Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <email@example.com> <3DC634B7.C303BC8E@scazon.com>
Subject: Re: Bullshit wins v. science
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Tue, 5 Nov 2002 08:06:10 -0000
NNTP-Posting-Date: Tue, 05 Nov 2002 08:06:15 GMT
"Don Klipstein" wrote in message
> In article , John Larkin
> >Certain instruments do sound different if the audio phase is
> >ie, compression/rarefaction are swapped from the original
> >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
> sound of instruments with asymmetric waveforms if the phase is
> Loudspeakers with "flux rings" to minimize flux modulation by voice
> current will do this less than others. Other factors in loudspeaker
> design include an adequately linear suspension, undercutting of the
> 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
> nonlinearity is. A good indicator of this nonlinearity is the
> second harmonic content when the loudspeaker is fed a sinewave. Try
> more than one frequency since at some frequencies (and maybe only at
> some signal levels) causes of distortion may cancel each other out.
An asymmetrical speaker as you note here, might well sound different on
inversion, but then, technically, it is not that inversion that the ear
is detecting, in the sense that there is some mechanism in the ear for
distinguishing between positive and negative pressure. The sound being
generated is actually different. An asymmetrical signal might be clipped
in one inversion, but not the other. Usually, when one is disusing
whether or not certain effects are detectable by the ear, the use of a
baseline of neutrality is used. That is, amplifiers, and such like are
being operated in their linear region and power ratings etc.
So it would seem that in a real speaker, it may be possible to notice
effects due to phase reversal, but that the ear itself is not responding
to the phase reversal itself, but to the different spectrum of harmonic
distortions that are generated. If the speaker was symmetric, phase
invasion would have no effect.
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