A recent experience with two excellent loudspeaker systems and two of the top power amplifiers raised a question that has been cropping up more and more frequently these days: When one component sounds more toppish or more bassy than another, which one is really flat and which isn't?

The question arose this time in connection with some listening tests on a pair of FMI 80 speakers and a pair of IMF Monitor III speakers, using Audio Research Dual 75 and Crown DC-300A power amplifiers.

Both speakers, according to their manufacturers, had been designed to produce the flattest, most-extended high end possible. Yet there was an obvious difference between the high-end character of each. Either the FMIs were up at the high end and the IMFs were flat, or the FMIs were flat and the IMFs were somewhat dull.

Okay, how would you determine which was correct? Connect each to a power amplifier of unimpeachable credentials, and listen to recordings that are known to have a flat high end on them? Okay, now name an amplifier of unimpeachable credentials. How about the two above-mentioned ones: the Dual 75 and the DC-300A.

Let's try the Dual 75 first. With that amp driving each speaker, the FMIs were obviously flat, the IMFs rolled down at the top. Now we have the answer! Or do we? Let's try the other amplifierthe DC-300A. Now the IMFs sound flat and the FMIs sound obviously tipped up and fiery.

Which is right? The average person's answer at this point will be prejudiced by whether he is a solid-state worshipper or a vacuum-tube infidel. If he believes in the inherent superiority of transistors he will know that the DC-300A is right because its extra "snap" is due to its superior rise time. If he is a tube man, he will say the Dual 75 is right because its "softer" sound is due to the fact that it produces less high-order harmonic distortion than do solid-state amplifiers.

Both assertions are true, and could account for the audible difference. But is the sound of either one "right"? Or is it possible that neither is right, and that the right sound lies somewhere in between?

We have observed the same thing at the low end. The Monitor IIIs have truly awesome low-frequency response, with a slight tendency toward heaviness. With the DC-300A, the low end is merely a bit "rich." With the Dual 75 it is intolerably woolly and turgid. Yet it goes almost without saying that both amplifiers have absolutely identical measured frequency response from 30Hz to 20kHz. And the Dual 75, which starts to roll off below 25Hz, elicits more bass from the Monitors than does the DC-300A which is flat down to 0Hz (DC)! And both have such low distortion at levels below overload that it is impossible to measure with most test instruments, and should not be audible to the most critically tuned ear.

So why the difference at the low end? Available power makes for tighter bass? Or is it higher damping factor that causes the DC-300A to better-control the IMF's low end?

And which one is right? The Crown, because it makes the IMF sound more natural at the low end and makes some other systems sound too taut and sparse? Or the Audio Research, which underdamps the IMFs and produces just the right bass quality from some other speaker systems?

We did not cite the IMF Monitors or FMI 80s as examples here because they are unusual in the way in which they react to different amplifiers, but because they are typical in this respect. (They differ from most other speakers in that they are good enough to reveal the amplifier differences rather conspiciously, and from one another in that the FMIs were designed for use with tube amplifiers while the IMFs were not.)

The point we're trying to make is that, at least at the present state of the audio art, there is no right or wrong, there's only incompatibility. The IMFs sounded best with the DC-300A because that amplifier aproximates what was used to design them. The FMIs and a few other loudspeakers sound best with the Audo Research Dual 75 because, by design or (in the case of most electrostatics) by happenstance, they work best with tubes.

If you're looking for an earth-shaking conclusion, we can give you that, too. Conclusion: There is no "best" amplifier; there is only a best one of the type that the speaker was designed for. And it's a pretty safe bet that, as of today, one is the Dual 75 and the other is the DC-300A.

If in addition you're looking for something new to worry about in the wee hours of the morning, try this on for size: Can we really trust the device that is used to calibrate the microphones that are used for recording and for measuring the frequency response of the loudspeakers we listen to? Can we be even reasonably certain that anything is right? Have you ever had an audiometry curve run on your ears?

Sleep tight, now!J. Gordon Holt