Amp advice for Sound Lab M-2's

Thx for explanation Ralph.

Chris

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

Chris-did you ever use the mod from jafox for the brillance
control in your speaker;if you did,how were your results?

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.

thanks Ralph

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, 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.

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.

Gammastrep, your speakers are fundamentally different from box speakers as you know. The impedance curve is the result of 2 factors, neither of which has anything to do with resonance.

The result is that the 'conventional wisdom' about using a transistor amp to make the speaker sing is wildly inaccurate.

first, read
http://www.atma-sphere.com/papers/paradigm_paper2.html

Your speakers are a Power Paradigm technology, so voltage-source power amps like big transistor amps are all going to have similar issues- too bright in the highs and not nearly enough bass. If you think about it, lets try the example of a 600 watt transistor amp. Into the bass, which is over 30 ohms in some areas, that amp will only make about 150 watts. IOW, any 200-watt tube amp will be able to keep up with it, as a tube amplifier will be able to deliver substantial power into an impedance like that. Any time you mix Voltage and Power paradigm technologies, you will get a tonal anomaly, in this case too much highs and not enough bass.

The bottom line is that you need to seek a tube amplifier if you wish to get the most out of this speaker. As you have noted, that tube amp should be capable of some power. IME you will need about 200 watts per channel to get things happening.

I have had M-1's for about three years, about 9 months ago getting the new PX panels. Initially, I was powering them with a hybrid tube amp made by the Moscode people with good results (this proprietary design was built on the old 600 with two power supplies and a bunch of other goodies on two chassis). The only problem was that there was not quite enough punch to the sound (I listen almost exclusively to classical music). I then changed to the Bryston 14B SST with excellent results. I had the amp upgraded to the Swedish choke and things got even better. For some reason, SL owners avoid this amp (maybe because they think it is too cheap).

The best Soundlabs I've heard were with tubes. Wolcotts are popular with SL users as are Atmasphere amps. VTL MB450 and up and possibly some ARC amps are worth considering. A used ARC VT200 MkI (better than the II imo) would be a cost effective solution.

I'd definitely explore the tube amps (and preamps). The M2s are outstanding speakers and they will provide detail and imaging and bloom and air and everything from lows to highs with great non-fatigue if you marry them to a good tube amp.

Let us know what you hear when you get it all together.

Spectron.

I think you maybe missing the boat going solid state on the m2's. Do you know if they have the impedance mods and diffusion ring?
If you can you should try a tube amp at least to see what these speakers can really do; The wolcott mentioned earlier is excellant advice; also higher powered vtl, manley,cary and my opinion the best match atma-sphere's ma1 or ma2 otl tube amps.
Also may want to try paul speltz's autoformers to help with the impedance curve these speakers have.

I 've used the aforementioned JC 1's with my Soundlab A1's, found that Nuforce 9 SE V2 worked better, which came as a surprise, and am now using Bel Canto Ref 1000's. All these amps drove the A1 well, The JC 1 was great, but the Nuforce and BelCanto's expanded the sound stage beyond what the JC 1 could and were somewhat more articulate. The bass has been better with the Nuforce and Bel Canto amps as well, which was the biggest surprise. Digital amps, they're not just for breakfast anymore....

I have experience with the Parasound JC-1's, Wolcott P220 tube amps, and now the Ayre MX-R's. All of these do a great job of driving the Sound Labs, but without doubt the Ayre amps are the best yet. The JC-1's are my least favorite among the 3, but still do a credible job. I can't speak for the others.

If considering used Bryston amps make sure they are the latest production incorporating the "swedish choke" mod which has become current production specs. Get the serial numbers and email Bryston to ensure you are getting the latest version. I had my 14B-SST upgraded and it tamed the top end a bit (at least to my ears) and made it a better amp over-all. You can have the amps upgraded I believe at a cost of $250 each but it will entail freight both ways, wait times, etc.

On a number of occasions, Sound Labs showed their speakers at CES in the late Bob Crump's room with the CTC Blowtorch pre-amp and Richard Schram's Parasound JC-1s. We had a ton of fun in that room - the sound was excellent and the company stimulating.

Regards,