From: John Woodgate
Subject: Re: Bullshit wins v. science
Date: Thu, 7 Nov 2002 05:26:25 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Thu, 7 Nov 2002 07:44:29 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that N. Thornton
wrote (in ) about
'Bullshit wins v. science', on Wed, 6 Nov 2002:
>Some speakers are designed to distort, eg bass reflex units. They
>produce resonant bass, consequently real life distortion is
>considerable, though that wont show up on a steady sine wave.
I don't think I've ever seen so much misleading information in three
lines. ALL moving-coil loudspeakers have a low-frequency resonance. A
very important part of system design is to control this resonance so
that a high-pass filter response, as close to maximally-flat as desired,
is obtained. This applies whatever the nature of the system - closed-
box, vented box ('reflex'), ABR ('drone cone'), double-chamber ....
The resonances (one or more) of these systems do not involve any non-
linearity at all, so no non-linearity distortion is produced. In fact,
by achieving tight control of cone motion over the low-frequency range,
the non-linearity distortion is normally much lower than the driver
would produce when mounted on a large, flat baffle.
The overall system response is that of a high-pass filter, and, just
like a wholly electronic high-pass filter (including any recording chain
that does not have a flat response down to d.c.), there is an associated
phase/frequency characteristic and a group delay/frequency
characteristic. It could be argued that these are 'distortions', but
this does not mean that they sound unpleasant or are even audible.
Of course, it's possible to design the system badly, so that the sound
pressure/frequency response is far from flat; this has been called
'linear distortion', a confusing term, and IS audible, of course. But
anything badly-designed is likely to be unsatisfactory.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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