[sdiy] ot: rotating speaker simulation or stupid approach

[Czech Martin]

Hey, I didn't say *Leslie* !

The sound of the real Leslie has also distortion
components and currently I have absolutely no clue
how to measure or understand these nonlinearities from
a black box view.

But if I'm not absolutely way off, all reflexions should
be there (i.e. the linear part of the stuff).

Also, I could think of recording a swinging speaker,
like a pendulum. Now problems with twisted cables ;->

I can imagine me sitting on my swivel chair with the speaker
in my arms, and my wife spinning me arround ... ;->

Better then getting arrested for firing a pistol
in some cathedral ;->


m.c.

-----Original Message-----
From: jhaible at debitel.net [mailto:jhaible at debitel.net]
Sent: Mittwoch, 2. Juli 2003 17:11
To: Czech Martin
Cc: Sdiy (E-mail)
Subject: Re: [sdiy] ot: rotating speaker simulation or stupid approach


Sounds like a good idea.

You should

a) find a way of interpolation that does not produce
   cancelation, as a simple crossfade would.
   (And as the Hammond Scanner Vibrato does.)

b) Use a cavity as close to the original as possible
   (i.e. make your measurements inside a real 122 if
    possible.)

I think creating the sound of a speaker rotating in free air
is quite easy. Catching all the reflections from the enclosures
of a classic cabinet isn't, so it's a good idea to do it
the way you proposed.

JH.

> I can record the transfer charactericstic of a loudspeaker with some
> microphone in some room (the impulse response, if you like).
> I can repeat that, turning the speaker a few degrees of axis.
> I can do this , say for 23 steps of 15 deg to make a full circle.
> I must be carefull in order to get the right time shift for
> each impulse response vs. all the others.
> I think the impulse response will be not too long, perhaps
> some 10ms.
> 
> So I get a picture of what happens when the speaker is turned,
> the reflexion pattern changes, etc.
> 
> Now I can take some signal and convolute it with those 23
> inpulse responses. Then I can interpolate between those
> impulse responses when doing play back, in order
> to simulate all the positions between two 15 Deg
> measurements. 
> 
> This could give a good approximation of a rotating
> speaker, though computationaly it could be more effective.
> Since all the phase information is preserved,
> even the Doppler effect should be visible.
> I guess that if the grid of angular position would
> be fine enough, this should work perfectly.
> 
> What problems will arrise, if I do it only with
> 15 Deg samples?
> 
> And another question:
> Has someone heard or read about a circular array of fixed speakers
> in order to simulate a rotating speaker?
> I mean N VCAs and N amplifiers together with N little fullrange speakers,
> with some control that will stear the speakers in a circular fashion.
> I think this would be a hardware implementation of the first idea,
> avoiding any rotating or heavy parts.
>  
> ??
> 
> 
> Martin Czech
> 
>  
> 
> 
> 




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