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In Reply to: RE: "even a true 97 dB is kinda low for serious fleapower" posted by Frihed89 on April 04, 2012 at 09:52:58
Or, a 3 Watt DC 2A3 amp with a "modern power supply" will do it . I hear and run that amp on 604 GPAs every year at RMAF, and it can go !!! Most SE amps have insufficient supplies !!
Jeff Medwin
Follow Ups:
It is not just the efficiency of 97 dB that is relevant. People seem to have consistently positive results running SETs with the GPA driver. If the cabinet is designed correctly (I don't think the classic BR alignments meet this criterion), this driver benefits from the high output impedance of a SET amp.For whatever reason - alignment, driver Q, sonic signature/balance at certain volumes - the 2226 in the 4Pi needs more stick than it would otherwise seem. I have said it many times: "Wayne, please design a 4Pi that uses the equivalent AE driver."
Cheers.
Edits: 04/07/12
Would an AE (never heard one) or other driver have the incredible mid-range of the 2226? Then, a lot of us Tent Sale recipients are running "J"s, 16 Ohm which should be more tube-friendly than 8 Ohm "H"s.
Not suggesting that Wayne drop the 2226; hey, the design is done, refined and available - why drop it if satisfies a market.
However, I recall a few requests on his ART forum for an AE version. Extrapolating from the positive comments about the 12" version of the AE in the 3Pi and others' comments about 15" AE drivers in various systems I'd guess that yes, the AE driver would likely have an incredible midrange and be more SET-friendly to boot.
I can understand Wayne not wanting to develop his speakers further. He is generous with his limited time and great knowledge, but he has other priorities than redesigning what is not broke. Still, I'd have gone with a 4Pi with his lovely wood horn if an AE version were available.
Cheers.
The only impedance plots (electrical load) I have seen of the 4-Pi is with the H model (8 Ohm).
Besides, you'd need a 16 Ohm tap on your opt, for it to be effective.
"You don't need to be a Weatherman to know which way the wind blows"
When he sent me the prototype board for the latest crossover a few years ago, we discussed that. All the values were changed to reflect the impedance with the caveat that there would be a very slightly consequential difference in the lobing characteristics of the driver.
Roger Modjeski of the RM-9/RM-200 amplifiers and other ground-breaking products, advises using the 4 ohm taps on his RM-10 amp into an 8 Ohm load to achieve significantly lower distortion and higher damping factor. Whether that is a general condition or unique to that amp I just don't know.
The P-P KT-88 monoblocs I'm trying to get finished will have 16 Ohm taps so then I'll have an answer. I hope to finish them before the end of May and perhaps schlep them to RibFest.
Yes, it is a general rule. Running speaker on a lower Ohm output tap - increasing the reflected load on the output tube - increases damping somewhat and lowers distortion at the cost of reducing power output.However, some speakers sound 'better', more flowing and better-balanced, with the higher output impedance (think low Q drivers).
Cheers.
Edits: 04/05/12
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