Soundlab speakers with sub woofers?

Mrmb heard the MA-1s and MA-2s here on the U-1PXs several months ago in our large custom designed, acoustically symmetric room. Since that time the speaker positioning has been improved, yielding better imaging and mid bass, along with a significant evolutionary improvement in the DAC he heard.

Brian Walsh

Bob, part of the disconnect here between you and Ralph is due to terminology. Including:

1)Strictly speaking, speaker efficiency refers to acoustic power out vs. electrical power in. It is also commonly used to refer to SPL at a given distance vs. electrical power in. SPL vs. voltage in is sensitivity, not efficiency.

2)When Ralph says that an amp "makes power," he is referring to how much power the amp delivers to the speaker.

3)When Ralph says that a Sound Lab is driven by power, not voltage, he is asserting that for the speaker to produce flat frequency response in its acoustic output, it must receive electrical power (not voltage) at its input that either is or approximates or approaches being flat as a function of frequency.

As you realize, given the huge decrease in the speaker's impedance between the bass region and the upper treble region, no. 3 can only occur if the voltage at the amplifier output terminals/speaker input terminals is NOT flat as a function of frequency.

Also as you realize, nearly all solid state amps will produce output voltages into varying load impedances that are essentially flat as a function of frequency, as long as the amp is operated within the limits of its maximum voltage, current, power, and thermal capabilities.

While on the other hand the interaction of the output impedance of a tube amp and the variation of a speaker's impedance as a function of frequency will result in nearly all tube amps coming at least a little bit closer to supplying power (not voltage) into a varying load that is flat as a function of frequency, when the amp is operated within its capabilities.

Also, the MAXIMUM power capability of a solid state amp into high impedances can generally be expected to decrease in close proportion to the impedance rise above 8 ohms. While that decrease will usually occur to a considerably lesser extent with tube amps, and an increase may actually occur with some amps over some range of impedance increase. Ralph is correct that a solid state amp rated at 600 watts into 8 ohms will generally be able to deliver only about 150 watts into 32 ohms.

Best regards,
-- Al

"Also, the MAXIMUM power capability of a solid state amp into high impedances can generally be expected to decrease in close proportion to the impedance rise above 8 ohms. While that decrease will usually occur to a considerably lesser extent with tube amps, and an increase may actually occur with some amps over some range of impedance increase. Ralph is correct that a solid state amp rated at 600 watts into 8 ohms will generally be able to deliver only about 150 watts into 32 ohms."

Looking at the above example, is it correct to assume that if the amp has no trouble driving the 600 watts into 8 ohms, it will have no trouble driving higher resistance with less watts, like 150 watts at 32 ohms? The logic being that even though the amp is not producing as much power, the higher resistance makes it easier for the amp to handle. Discussion on this topic doesn't come up too often, where as there's plenty of talk on the other end of this; needing a more powerful amp to drive low resistance loads. I've always assumed that if an amp is OK driving a load at a given resistance, like 8 ohms, it will have no problems with loads of a higher resistance.

ZD, yes, that all sounds right to me, with respect to the sonic performance of the solid state amp in itself. That is a separate issue, of course, from the question of how suitable the amp may be for use with a speaker which doesn't want to see constant voltage as a function of variations in load impedance.

Also, although you are referring to solid state amps, I'll add that in the case of tube amps having output transformers a caveat might be that if there is a substantial mismatch between load impedance and the impedance the output transformer tap being used is designed to work into, there may be a significant increase in distortion (as well as a reduction in maximum power capability, relative to what it would be if that match were optimal). Ralph can most likely provide a better quantitative perspective on that than I can.

Best regards,
-- Al