Mobile Solutions
A reader writes, "I have recently moved into a travel
trailer, and this is posing a serious space problem. I can accommodate my audio components
but not my speakers. I need speakers about 10 x 10 x 8 inches. How do I reconcile this
requirement with full, rich, deep bass?"
One of the fortunate things about low-frequency sound is
that it is relatively non-directional, and so doesn't necessarily have to come from the
same place as the midrange and high frequencies. Purists will argue the point, saying that
coherence is very important and that all sound sources should be carefully time-aligned,
and they are probably right on technical grounds. But sometimes it's better to have a
less-than-ideal arrangement than no arrangement at all (in fact, all stereo setups involve
compromises of one sort or another).
In your case, the best solution could be to use a pair of
small speakers -- there are lots of them available -- located in the best position for
good stereo, and supplemented with an outboard bass unit. Such a subwoofer need not be
huge, and you can probably make do with just one.
The question is: where to put it? Trailers, like boats and
airplanes, allow very little flexibility in this regard, but as long as you can fit the
subwoofer in somewhere, it should do the trick. Depending on its size and shape, you might
consider mounting it on the ceiling. To avoid bumping your head on the cabinet, you could
position it over another piece of furniture -- your listening chair, say.
Alternatively, a first-class car audio system might be a
good solution to your problem. The best ones can give home audio components real sonic
competition.
Another moving bass problem: "I have installed a
high-quality stereo system in my car, a hatchback, but I have no bass. I built airtight
enclosures for the rear speakers, and that helped, but the bottom end still doesn't equal
the rest of the signal."
My first thought is that your rear speakers may be out of
phase. This would certainly result in weak bass, particularly in an automobile, where the
speakers are close enough to each other for low frequencies to cancel pretty thoroughly.
Normally, this would be associated with some degradation of stereo imaging, but this may
be offset by your front speakers if they are in phase. One quick check is to play a piece
of program material with lots of bass and turn the balance control from one channel to the
other. If the bass changes appreciably, being greater when the control is at the extremes
than in the middle, it’s almost certainly a phasing problem. The cure is simply to
reverse the polarity of the connection to one speaker (you might try this anyway if
the result of your test with the balance control is ambiguous).
If that’s not the trouble, the airtight boxes you
built might turn out to be unsuitable for your speakers, resulting in over-damping. The
owner's manual should help here, or failing that, drop a line to the manufacturer. Or it
may be a simple matter of different sensitivities between your front and rear speakers, in
which case the equalizer built into your amplifier should be able to correct the
situation.
...Ian G. Masters
ian@mastersonaudio.com
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