[sdiy] vocoder filters

[Magnus Danielson]

Dear David,

Many other vocoders used higher Q setups, and Jürgen and I agreed that
you need to avoid that. The reason is that higher Q gets you into higher
group delay, making the filter more sluggish to respond and rings longer
after the end of a sound. It also causes different time-shifts between
bands to become bigger than if you use low Q.

Jürgen was inspired by the EMS3000 vocoder until I sent him the EMS5000
manual and schematic, which derailed the project a little. :)

So, it is not recommended to go for higher Q, and I think you get why.

Cheers,
Magnus

On 2019-08-31 06:05, David G Dixon wrote:
>
> Hey SDIY Team!
>
>  
>
> I’m thinking about building a vocoder, and I have a general question
> about the bandpass filters.
>
>  
>
> I’ve looked at Jurgen Haible’s Living Vocoder, and he used 8-pole
> filters with low Q.  These give a reasonably broad band with fairly
> steep slopes.  He makes the filters from two pairs of LP and HP.
>
>  
>
> I was thinking about using BP filter sections, but just 4-pole, and
> with higher Q (around 10).  This gives a somewhat narrower band, and
> the slope is steep near the corner, but fairly shallow around the
> skirt.  This idea uses a lot fewer components (about half as many).
>
>  
>
> What I’m asking is, does anybody here have any insight into what the
> “proper” approach to vocoder filters would be?  What is the design
> goal?  Do you want significant overlap from one band to the next, or
> should they be fairly distinct?  I guess I’m just looking for some
> general guidelines and conventional wisdom.
>
>  
>
> Cheers,
>
> Dave Dixon
>
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20190902/95ec4a7e/attachment.htm>