Friend Biquad

[Dune'nQuadzilla]

Some audio comapanies use the Friend Biquad (S.A.B.) stages as placeholders when designing their products, this way when the finalized drivers / enclosures are determined or they are changed mid production etc. they have reasonable assurance they can hit most any "target" curve. The goal here is minimization of opamps and insertion losses from passive components (read by definition S.A.B.).
Most have no idea what this is letalone use them. Since they are rather difficult to design what would you recommend would be the best approach to realize component values within Filtershop? (Obviously some components are not needed in the final circuit realization).

Also, I see the RAT2 function is seemingly close, is there a recommended topology to achieve a RAT2 filter function (analog version of course).

Last one I promise...Is there a way to splice two curves together?

[cstrahm]

Suggesting component values without any details or more target info is impossible.

Probably the only circuits which might be able to handle a RAT2 target would be some of the state variable filters. Even most of those would not.

A RAT2 target is a fully generic rational 2nd order polynomial. It can do anything in 2nd order land. Very few circuits can produce every type of 2nd order function possible, and then across any parameter range.

We have a Splice function in our other programs, but I don't think it is in FilterShop (I guess I should add it!). You can do it by exporting the two curves to ASCII data files, and then just use a text editor to splice the data at whatever frequency you want. Then import the result back in.