I hope that this is OK with Frank. I wish to post here for my AVA friends before I post in the classifieds or A'gon.
With the gracious assistance of Jeff Bagley, I built (4) subwoofers. They each have (1) 15" Dayton RSS390HF-4 driver and (2) CSS APR15 passive radiators, each of the radiators damped with 1000 grams of weight, in a 5.5 c.f. cabinet constructed of 3/4 " MDF laminated to 3/4" Baltic Birch plywood, driven by a plate amp.
My difficulty is integrating the subwoofers into my system. I purchased a Behringer DCX, DEQ, and Feedback destroyer, but I was not sufficiently educated about the difficulties connecting balanced outputs to unbalanced inputs and vice-versa, and rather than purchase additional active transformers for the inputs and outputs, I am considering a simpler option, thanks to Ogogliby, and buying a Velodyne SMS-1 active crossover, which includes a room measurement mic.
Consequently, I wish to offer, at 85% of my (rock bottom) cost, the DCX ($299.00-15%=$255.00, for example), the DEQ, the Feedback Destroyer, which I believe Terry @ the Salk Circle uses, and (6) 6' XLR interconnects, (6) XLR to RCA adapters, a Behringer room measurement mic, a 25' mic cable, and a Behringer fantom power supply.
These products were used one time, gingerly, and are otherwise brand new. If anyone is interested, please PM me to discuss prices, shipping, etc. I also intend to sell my Insight DAC/preamp combination with phono board and remote volume control but will submit a separate post.