produce Par
PeakSPL = Thermally-limited SPL in passband
Now calculate for each frequency F,
Fr = (F/Fb)2
dBmag = 10LOG(Fr2/((Fr-1)2+Fr/Qtc2))
SPLd = K2+40log(F/Fb)
Pmax = K1((Fr-1)2+Fr/Qtc2))/n0
SPLt = dBmag+peakSPL
SPLd = displacement-limited SPL at F (dB)
Pmax = power required to produce SPLd at F (W)
SPLt = thermally-limited SPL at F (dB)
CAN AN IB ENCLOSURE BE SMALLER THAN THIS?
Yes, it can. If you plan to stuff the enclosure with longhair wool,

calculate the volume of the enclosure as 0.75Vb. When it is built, continue
to add stuffing until the resonance frequency of the assembly stops falling.

Post by Anonymous
SHOULD AN IB ENCLOSURE BE SMALLER THAN THIS?
No, it shouldnt. The best results are achieved by building it fullsize and

leaving it unstuffed, as is most often done in France, where audiophiles are
particularly refined. A fullsize enclosure also leaves scope for a little
judicious stuffing to finetune the enclosure.

Post by Anonymous
CAN THE ENCLOSURE BE ANY SHAPE?
In theory, yes, but in practice non-standard shapes may require so much

extra bracing for resonance-control that you may have to build a second set
of enclosures to recover the volume lost to bracing. The standard tower
shape has the advantage of a small footprint.

Post by Anonymous
The best of the two proven low resonance tower formats is phi or

(1+sqrt5)/2 or 1.618033988749895, where the internal measurements stand in
the golden section ration of 0.618:1:1.618 to each other, and the bracing is
similarly arranged for resonance cancellation. The other common ratio, for
slack designers, is 0.8:1:1.25.

Post by Anonymous
Multiple drivers can be arranged in the familiar dApolito configuration.

The front baffle should be narrow, barely wider than the driver. This gets
more important the higher the quality of the drivers. Tapering of the box is
good, and some of the better commercial designs are tapered on all sides and
thus appear to be pyramids with the sharp point lopped off.

Post by Anonymous
The best shape for an infinite baffle is a sphere, which can be built out

of dense foam or papier mache style from cold molded strips of ply.

Post by Anonymous
Copyright (c) 2003 Andre Jute/Real McCoy Audio

One of the better speakers enclosures I have built used concrete. It was
built in place on either side of the fireplace when the house was built.
Prior to this I had built the same size speaker enclosure size using thick
particle board laminated with plywood for appearance. I thought these wre
great sounding speakers until I built the masonry ones.

[Robert Casey]

Post by Anonymous
THE INFINITE BAFFLE SPEAKER

I'm completely baffled.... :D ;-)

[Tim Williams]

Post by Robert Casey

Post by Anonymous
THE INFINITE BAFFLE SPEAKER

I'm completely baffled.... :D ;-)

*I'm* completely baffled why people keep giving in!

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

[Brian]

Post by Anonymous
THE INFINITE BAFFLE SPEAKER

I decided to try one of these, or a quick approximation, a few months
back. I had found a JBL D208 at an estate sale. It was mounted on a
small rectangular board, apparently the front panel of a missing
cabinet. I tried the thing in open air just to see if the driver
worked. It sounded so good that I propped it in the gap between the
sliding doors of my lab closet. The board rested at ear level on top
of a sofa placed in front of the doors. I did nothing to cover the
gaping hole above the board. It sounded just great, with remarkably
deep bass (audible down into the 30s).

After I played around with a speaker-modeling program, I understood
what was going on. Infinite baffles or dipoles roll off at 6 dB/octave
instead of 12 for a closed box or 18 for ported. The model predicted
that the bass would be 3 dB down at 175 Hz, but would drop slowly and
go deep. That's just what I heard.

I was perfectly happy with the speaker, driven by push-pull 6V6s and a
mono FM tuner, for months. Last weekend when I came across a JBL
Apollo system with a D130/075/N2600 combination in a 5 cubic-foot box,
I took down the D208. The D130 system has much more bass, though it's
not noticeably deeper.

I was really surprised how effective a kludgy infinite baffle could
be.

Brian

[George Orwell]

rec.audio.tubes
Re: THE INFINITE BAFFLE SPEAKER

The sort of speaker you mean is a flat baffle. It becomes an infinite baffle when you fold it into a sealed box. Mind you, if Phil hadnt already twitted me for careless nomenclature, I too would have included a flat baffle into the ranks of the IB. . .

Ive never been much into flat baffles, though I once had electrostats in the wall between two rooms. I dont seem to remember any huge advantage. It was just a convenient place to put them.

The last thing I wrote on flat baffles was in GA, or perhaps VALVE, about an 11 part division scheme, 7 and 4, for placement of the speaker on the flat baffle. That one used the cheap drivers that Dan Schmalle used to sell four for thirty bucks with his SEX amp, which later also featured in my notorious carpet tube speaks for hugely bass-enhanced Gregorian Chant.

Sorry I cant be of more help. If you ever get around to a sealed box speaker, remind me that I prepared the second part of "THE INFINITE BAFFLE SPEAKER" posting, called Carte Blanche, which I was holding until Turner stopped ruining the first part of the posting with his dull advertisements for himself. It is a description of the last IB I designed, with Scan Speak drivers. At that time Ill pull it out and well take it from there.

I certainly hope you will describe your thoughts and experiments here.

Andre Jute

John Byrns <***@rcn.com>
Hi Andre,

Thanks for the emailed version of the "THE INFINITE BAFFLE SPEAKER", it
looks like the punctuation came through correctly in the email text. My
antique computer/software was unable to decode the Microsoft Word version
you attached though. I suspect it may be the email program I am using
that somehow messes up the separation of the attachment from the email, as
I think I have had this problem with Word documents before, and was able
to resolve it by processing the "raw" email file with a separate file
extraction utility, to recover the Word document, but I just remembered
about that, and havent tried it yet. Im not sure why it is only Word
documents that seem to get screwed up that way, while pictures and other
binary attachments make it through unscathed.

Unfortunately I misinterpreted what you originally meant by an "IB". I
assumed you were referring to a large open back baffle. I think a number
of years back "Tube Garden" described some smallish versions of open back
baffles that he had built. Many years ago when I was in Junior High
School I built a Hartley sand baffle. That was a long time ago and I
could be wrong about the Hartley part, maybe it was Warfdale, or maybe
those are the same, I forget my British speaker history. This was an open
back floor standing design of medium size that used two speakers, one
somewhere around 8 inches that was slot loaded to disperse the high
frequencies, and one of about 12 inches or so for the bass. Being a
penniless teenager I didnt use the fancy drivers that were recommended in
the construction article, but just used the first 8" and 12" drivers that
feel to hand. I used the speaker system for a year or two and then when
stereo appeared I retired the sand baffle to the attic in favor of a more
manageable pair of speakers for stereo. Being into weird speakers I think
I had a very brief fling with a Karlson enclosure after the sand baffle,
but that Karlson was the worlds worst speaker enclosure.

When I saw "IB" I was thinking of something more on the order of that old
sand baffle.


Regards,

John Byrns

[Henry A. Pasternack]

Post by George Orwell
The sort of speaker you mean is a flat baffle. It becomes an infinite
baffle when you fold it into a sealed box. Mind you, if Phil hadnt
already twitted me for careless nomenclature, I too would have
included a flat baffle into the ranks of the IB. . .

