Hi Kamikaze,

First you have to determine the f(0) and Q(0) for your box. The spreadsheet in this link can help you, assuming you have a closed box. In the tab "box" you fill in your parameters Fs, Qts, Vas and Vb. The spreadsheet calculates the Qtc [= Q(0)] and Fsc [= f(0)]. With your parameters these are 0.57 and 36.6Hz.
Now determine the desired Q(p) and f(p) and use the spreadsheet in this thread to calculate the biquad coefficients.

Hi knuisje,

Thank you for answer. As I understand, final Q(p) must be 0.5-0.7? and F(p) as lower as better? Can you please give some example with it(with calculated biquad's), maybe I do not really understand this. Thank you in advance.

Kamikaze,

please read the article linked in my previous post on how the Linkwitz transform works.

Ok, I think all done.

and xls calculations

p.s. can't attach image. here is the link rghost.ru/2624222

I added some tabs for LPF, HPF, BPF and APF calculations based on the cookbook formulas. Also included are the coefficients for a RIAA correction.

Edit: Added are the remaining cookbook filters (BPF1&2, notch, PeakingEQ, lowshelf, highshelf). Also added approximation plots of the phase and group delay for the APF.