I think the idea is a terrible waste of the excellent JTR subs. The JTR subs can do it all - and better. You cannot escape the compression that will occur with the DD-15 at the mid to upper range of the T12's output. There is no bandpass that will avoid this reality. If you wanted to highpass the DD-15 and use it at a much reduced gain as a filler sub to improve FR ala Geddes, then maybe. But a pair of Captivators will make the DD-15 irrelevant and simply hamper your system headroom.
Sell the DD15 and put those funds towards the JTR's.
Of course, that's just my 2$
Sent from my Galaxy Nexus using Tapatalk 2
I agree with you! I have tried it both ways and the best impact with audio and bass is running speakers small and let the subs carry the bass load. Dual subs is good, Triple is better, and Quads are insane.