I'm building out my home theater, and unfortunately my ceilings are fairly low. I can just barely fit a 2.35:1 135" screen in, but that gives me about 10" of clearance from the floor to build subs. The good news is I can use the full width of the room -- 11.5 feet, and I could go up to 2-3 feet of depth.

Existing Hardware

• Emotiva XMC-1 Processor with Dirac Live full
• DIYSG HTM-12 for LCR
• DIYSG Volt-10's sealed angled for surrounds
• 2x Dayton Audio RSS390HO-4 15" drivers in a MicroMarty enclosure -- would be nice to reuse the drivers, but don't have to
• Crown XLS 2500 -- Again would be nice to reuse this but if the subs require more power I can either pick up another XLS2500 and bridge them, or upgrade to something more powerful (looking at FP14000 clones)

Design Goals/Considerations

• $1k to $2k budget for materials/drivers/amps
• Room is wired up for stereo subs -- both passive and RCA connections available
• Placement is pretty much locked unfortunately: front of the room, under the screen
• The projector screen wall is an 18" deep false fabric wall, filled top to bottom with fiberglass to absorb bass
• Rear of the room has a 10" high riser that I'll add vents to for bass absorption
• 10" max height for the subwoofer enclosure, 12" if it's really going to improve things though that will mean a smaller screen size
• 11.5' room width -- probably best to aim for 4' to 5' width per sub
• Leaning towards sealed designs for the best group delay (unless this doesn't really matter that much?)
• Aiming for plenty of low-end output, > 100 dB at 15 hz ideally

I've modeled a few different subs in WinISD already and they'll all meet my needs, but I don't know how well they'll actually interact with the room. This list is the design per subwoofer, so overall I'll build a pair of one of these designs.

1. Four 10" drivers per enclosure, sealed Dayton Ultimax UM10-22 - Front facing, max spl is 103 dB at 15 hz, 118 dB at 40 hz
2. Two 15" drivers per enclosure, sealed Dayton RSS390HO-4 - Down firing, max spl is 101 dB at 15 hz, 118 dB at 40 hz
3. Three 15" drivers per enclosure, sealed Dayton RSS390HO-4 - Down firing, max spl is 104 dB at 15 hz, 121 dB at 40 hz
4. Two 18" drivers per enclosure, sealed Dayton Ultimax UM18-22 - Down firing, max spl is 108 dB at 15 hz, 121 dB at 40 hz

The problem with the down-firing options is I can maybe only have 2" of clearance at most from the bottom of the driver to the carpet. This seems like it would muffle output quite a bit. I considered up-firing instead but I have a cat who will undoubtedly walk on top of the subs and I don't know how to protect the drivers well enough.

There is one more option though which would be building the subs into the false wall behind the projector screen in between the L + C, and C + R speakers. I have about 18-19" of width, ~15" of depth, and up to 6-7' of height then. Bonus: the subs don't take up any floor space. If I go with this option, I'd probably go with design #3 of the three 15" drivers per enclosure. (Or 4!) My main concern here was there's no option of messing with subwoofer placement.

Thoughts? Am I putting too my much value in the low group delay and should I just stick with ported subs? If so, would a larger down-firing sub + front facing port work? Is there a design similar to the Danley DTS-10 that might work, but shorter? (Probably using 10" or even 8" subs?)

Go with sealed Um18 up firing. Your cat won't walk them for long once they are playing and the bass hits The Um18 is so durable you cat is not going to hurt it and if they walk on them one or two times when they are playing they will stay away from them after that. Do take a video though. Should be comical

In all seriousness, your cat is not going to hurt the UM18 by walking on it. They are built like a tank and they are not going to hurt the cone or the surround.

There's the Danley TH-SPUD clone which is about 12" tall and produces some serious bass with very little power using two Tang Band W8-740P 8" drivers. You could build a pair if those for about $300 in drivers, $200 in wood, and use your current amp. They one would come out from the wall a little more than "a few feet" though, each one is 45" x 48".

Or if you decide to put them behind the wall you could go with a pair of THTLP subs which are 15"?18"?72" tall. You already have the exact drivers you'd need, and a single one of those can hit 120dB @ 20Hz so a pair would be good for 126dB+, using only a couple hundred watts each. And I've read posts from people getting flat output down to 15-17Hz depending on room gain. Your existing amp would work fine for those too, meaning all you'd need to buy is some wood.

The height under the screen is not linear as you move towards the MLP.....



If you have 12 inches under at the sreen.....by the time you get 3 foot into the room you can be almost 24 inches tall and still not block the screen.......


For our purposes here, the yellow line is important.





EDIT:...oops, forgot to toss my 2 bits in.


I would do 18`s facing the MLP...

That means the result will also be locked in, and it might not be what you want it to be.
If group delay was a real issue there would be no such thing as ported subs, or horns for that matter.

Hah! I can just picture her sleeping in that nice bowl shape of the driver and then being startled awake by some low bass. I'll consider this though, maybe I can find some good material to make a grill out of.

That would probably be doable... I'll do some research on these.


It might not be quite that generous if I'm sitting down but I might cut up some cardboard panels tonight and see how high they can be before blocking off the screen.

It seems like Dirac Live takes group delay into affect though and time aligns all other speakers to compensate. I might be interpreting the results incorrectly, but with my current setup it's adjusted the impulses for all the main speakers to 26 ms later than usual, but barely adjusted the impulses for the subs. It seems like going with sealed designs may improve this across the board and give Dirac a more predictable system to correct.

I don't have Dirac, so I can't comment on what it's doing. However, there's no need to 'correct' for very low frequency group delay, because you can't hear it. Sealed versus ported is based on room size. Smaller rooms have enough cabin gain so that the high F3 of sealed is adequate. Larger rooms don't have much cabin gain, so there ported is usually better.

You only need 20 inches to fit a front facing 18 ....!

Yeah, but gaining that height back from the screen means dropping to 110" diagonally, and I think that'll end up putting the screen frame right in the path of the L/R tweeter horns. (Assuming the diagonal trick doesn't pan out)

I bet 24-30 inches from the front wall, 20 inches is no problem.......20 inches still leaves some room.........I bet with careful planning easily make it 19 inches and with some precision layout about 18.5......


You could always angle the front...either towards the ceiling of towards the floor and gain a couple inches too.......

You can find a lot of info on it here, with build pics and layout schematics. http://www.diyaudio.com/forums/subwo...th-spud-3.html

And here's a really good build thread where he actually models up the Tang Band 740P driver in Hornresp to make sure it'll work before building it: http://wp.volvotreter.de/projects/th...b-tapped-horn/

I also have a 3D Sketchup file that I created to build one, I can send it to you if you'd like (see attached pic).

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