The acoustic suspension loudspeaker is a distinct variation and
improvement over the infinite baffle design that predates it. I
don't understand why the two terms are being lumped together in
the popular literature these days. I would have to guess it's
just a matter of the design principles not being understood well
enough by average audiophiles and the marketing types that cater
to them. Certainly, when Edgar Villchur invented acoustic suspension
in the early 1950's, he realized it was a significant departure from
the prevailing technology.

The tradeoff of acoustic suspension is, all other things being
equal, that the driver requires a more massive cone to achieve
the same LF cutoff. This makes the loudspeaker less efficient.
The advantage is a smaller enclosure. For a given F3 and system
Q, the frequency response, phase response, transient response,
and cone excursion of an infinite baffle and acoustic suspension
speaker will be identical. The acoustic suspension speaker may
have lower distortion due to the inherent linearity of the air
in the box that forms part of its suspension compliance.

A flat baffle loudspeaker is a dipole. Because the rear wave isn't
isolated from the front wave, as the frequency drops the two waves
will cancel. Flat response can be restored with bass equalization
at the expense of very high amplifier power and corresponding large
cone excursion. See http://www.linkwitzlab.com for an authoritative
treatment of open baffle loudspeaker design.

Contrary to stated opinion, a bass reflex speaker, properly designed,
does not have one-note bass or poor transient response. Anyone who
believes that hasn't listened to kick-bass being reproduced by a
JBL 18" pro driver in a bass reflex enclosure.

Equations are only part of the equation. It's knowing what to do
with them that counts.

Have a nice day.

-Henry

[John Byrns]

Post by Henry A. Pasternack

Post by George Orwell
The sort of speaker you mean is a flat baffle. It becomes an infinite
baffle when you fold it into a sealed box. Mind you, if Phil hadnt
already twitted me for careless nomenclature, I too would have
included a flat baffle into the ranks of the IB. . .

The acoustic suspension loudspeaker is a distinct variation and
improvement over the infinite baffle design that predates it. I
don't understand why the two terms are being lumped together in
the popular literature these days. I would have to guess it's
just a matter of the design principles not being understood well
enough by average audiophiles and the marketing types that cater
to them. Certainly, when Edgar Villchur invented acoustic suspension
in the early 1950's, he realized it was a significant departure from
the prevailing technology.

I guess you can count me among those who do not understand the design
principles well enough. To me the mechanical system of the so called
"acoustic suspension loudspeaker", and what we are calling an "infinite
baffle speaker", or large closed box loudspeaker, are identical in
topology. The only difference between the two is the choice of the values
of the different mechanical components that make up the systems. The
number and type of components used, as well as their arrangement into a
mechanical system is identical in each case. Where am I going wrong,
please enlighten me as to how these two systems are fundamentally
different?

Post by Henry A. Pasternack
The tradeoff of acoustic suspension is, all other things being
equal, that the driver requires a more massive cone to achieve
the same LF cutoff. This makes the loudspeaker less efficient.
The advantage is a smaller enclosure. For a given F3 and system
Q, the frequency response, phase response, transient response,
and cone excursion of an infinite baffle and acoustic suspension
speaker will be identical. The acoustic suspension speaker may
have lower distortion due to the inherent linearity of the air
in the box that forms part of its suspension compliance.

OK, that sounds like you have changed your mind and agree that the
topology of two systems are identical, with the only difference being the
choice of mechanical component values used.

Come on Henry, wake up and smell the coffee, they are the same that's why
they are lumped together. That doesn't diminish the importance of
Villchur's insight when he realized the advantages of using a set of
component values that differed from the tradition of the time. This is
analogous to Armstrong's invention of FM, where FM already existed, and
Armstrong simply had the insight to realize the advantages that would be
gained by using a different set of parameters for the system than people
had been using up to that point.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

[Henry A. Pasternack]

Post by John Byrns
I guess you can count me among those who do not understand the design
principles well enough. To me the mechanical system of the so called
"acoustic suspension loudspeaker", and what we are calling an "infinite
baffle speaker", or large closed box loudspeaker, are identical in
topology. The only difference between the two is the choice of the values
of the different mechanical components that make up the systems. The
number and type of components used, as well as their arrangement into a
mechanical system is identical in each case. Where am I going wrong,
please enlighten me as to how these two systems are fundamentally
different?

In an acoustic suspension speaker, there are two "springs" in the
cone suspension, the mechanical spring in the driver itself, and
the air "spring" due to the small box volume. This is a pretty
major conceptual leap, to use air pressure to augment the mechanical
properties of the driver. At the time Villchur introduced the
idea, it was rejected by the speaker manufacturers he proposed it
to. So he and Henry Kloss started Acoustic Research.

Not that patents or commercial success necessarily mean anything,
but Villchur did patent the acoustic suspension design, and AR's
products revolutionized the speaker industry.

Post by John Byrns
OK, that sounds like you have changed your mind and agree that the
topology of two systems are identical, with the only difference
being the choice of mechanical component values used.

No, in my mind they are distinct. Both are second-order high-pass
filters, but the design tradeoffs are different. They require
different types of drivers and they do, in general result in boxes
that are of significantly different size and efficiency. In the
taxonomy of speaker design, they are well-defined endpoints along
the continuum of sealed-box alignments. There is certainly value
in drawing out the distinction.

Post by John Byrns
Come on Henry, wake up and smell the coffee, they are the same
that's why they are lumped together. That doesn't diminish the
importance of Villchur's insight when he realized the advantages
of using a set of component values that differed from the tradition
of the time. This is analogous to Armstrong's invention of FM,
where FM already existed, and Armstrong simply had the insight
to realize the advantages that would be gained by using a different
set of parameters for the system than people had been using up to
that point.

Well, I have to disagree. Acoustic suspension and infinite baffle
are distinct because the design principles are different. I think
if you spent more time working with speakers and absorbing the
general mindset of speaker design, you might come to appreciate
that the two types of speakers are not the same.

-Henry

[Phil Allison]

"Henry A. Pasternack" <

Post by Henry A. Pasternack
In an acoustic suspension speaker, there are two "springs" in the
cone suspension, the mechanical spring in the driver itself, and
the air "spring" due to the small box volume.

** Exactly the same situation with IB.

Post by Henry A. Pasternack
This is a pretty major conceptual leap,

** Total madness.

It is no more a conceptual leap than fitting pneumatic tyres to a
wheelbarrow.

Post by Henry A. Pasternack
to use air pressure to augment the mechanical properties of the driver.

** Doubletalk - at best.

Post by Henry A. Pasternack
Not that patents or commercial success necessarily mean anything,
but Villchur did patent the acoustic suspension design, and AR's
products revolutionized the speaker industry.

** The two facts are not in the slightest related.

From the same era came the full range, push- pull, electrostatic
acoustic doublet which set a new performance standard for loudspeakers that
is still at the apex.

Post by Henry A. Pasternack
No, in my mind they are distinct.

** So you suffer from schizophrenia.

Post by Henry A. Pasternack
There is certainly value in drawing out the distinction.

** Only a commercial one - the use of a cute sounding name.

Post by Henry A. Pasternack
Well, I have to disagree.

