Hi Phil - here's Carl's note from K-forum
Re: trying to build new K's - can it be done? klam question
Author: Carl
Date: 01-07-06 03:24
Sealed Clam: System Q target for .7 , size back volume accordingly. High Qts drivers can compromise the design. Remember, if an optimum sized sealed box , systen Q = .7, is made bigger, f3 raises. Remember, the
addition of the K-Coupler raises the Q, lowers fs. You can test the speaker in air, and with the coupler in place to measure these effects. Then finalize the back volume for a system Q of .7 for the lowest f3. Add a Leach transform set to get the low cutoff you want. Without the transform, we were able to get a good dynamic response 60hz. We found coupler lengths as short as 26 inches and back volumes 1 to 1.75 cu ft to work well. The taper we liked best for the 12 was a Trax recommended by Ken. The length affects f3 more than the width. However, the projection pattern changes also with length so for home use shorter lengths might be more practical.