[sdiy] ot: rotating speaker simulation or stupid approach

[Peter Grenader]

You do not believe you can achieve Doppler effect if the source of the sound
is stationary unless you induce it through synthesis.  If the transducer
moves, then you're golden, but if the sound just swirls from one speaker to
the next, it won't get you there.

Further reading (with animated examples):


http://www.gmi.edu/~drussell/Demos/doppler/doppler.html



onCzech Martin wrote:

> 100 speakers was just an example, a thought experiment to
> make my often confusing or unclear statements
> better understandable.
> 
> I'm not really intending to spend so much money,
> I'm just thinking about a virtual implementation.
> 
> m.c.
> 
> -----Original Message-----
> From: Jaroslaw Ziembicki [mailto:aon.912230836 at aon.at]
> Sent: Donnerstag, 3. Juli 2003 18:50
> To: Czech Martin
> Cc: SDIY
> Subject: Re: [sdiy] ot: rotating speaker simulation or stupid approach
> 
> 
>> -----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
> 
> 
> 
>