Dual RL-p15 D2 LLT Sub Project...

**Sonnie** · **02-12-07, 04:54 PM**

My IB idea wasted away (actually Rodny took it all from me)... but I'm still wanting to play, so the next idea is a dual 15 LLT design. I believe I can follow through with this because it won't require near as much work as the IB I was planning.

Obviously there is some fun factor to this, which is probably much of the driving force behind the project, but there is also somewhat of an objective I'd like to meet at the same time.

My room is 11.5' wide x 19.5' deep x 8' high.... ~1800ft^3. If you check out my HT construction pages you'll see it is built extremely solid, tight and well sealed.

Currently I have a pair of SVS PB12-Plus/2 subs in the room, both tuned to 16Hz. Initially I had these up front in symmetrical corners, but I had always dealt with a nasty trough in my response around 30-55Hz… here’s what that looked like:

I tinkered with placement and the best I could do is one of the Plus/2's being located in the rear, behind one of my recliners. For the best response I crossover the rear sub at 60Hz and the front sub at 80Hz... and it sounds like I want it to now…

Here it is filtered:

With this one sub being located where it is... it hinders the full use of the recliner, I actually have to pull the recliner out further from the back wall than the other two recliners. At any rate... the sub just doesn't fit back there and I wanna move it back up front and have my pair of Plus/2's symmetrically located in the front corners.

To over compensate I want to build the dual RL-p15 LLT to place behind the recliners across the back wall. I know I'm crazy

... you don't have to remind me. Can I just do it... thanks! This should take care of the initial problem area I have between 30-55Hz with the dual Plus/2’s up front.

I'll use a pair of SoundSplinters:

RL-p15 D2
Qts: 0.333
Qes: 0.363
Qms: 4.032
Fs: 23.426 Hz
Re: 3.66
Ls: 5.236 mH
Lp: 7.277 mH
Rp: 10.46
Dia: 330 m
(% shift): 23.7 %
Vas: 163.0 L
Mms: 290.9 g
Cms: 158.6 u
Bl: 20.76 T*m
n0: 554.4 m
SPL: 89.43 dB
Sd: 0.0806 m^2
Xmag: 27.4 mm
Xmax: 24.6 mm

This will be paired with a Behringer EP2500 which should bring me to about 650 watts per sub at 4ohms each.

To give you an idea of my listening levels... I measured the SPL in the room from my main listening position at the level I normally listen… about 80 on my Maestro M2. Watching WOTW I was peaking at 115db at the beginning of the movie when the machine first comes out of the ground and starts blasting/frying people. I'm not sure exactly what the bass response is in those scenes, but it vibrates and shakes me pretty good… any louder and it’s just too loud. Anyway... that's just to give you an idea of how loud I listen and the levels I'd like to accomplish... or as close to it as I can get.

In speaking with Stevecallas, it appears I’ll need somewhere around 520 liters / 20ft^3 with a 9” diameter port x 33” long. Rough dimensions will be something like 12" high (excluding the downfiring space) x 16.5" deep x 72" wide/long internal measurements. I believe this is tuned to 14Hz? Although we may try to tune it lower. Stevecallas may correct me on this. The idea is to build it so that it downfires and fits behind the three rear recliners causing no issues with the recliners functioning normally.

I appreciate any and all suggestions, comments, ideas, recommendations… keeping in mind what I would like to accomplish.

I really need someone to help me figure out what it would be best to tune it to, the exact measurements/cuts I’ll need to make, the proper bracing, design, etc.

Thanks!

**Darren** · **02-12-07, 04:54 PM**

What happened to the IB plan?

**Sonnie** · **02-12-07, 05:01 PM**

I got lazy and Rodny got all my stuff... and I really didn't want to fiddle with the attic like I was going to have to do... on top of it creating more possible whole house noise problems via the attic. This project is more in line with something I can manage easier.

**Sonnie** · **02-12-07, 07:08 PM**

Here's a pic of behind the recliners and back wall where the DIY sub will be located...

**SteveCallas** · **02-12-07, 10:04 PM**

The Plus/2 has roughly a 36db/octave rolloff ground plane, you're showing roughly 28db/octave, so about 8db/octave gain. That's pretty good. Room Mode Calculator shows that gain should be starting ~28hz, and that's almost fully realized with the Plus/2. That would work nicely with a very low tune, I'm thinking 13hz - Steve and Ryan's are both tuned ~16.2hz. Can you afford to make it a bit longer, or is 72" it? 570 liters would mate very well and allow you to get away with an 8" port that is ~34" long.

**SteveCallas** · **02-12-07, 10:07 PM**

Woah, wait a second, 12"x16"x72" doesn't get you anywhere near 520 liters?

**Sonnie** · **02-12-07, 10:39 PM**

Yup... I forgot to convert my inches to feet...

I can go up to 92"... but even at 12" x 16" x 92"... that's only about 10.5 cubic feet or 297 liters.

I guess doing a pair of these is not gonna be feasible, unless I make a weird shaped box ... like maybe an L shape with the 12" x 16" x 92" on the bottom opening up into a 24" high x 8" deep x 92" wide/long section on top of the bottom section. That would still give my recliners plenty enough room to function properly and would make the total unit somewhere around 40" tall including the downfiring section.

It really sounds like I probably need to just try one sub and maybe go with EP1500 which should be a lot more power into the one sub... it's rated at 800 watts bridged mono into 8ohms. It's showing 1400 watts into 4ohm bridged mono but that is only at 1KHz... so I don't know the real power rating, but it makes sense it would be at least 800 watts.

