Flaming Oak Cinema - (S)LLT sub design/build

[Cathan]

One more thing. The main speakers are being placed behind the screen wall. The sub needs to be constructed so that it doesn't screw with the main speaker placements. So carving out that red area behind the screen may not work if that is suppose to be floor to ceiling area.

I don't know if it's feasible, but what about something like this where the ports and drivers could be mounted below the screen? (Pardon the crude sketch-up)

[brucek]

I'd be weary to only use a single 10" for two high excursion 18" drivers. I'd use no less than two 8" ports.

Yeah, that does looks better with two 8" ports @ 29.5" in a 1500 litre working volume (tuned to 12Hz).

That would mean he would have to extend the two ports through the driver wall a bit to allow for space behind the ports.

I think it would be easier to not use the middle wall shown and simply build the 1500 litre (52.97cu.ft) (working volume) structure and then the ports would mount fine using the MDF for the flares. He could build it structurally with 2" x 4" 's and then cover it with MDF, with a double front thickness.

Really, really rough (on a napkin) calculation would be about 60" high, 40" wide and 45" deep outside dimension (would realize near the 1500 litres inside with bracing etc, etc). You would have to of course work that out correctly. This is just messing around to give you ideas (and others to refute them).

That would give enough room I would think to mount the two drivers on top of each other and the same for the two ports. It would leave about a 15" in front of the ports to the screen wall - you'd have to work that out to be sure.

Something like this pic below. I'm assuming about 5 feet behind the screen to the wall.

See any real problems with that Steve? Rodney?





brucek

[bpape]

Having the sub box off to that side is not an option - sorry. Those corners are needed for bass absorbtion - not to mention having the ability to have the speakers basically at the edges of the screen. I also don't want any boundaries any closer to the main speakers than necessary to avoid additional SBIR issues.

If the box can be made smaller than the 'room' we originally designed for IB use, that's great. We just need to figure out how to do the porting. IMO, we could do the box down low and behind the wall still - just not as large. That would allow approx 4'5" from wall to cloth wall. Part of the port would stick out in front of the box or the box could be built to be deep enough provided it doesn not intrude with proper main speaker placement.

Bryan

[WillyD]

Maybe I am crazy...but why not use four or more of those $125 15" Brahma-like drivers in such a situation? They need a lot of volume, but he certainly has that.

http://www.soundsolutionsaudio.com/forum/index.php?showtopic=10024

[SteveCallas]

Cathan wrote:

The main speakers are being placed behind the screen wall. The sub needs to be constructed so that it doesn't screw with the main speaker placements. So carving out that red area behind the screen may not work if that is suppose to be floor to ceiling area.

Not a problem, I didn't realize that was a false wall. You are fine with leaving that behind the screen area open and starting from the original wall you planned, just shorten the original length and increase the depth. See attached.

Now on that picture you posted, it leads me to believe you will be using bookshelves for your mains? If that's the case, they will be way, WAY behind in terms of performance compared to the sub. You will be extremely limited on how much of the sub you can put to use before the mains get harsh and distortion-laden. A great sub needs speakers with great midbass, otherwise the mismatch becomes very noticable. Just something to keep in mind.

What is the false wall going to be made of?

[Cathan]

Right now the plan is to use Ascend CMT's. If in the end they are lacking and I once again have a budget it's an easy upgrade. What's more important is to get the bones of the theater correct from the start.

The false wall will hold the screen, and is made of SMX screen material and black GOM.

[bpape]

Is there a reason why the box has to be over on the one side like that? How tall is this box going to be? I'm very concerned with SBIR issues - especially being different from left to right side which will voice the mid/upper bass in the mains quite differently.

If at all possible, it would be nice to keep the box to less than 30" high and make it symmetric to the room left to right. IOW, wider, deeper, shorter, and centered.

Bryan

[Sonnie]

Or maybe do two boxes... one on each side... kinda like Rodny did on his IB makeover?

[brucek]

Is there a reason why the box has to be over on the one side like that? How tall is this box going to be?

That's up to Cathan. I had it about 5' high, but I don't see why you can't have it any height that you want as long as it houses the two 18" drivers and two 8" ports.

it would be nice to keep the box to less than 30" high and make it symmetric to the room left to right. IOW, wider, deeper, shorter, and centered.

Yep, it could be centered. It may not be the best spot to take advantage of room gain, but it would certainly fit in the center.

(In lieu of any direction), if you accepted 1500 litres of working volume tuned to 12Hz, using two SS RL-P18 D2 drivers and two 8" ports @ 29.5" in length, then (a rough) size of ~30" (Height) x ~50" (Deep) x ~72" (Wide) would be the required for 52.97 cu.ft. (1500 litres) volume. You'd have to account for framing thickness and thickness of panels and bracing and ports and driver volumes, so that you obtain a final interier working volume of 1500 litres (if that's what Cathan wants).

Really rough idea of that below..... You have to get a general idea of what's wanted first and then details would come from that.



brucek

[Cathan]

That's helpful. Thanks, Bruce.