Originally Posted by smokarz
so which sub(s) would you suggest as a better match for my mains, in terms of output capability?
Well, when fed 100 watts, your mains can do a legit 115 dB each at a meter, groundplane, and you have a pair. Remember - your mains have 15" bass drivers, and you're looking for a sub to augment that, and reproduce what they can't. In a grossly-oversimplified nutshell, you'd want a sub or subs that can add 10 dB to that number.
That's 125 dB. Since we're talking about a sub, let's eliminate anything that can't reproduce 25 Hz at 125 dB/1M groundplane.
Wow, the list just got really short.
This takes us to some pretty elite territory for a single sub. A DTS-10 can't manage that in a groundplane setting, the TH-50 gets close. The TH-221 can do it. I'm sure there are a few others that can as well (JTR Orbit Shifter LF comes to mind).
You can get there via DIY stuff too. Many ways to accomplish this, the easiest is a whole lot of 15s and a whole lot of power. In a groundplane setting, multiple THTs or similar horns could get there, two would be a good start. I have the offset-diver horn for the MFW underway, but that won't get there either, according to the simulations, 115 dB is about all it can do in a 2pi setting, so you'd need more than 2.
Thankfully, you listen indoors, in a room with corners. Boundary loading and room gain will help things considerably. If you can corner load your subs into corners that are actually effective acoustically, you can gain up to 10 dB of "free" output. That helps a lot.
A single THT or similar, in an effective corner will get you close, as will the MFW horn I'm working on. The DTS-10 in a corner will also get close. These cabinets are all large, to say the least. I have a smaller tapped horn design I am working on that will perform in this league (according to the models - again - still pixels at this stage - not plywood yet). It is about 12 cubic feet, with a ~2-square-foot footprint. A pair of these corner loaded will definitely do the trick, and will take up a lot less space in the room than the other options.
How loud do you really listen? If things are cranked wide open and you're shaking stuff off the walls, the subs had better be overdesigned and overbuilt. If you're listening at background levels, maybe not so much.