FS and "AKO Phasing" update

Magnus Danielson magnus at analogue.org
Fri Jan 16 21:46:32 CET 1998


>>>>> "DT" == Don Tillman <don at till.com> writes:

 DT>    From: Haible Juergen <Juergen.Haible at nbgm.siemens.de>
 DT>    Date: Thu, 15 Jan 1998 14:46:28 +0100

 DT>    Second, another look into Bode's patent showed that he uses
 DT>    a configuration with a pure all pass filter in front of the FS, and
 DT>    not a whole phaser/comb filter as I thought. Sorry Don - you
 DT>    were absolutely right. The effect is there (slightly). And you can
 DT>    further increase the effect with additional phase shift in front of the
 DT>    hilbert transform network. I tried pure all pass, a complete phaser,
 DT>    and a phaser with its own resonance. All different, and all interesting.

 DT> Very cool!  So those initial phase shift stages in HB's patent just
 DT> make the effect more pronounced.  That makes sense.

 DT>    Magnus:
 >> This is similar to the Lesley dual doppler effect where you
 >> would have an table close to this:
 >> 
 >> Number	Original	Horn1	Horn2
 >> 1	100		99.8	100.2
 >> 2	200		199.8	200.2
 >> 3	300		299.8	300.2
 >> 
 >> And so on... 
 >> 
 >> Horn1 - moving away from you
 >> Horn2 - moving towards you


 DT>    I always thought the doppler effect would really cause a pitch
 DT>    shift, not frequency shift, but I am not sure at all, so I have to
 DT>    think of this again.

 DT> Yes, absolutely.  Think about the mechanism involved -- storing the
 DT> soundwave in air is effectively the same as storing the sound in a BBD,
 DT> or tape for that matter -- so it'll definitely be pitch shifting.

So sorry, was a bit tired at the moment, so I forgot connecting the
brain into the processing stream... so sorry.

Cheers,
Magnus





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