Do stereo systems ever catch cold? Do they get temporary indigestion, headaches or backaches?

Yes, figuratively speaking of course. But over the years there have been reports of normally functioning sound systems that develop symptoms of malfunctioning that are alike in two ways:

1) There seems to be no objective reason for the malfunctioning, and

2) The problem usually is self-limiting, and often "cures itself" without the owner's having "done anything."

Typical is the report from many stero owners that on some days the sytems sounds "restricted" as if the highs are being squashed down and the bass not sounding as full as before. You check switch settings, input and output connections, stylus, and so on. Everything seems okay.

You decide that if the sound does not improve in a day or so you will have to contact your local service shop. However, two days later you find that the system again sounds as good as it used to. The sonic restriction is gone; the highs are once again smooth and extended, the bass is solid and ample.

So what happened? One very strong possibility here is the effect of atmosphere -- humidity, temperature, or both. A change in these conditions could have an effect on the transducers in a sound system, and especially on the diaphragms of speakers in direct-radiating systems (such as air-suspension types). In such speaker systems, the air in the room "loads" directly to the speaker cone and thus can influence its vibrations (for better or worse) fairly actively. In an indirect-radiating system (base-reflex, or horn-type speaker) the sound is loaded to the air more gradually and more efficiently and so it is, to that extent, less dependent on internal damping for control of its vibrations. A multiple-driver type of speaker also has this property.

Another likely cause of mysterious ailments that crop up and then vanish is the slow build-up of a corrosive and resistant coating on the metal part of plugs, jacks, and wire-connecting screws. The last applies especially to leadins from outside antennas. But this build-up can develop even on the plugs connecting your turntable to your receiver or amplifier. It actually can impede the transfer of signal energy from one component in the system to another. Interestingly enough, many stero-system owners hit upon the solution to this problem almost instinctively -- in many cases, merely removing a plug from its mating signal jack and then reinserting it is enought to remove the "coating" on the metal surface and thus restore full signal contact. Very often, the stero owner who reports having "done nothing" will admit to having pulled and reinserted the plugs, which somehow mysteriously cleared up the sound.

For this reason, it is a good idea to do just that about once every six months, with the power turned off of course. When the plug has been removed, study it for obvious signs of discoloration as well as physical deformity. Replace it with a new plug -- shiny and perfectly formed -- if necessary.

If soldering a new plug to signal cable is beyond your ability, and you can't get someone to do it for you, the price of an entirely new cable with plugs attached may be well worth it. Feedback

Q. My speakers have the legend "4-8 ohms" and my old, but still good, amplifier has outputs I vvan switch for "4" or "6" or "8" ohms. To which of these should I connect the speakers?

A. Use the 8-ohm connection to assure that enough voltage will be fed to the speakers.