How low for bass

[gmc]

I use my HT for 95% movies. I have a sono tube sub I built probably 12 years ago it 120L 12" driver tuned down around 18.Sounds really good.I was wondering how low these IB subs go and are they ideal for movies. I have a room 17x12. At the front of my room is my tv and speakers and sub in the right corner.This is a fake wall i built so i could have all my wiring behind it for all my equipment to make my wife happy.So the space behind the wall is 17x2feet deep x8 feet tall,about 270sq "7645liters" .I only have room for 2 drivers at the right where my sono tube is now.Does this sound like it could work and if so what could I expect.Thanks so much.
I'm getting the itch to build something again,
oh where my stereo receiver is there is some open space between the two rooms.Not sure if that matters

what about 2 of these www.parts-express.com/dayton-audio-ib385-8-15-infinite-baffle-subwoofer--295-455

[ThomasW]

IB subs are without equal for either HT or music.

Per the FAQ their output is limited by excursion so you want as much radiating area as you can afford.

I strongly recommend something like stereointegrity.com/product/ht18-18-subwoofer/ as opposed to the 15"s from PE

The space for the IB rearwave must be sealed/airtight, and you'll need to line it with fiberglass