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In Reply to: RE: You won't believe me... posted by Enophile on April 02, 2012 at 16:21:08
... even a true 97 dB is kinda low for serious fleapower...
all the best,
mrh
Follow Ups:
That's true.
My 97dB 4Pis and 1.8 watt 45 amp sound natural only for Guy/Girl with guitar or small combo Jazz/Classical. Wonderful though.
Count Basie or Jazz combo with Piano the 45 gets confused and I switch to single-ended pentode (6550s) with about 7 watts. That combination almost works with major symphony orchestra. I've got a pair of 50 watt Push-Pulls on the bench awaiting my imminent retirement to finish and they, hopefully, will give the JBL 2226s the ride they need.
I'll still rotate amps tho'; each has a heavenly aspect I miss after too long with another.
nt
This is one reason (of many) to bi-amp. You get the best of both worlds.
the time I tried I used a cheap ART 311. The benefits of bi-amping and crossover/tone-shaping were clearly audible but so was the 311s circuitry. Can't afford the Marchand, darn it!
That's very helpful feedback amioutaline?. I have wondered whether the 4 pi will provide the sensitivity and performance I'm looking for with my 45/2a3 amp. I have the 2226s on hand so may build them anyway, but it sounds like (based on your experience) nothing but a full blown horn speaker arrangement will be sensitive enough to work well with flea power.
I think about 12W of class A PP would also do the job! This is about what a pair (pp) of KT88 will put out per channel.
"You don't need to be a Weatherman to know which way the wind blows"
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
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
Only the Seven Pi Corner horn exceeeds the sensitivity of the Cerwins and has the poster's requisite 15 inch woofer...for 3 times the price.
At 97 or below, none of the Geddes or Audio Kinesis speakers would fit your criteria of greater than 97 dB sensitivity and only one Pi model.
There's alot of flea guys doing it wrong!
Klipsch cornerhorns and Cornwall fit both his bill and yours, but at a much greater price.
nt
all the best,
mrh
(Edit: 604)-8H-III duplexes for a smallish space. This was after much over-thinking the various options. Still waiting though (7+ months to build and counting), so can't claim 1st hand whether this project has been successful.With Rick Craig crossovers and suitably designed cabinets, the duplex seems to be one of very few achievable (for me) design approaches that suits my preferences and constraints, and has consistently received positive feedback when used with low-power SETs (a few people who did not design the cabinet appropriately to obtain acceptable balance notwithstanding) across a range of volume levels.
The big, low QTS driver is ideal for use in a lowish power SET-driven system, especially when cabinet design takes into account said system. Convincing dynamics, even if ultimate loudness is slightly compromised (amplifier and listener dependent).
Cheers.
Edits: 04/04/12 04/05/12 04/06/12
Hi, when-ever your project is finished, can you please post some pics and listening impressions, along with what type of amp you are using to drive them. I'm most interested in your outcome with these particular GPA speakers.
Cheers
Frank M
I've been running my GPA 604-8HIII's in MTLT cabinets now for about 3 years now.
When the cabinets were first built I had Altec 604-8K's in them. The 8K's were really nice drivers. But going to the GPA 604-8hIII's made a world of difference in the upper end. The GPA's are much clearer at the upper end and the imageing and stageing is superb.
It took me about two years of comparing the MTLT/GPA to my Altec A5 setup to decide I liked the MTLT/GPA system better than the A5's .
The GPA's were were so satisfying I eventaully sold the A5's and had
no regrets.. works great with a Stereo 2A3 DC amp with a modern power supply!
Have fun !
Willie
what is a MTLT cabinet ?? and where did you get plans for this cab ?
I like the joinery of the panels across the top and the squat look (I wanted that, but it would not quite work for my needs).
Now I need to finish my amp (every time I look at it I am disappointed) so I can start my second, much better laid out and executed design... with a modern power supply also!
Thanks for sharing.
Hopefully they are not far away - most recent progress shot above. A few weeks ago they just needed the piano black finish applied to the sides, then final finishing and testing. Of course, then they need to be delivered and set up in room.The amp will be a partial kit/DIY 6C6 driving a 2A3; it is nothing special - actually, I have a swag of issues with its design and layout (I am already planning to rebuild it despite being not yet finished) - but it should give some idea as to how the speakers sound with a decent high-ish output impedance amp.
Without having heard them, but from what I have read, the crossover and cabinet design make or break these drivers. I spent the money on having a custom enclosure and Rick Craig crossover designed to suit my musical preferences. It will be interesting, because I am sensitive to the 'electronic' or reproduced signature of many systems and the GPA 604 with standard crossover is noted to have a slight upper midrange glare. The Rick Craig crossovers reportedly absolutely remove the glare and do so much more; we will see.
I will do whatever I realistically can to help you decide whether it is worth taking this route - I will be honest - and help make it happen should you decide to...
Cheers.
Edits: 04/06/12 04/06/12
Beautiful work !
Willie
I need some encouragement at the moment...
I hope it will be nice. Book-matched Red Heart Eucalypt for the front; piano black for the sides, stand (and rear, I think). The builder seems to be a perfectionist: excellent quality but it is taking longer than I would ideally like. That said, I can be a little perfectionist(ic) and would rather he take his time and produce a quality product... which is what he seems to be doing. He is also doing the build at a pretty low cost, so I have to put my occasional frustration aside.
Keep well.
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