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From: firstname.lastname@example.org (Don Klipstein)
Subject: Re: Bullshit wins v. science
Date: Tue, 5 Nov 2002 00:20:05 +0000 (UTC)
Organization: MGT Consulting
References: <email@example.com> <3DC634B7.C303BC8E@scazon.com>
NNTP-Posting-Date: Tue, 5 Nov 2002 00:20:05 +0000 (UTC)
User-Agent: slrn/0.9.6.2 (SunOS)
In article , John Larkin wrote:
>Certain instruments do sound different if the audio phase is reversed,
>ie, compression/rarefaction are swapped from the original performance.
>Almost nobody tries to control this.
There is a grain of truth to this. Human ears have a nonlinearity,
although this is usually negligible in affecting asymmetric waveforms.
Many loudspeakers have a more significant nonlinearity that can affect the
sound of instruments with asymmetric waveforms if the phase is inverted.
Loudspeakers with "flux rings" to minimize flux modulation by voice coil
current will do this less than others. Other factors in loudspeaker
design include an adequately linear suspension, undercutting of the center
pole piece to make the magnetic field more symmetric, and voice coil
properly centered in the magnetic field. Loudspeakers with everything
done right do not have to cost thousands of dollars.
Effects of phase reversal vary directly with volume no matter where the
nonlinearity is. A good indicator of this nonlinearity is the presence of
second harmonic content when the loudspeaker is fed a sinewave. Try at
more than one frequency since at some frequencies (and maybe only at
some signal levels) causes of distortion may cancel each other out.
- Don Klipstein (firstname.lastname@example.org)
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