Dayton RSS315HF-4 12" Reference HF Subwoofer 4 Ohm

Built 18"x48" sonosub with 6" port tuned to 19Hz powered by PE 240W plate amp. Sounds fantastic in my HT. Total build price was just over $300 and pretty simple if you have a plunge router. Can easily make you're own circle jig. This was so simple and cheap, I might have to make a second one for total overkill.

I bought two and put them in a pair of 35 year old sealed boxes each of which originally had a set of 4 Jantzen electrostatics and a 12" driver. I had removed the ES drivers and covered over the openings. The new 12" drivers fit in perfectly, even the mounting holes. The sound is deep and clean, with no doubling over at high volumes. They seem to improve as time goes buy. I found them best positioned in a corner, one on top of the other, and each facing down an opposite wall. I run the subwoofer output from my Yamaha receiver to an old Onkyo receiver with 2 x 100 W, which is now the subwoofer amp. The new drivers handle everything below about 100 Hz, which is the best crossover frequency for subs because it eliminates the Doppler distortion in the lower midrange. Because of the huge magnet and stiff suspension I believe they can be mounted in almost anything. The enclosure should has only a small effect on performance.

Built a 3.3 cu.ft. box for it, tuned to it's free air resonance. Measures flat in my largish room to below 20Hz. Very musical bass, great LFE. I was leaning toward getting the Titanic, but I'm glad I chose this one instead. It's really well built, very stout.
Literally shakes the room like an earthquake, and it's very efficient. At the moment I'm only running 100W into it. I can't imagine what it will do if run at it's rated power, but I intend to find out!