Post by Big Bad BobPost by Andre Jutehttp://www.audio-talk.co.uk/fiultra/JUTE%20on%20BESSEL.htm
too brief, though you piqued my curiosity.
http://www.angelfire.com/sd/paulkemble/soundf.html
and my curiosity 'peaked'. Interesting, but why do you WANT "that much"
sound pressure now?
my ears bleed just thinking about it...
If you want an excellent example of a really *bad* array, look at the Bose 901 in any of its iterations. Bleeding ears are very nearly a certainty with such a device. Further, as this case illustrates all to well, William of Occam had it right: Eschew needless complexity. There is no valid reason other than as a tour-de-force to create such an array in a non-specialized application when many and far better alternatives are available, including any of several well-established planar options.
As to very large tube power-amps, given the inherent physical and safety issues involved mixed with the very real costs mixed with the time involved - this is almost why PERT would be a better project management tool than CPA. CPA is designed to reach a specific goal by a specific time. PERT is designed to reach a specific goal by the most effective process - time not being at issue. Getting a man on the moon was done via PERT, developed by the US Navy for their ballistic missile (Polaris) program. Coupled with CPA/M it became the tool-of-choice for complex projects delving into uncharted processes.
Speakers are an exercise in moving air. Not in large distances, but in many, very small movements so as to attempt to duplicate sounds recorded somewhere else. Complex sounds in considerable volume require complex means to reproduce - also in considerable volume *relative* to the listening area. If we exclude headphones (no one needs 500W for headphones), the amount of energy required to move sufficient air will be proportionate to the volume to be filled, but that proportion will not be linear.
My personal gold standard for testing a system is this:
https://www.discogs.com/Saint-Sa%C3%ABns-Eugene-Ormandy-Philadelphia-Orchestra-Michael-Murray-Symphony-No-3-Organ/release/7664706
Recorded right down the street from where I was living at the time. My listening room was then 16 x 27 x 9.5 feet (~4,100 c.f./410 c.m.), so not a small venue. Today it is 17 x 28 x 10 - a touch more difficult. I could do a credible reproduction in the former location with a 425 watt/4/rms amp into AR 9 speakers. Today, it is a 225 watt/6/rms amp into big maggies (MGIIIa).
Between the two ARs, I had 570 square inches of active radiating surface. Between the two Maggies, I have 2,550. Maggies, albeit power-pigs, are spoilers and will ruin a listener forever. But, the point is that single-source/single-driver speakers simply cannot move enough air to make a dent in complex sources at complex volumes in challenging settings - may as well not even waste one's time. Bessel Arrays are possible options - but pretty much doomed to failure unless taken as an exercise in their own right. And, as it happens, when proposed 'back in the day' they were listed as a "high-powered option".
(My, but this is turning into a bit of a rant)
As it happens, the differences between tubes and SS are being discussed in another forum, and citing all kinds of sources, one of which is: http://www.dwfearn.com/tubes_vs_transistors.html Note the date.
Solid-state has evolved considerably in the last 44 years. To the point where the actual differences between the two, while real, are to where one will be challenged to say which is a superior option for the reproduction of music. Tube technology and/or topology has not evolved in any meaningful way over that same time. I would suggest that the OP go ahead and purchase a couple of 500 watt Class D modules (https://www.amazon.com/1000W-Stereo-Class-Power-Amplifier/dp/B002EE7350/ref=pd_sbs_23_img_0?_encoding=UTF8&psc=1&refRID=PJSR4BX6CTSDKFRGB39M as a full kit) and see what 500 watts sounds like before spending perhaps 20 x that cost for a similarly powerful tube device.
I am emphatically *not* attempting to discourage the OP from pursuing a dream. What I am suggesting is that the OP do the research (other than here), perhaps check in a few of the DIY venues for similar projects, get some advice from those that have done it. I would also strongly suggest getting in touch with Patrick Turner ( http://www.turneraudio.com.au/ ) who is a past-master at specialty and exotic tube amps, winds his own transformers and might be convinced to wind again for others (at a cost, but well worth it). In other words, set a goal and make a plan to reach it.
Many of us here have the solder scars and history to show for some passing acquaintance with the means, methods and related skills and processes associated with the tube hobby. Several glaring examples do not, having a more developed Munchhausen complex to make up for that lack. Writing for myself, my preference is towards the restoration, care and feeding of vintage equipment designed by others but open to improvement. I have designed and built one (1) amp 'from parts' for myself, and have the makings (Iron) for one other. The former is based on the venerable 6BQ5 in PP. For the other, I am torn between several from the 6V6 at one end and the 5881 at the other. It will be some years. But, the point, again, is that there is very little new under the sun in tubes. No need to invent the wheel from scratch when there is so much knowledge and material available that needs only to be refined and executed.
Rambling back to speakers: one wants speakers to be able to handle the most quiet passages with grace and clarity, yet bring that same grace and clarity to those that are 30dB louder. And electronics that are capable of the same. Many speakers 'break up' if required to produce across that range cleanly.
Gets down to Horses for Courses. If one lets the amount of power available drive the choice of speakers, one severely limits one's choices and options, as well as severely limits the types of signal as may be processed cleanly. If, on the other hand, one lets the speakers drive the power requirements, then the choices are near-infinite. And why I fully support the concept of a 500 watt tube amp - overcoming the primary fault of tube amplifiers everywhere *NOT* enough power. I am _always_ curious of what can be done with various parts-and-pieces. Over the next several months, I will be culling the herd developed by this curiosity and parting with five power amplifiers, two pre-amps, two tuners and various other bits and pieces. All fun. None very costly, none very significant. But, to repeat, all fun. And I have to make room for the next lot!
End ramble/rant.
Peter Wieck
Melrose Park, PA