** You always fucking do - a direct result of your brain damage.

Post by Henry A. Pasternack
Acoustic suspension and infinite baffle are distinct because the design

principles are different.


** Sorreeee - they are basically just the same.


( snip more posturing personal abuse )




........... Phil

[Henry A. Pasternack]

Post by Phil Allison
** Exactly the same situation with IB.

If you define "infinite baffle" to mean the same thing as "acoustic
suspension", then of course there is no difference between them.
But that's a semantic argument, not a technical one.

When Edgar Villchur and Henry Kloss formed Acoustic Research, the
acoustic suspension loudspeaker was a conceptual breakthrough and
a major advancement in the state of commercial loudspeaker
manufacturing.

In loudspeaker design it's fundamental to speak of box alignments.
There must be at least a half-dozen named bass reflex alignments.
Although they only differ in the parameters of their components,
they are sufficiently distinct to have separate identities in the
minds of speaker designers. Nevertheless, there is nothing to
prevent building a bass reflex box tuned to an "in-between"
alignment. Likewise, "acoustic suspension" and "infinite baffle"
are two distinct sealed box alignments. While the difference
between them is not as great as, say, the difference between a
sealed box and a bass reflex system, the distinction is very real.

Your other comments are frivolous.

-Henry

[Henry A. Pasternack]

I thought it might be a good idea to turn to a recognized authority
on loudspeaker design, Dick Pierce. Fortunately, we don't have to
talk to Dick directly because he's posted on this subject often
enough in the past.

What I'm surprised to see is that the term "infinite baffle" does,
according to Dick, apply to any loudspeaker system where the rear
wave is isolated from the front wave, regardless of the size of the
box. On the other hand, he also clearly distinguishes between the
two types of sealed box alignments. You will also see in Dick's
and others' postings the use of phrases like "true infinite baffle"
to refer to a loudspeaker mounting, e.g., in a hole in a large wall,
where the baffle size and enclosed volume are effectively infinite,
in contrast to a small sealed box that traps and absorbs the rear
wave, but that also contributes to the cone suspension compliance.

I've attached two of Dick's postings. I've left them unedited for
completeness even though some of the material is extraneous to this
discussion. Dick unambiguously says:

...you can have two basic types of sealed enclosures: infinite
baffle... and so-called "acoustic suspension"...

So, while both are instances of the general class of sealed boxes,
they are sufficiently distinct as to deserve different labels and
descriptions. This is the point I wish to make. If anyone cares
to complain, I suggest they take it up with Dick himself, as I have
little else to add.

-Henry

-----
Newsgroups: rec.audio.tech
From: ***@world.std.com (Richard D Pierce)
Subject: Re: Box Design
Message-ID: <***@world.std.com>
Organization: The World Public Access UNIX, Brookline, MA
References: <3aa5hk$***@yarrow.csv.warwick.ac.uk>
Date: Tue, 15 Nov 1994 13:06:05 GMT
Lines: 85

Could someone describe the difference between :-
Bass Reflex
Coupled Cavity
Ported / Sealed Enclosure
etc ...

Starting from the simplest and working towards greater complexity in your
list, all of them fall in the class of "direct radiator" enclosures, so
called because the sound is, essentially, produced directly from the
driver (the "radiator") without the assistance of a contrivance such as a
horn.

Sealed box:
The simplest direct-radiator system. The rear of the driver sees
a sealed enclosure, and none of the rear output of the driver
contributes in any way to the total output of the system. Depending
upon the relative values of some critical parameters, specifically
how stiff the mechanical suspension is vs how stiff the enclosed
air in the enclosure is (and that's a function of the size of the
box), you can have two basic types of sealed enclosures: infinite
baffle enclosure, in which the mechnical suspension is the dominant
source of system stiffness and the box is generally large; and
so-called "acoustic-suspension" enclosures, where the air in the
box is the dominating stiffness, and the boxes tend to be small.

Because of the nature of things, sealed boxes generally tend to be
the lowest efficiency systems for a given box size and bass cutoff
frequency.

Vented enclosures
Also the same as bass reflex, ported, or passive radiator systems.
Here, an aperture in the box provides a means for the rear output
of the cone to contribute to the total output of the system. Unlike
most peoples impression, though, it does not do so at all frequencies,
but only over a very narrow range of frequencies. In fact, in a
properly designed system, the front output of the cone is reduced at
the same time the output of port increases, so the port DOES NOT ADD
to the output of the woofer, it REPLACES the output of the woofer at
these frequencies. This, if done properly, can significantly reduce
distortion and increase power handling at very low frequencies, a
region that can be difficult for a driver to do.

Again, because of the nature of things, vented systems can be up to
3 dB more efficienct than a sealed box system that has the same
bass cutoff frequency and enclosure size.

Bandpass
These are compound systems in the sense that they have at least
two enclosures: one on the front and one on the rear of the driver
(and one might argue that they are, therefore, not direct-radiators).
The enclosure on the front, which looks remarkably like a vented box
(because, well, it IS), acts as a low pass filter, and, at the same
time, can couple the output of the woofer somewhat more efficienctly
to the outside. They have several useful advantages. For example,
the front enclosure can be used as a very effective acoustic
crossover,
filtering out mechanical nboises generated by the woofer, something
no electronic crossover can do. For very low frequencies, such an
acoustic crossover can be far less expensive and more easily designed
than an equivalent passive or active electronic crossover.

They are called "bandpass" because the combination of the rear
enclosure and the driver form the high pass portion while the front
enclosure forms the low pass section (in effect). Making the bandwidth
of the system narrower generally raises the efficiency of the system.

Coupled cavity
A variation and an aglomeration of bandpass and vented systems, they
are the results of a designers attempt to solve specific problems.
They consist of two or more rear enclosures, each coupled to the next
by a vent. Each enclosure/vent combination is another resonant system,
and the combination is, essentially, a high order, multi-tuned
resonant system.

Generally, these systems have quite complex response functions and
are difficult to design, as there exists no comprehensive theory on
their operation like exists for sealed, vented and bandpass systems.

--
| Dick Pierce |
| Loudspeaker and Software Consulting |
| 17 Sartelle Street Pepperell, MA 01463 |
| [phone] (Voice and FAX) |

Newsgroups: rec.audio
From: ***@world.std.com (Richard D Pierce)
Subject: Re: Acoustic Suspension vs. Infinite Baffle?
Message-ID: <***@world.std.com>
Organization: The World Public Access UNIX, Brookline, MA
References: <***@ban.aid.no>
Date: Thu, 5 May 1994 12:48:40 GMT
Lines: 65

What exactly is the difference in SOUND quality between Acoustic Suspension
and Infinite Baffle. If there is none, what's the point in differentiation
them...?

First, the physical difference between an infinite baffle and an acoustic
suspension would help.

An infinite baffle is essentially any speaker enclosure which isolates
the rear radiation from the front radiation of the cone. It can be
represented by anything from the proverbial "infinite baffle", a very
large wall with the driver mounted in the middle of it, down to a small
sealed box (at least as far as low frequencies are concerned.

An acoustic suspension enclosure is a type of infinite baffle, sealed box
enclosure where something called the "tuning ratio", the ratio between
the compliance of the driver's suspension and the compliance of the air
in the box is high, usually more than 2 or 3 to one. Or, in Thiele-Small
parlance, Vas, the equivalent volume of compliance, is at least 2 to 3
times the Vb, the volume of the airt in the box.

