[sdiy] ot: rotating speaker simulation or stupid approach

[Jaroslaw Ziembicki]

> -----Original Message-----
> From: Jaroslaw Ziembicki [mailto:aon.912230836 at aon.at]
> Sent: Mittwoch, 2. Juli 2003 17:58
> To: Czech Martin
> Subject: Re: [sdiy] ot: rotating speaker simulation or stupid approach
>
> Many, many years ago I read an article where such method has been
> described. It was a kind of a loudspeaker box. I think there were 4 (maybe
> 6)
> loudspeakers, 90 (60) degrees one from another. They used silicon diodes
in
> the
> electronics for gating the signal (a very primitive VCAs). I have no idea
> how it
> worked. I don't believe it's possible to get the Doppler effect on that
way.
> You
> would get some kind of 3D effect - and it may sound very nice, but not
very
> close
> to the original Leslie...
> There was another approach described in this article: the (heavy)
> loudspeaker is
> mounted inside the box and it doesn't move - and there is a rotating
> (lightweight)
> "horn" that leads the sound to outside.
> Regards
> Jarek
>
> Why would the doppler effect be lost?
> Imagine the following: 100 speakers in a single line, every cm a speaker.
> A "sequencer" with interpolation and VCA will make the active of those
> speakers move forth and back. What is the difference of that arraw
> to a single speaker on a model railway track waggon, moving
> foth and back?
> The question is: how many virtual speakers do I need in order to avoid
> cancelation effects when doing the interpolation from one
> speaker to the next.
> m.c.
>

Martin, the more I think it over, the more I'm convinced that you are
right. Especially if you actually intend to use 100 speakers...
With just some speakers (eg. 4), the way of crossfading between the
amplifiers seems to have great influence on the effect. I mean the form
of the gating signal (triangle? cosine? exponential?). It's something like
choosing a right window function for a digital FIR filter...
Regards,
Jarek