I do not have a home theatre set up but do have a fairly good quality 2 channel stereo system in which I have been using a sub woofer for some time to reproduce the lower bass. I listen to many types of music including classical so the sub woofer is used to enhance the music. It is integrated properly and not set to be bass heavy or to give exaggerated bass. I originally owned a BK Electric XLS200 that was very good but not really powerful enough for my room that is approx. 7m x 4 m. Next I purchased a B&W ASW610 that I expected great things from but again it did not quite have the power required for my room. I changed the driver in the B&W to an RE Audio SR10 and got quite an improvement but then found the B&W amplifier was limiting things so changed this to a BK Electric BSBPV500 watt model. This amplifier is quoted at 500wattsRMS into 4 ohms and 1000 watts peak. So then I had quite a good driver and an excellent amplifier therefore my next step was to build a new sub woofer cabinet in which I would house a really great driver and after considerable investigation I decided on a Fi SSD12 dual 2 ohm unit. As a matter of interest the amplifier is in its own housing in my equipment rack, I feel is a better way of doing things and also means only one lead is required to the sub woofer cabinet. I have again gone for a sealed unit for two reasons the first being that I am looking for sound quality and the second is that I do not have space for a larger cabinet. Whilst investigating the Fi SSD12 here I discovered that there is a high Qts version to enhance the performance of the driver in a sealed cabinet and that is the version that I am using. Apparently the standard Qts version is best for ported cabinets. I purchased the driver from here and also discovered that there is an HT spec available for this model and of course that is what I have gone for. In the words of Am Singh the owner of the company where I purchased the Fi unit his description of the HT spec is as follows: “The HT Spec is a slightly different grade of spiders. The Car Audio drivers must be more abuse tolerant, this comes at a cost of sound quality. We've actually had Car Audio customers use this option where they are not pushing the driver to the limits mechanically. In a home audio or home theatre environment this spec optimises the drivers performance.” So in case there are any doubters out there the Fi SSD12 is entirely suitable for home use and sealed cabinets also. Am Singh is a great guy to deal with and really knows his stuff. I told him that I wanted to build the cabinet while awaiting delivery of the driver and he even sent me free of charge an old chassis to get all the drilling and cut out details from. You cannot beat that for service. On to the build, the cabinet is forward firing. As stated earlier I do not have space for a large cabinet so after all displacements (driver, battens and braces etc) my cabinet is only 1.1 cu ft (31.15 litres)sealed and is not damped. Outside dimensions are 481mm wide x 362mm high x346mm deep. The driver is recessed 36mm so that there are no protrusions past the front panel. This means that the front panel is 54mm thick including the baffle. Walls are 18mm MDF all joints have 21mm x 21mm battens to give strengthand stop leakage and there is also some bracing. Battens and braces were drilled and then screwed to the inside of the MDF panels so there are no screwholes on the outside to fill. I have made many stereo speaker cabinets over the years and have always used battens to fix panels together. In the early days speakers were fitted behind the baffle (just given my age away) and so back panels had to be removable. Using battens means you can do this provided you use a sealing strip in lieu of glue. I also use PVA glue and plenty of it to stop leaks. The driver is fixed to the baffle with M5 self colour socket cap head screws (Allen bolts) with insert nuts on the rear of the baffle, I'm not a great fan of T nuts as they often fall out. Once finished any dents were filled and raw edges coated with PVA glue then the cabinet was rubbed down well finishing with 400 gradepaper. Next a coat of black spray can primer, rubbed down again and finished with a few coats of spray can black gloss. In the past I have veneered cabinets and varnished them but this time I fancied a black gloss finish which I think is easiest because if you use say a satin finish and it does not go to well when you compound it down you end up with gloss anyway. How does it sound, well in my opinion just right, clean,clear and musical with good speed exactly what I was looking for. Unless I move to a larger house I don't think I will be updating again unless of course it wears out. The crossover from the bookshelf speakers is at approx. 70Hz and response is almost flat to 30Hz. The BK Electric amplifier gives 6db boost at25Hz which of course helps give the flat response. This 6db boost is available at different frequencies(15Hz, 20Hz, 25Hz, 30Hz and By Pass) but I find setting it at 25Hz is about right for me. Total cost was about £ 600 for the BK Electric amplifier, Fi driver and cabinet materials and I would imagine that if a ready made unit was purchased it would cost considerably more to equal the performance.