Edgar Vilchur invented the principle in th 1950's in an attempt to deal
with the then lousy linearity of woofers, on the presumption that if you
let the air in the box be the predominant stiffness in the system, then
you'll be dealing priomarily with the linearity of the air in the box,
which is arguably better than that of drivers.

However, in order to exploit this, he had to make his drivers very linear
to begin with. The compliance of the suspension can change by a factor of
2-3 over the "linear" range, thus if you start with the box compiance
dominating at low excursions, then at high excursions the suspension
dominates, what have you gained? Further, he dramatically improved the
drive linearity by using overhung voice coils in an attempt to make the
drive parameter (the Bl product) independent of position.

In the process, he developed a driver that was more linear to begin with.
It's not clear that the enclosure design, then, bought him much of anything.

There is a side advantage to having a high tuning ratio. With the cabinet
volume dominating the system stiffness, the normal manufacturing
tolerances inherent in the stiffness of the suspension is essntially
unimportant, since it's the box stiffness that predominates. Normal
manufacturing variations of +- 20% in driver compliance are reduced to
actual system resonant frequency variations of about +-2% in a system
with a compliance ratio of 4:1 (assuming mass is held constant).

How do they sound compared to one another? Absolutely impossible to tell,
because to compare the two, you'd need to compare two drivers that are
otherwise identical, one in each type of enclosure. But if the driver is
designbed to work well in an infinite baffle, it's resonance and system Q
will be much higher in the acoustic suspension, whereas if it's designed
to work well in the acoustic suspension, its resonance and system Q will
be much lower in the infinite baffle. You'll end up hearing whatever
difference completely predominated by the differences in the system
response that result. If you try to use drivers optimized for each
loading, you'll probably then hear the differences in the drivers, not
the loading.



--
| Dick Pierce |
| Loudspeaker and Software Consulting |
| 17 Sartelle Street Pepperell, MA 01463 |
| [phone] (Voice and FAX) |

[scottp]

Great post Henry.

Scott

Post by Henry A. Pasternack
I thought it might be a good idea to turn to a recognized authority
on loudspeaker design, Dick Pierce. Fortunately, we don't have to
talk to Dick directly because he's posted on this subject often
enough in the past.
What I'm surprised to see is that the term "infinite baffle" does,
according to Dick, apply to any loudspeaker system where the rear
wave is isolated from the front wave, regardless of the size of the
box. On the other hand, he also clearly distinguishes between the
two types of sealed box alignments. You will also see in Dick's
and others' postings the use of phrases like "true infinite baffle"
to refer to a loudspeaker mounting, e.g., in a hole in a large wall,
where the baffle size and enclosed volume are effectively infinite,
in contrast to a small sealed box that traps and absorbs the rear
wave, but that also contributes to the cone suspension compliance.
I've attached two of Dick's postings. I've left them unedited for
completeness even though some of the material is extraneous to this
...you can have two basic types of sealed enclosures: infinite
baffle... and so-called "acoustic suspension"...
So, while both are instances of the general class of sealed boxes,
they are sufficiently distinct as to deserve different labels and
descriptions. This is the point I wish to make. If anyone cares
to complain, I suggest they take it up with Dick himself, as I have
little else to add.
-Henry
-----
Newsgroups: rec.audio.tech
Subject: Re: Box Design
Organization: The World Public Access UNIX, Brookline, MA
Date: Tue, 15 Nov 1994 13:06:05 GMT
Lines: 85

Could someone describe the difference between :-
Bass Reflex
Coupled Cavity
Ported / Sealed Enclosure
etc ...

Starting from the simplest and working towards greater complexity in your
list, all of them fall in the class of "direct radiator" enclosures, so
called because the sound is, essentially, produced directly from the
driver (the "radiator") without the assistance of a contrivance such as a
horn.
The simplest direct-radiator system. The rear of the driver sees
a sealed enclosure, and none of the rear output of the driver
contributes in any way to the total output of the system. Depending
upon the relative values of some critical parameters, specifically
how stiff the mechanical suspension is vs how stiff the enclosed
air in the enclosure is (and that's a function of the size of the
box), you can have two basic types of sealed enclosures: infinite
baffle enclosure, in which the mechnical suspension is the dominant
source of system stiffness and the box is generally large; and
so-called "acoustic-suspension" enclosures, where the air in the
box is the dominating stiffness, and the boxes tend to be small.
Because of the nature of things, sealed boxes generally tend to be
the lowest efficiency systems for a given box size and bass cutoff
frequency.
Vented enclosures
Also the same as bass reflex, ported, or passive radiator systems.
Here, an aperture in the box provides a means for the rear output
of the cone to contribute to the total output of the system. Unlike
most peoples impression, though, it does not do so at all frequencies,
but only over a very narrow range of frequencies. In fact, in a
properly designed system, the front output of the cone is reduced at
the same time the output of port increases, so the port DOES NOT ADD
to the output of the woofer, it REPLACES the output of the woofer at
these frequencies. This, if done properly, can significantly reduce
distortion and increase power handling at very low frequencies, a
region that can be difficult for a driver to do.
Again, because of the nature of things, vented systems can be up to
3 dB more efficienct than a sealed box system that has the same
bass cutoff frequency and enclosure size.
Bandpass
These are compound systems in the sense that they have at least
two enclosures: one on the front and one on the rear of the driver
(and one might argue that they are, therefore, not direct-radiators).
The enclosure on the front, which looks remarkably like a vented box
(because, well, it IS), acts as a low pass filter, and, at the same
time, can couple the output of the woofer somewhat more efficienctly
to the outside. They have several useful advantages. For example,
the front enclosure can be used as a very effective acoustic
crossover,
filtering out mechanical nboises generated by the woofer, something
no electronic crossover can do. For very low frequencies, such an
acoustic crossover can be far less expensive and more easily designed
than an equivalent passive or active electronic crossover.
They are called "bandpass" because the combination of the rear
enclosure and the driver form the high pass portion while the front
enclosure forms the low pass section (in effect). Making the bandwidth
of the system narrower generally raises the efficiency of the system.
Coupled cavity
A variation and an aglomeration of bandpass and vented systems, they
are the results of a designers attempt to solve specific problems.
They consist of two or more rear enclosures, each coupled to the next
by a vent. Each enclosure/vent combination is another resonant system,
and the combination is, essentially, a high order, multi-tuned
resonant system.
Generally, these systems have quite complex response functions and
are difficult to design, as there exists no comprehensive theory on
their operation like exists for sealed, vented and bandpass systems.
--
| Dick Pierce |
| Loudspeaker and Software Consulting |
| 17 Sartelle Street Pepperell, MA 01463 |
| [phone] (Voice and FAX) |
Newsgroups: rec.audio
Subject: Re: Acoustic Suspension vs. Infinite Baffle?
Organization: The World Public Access UNIX, Brookline, MA
Date: Thu, 5 May 1994 12:48:40 GMT
Lines: 65

What exactly is the difference in SOUND quality between Acoustic Suspension
and Infinite Baffle. If there is none, what's the point in differentiation
them...?

