Soundlab speakers with sub woofers?

Mrmb when you were listening with the ma1 and ma2; did you hear a difference that would justify the extra cost of the ma2 over the ma1.
I am a owner of M2's with tordial upgrade and impedance mods and was just curious about how the 2 of these amps compared.

Wow! Has anybody else been unable to log it to the forums for days!? I've been wanting to respond to the forum but have been unable to get in. Anyway... Statman - how did you incorporate the subs with the crossover point? I assume one sends a full signal from the preamp to the sub and then the crossover point is implemented at the sub? Thanks. I'm currently running Pass Labs XA160.5's but I'm thinking that I may go with the Pass 600.8 if I run the Soundlabs. I have never been a fan of the Atma-sphere amps, but I've never heard them with the SL speakers.

Rleff: Hearing the MA1 and then the MA2 with Soundlab U1PX's was a real treat. As could be imagined, the overall sound was very, very similar. The MA2's had a little more gravitas -- i.e., control and thus, refinement. The difference was minimal & as such, wouldn't be noticed without A/B'ing them back to back. Would I have been able to blindly discern the difference? I really can't say, which to me, suggests how close they really were.

Of course the speakers were "PX's with the new consummate upgrade. Hence, they present a more benign load than they formerly did. I would imagine that the non-PX panel and previous generation toroidal transformer speakers would benefit more from the higher power MA2's.

If dollars weren't an issue & I hadn't heard the MA2's, I could be quite happy with the MA1's. I must admit however that the comparison wasn't lengthy, nor with overly complex material. If I had both amps in my system and had several days to compare, the differences may have been more pronounced, but then again maybe not.

Certainly with new Soundlab PX panels and backplate electronics, one needn't be concerned with the MA1's driving ability. Then and only then if that last few percentage points of refinement were appreciated & the extra funds and heat weren't a concern, then MA2's may be just the ticket....

In my feeble mind I imagine a relatively fixed voltage across the speaker terminals. As the impedance changes with frequency so will the current drawn from the amp and so will the power supplied by the amp. When the impedance rises in the bass, the current drawn from the amp will decrease as will the power supplied by the amp. Likewise when the impedance decreases in the midrange and treble, the current drawn from the amp will increase as will the power supplied by the amp. I think that's based on Ohm's law.

Hi Bob- your statement here is correct. So the impedance curve of the Sound Lab goes up to just over 30 ohms in the bass, and is about 1.5-3 ohms at 20KHz depending on the setting of the Brilliance control.

So let's do the math. We will assume a constant voltage, and for fun a 600 watt transistor amplifier driving 8 ohms.

Power = Current (I) x Resistance squared. So we need to solve for current.

600 = I x 64, 600/64= 9.375 is the current of 600 watts into 8 ohms. Using Ohms law: 8 Ohms =V/9.375 Amps, we see that the voltage is 75 volts.

Now we change the Resistance to 30 ohms, keeping the voltage constant. So: 30=75/I, solving for I we get 2.5 Amps.

Power is Voltage x Current, in this case the 600 watts is now 187 watts.

At the other end of the frequency range, the amp can put out over 1200 watts, as there is a 10:1 difference in impedance.

Basically what the math shows is that a 600 watt amp can't make that kind of power- and so a 150 watt tube amp can easily keep up with it, as the difference between 150 and 187 watts is not even 1db. If you have a 200-watt tube amp, you would need a transistor amp with about 800 watts in order to keep up.

The math also shows that there is a good chance that the transistor amplifier will be bright on the Sound Lab.

Now the application of negative feedback will cause the amplifier to reign in its power somewhat at higher frequencies. But since the feedback voltage is really not correct on this load, there will be an error that causes the amp to make too much power at the higher frequencies. Its is easily audible.

Now the speaker curve is not based on a driver in a box as we all know. Its based on a capacitor. Its efficiency is thus not a function of its impedance- its about the same at high frequencies as it is at low frequencies. You can see that a constant voltage characteristic in the amplifier is not really all that desirable. You can read more about this phenomena at this link:

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php