Thank you for an interesting
article ["Loud TV
Commercials a Matter of Signal Processing", August, 2002]. As you mentioned, I
just assumed the commericals were purposely louder to get our attention. It would be an
interesting statistic to know how many viewers start channel surfing when ads come on.
...Lloyd Smith
Most, I would guess. That's why dual-tuner
picture-in-picture (PIP) is so useful: you can duck the commercials, but still switch back
when the program resumes...assuming, of course, that you don't find something better in
the meantime.
Incidentally, the Canadian broadcast regulator, the
CRTC, has produced a short fact sheet on the causes of seemingly loud commercials. You can
read it at www.crtc.gc.ca/ENG/INFO_SHT/G3.HTM.
...Ian G. Masters
I really enjoyed reading your column about "all amplifiers being
equal" [September, 2002], but it raised a confusing question for me. When I went
shopping for a new A/V receiver, I auditioned a couple of models and there was an
immediate and obvious difference in sound quality. The unit I expected to be the better
performer turned out to be the lesser of the two. If both receivers were playing the same
music from the same CD player through the same speakers, and there is no qualitative
difference between amplifiers, just what does make the difference in sound quality?
...Frank Warsh
I'd have to know more detail about how the comparison
was conducted to say for sure, but I can suggest some things that might have been factors.
First, the speakers have to be the exact same units, not just another set of the same
model. Not only do different samples of the same speaker often exhibit sonic differences
(including subtle level differences), but the fact that they must necessarily be in
slightly different acoustic environments can create significant variations. The
relationship between each speaker and nearby walls, plus your listening position, can have
profound audible effects -- and we're talking just inches here.
If the amps under consideration were indeed feeding the
same speakers, with the switching taking place after the amplifier outputs and before the
speakers -- a setup not many dealers are able to arrange -- there still could be audible
differences, even with amplifiers capable of identical sonic character. The outputs of the
two amplifiers have to be matched very closely, within a fraction of a decibel, otherwise,
the louder one (even if we don't perceive a level difference) will almost always sound better.
There is also the possibility that the speakers you chose
for the comparison presented a "difficult" load to the amp outputs, one of which
may have been better able to cope than the other.
Or, depending on the equipment, it might be a deliberate
tweak. Some years ago, I was involved in testing a well-respected piece of equipment (a
preamp, in this case) that was touted as having unusually "airy, silky highs."
On the test bench, it turned out that it didn't have flat frequency response, but a
significant bump in the upper mids. An audio component that isn't linear will always
identify itself during comparisons, even though you might, in fact, prefer it.
...Ian G. Masters
Thank you so much for your article [on amplifier
sound]. It was well written, balanced, and polite (although I'm sure you've been bombarded
with e-mails from the tweako-fringe element, regardless of how polite you were to them).
Not many audio critics these days give such practical and honest advice. I'm considering
investing in a subwoofer to extend the frequency range of my (two-channel) system. Is
there any benefit to using two subs vs. one, or is that just a myth? As a general rule,
will a 10" woofer do the trick or should I consider a larger 12" unit?
...Neil Batts
In most rooms, dual subwoofers are rarely required from
the point of view of output. Most powered subs can pound out more bass than you'll ever
want. Using two does, however, allow you to place them in acoustically dissimilar
environments, which can be useful for smoothing out room effects. I'd try one first, and
if you have problems, get another.
On its own, cone size is irrelevant. The amount of air a
speaker can move depends not only on the area of the diaphragm, but also its excursion --
the distance it travels in and out. An 8" with long excursion might well outperform a
more restricted 12" model.
...Ian G. Masters
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