First, the physical difference between an infinite baffle and an acoustic
suspension would help.
An infinite baffle is essentially any speaker enclosure which isolates
the rear radiation from the front radiation of the cone. It can be
represented by anything from the proverbial "infinite baffle", a very
large wall with the driver mounted in the middle of it, down to a small
sealed box (at least as far as low frequencies are concerned.
An acoustic suspension enclosure is a type of infinite baffle, sealed box
enclosure where something called the "tuning ratio", the ratio between
the compliance of the driver's suspension and the compliance of the air
in the box is high, usually more than 2 or 3 to one. Or, in Thiele-Small
parlance, Vas, the equivalent volume of compliance, is at least 2 to 3
times the Vb, the volume of the airt in the box.
Edgar Vilchur invented the principle in th 1950's in an attempt to deal
with the then lousy linearity of woofers, on the presumption that if you
let the air in the box be the predominant stiffness in the system, then
you'll be dealing priomarily with the linearity of the air in the box,
which is arguably better than that of drivers.
However, in order to exploit this, he had to make his drivers very linear
to begin with. The compliance of the suspension can change by a factor of
2-3 over the "linear" range, thus if you start with the box compiance
dominating at low excursions, then at high excursions the suspension
dominates, what have you gained? Further, he dramatically improved the
drive linearity by using overhung voice coils in an attempt to make the
drive parameter (the Bl product) independent of position.
In the process, he developed a driver that was more linear to begin with.
It's not clear that the enclosure design, then, bought him much of anything.
There is a side advantage to having a high tuning ratio. With the cabinet
volume dominating the system stiffness, the normal manufacturing
tolerances inherent in the stiffness of the suspension is essntially
unimportant, since it's the box stiffness that predominates. Normal
manufacturing variations of +- 20% in driver compliance are reduced to
actual system resonant frequency variations of about +-2% in a system
with a compliance ratio of 4:1 (assuming mass is held constant).
How do they sound compared to one another? Absolutely impossible to tell,
because to compare the two, you'd need to compare two drivers that are
otherwise identical, one in each type of enclosure. But if the driver is
designbed to work well in an infinite baffle, it's resonance and system Q
will be much higher in the acoustic suspension, whereas if it's designed
to work well in the acoustic suspension, its resonance and system Q will
be much lower in the infinite baffle. You'll end up hearing whatever
difference completely predominated by the differences in the system
response that result. If you try to use drivers optimized for each
loading, you'll probably then hear the differences in the drivers, not
the loading.
--
| Dick Pierce |
| Loudspeaker and Software Consulting |
| 17 Sartelle Street Pepperell, MA 01463 |
| [phone] (Voice and FAX) |

[Phil Allison]

Post by Henry A. Pasternack
So, while both are instances of the general class of sealed boxes,
they are sufficiently distinct as to deserve different labels and
descriptions.
This is the point I wish to make.

** Liar - it is nothing like the insane point you have been posting.

Quoting absent experts as agreeing with you is one of the dirtiest tricks
in the arsenal of a debating cheat.




.......... Phil

[Henry A. Pasternack]

Post by Phil Allison
Quoting absent experts as agreeing with you is one of the dirtiest tricks
in the arsenal of a debating cheat.

Seriously, Phil, what is your problem?

-Henry

[Phil Allison]

Post by Phil Allison

Post by Phil Allison
Quoting absent experts as agreeing with you is one of the dirtiest

tricks

Post by Phil Allison
in the arsenal of a debating cheat.

Seriously, Phil, what is your problem?

** Seriously Henry - your are a brain dead menace.

Bugger off.



........ Phil

[Henry A. Pasternack]

Post by Phil Allison

Post by Henry A. Pasternack
Seriously, Phil, what is your problem?

** Seriously Henry - your are a brain dead menace.
Bugger off.

No, that's not constructive. I am genuinely curious to know, and I imagine
you should be willing to explain, what it is -- in general -- that puts you
in such a contrary and aggressive mood.

-Henry

[Patrick Turner]

Post by Henry A. Pasternack

Post by Phil Allison

Post by Henry A. Pasternack
Seriously, Phil, what is your problem?

** Seriously Henry - your are a brain dead menace.
Bugger off.

No, that's not constructive. I am genuinely curious to know, and I imagine
you should be willing to explain, what it is -- in general -- that puts you
in such a contrary and aggressive mood.
-Henry

Ever since Phil arrived first at aus.hi-fi,
he has been everything he accuses us of.
And to say so, he employs the worst of language,
and whilst calling us liars, charlatans, criminals, et all,
he says he stands for the truth.

It is utterly useless to argue anything rationally with Phil,
who studied at a university, where he never gained a degree
in debating.

So Henry, its impossible to change this animal.
His satisfaction in life is to kick folks in the guts all day,
and try to convince those who have not kilfiled him to believe his victims
deserved it.

Changing Phil is like trying to teach Andre to behave, an impossible task.

I am sure both ruffians have been trying to explain why they are so aggressive,

so often, by just being aggressive almost everyday, in their meaningless posts
which most of us ignore.

Now just you watch Henry, what I have said will wind them up, and away they'll
go, just like clockwork toys across the patio.....

Patrick Turner.

[Phil Allison]

"Patrick Turner" <
..

Post by Patrick Turner
Ever since Phil arrived first at aus.hi-fi,
he has been everything he accuses us of.

** Lies.

Post by Patrick Turner
And to say so, he employs the worst of language,
and whilst calling us liars, charlatans, criminals, et all,
he says he stands for the truth.

** More non specific complaints - so just more fucking abuse.

Post by Patrick Turner
It is utterly useless to argue anything rationally with Phil,

** Lies - Turner has no functioning brain.

Post by Patrick Turner
So Henry, its impossible to change this animal.

** More abuse.

Post by Patrick Turner
His satisfaction in life is to kick folks in the guts all day,

** Lies - I would much prefer to talk about audio.

Post by Patrick Turner
Changing Phil is like trying to teach Andre to behave, an impossible task.

** Andre behaves impeccably already.

His patience with posturing fools and liars is amazing.




.......... Phil

[Phil Allison]

Post by Henry A. Pasternack

Post by Phil Allison

Post by Henry A. Pasternack
Seriously, Phil, what is your problem?

** Seriously Henry - your are a brain dead menace.
Bugger off.

No, that's not constructive. I am genuinely curious to know, and I imagine
you should be willing to explain, what it is -- in general -- that puts you
in such a contrary and aggressive mood.

** Liars like you.



......... Phil

[Henry A. Pasternack]

Post by Phil Allison
** Liars like you.

Since I'm a liar, everything you say is true.

Have a nice day.

-Henry

[Patrick Turner]

Post by Henry A. Pasternack

Post by Phil Allison
** Exactly the same situation with IB.

If you define "infinite baffle" to mean the same thing as "acoustic
suspension", then of course there is no difference between them.
But that's a semantic argument, not a technical one.
When Edgar Villchur and Henry Kloss formed Acoustic Research, the
acoustic suspension loudspeaker was a conceptual breakthrough and
a major advancement in the state of commercial loudspeaker
manufacturing.
In loudspeaker design it's fundamental to speak of box alignments.
There must be at least a half-dozen named bass reflex alignments.
Although they only differ in the parameters of their components,
they are sufficiently distinct to have separate identities in the
minds of speaker designers. Nevertheless, there is nothing to
prevent building a bass reflex box tuned to an "in-between"
alignment. Likewise, "acoustic suspension" and "infinite baffle"
are two distinct sealed box alignments. While the difference
between them is not as great as, say, the difference between a
sealed box and a bass reflex system, the distinction is very real.
Your other comments are frivolous.
-Henry

Indeed there are many types of alignments at low bass F.

