[sdiy] 'State-Variable' vs. 'Multi-Mode' filters - differences?

[Tom Wiltshire]

On 4 Jul 2012, at 13:17, Justin Owen wrote:

> With regards to filter types - are the terms 'State-Variable' and 'Multi'Mode' essentially interchangeable or do they refer to two different filter types?
> 
> If they refer to two different filter types - what are the differences?

In my view it's a "squares and rectangles" situation. A state variable filter is a type of multimode filter, but not all multimode filters are state variable.

A multimode filter is one that has multiple different responses available. How that is implemented is up to you. An SVF is one convenient way to do it. Switchable LP/HP stages like in the Synthex is another approach, or summing various output taps like the Xpander is another.

HTH,
Tom