Thomas J. Norton

The future is rarely what anyone expects it to be. I still remember reading, as a child, predictions in Popular Science that everyone would have a personal helicopter by 1980. It never happened, though it sure seemed like a reasonable projection of events. Events, however, have their own agenda.

On a number of occasions we have commented on the effects of an amplifier's output impedance on a system's performance. A high output impedance—such as is found in many tube amplifiers—will interact with the loudspeaker's impedance in a way which directly affects the combination's frequency response. The Cary CAD-805, for example, has a lower output impedance than most tube amplifiers, and should be less prone to such interaction. Some months back—before the CAD-805 arrived—I investigated this phenomenon in conjunction with measurements for a forthcoming review of the Melos 400 monoblock amplifier. Since the Melos 400 also had a relatively low output impedance for a tube amplifier (at 0.43 ohms at low and mid frequencies, rising to 1.2 ohms at 20kHz, from its 8 ohm tap), I took that opportunity to run some frequency-response measurements using an actual loudspeaker as the load for the amplifier.

Room acoustics, and their importance, may not be subjects which we ponder daily here at Stereophile, but they are never far from our consciousness. Two recent events served to spotlight them yet again: the setting-up of our first-ever panel listening test of moderately priced loudspeakers (Vol.14 No.7), and a letter from a reader requesting advice on room problems. Both reminded us---if a reminder was needed---that although the perfect room does not exist, there are things that can be done to make the most of even an admittedly difficult situation. That reader's letter, in particular, brought home the fact that we cannot really discuss this subject too often. It's easy to forget that comments made here months (or years) ago are beyond the experience of newer readers. A new audiophile's most frequent mistake is to overlook the significance of his or her listening room, while the experienced listener will too often take the room for granted.