Thanks
Guys,
Thanks for the helpful suggestions. A mutual friend of Moray n' me has built some BR enclosures for some 18" mid-bass (pro) drivers to match to dh1a compression drivers and Celestion mids in Yorkville Synergy horns (under license from Danley). These enclosures are 7 cu. ft. each, so pretty large in a home environment.
Because I know little about the Karlson enclosures I thought I'd ask. As I understand it the Karlsons have very low distortion and are quite efficient, assuming a suitable driver is used. In this case the the drivers are high efficiency (99dB) and the Qts is 0.34.
Should I choose to go this route in the future I think a Karlson might be THE way to implement a HE mid-bass for use with Synergy horns