Jim, at what frequencies are HT3 owners tending to cross-over your various sub designs?
I know of no HT3 owners using a sub with them (although there may well be, I am just not aware of it). I am currently completing two 15" subs and will let you know as soon as I finish them and test them with a pair of HT3's.
How low does the 15" sub go?
Again, it is a little premature to say for certain. There are two factors involved here. First, the size of the cabinet and whether or not it is ported. These first subs will be sealed, so they will not go as low as a ported design. Ported subs will go lower, but the cabinet will be much larger.
The second factor is the EQ capabilities of the plate amp. These first units will use ADA plate amps
. They cross as low as 35 Hz (which is probably what would be used with HT3's) and have dual bands of parametric EQ (to both deal with room issues and extend the response). I would imagine these would play to about 20Hz (or slightly lower) with EQ and could move a good deal of air. Again, a much larger vented cabinet will obviously play lower.
Subs using the 15" TC drivers can be designed to play into the mid-teens or even lower. But the cabinet size, number of drivers, plate amp power and EQ requirements would all have to be taken into consideration. The lower you go, the larger the cabinet required, the greater the number of drivers and the more power required. That is why, to date, I have approached each subwoofer project as a one-of-a-kind proposition (these subs may be an exception as I may offer them as a standard product).