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Amp advice for Sound Lab M-2's

Looking for opinions for a amp to use with my Sound Lab M-2 speakers. I am down to considering the Bryston 7b – SST, Parasound JC – 1, and the new Sanders Sound ESL amp. The former owner of the M-2’s used a Pass X-350, but I found that it sounded dry, and very thin. No warmth at all. Lots of older Krells out there, great bottom ends, but again often very cool sounding. I’m not that familiar with the Levinson’s, another option, maybe. The Sound Labs do need a good honest 300 watts > 8 ohms, and 600 watts > 4 ohms. Most amps don’t have the combination of voltage and current ratings to handle the speakers. I am leaning towards the Brystons. Overall they seem to be an amp that is easy to live with, while maybe not the best over all, they do a lot right. Ideas and experiences appreciated. By the way, the listening room is 23x21, with a ceiling that is 9 feet on one long wall, and slopes up to 16 feet on the other long wall. 15 feet of the highest long wall is open right in the middle of the wall. So the room can really suck up speaker output. Thanks.
gammastrep
rleff
1,065 posts
 
Ralph;if you pop your head back onto this thread;I have m2's with impedance mods;would your 60 watt amp with the autoformers drive these;I don't listen to large SPL's on my m2's; music is mostly vocals,jazz and acoustic but sometimes pink floyd does shown up.
atmasphere's avatar
atmasphere
12,116 posts
 
Rleff, if you have a set of ZEROs a set of M-60s will do OK. The big problem is the highs- M-60s don't drive 2-3 ohms all that well and that's where the ZEROs help out.
dazzdax
599 posts
 
Ralph, one thing I don't understand: why should a solid state amplifier run out of steam in the lower frequencies when driving Soundlab A-1's. I've always thought an amplifier has less to do (doesn't have to deliver lots of current) with rising speaker impedance. But in your terms this amplifier would have difficult times when facing a 50 Ohms impedance like in the case of the Soundlabs. Can you elucidate this a bit? Thank you in advance.

Chris
rleff
1,065 posts
 
thanks Ralph
atmasphere's avatar
atmasphere
12,116 posts
 
Hi Chris, the answer has to do with the 'voltage source' quality of most transistor amps. What we are talking about is the fact that regardless of load, a transistor amp will (attempt, at least, to) put out the same voltage.

For example, in the case of an 8 ohm load, a 100 watt transistor amp will put out about 28 volts. Into 4 ohms, it makes that same voltage- that's 200 watts. What happens with higher impedance loads? It makes the same voltage- 16 ohms and 28 volts is 50 watts; into 32 ohms that would be only about 25 watts.

Most transistor amp employ a fair amount of feedback, which helps to 'linearize' the voltage response (according to the rules of the Voltage Paradigm); this helps flatten the frequency response of the amp a little but also means a 100 watt amp is not going to be making much power on the Sound Labs, and is why the speaker gets paired with what appear otherwise to be some very high powered transistor amps, to get around this phenomena. But regardless of the power, it will never be 100% successful if the amplifier cannot satisfy the rules that the speaker operates by.

IOW, the rules of the Voltage Paradigm don't help you all that much when faced by the load of a typical ESL. If you had an amplifier that made constant **power** into all loads, then you would get much flatter response out of the speaker (most people have **no idea** how well they play bass, for example). Amps that can do that on the Sound Lab are very few and far between. This is part of the reason that the speaker has such a varied reaction amongst audiophiles: no doubt most people have not heard what the speaker can really do when driven right.
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