[jhm731]

Built some frames like the ones picture below a couple of years ago. Tried them with some Audio Nirvana 'Super 8 ALNICO drivers, but the results were poor.



Any recommendations for other 8" drivers to try? Add a woofer?

[jparkhur]

Tang Band 1808

Dayton Audio 8 FR

Both are good and cheaper. 

[jparkhur]

[Poultrygeist]

Wild Burro Audio Lab Betsy's. But you'll need some helper woofers.

[frperdurabo]

Helper woofer that's 10db (or more) efficient than the main driver.  This paper will explain a lot; I just built the system he describes, and bass response is excellent.

http://www.quarter-wave.com/OBs/OB_Design.pdf

ETA: you can, of course, pad the main FR driver down as much as you need - the important thing is to compensate for baffle step loss.

[bladesmith]

http://www.audiocircle.com/index.php?action=gallery;area=browse;image=20433

Scott F has an OB set simular to your design, I think he uses Lowthers.

They look sweet.

[Poultrygeist]

Helper woofer that's 10db (or more) efficient than the main driver. 

If you bi-amp it's not an issue.