sealed vs vented subwoofers

Duke,

Thanks for the link - interesting reading. In simple terms, GedLee is saying
that higher order harmonic distortion is much worse than low order
distortion. This means 2nd order is better than 3rd order ...etc. etc. This jives
with everything we know - Class A amps sound better at low volumes - IMD
distortion is the worst - and that the "masking" effect means that
we may not hear nearby frequencies to a fundamental as easily as we might
hear a 9th harmonic (BAD).

This matches what Ralph has said so many times on these forums...high order
odd harmonics are bad - even in relatively much smaller amounts. To take
your example above, 30% second order harmonic distortion (barely or not
quite audible) may be akin or equivalent to 0.3% distortion in the 9th
harmonic. In that sense, an amplifier with THD of 1% all in the 9th harmonic
would likely sound much worse than an amplifier with 10% THD but all in the
2nd harmonic.

One could jump on this and say that all measurements are meaningless,
however, one must reflect that if an amplifier has a measured THD at full
power of less than 0.004% (vanishingly small) then it will likely sound good
anyway - irrespective of a GedLee higher weighting to the higher order
harmonic distortion (as, be it low order or higher order, the distortion is
simply very small).

Perhaps the problem (what listeners observe) begins when you hook up an
amplifier to a complex load and make the poor amp send bucketloads of
current to drive the woofer and then mere milli-amps to drive the delicate
little tweeter. When the rubber hits the road (in the real world and not a lab
test) the amp find itself being asked to perform two rather diametrically
opposing tasks: extreme butterfly wings delicacy and elephant brute force. A
case where IMD distortion seems inherently likely - so why does the industry
stick so vehemently to this design approach? And why is GedLee largely
ignored in manufacturer spec sheets?

Duke, thanks for those articals.

Shadorne, check out Nelson pass's 11/1/08 artical on his website entitled " Audio, Distortion and Feedback." I think he's right when he says that preference for 2nd or 3rd order harmonic distortion is listener dependent. IMHO it's not so simple to classify lower order distortion as uniformly preferable. - Jim

I have never heard of Floyd Toole . In just what way is frequency response predictive? I will refure you to the review of the Spendor SP1 at WWW.regonaudio.com. " Many speakers look good in the anechoic test chamber or on the computer analyzer. Few of them sound good at home. And if sounding good means producing an audible facsimile of the input for a real listener in a real listening room, then most speakers do a rather poor job indeed. ". He adds: "Of course, one might hope to verify such an impression through measurement, but no one has ever been quite sure what to measure in order to evaluate performance in real living rooms. (Most of what has been passed off as "scientific" analysis has been either too crude or too biased to be of any real use or validity". Your general thesis that measurement alone is definitive of sound quality I had thought to have been abandoned years ago. Your further corollary expressed in a previous exchange that, while you had never heard the equipment I was using , logic would tell you what they sound like I find to be breathtaking in it's naïvety.