**Sonnie** · **02-12-07, 11:16 PM**

Okay... I went back out to the HT room and took some more measurements. Using an old LD player up on its side, it is 16" deep by 17" wide. I could pull it 2" out from the wall for a full 18" in depth and the 17" was the absolute max height before the recliner hit it. I can go up to 96" on the width max.

So internal dimensions could be 12.75" high x 16.5" deep x 94.5" wide.

Using 3/4" MDF:

**SteveCallas** · **02-12-07, 11:37 PM**

Man, seriously, sell the SVS subs and use the newly acquired space to build some nice DIY subs - you'd end up not only ahead on bass capability and quality, but you'd have plenty of dollars left in your pocket as well. The Brotherhood wouldn't steer you wrong

**Sonnie** · **02-12-07, 11:50 PM**

That's not an option... seriously... I like my SVS subs and I'm gonna keep them. They do fine for me except for the size in the rear. I can assure you with my ears, I'll not notice enough quality difference. Sure, I might save a little money, but that's not my objective here.

If you can help with what I've got to work with... I would greatly appreciate it...

**Rodny Alvarez** · **02-13-07, 12:05 AM**

Quote:

Sure, I might save a little money, but that's not my objective here.

money is NOT a problem

Its 3/4" MDF thick enough? I guess a lot of bracing is needed!!

Don't forget you have to count for all the braces inside of the box.

**aceinc** · **02-13-07, 12:25 AM**

I am not sure I follow everything in this thread, but in looking at the photo of your recliner, when in the reclined position it appears to be ~6" from the wall. Since this is a purpose built piece can you build the box the height of the recliner. When looked at from the side it would look like a square with a truncated triangle on top.

You would have a nice 6" shelf that you could glue some knick knack's to when done.

Paul

**SteveCallas** · **02-13-07, 12:54 AM**

Quote:

Sonnie wrote:

If you can help with what I've got to work with... I would greatly appreciate it...

Fine, fine

Well 325 liters is plenty for a single RLp-15. An established design that many have used is 260 effective liters with a 6" diameter port that is 30" long and 700-1000 watts. Use a roundover on the outer layer of MDF at the port opening to create a flare, the larger the roundover bit, the better. 3/4" is common, though you can get up to 1.5", possibly larger. If you are willing to go the extra mile, you can create a flare for the interior port opening by cutting a couple donuts with the same ID as the port and a couple with the same ID as the OD of the port. The larger hole donuts will be glued to the port to meet the end flush, the smaller hole donuts will essentially lengthen the port - put a rounover on these outer donuts and you have an internal flare. This design is for the D2.

Your bracing will be the main variable, but I'd imagine ~300 raw liters would end up being pretty close to 260 effective all said and done.

**Sonnie** · **02-13-07, 01:58 AM**

Actually Paul... you may very well have something there. Although I'm terrible with angle cuts like that ... I can accomplish something similar to what you suggest in a different way. I've been needing more DVD storage space so why not go ahead and build a couple of rows of storage on top of the sub cabinet.

**Sonnie** · **02-13-07, 02:00 AM**

Rodny... what you got on the agenda for Wednesday... we got a really big box to build...

**Chrisbee** · **02-13-07, 03:28 AM**

Paul's sloping panel design will help to break up internal box resonances and should be stronger than a parallel-sided, L-shaped box.

The front to back depth is also rather short in your L-shaped box.

Volume is greater with any chosen length with the sloping panel box than the L-shaped box.

If you can't build it yourself then get help.

Shame about the IB.

**Sonnie** · **02-13-07, 09:40 AM**

I'm sure Rodny can build it, although I'm thinking we could angle it from the bottom all the way to the top.

**aceinc** · **02-13-07, 11:09 AM**

If you take your time, use a skil saw, some scrap wood and a couple of clamps as your guide you should be able to cut the sides out ok. That only leaves the bevel cuts. Not being a carpenter/cabinet maker I would just cut my sides, front, back & top, tack it together, and using some scraps use trial & error to get the bevel cuts right.

Be careful with what you put on top of the sub, you don't want a rattle trap, or things vibrating off.

Paul

**Sonnie** · **02-13-07, 11:27 AM**

I actually did pretty good the last sub box I made for the car... it had an angled front and a strange build to say the least...

**WillyD** · **02-13-07, 12:43 PM**

On a slightly related note..why couldn't you place the drivers along that back wall, so that the rest of the garage area would be the "IB". It looks like it is big enough to me...

**Sonnie** · **02-13-07, 12:46 PM**

Yes... I've considered it, but I don't want the IB backlashing into the garage and creating more noise for the house. I would lose the sound insulation of the room... which is something I worked very hard to accomplish.

**WillyD** · **02-13-07, 12:52 PM**

Gotcha.

**Sonnie** · **02-13-07, 08:12 PM**

Here's what Rodny and I talked about doing today...

We can adjust it a little bit if needed.

**steve nn** · **02-13-07, 09:57 PM**

Hey Sonnie, what a neat project! This isn't going to help matters I know, but there is a calculation for it. What it boils down to is your going to need a 3.25 gap from the top of the base plate to the baffle instead of 2" I'm sure if we put our heads together.. we could figure something out, even though (in my perception) things just got a little more restricted.

**Sonnie** · **02-13-07, 10:17 PM**

3.25" is not a problem at all... we can handle that. I stuck 2" in there just because that's what my PB12-Plus/2's are. I just figured it would be the same. But since we changed it to a front angle... thanks to Paul's suggestion, it gave me plenty of room. I can get more volume if needed... probably up to about 24 cubic feet.

I guess the next steps are:

Making sure we are close enough in the ball park for volume.
Determining what frequency to tune it to.
Port size and length.
Where to install the port (will it fit top to bottom and can it be fired out the bottom center or top center ... or does it need to be out one side... or two ports, one on each side).

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