And should one have a ported box, it is amazing that some folks
cannot hear the slighest difference if the port is stuffed with a sock,
and they have not been told of the sock stuffing trick.

Try it, you will see.

Perhaps the same could be said for closed box designs for midranges.
They too interact with a box, and have a single peak in the impedance,
which can be a problem if a capacitance is placed before the
Mid to filter out the bass F, but the capacitance drive increases its
Z as F falls, and peaked Z of the driver in the box means the decoupling
pole
desired is difficut to arrange, and maybe you get a peak before roll off

occurs, which means the mid has too much cone motion at LF to prevent
the
benefits of low imd, which acrues from filtering out bass from the mid.
The answer is to place the cut off well above the resonance of the
midrange.
In this case running midrange as a ported box
may not make a discernable difference to most listeners, unless they are
told about it,
and have one eyed notions that ported boxes all suck.

I have found that many ported bass boxes where the Fs = Fb and
Vb = Vas, the sound is OK.
With modern drivers with low VAS figures, and low Fs, say below 30 Hz,
the reactive resonant exploiting reflex speaker is at its best,
because the bass above 50 Hz is untroubled by reactive behaviour.
Below 50 Hz to 20 Hz, there isn't much in most music,
unless its been dialed in deliberately, usually by electronic methods.
You get few low notes from an organ, and drums,
But just what is best with a sealed box is more difficult to say.
As F rises above 50 Hz in either sealed or ported boxes, where
the resonace peaks are below 45 Hz
little difference to the sound is heard.
I'll get hung drawn and quatered saying what I have,
but what I do know is that some of the preferences being aired here
are one eyed, and ppl are intolerant of seeing there is
more than one way to build a good system.

Notice how the posters fostering IB don't have
a few exact recipes which they could guarentee gives great sound,
but do have a lot to say about design.
Nothing much about specific drivers, exact box sizes,
etc.

And despite all the theory and maths, at the end of the day
it sill has to sound right, and not every really well calculated design
does.

Some would say a triamped system with active digital phase shift free
pre power amp active Xovers is the way to go, and that would make a
bigger improvement
than whether the speakers were IB, or ported.

Six amps for a stereo system? I have not tried it yet.

[Phil Allison]

Henry A Pasternak<

"Phil Allison" <

Post by Phil Allison
** Exactly the same situation with IB.

If you define "infinite baffle" to mean the same thing as "acoustic
suspension",

** No - there is simply no difference in the principle of operation.

That you started your sentence with a posturing " if " destroyed
it totally.

When Edgar Villchur and Henry Kloss formed Acoustic Research, the
acoustic suspension loudspeaker was a conceptual breakthrough and
a major advancement in the state of commercial loudspeaker
manufacturing.

** That is a marketing claim - you sound like a parrot.

In loudspeaker design it's fundamental to speak of box alignments.
There must be at least a half-dozen named bass reflex alignments.

** Here comes the smelly red herring.

Although they only differ in the parameters of their components,
they are sufficiently distinct to have separate identities in the
minds of speaker designers.

** Now the straw man.



Nevertheless, there is nothing to

prevent building a bass reflex box tuned to an "in-between"
alignment. Likewise, "acoustic suspension" and "infinite baffle"
are two distinct sealed box alignments.

While the difference

between them is not as great as, say, the difference between a
sealed box and a bass reflex system, the distinction is very real.

** You have just gone round in a circle and disappeared up your own
arse - fool.

Your other comments are frivolous.

** Like hell they are - you are demented.



......... Phil

[Chuck Harris]

I see the difference between an "infinite baffle" enclosure,
and an "acoustic suspension" enclosure being more about where you
place the resonant frequency of the driver relative to the
resonant frequency of the enclosure.

In an "infinite baffle" enclosure, you pick the resonant frequency
of the enclosure to be BELOW the resonant frequency of the driver.

In an "acoustic suspension" enclosure, you pick the resonant frequency
of the enclosure to be ABOVE the resonant frequency of the driver.

This causes a definite difference in the size of the enclosure!

It is important in both cases to not put the resonant frequency of the
driver and enclosure at the same point, but rather to adjust the
separation of the resonant points to improve the transient
response, and the low frequency reach of the bass system.

Because of the philosophy differences in driver/enclosure resonance,
you tend to end up with different types of drivers for each application.
The acoustic suspension system needs a very stiff, cone with a highly
compliant surround and a very low resonant frequency. The infinite
baffle compresses the air less, so it often ends up with a lighter
weight cone, less compliant surround and a higher resonant frequency.
There is generally no problem with using a driver meant for acoustic
suspension use on an infinite baffle, save for a much larger enclosure
size. The converse is rarely true. **

The acoustic suspension enclosure has one other characteristic that is
interesting. And that is insulation stuffing. The insulation is doing
the same thing it does in your refrigerator, it is slowing the
propagation of heat. In the case of the acoustic suspension enclosure
the heat propagation that is being slowed is the isobaric temperature
rise and fall caused by the driver's compression and decompression of
the air in the enclosure. The insulation makes the isobaric temperature
rise and fall more slowly than it otherwise would ...making the
enclosure's characteristics more closely resemble those of a much
larger enclosure....at the mere cost of a great loss of efficiency.

I may have some of this wrong. I haven't visited this area of my brain
since the early 1980's... I had a right nice little amateur speaker
factory going back then... A lot of my friends and family had to
"suffer" being given the prototypes I cast off as I experimented with
the theories presented by Dr. Small.... All because I couldn't afford
a "proper" set of store bought speakers on an EE graduate student's
stipend.

-Chuck

** as a note, I was never able to find a commercial driver that had the
proper characteristics for a bass reflex enclosure. They all required
serious amounts of damping material applied to the back of the driver
frame. If you pressed on and used them without the damping material,
they ended up with a very peaky Chebeychev response...one bass note
wonders. With the damping material, they develop a nice bass
response... Almost as clean and resonance free as an A-S design.... PITA
to adjust the damping material. (to check for resonances, take a 1.5V
battery, and a telegraph key, connect them to the driver terminals. If
when keyed the speaker goes "boing, boing, boing" your bass will do the
same.)

Post by Henry A. Pasternack
In an acoustic suspension speaker, there are two "springs" in the
cone suspension, the mechanical spring in the driver itself, and
the air "spring" due to the small box volume. This is a pretty
major conceptual leap, to use air pressure to augment the mechanical
properties of the driver. At the time Villchur introduced the
idea, it was rejected by the speaker manufacturers he proposed it
to. So he and Henry Kloss started Acoustic Research.
Not that patents or commercial success necessarily mean anything,
but Villchur did patent the acoustic suspension design, and AR's
products revolutionized the speaker industry.

Post by John Byrns
OK, that sounds like you have changed your mind and agree that the
topology of two systems are identical, with the only difference
being the choice of mechanical component values used.

No, in my mind they are distinct. Both are second-order high-pass
filters, but the design tradeoffs are different. They require
different types of drivers and they do, in general result in boxes
that are of significantly different size and efficiency. In the
taxonomy of speaker design, they are well-defined endpoints along
the continuum of sealed-box alignments. There is certainly value
in drawing out the distinction.

