Audioclinic (Mar. 1981)

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Speakers Stacked Against Him

Q. I have a pair of stacked speakers, one for each channel, and the sound produced by this arrangement is always good. The sound is not as loud, however, with all speakers operating as when either the A or B set of speakers operates alone. Why is this?

-Jerry H. Ervin, Flint, Mich.

A. I believe the reason for the loss of volume when both sets of speakers are operating is that the two speakers within each stack are out of phase.

To correct this, take one stack of speakers and reverse the common and hot leads of one of the speakers in the stack. Then go to the other stack and repeat. This process should produce the desired volume increase.

If the loss of volume is now even greater, and includes a loss of bass response, you'll have to replace all connections as they were initially. In this case, it's probable that a volume loss was intentionally designed into your amplifier to provide a means of safeguarding the unit from overloads.

Leaving Single Switches On

Q. I have a Heathkit Audio Control Center, and all of my components are plugged into it. When I turn the control center on, this automatically turns every thing on. Is there any harm in leaving all the power switches in the "on" position?

-Dan Tremaine, Sandusky, Ohio

A. If the power used by all the equipment does not exceed the ratings for the power switching in your control center, you can safely leave all equipment turned on and use that single switch in the control center to turn the system on and off.

In the case of a tape recorder which may not be frequently used, it may be better to keep it turned off, because many tape recorders are designed so that their motors turn all the time once power is applied--regardless of whether or not they are pulling tape.

Since this adds wear to the motor, it should be avoided if possible.

Rock vs. Home Sound Equipment: Watts the Verdict?

Q. I recently got into a heated discussion with a sound technician working with a popular rock group. The group uses a dozen or more 200-watt amplifiers, along with expanders and equalizers, feeding into several speakers. The technician told me that this $50,000 worth of equipment is necessary to achieve the best sound available! I flatly disagree. High-end home audio offers much cleaner, more transparent reproduction at a fraction of the price.

There seems to be much more technology offered in this area, too. Who is correct regarding accuracy in the reproduction of music?

- Steve Grossman, Middletown, N.Y.

A. You and the sound technician are both right! Home entertainment equipment will reproduce sound about as accurately as anyone could measure. This is not necessarily the aim of the rock group that you were discussing, because the group is not reproducing anything; it is creating something. The fact that some of today's music is created electronically is not the issue. The group is creating something which you, with your home system, must be capable of later reproducing.

Each rock group wants a sound which gives its music a specific character. One means of achieving this to use speakers which have rather severe coloration--even without other electronic coloring. This coloration, or distortion if you like, is enhanced by the use of equalizers and other devices. (One form of distortion is that of frequency response, as produced by an equalizer. Other kinds of distortion are perhaps more obvious, involving changes in the envelope of the waveforms, the fuzz guitar and the ring modulator being typical examples of this.)

Once rock groups have established their particular sound, they must perform their music in large spaces. Equipment used for home entertainment probably could not fill such large halls or carry well in open-air concerts. Achievement of good sound at concerts requires a large number of speakers with amplifiers to power them so that the audience will hear the music at the intensity the performers feel is correct.

Some additional equipment is needed just to enable the performers to hear themselves on stage. Problems involving the performers hearing themselves can be very significant and difficult to solve.

If you have a problem or question about audio, write to Mr. Joseph Giovanelli at AUDIO Magazine, 1515 Broadway, New York, N.Y. 10036. All letters are answered. Please enclose a stamped, self-addressed envelope.

(Source: Audio magazine, Mar. 1981; Joseph Giovanelli )

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