July 4, 2005

Q: Are there precautions I can take to prevent damage to my audio gear?

Tony B.

A: An audio system represents a fairly major investment for most of us. Fortunately, it’s also reasonably low in maintenance; sound equipment can chug along for years without problems. Obviously, if you crank your amplifier to its top level and pound Metallica through your speakers for a couple of hours, you can expect trouble. And if you drop your CD player on the floor, it may not like it. But most things that can harm your equipment and recordings are much more subtle, and can usually be averted by some simple precautions.

Don’t starve your speakers. It’s not always obvious, but you’re just as likely to damage your speakers by providing too little amplifier power as too much. If your amplifier has insufficient power to drive your speakers to satisfying levels, you may overdrive it in trying to get those levels, and that means the amp will be driven into clipping for a significant amount of its operating time. The clipped waveforms are a type of squarewave containing immense amounts of unwanted harmonic information that the tweeter was never designed to handle. Under such conditions, the delicate wire that makes up the tweeter’s voice coil can fry in seconds.

Don’t bake your gear. Your stack of components may look great in that smoked-glass-and-chrome rack, but placing all your electronics gear so close together may cause problems if care isn’t taken to let them breathe. All audio/video components generate some heat, and this is greatly magnified in a closed space.

The bulk of this heat is usually produced by the power amplifiers, so these should have lots of ventilation. You don’t often have to get at a power amplifier’s controls, so you may be tempted to place it at the bottom of the stack. This is usually a bad idea; heat rises, and can flow upward through your other components. Even if this doesn’t cook them, the airflow may be laden with dust that can foul the innards of your other gear. If you must put the power amplifier in the rack, put it at the top; better still, tuck it away somewhere else entirely, with lots of breathing space.

Don’t short it. Many of today’s power amplifiers -- freestanding or built into other components -- are able to handle some fairly difficult loads, but none can tolerate a short circuit in their output stage, even for a moment. It doesn’t take much to create such a short: a single strand of speaker wire snaking across from one terminal to another can do it.

Presumably you were very careful in setting up your system in the first place, but moving equipment even slightly can disrupt your connections and possibly create a damaging condition. This is less likely to happen if you’ve tinned the cables with solder before connecting them, or if you use banana plugs. Even so, whenever there has been disruption of the cables, either at the amplifier’s output or at the speakers’ terminals, inspect the connections carefully for possible shorts before you apply power to the amp.

Don’t add too many. The notion of being able to throw on a CD in the living room and then wander about the house listening to it in other rooms is a pleasant one, and there are various techniques for doing that. But simply to run a bunch of speaker wire to each room and hook them all up to the main amplifier is a bad idea. One reason is that each of these speakers takes power to operate, and unless your amplifier is truly huge, it’s not likely to be happy under the strain of driving all of these speakers simultaneously.

The real reason not to go for this arrangement, however, is that it presents a very difficult -- and possibly ruinous -- load to the amplifier’s output stages. Today’s solid-state amplifiers are essentially constant-voltage devices: for a given power output, current rises as the speaker impedance drops. Few amplifiers are recommended to run speakers with impedances of less than 4 ohms, and most speakers behave just fine with almost any amplifier. But as soon as you start adding extra speakers, things change -- the more speakers you add, the lower the total impedance drops.

You may get away with a second pair of speakers, as long as there aren’t specific frequencies where the combined impedance is too low (the "nominal impedance" is just an average), but any more than that can cause serious problems. It’s far better to distribute the signal at line level and amplify it separately in each room. That also gives you individual control over local levels.

Don’t expose your speakers. Placing speakers in a listening room can be a tricky process, and one that most of us do mainly with acoustic characteristics in mind. That’s as it should be, but it’s worthwhile to also look at some environmental factors if you want your equipment to last.

One of these is sunlight. Those ultraviolet rays that can do so much damage to you on the beach can be murder on speakers as well; specifically, UV is great at disintegrating foam surrounds, which can be tough to replace if your speakers are more than a few years old. If the sun shines directly on your speakers and you can see the drivers through the grille cloth, you may have a problem. Pulling the curtains at the appropriate time of day might be the best solution.

Dust can also be a problem. It’s not usually a good idea to place your speakers (or any other audio gear) too close to a heating duct. If you have no choice, try to find a way of deflecting the contaminant-bearing air.

And, while it’s unlikely to affect your sound, placing a houseplant on a speaker is asking for trouble whenever the plant is watered: vinyl surfaces may survive; wood veneer and electrical wiring won’t.

...Ian G. Masters