http://forums.klipsch.com/forums/p/104791/1057774.aspx#1057774

I've posted in the Technical Questions thread asking for help with a DIY subwoofer. Thought I'd mention this here, too, knowing that some folks in the Sub forum might not browse Technical.

I've got a pair of K-26 subwoofers. These are 12 in subs used in the SW-12 subwoofer which is rated at 28hz to 120 hz. The internal volume of this cab as built by Klipsch is  about 3' and employs a passive radiator.

What we've imagined so far is building cabs of the same size as the SW-12 and using ports instead of passive radiators.

Does this sound like a reasonable plan. One thing I'm wondering is to what frequency should the cab be tuned to accomplish this?

Any help appreciated.

If the SW12 works in a 3cu ft cabinet(make sure you,factor the cabinet walls,amp and brace volume)and the spec ...low extension is at 28Hz you can gues under that volume the ideal tune for a flat resonse would be ~30Hz probably.

Now you can tune lower,but will need a longer port. I would recommend a 4 in diameter port. Flared.

To know how long the port will have to be you should also have the driver's paremeters. There is a Woofer Tester...on PE sold for $99 that can test any bass/sub bass driver and provide you with the basic parameters(when not specified).