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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.
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rleff
1,065 posts
 
thanks Ralph
atmasphere's avatar
atmasphere
11,849 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.
rleff
1,065 posts
 
Chris-did you ever use the mod from jafox for the brillance
control in your speaker;if you did,how were your results?
dazzdax
599 posts
 
Hi Rleff, I haven't done any modification yet. I think you can use a single resistor for the brillance control. But it should be noted that this single resistor could be a mismatch if you for instance change amplifiers or in case of another acoustical environment (another listening room). So this resistor should be easily replaced by another. It would be ideal to use some kind of socket to accommodate the resistor (so you can insert the resistor legs into it without soldering). But as you know there are much more suggestions how to modify the Soundlab crossover. I can refer to the extensive discussions you can find at the SLOG forum.

Chris
dazzdax
599 posts
 
Thx for explanation Ralph.

Chris
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