Post by John Byrns
Come on Henry, wake up and smell the coffee, they are the same
that's why they are lumped together. That doesn't diminish the
importance of Villchur's insight when he realized the advantages
of using a set of component values that differed from the tradition
of the time. This is analogous to Armstrong's invention of FM,
where FM already existed, and Armstrong simply had the insight
to realize the advantages that would be gained by using a different
set of parameters for the system than people had been using up to
that point.

Well, I have to disagree. Acoustic suspension and infinite baffle
are distinct because the design principles are different. I think
if you spent more time working with speakers and absorbing the
general mindset of speaker design, you might come to appreciate
that the two types of speakers are not the same.
-Henry

[John Byrns]

Post by Henry A. Pasternack
In an acoustic suspension speaker, there are two "springs" in the
cone suspension, the mechanical spring in the driver itself, and
the air "spring" due to the small box volume.

These same two springs exist in any closed box speaker system be it an
"infinite baffle" or an "acoustic suspension" design, the only difference
in the "springs" used in the different closed box variations is their
relative stiffness.

Post by Henry A. Pasternack
No, in my mind they are distinct. Both are second-order high-pass
filters, but the design tradeoffs are different. They require
different types of drivers and they do, in general result in boxes
that are of significantly different size and efficiency. In the
taxonomy of speaker design, they are well-defined endpoints along
the continuum of sealed-box alignments.

Exactly, they represent well-defined endpoints along the continuum of
sealed-box designs. I would not use the word "alignments", as I would
take that to refer to the type of response around cutoff, which is mainly
dependent on the system Q, and both the "infinite baffle" and the
"acoustic suspension" versions of the closed box can be built with a range
of system Qs, or "alignments".

Post by Henry A. Pasternack
Well, I have to disagree. Acoustic suspension and infinite baffle
are distinct because the design principles are different.

In what way are "the design principles different"?

Post by Henry A. Pasternack
I think if you spent more time working with speakers and absorbing
the general mindset of speaker design, you might come to appreciate
that the two types of speakers are not the same.

Clearly they are not the "same" but that does not mean that they are based
on different topologies or design principles, they are simply variations
on a single basic theme. On the other hand a "bass reflex" would be an
example of a speaker system with a fundamentally different design
principle.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

[Patrick Turner]

Post by George Orwell
rec.audio.tubes
Re: THE INFINITE BAFFLE SPEAKER
The sort of speaker you mean is a flat baffle. It becomes an infinite baffle when you fold it into a sealed box. Mind you, if Phil hadnt already twitted me for careless nomenclature, I too would have included a flat baffle into the ranks of the IB. . .

To me, sealed boxes are "spring boxes" and the speaker is restricted from
easy movement the lower the F. By jiggling around with Fs, Fb, and
Q of this and that, such boxes are capable of good transient behaviour
An infinite baffle is something infinite, so a wall ten miles long and ten miles high,
with a hole for the speaker might be infinite.

But a flat baffle board able to fit into a lounge room and accepted by
the missus isn't infinite.
To get good bass
from what is actually a dipole speaker the baffle board has to be large,
but if all we want is to get to 250 Hz, then smaller will do.
But a hole cut in a wall for a bass speaker is like being inside a sealed box
enclosure, with the walls being the box, and the amount of air
is such that the "springiness of the air" isn't a problem for the design.

Post by George Orwell
Ive never been much into flat baffles, though I once had electrostats in the wall between two rooms. I dont seem to remember any huge advantage. It was just a convenient place to put them.
The last thing I wrote on flat baffles was in GA, or perhaps VALVE, about an 11 part division scheme, 7 and 4, for placement of the speaker on the flat baffle. That one used the cheap drivers that Dan Schmalle used to sell four for thirty bucks with his SEX amp, which later also featured in my notorious carpet tube speaks for hugely bass-enhanced Gregorian Chant.
Sorry I cant be of more help. If you ever get around to a sealed box speaker, remind me that I prepared the second part of "THE INFINITE BAFFLE SPEAKER" posting, called Carte Blanche, which I was holding until Turner stopped ruining the first part of the posting with his dull advertisements for himself.

Oh poor little Andre, I messed up your sand castle did I diddums!

Please don't let me disturb your building of giant billboards in this group
to favour your point of view.

Patrick Turner.

Post by George Orwell
It is a description of the last IB I designed, with Scan Speak drivers. At that time Ill pull it out and well take it from there.
I certainly hope you will describe your thoughts and experiments here.
Andre Jute
Hi Andre,
Thanks for the emailed version of the "THE INFINITE BAFFLE SPEAKER", it
looks like the punctuation came through correctly in the email text. My
antique computer/software was unable to decode the Microsoft Word version
you attached though. I suspect it may be the email program I am using
that somehow messes up the separation of the attachment from the email, as
I think I have had this problem with Word documents before, and was able
to resolve it by processing the "raw" email file with a separate file
extraction utility, to recover the Word document, but I just remembered
about that, and havent tried it yet. Im not sure why it is only Word
documents that seem to get screwed up that way, while pictures and other
binary attachments make it through unscathed.
Unfortunately I misinterpreted what you originally meant by an "IB". I
assumed you were referring to a large open back baffle. I think a number
of years back "Tube Garden" described some smallish versions of open back
baffles that he had built. Many years ago when I was in Junior High
School I built a Hartley sand baffle. That was a long time ago and I
could be wrong about the Hartley part, maybe it was Warfdale, or maybe
those are the same, I forget my British speaker history. This was an open
back floor standing design of medium size that used two speakers, one
somewhere around 8 inches that was slot loaded to disperse the high
frequencies, and one of about 12 inches or so for the bass. Being a
penniless teenager I didnt use the fancy drivers that were recommended in
the construction article, but just used the first 8" and 12" drivers that
feel to hand. I used the speaker system for a year or two and then when
stereo appeared I retired the sand baffle to the attic in favor of a more
manageable pair of speakers for stereo. Being into weird speakers I think
I had a very brief fling with a Karlson enclosure after the sand baffle,
but that Karlson was the worlds worst speaker enclosure.
When I saw "IB" I was thinking of something more on the order of that old
sand baffle.
Regards,
John Byrns

[Anonymous]

Re: THE INFINITE BAFFLE SPEAKER
rec.audio.tubes

Patrick Turner <***@turneraudio.com.au> wrote:

SNIPPED 385 WORDS OF OFF TOPIC AND IRRELEVANT COMMERCIAL PROMOTION FOR TURNERS REFLEX SPEAKERS IN A THREAD ABOUT INFINITE BAFFLES. PAY FOR YOUR ADVERTISING, TURNER.

Notice how the posters fostering IB dont have
a few exact recipes which they could guarentee gives great sound,
but do have a lot to say about design.

We exercise our intellect, because we have it. But actually the recipe for success was in the second part of my posting, which you sneered and jeered I could not post because of your continued thread invasions.

See my separate post TURNERSPEAK for hints on improving the way you speak, spell, and use the language.

Nothing much about specific drivers, exact box sizes, etc.

The specific drivers and box sizes, which you want so much in order to copy someone elses work (1), were in the second part of my posting, which you sneered and jeered I could not post because of your continued thread invasions. Also the box proportions for resonance control, which you seem to have overlooked, as in your own ugly speakers you overlook this essential consideration.

And despite all the theory and maths, at the end of the day
it sill has to sound right, and not every really well calculated design
does.

