Dear Andy, Wayne with interest I followed your discussion about Piezo filtering. Perhaps you could help me out with the following: I would try to add a Piezo to a Tannoy dual-concentric speaker design. To add some brilliance. The objective however is to use a 6 db. per Octave filter with the cut off starting somewhere at 20 khz. (To not intefere with the idee of the Tannoy principle of superior Phase carateristics by using a point source). Yust adding some upper brilliance! Could you guys help me out with the values of the C's and R's? B.t.w if you don't mind I would like to post your reply in the Tannoy forum.