Let me begin by saying I don't want to spend more than $250 for the speaker.
I going to build a sub enclosure to supplement a set of psudo-L100s I'm building. My initial thought was to use a pair of Infinity Kappa 12.1D subs. However, on reflection I'd like to go JBL and all things being equal vintage would be nice. I'm now considering using a single 15" JBL. I'm eager to hear your thoughts as to best speaker (within my budget) and cabinet design. Don