That is why the second part of my posting, which you sneered and jeered I could not post because of your continued thread invasions, also describes the development process.

What a sour little man you are, Turner. Nothing that anyone else does is to your taste, and everything you do is above criticism.

SNIPPED 93 WORDS ON OVEREQUALIZED HOME VIDEO NONSENSE THAT IS OFF TOPIC AND OFFENSIVE IN A HI-FI FORUM.

Pay for your own advertising, Turner. Develop your own designs, Turner. Think your own thoughts, Turner. Stop being a parasite, Turner.

Andre Jute

(1) Turner is also notorious for demanding with menaces winding schemes from other winders, and even from third parties where they are known to have the confidential design data of custom transformers.

-=-
This message was posted via two or more anonymous remailing services.

[Patrick Turner]

Post by George Orwell
Re: THE INFINITE BAFFLE SPEAKER
rec.audio.tubes

Snip all the Andre Jute pollution.

Patrick Turner.

[John Byrns]

There is at least one other type of "infinite baffle speaker" system
besides the traditional large closed boxes, and the air suspension types
already mentioned. That is the third order closed box. One of the
British speaker companies offered a line of these, it may have been
Celestion, which were similar in size to an ordinary second order closed
box system. The distinguishing characteristic of these third order
systems was a capacitor in series with the woofer.

Daniel Von Recklinghausen published a paper on third order closed box
systems in the JAES. It's been a while, but as I remember it, my take on
this was that the only advantage I could see to the third order system was
that it allowed the use of a driver with a less efficient motor, without
sacrificing either frequency response or cabinet size. Presumably the
advantage here was a cheaper speaker, although I assume the efficiency was
lower than a similar second order system, while I had been hoping that the
technique would yield a more efficient small system. I need to think
about this a little, or find Von Recklinghausen's paper. Perhaps I have
got the pluses and minuses wrong?


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

[Chris Hornbeck]

Post by John Byrns
There is at least one other type of "infinite baffle speaker" system
besides the traditional large closed boxes, and the air suspension types
already mentioned. That is the third order closed box. One of the
British speaker companies offered a line of these, it may have been
Celestion, which were similar in size to an ordinary second order closed
box system. The distinguishing characteristic of these third order
systems was a capacitor in series with the woofer.

Hi John,
This can be an especially useful technique for B3 high pass
crossover alignments. Many good drivers can be operated down
to their f-sub-C, but would benefit from an electrical pole
of high pass.

The coupling of capacitor and driver electrical resonant rise
can also *increase* the Q, sometimes enough to bring the total
up to 0.7 for Butterworth response. Win-win.

Excellent memory, dude. Thanks,

Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk

[Patrick Turner]

Post by Chris Hornbeck

Post by John Byrns
There is at least one other type of "infinite baffle speaker" system
besides the traditional large closed boxes, and the air suspension types
already mentioned. That is the third order closed box. One of the
British speaker companies offered a line of these, it may have been
Celestion, which were similar in size to an ordinary second order closed
box system. The distinguishing characteristic of these third order
systems was a capacitor in series with the woofer.

Hi John,
This can be an especially useful technique for B3 high pass
crossover alignments. Many good drivers can be operated down
to their f-sub-C, but would benefit from an electrical pole
of high pass.

Quite a few SS amps used to have a cap coupled output,
and Sugden class A still do.

The older (and somewhat doubtful quality) SS amps typically
had 2,200 uF used to couple 8 ohms, which gives a pole at
9 Hz.

What sort of values for a coupling cap to a bass speaker
were you thinking of ?

Patrick Turner.

Post by Chris Hornbeck
The coupling of capacitor and driver electrical resonant rise
can also *increase* the Q, sometimes enough to bring the total
up to 0.7 for Butterworth response. Win-win.
Excellent memory, dude. Thanks,
Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk

[Chris Hornbeck]

On Fri, 12 Dec 2003 11:37:57 +1100, Patrick Turner

Post by Patrick Turner
What sort of values for a coupling cap to a bass speaker
were you thinking of ?

Hi Patrick,
Can't see any compelling reason to use on a woofer, but it's
sometimes a useful "crossover" to a bass-midrange driver.

Typical 5" or 6 1/2" drivers may operate well down to their
resonant point in-box, but still benefit from a pole of
electrical high pass filtering to limit excursion, etc.

If their Q-sub-TC is high, you'd want the electrical pole to
not interact with the driver's resonant impedance rise, to
bring a total Q down to about 0.7 for Butterworth response (B3).

But better drivers may have a Q in-box of 0.5 or less. Here's
where a capacitor interacting with the driver's resonant
rise can be useful, to bring total Q *up*.

Wish I could find that old article, but it must have been
25 years ago, at least. Where to start cutting? X-sub-C about
equal to R-sub-DC? Adjust for 90 degree phase shift at F?

Any thoughts? Thanks,

Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk

[Patrick Turner]

Post by Chris Hornbeck
On Fri, 12 Dec 2003 11:37:57 +1100, Patrick Turner

Post by Patrick Turner
What sort of values for a coupling cap to a bass speaker
were you thinking of ?

Hi Patrick,
Can't see any compelling reason to use on a woofer, but it's
sometimes a useful "crossover" to a bass-midrange driver.

I always use a cap in series with an L in series with a mid, and
some impedance equalising RC and perhaps LR network across the speaker
to
get the desired bandpass filter effect.

But using a C in series with a woofer was cited as a way to
have an additional LF pole, on an IB, something
I have seen no need for.

Post by Chris Hornbeck
Typical 5" or 6 1/2" drivers may operate well down to their
resonant point in-box, but still benefit from a pole of
electrical high pass filtering to limit excursion, etc.
If their Q-sub-TC is high, you'd want the electrical pole to
not interact with the driver's resonant impedance rise, to
bring a total Q down to about 0.7 for Butterworth response (B3).

Indeed...

Post by Chris Hornbeck
But better drivers may have a Q in-box of 0.5 or less. Here's
where a capacitor interacting with the driver's resonant
rise can be useful, to bring total Q *up*.
Wish I could find that old article, but it must have been
25 years ago, at least. Where to start cutting? X-sub-C about
equal to R-sub-DC? Adjust for 90 degree phase shift at F?
Any thoughts? Thanks,

I don't always gor for a maximally flat roll off 2nd oder
filter profile, but prefer the over damped but ultimately 2nd oder type,

and I between mid and bass, I sometimes use a little extra overlap...

It all depends on the measurements, and the way it sounds.

Patrick Turner.

Post by Chris Hornbeck
Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk

[Chris Hornbeck]

On Fri, 12 Dec 2003 13:38:31 +1100, Patrick Turner

I don't always go for a maximally flat roll off 2nd order
filter profile, but prefer the over damped but ultimately 2nd order type,
and in between mid and bass, I sometimes use a little extra overlap...
It all depends on the measurements, and the way it sounds.

You mean like a Linkwitz-Riley second-order? Yeah, I like
the sound of those better than B3's too, at least for the
woofer to mid crossover.

They're tough to get to, though, from a closed-box midrange
with its two poles of high pass built in. Usually within an
octave of where you'd like to put your crossover.

Walk down this path far enough and you're starting to think
about B3's again..... Oh well.

Thanks,

Chris Hornbeck
"That is my Theory, and what it is too."
Anne Elk