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Hi!<br>
<br>
I agree with Martin Peach in most points and want to add some
sentences.<br>
<br>
On 22.10.2010 01:17, Martin Peach wrote:
<blockquote cite="mid:BLU0-SMTP867E95321032B61070C0D4ED5D0@phx.gbl"
type="cite">A perfect speaker will reproduce the sound exactly by
transforming the instantaneous voltage to a displacement in or
out. That's called 'compliance' in the speaker biz. The ideal
speaker has zero mass and is totally rigid.
<br>
So nonlinearities will show up:
<br>
1> when the speaker is massive and can't reach the ideal
position quickly enough.
<br>
</blockquote>
this mainly filters the signal in a way of an analog lowpass filter
and influences the intensity and phase spectra. It doesn't add new
frequencies to it, so it's still called 'linear'. However throug the
mass the system also has to deal with the stiffness and this causes
some nonlinear effects.<br>
<blockquote cite="mid:BLU0-SMTP867E95321032B61070C0D4ED5D0@phx.gbl"
type="cite">2> when the speaker deforms as it is accelerated
from the centre but lags at the edges.
<br>
</blockquote>
I'm also sure these material nonlinearities will produce a main part
of distortion frequencies in the spectrum. Especially when the
speaker surround and spider are at their limits their imperfection
will cause the whole cone to move 'sideways' and build up different
modes. So this is definitely of interest for a (dying) speaker
simulation. Probably this is one of the most challenging too...<br>
<blockquote cite="mid:BLU0-SMTP867E95321032B61070C0D4ED5D0@phx.gbl"
type="cite">
<br>
Also the stationary magnet is driving a coil in the speaker cone.
When the speaker is overdriven the coil will be pushed away from
the field of the magnet on the outward stroke and so the coil will
be less able to move the speaker, so a kind of soft clipping will
occur.
<br>
But on the inward stroke the coil will bottom out and slam into
the support structure, giving a hard clipping and possibly some
bouncing.<br>
</blockquote>
dependant on the construction of the speaker this slam will not
occur, because the spider prevents this. (In most new speakers the
spider is linear for small amplitudes and starts to become very hard
and thus nonlinear at both ends. In a simulation one might want to
chose if that slam (or i called it crash) happens or not. In a real
speaker this often is really the death of the speaker because the
coil is damaged permanently and then scratches on the magnet surface
on every movement - I don't feel like I want to simulate these
sounds <span class="moz-smiley-s7"><span> :-\ </span></span><br>
<blockquote cite="mid:BLU0-SMTP867E95321032B61070C0D4ED5D0@phx.gbl"
type="cite">
<br>
I don't think the nonlinearities of the air are relevant here, or
the doppler effect of the moving speaker.<br>
</blockquote>
I also agree that doppler effect is not the dominant parts of the
distortions in a conventional speaker enclosure for music
reproduction. Countermeasures are taken to reduce doppler effect as
good as possible in these systems. In real speaker enclosements
doppler effect is largely reduced by separating the audio spectrum
on several speakers, so the bass speaker which does most of the
movements only has to produce frequencies up to several hundreds of
hertz. For example bass speakers in 3-ways systems are driven below
150 Hz in most cases - doppler effect becomes very low in this
spectrum and mid range speaker have almost no visible travel
anymore. However the doppler effect occurs in every speaker with
moving parts and especially for full range speakers this becomes
important. Guitar amps often use bass drivers in full range, so this
has some practical relevance for musicians too.<br>
<br>
I'd be interested what kind of speakers fallen_devil was interested
in when originally posting his question to the list. Also a record
of the noise would be nice for comparison...<br>
<br>
cheers<br>
Martin<br>
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