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post #1 of 12 Old 07-08-2019, 02:09 PM - Thread Starter
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Building a boxed sub into a wall—should I do it?

Hi all, before I start tearing into my walls, I was wondering if y’all could give me some opinions about building subs into walls. Currently I have 2 subs (SVS SB12-NSD) in a dedicated, enclosed home theater where each are located in the middle of the wall, on either side of the seating area. The room is about 2,300 sq ft—13’ x 18’ x 10’, rectangular shaped. While this is good for sound, it’s not good for foot traffic. There’s only about 8” of space between the subs and the chairs so you always have to step around the subs to get to the front row of seats.

I am considering cutting holes in each side of the theater and creating a recessed box that’s big enough to fit the subs (and maybe leaving extra room to accommodate future sub upgrades, like the Monoprice Monolith 12s that are currently on sale). I have plenty of room to expand the room outwards as each side of the theater is unfinished attic.

My question is: would having the subs in these recessed spaces audibly hurt sound quality? If only minimal loss of fidelity, how would y’all recommend I build that space out? Regularly spaced 2x4s and 2 layers of dry wall? Maybe stacked 2x4s to increase reflections inside the sub enclosure?

The room is used for 90% movies, 10% music. I’d love any opinions! Thanks!
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post #2 of 12 Old 07-09-2019, 06:03 AM - Thread Starter
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Originally Posted by John M Miller View Post
Hi all, before I start tearing into my walls, I was wondering if y’all could give me some opinions about building subs into walls. Currently I have 2 subs (SVS SB12-NSD) in a dedicated, enclosed home theater where each are located in the middle of the wall, on either side of the seating area. The room is about 2,300 sq ft—13’ x 18’ x 10’, rectangular shaped. While this is good for sound, it’s not good for foot traffic. There’s only about 8” of space between the subs and the chairs so you always have to step around the subs to get to the front row of seats.

I am considering cutting holes in each side of the theater and creating a recessed box that’s big enough to fit the subs (and maybe leaving extra room to accommodate future sub upgrades, like the Monoprice Monolith 12s that are currently on sale). I have plenty of room to expand the room outwards as each side of the theater is unfinished attic.

My question is: would having the subs in these recessed spaces audibly hurt sound quality? If only minimal loss of fidelity, how would y’all recommend I build that space out? Regularly spaced 2x4s and 2 layers of dry wall? Maybe stacked 2x4s to increase reflections inside the sub enclosure?

The room is used for 90% movies, 10% music. I’d love any opinions! Thanks!
Bump. Anyone?
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post #3 of 12 Old 07-09-2019, 06:12 AM
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I recommend looking into a DIY Infinite Baffle setup. I've never done one, but it seems like a great idea for those who have unfinished space surrounding their theater and want to get subs out of the floor - you seem like a perfect candidate.



My guess is you could sell your existing subs to cover the cost and end up with a better performing product then what you currently have without having any subs taking up floorspace in your room. Head one forum down (DIY) and start researching infinite baffle sub setups, the experts over there will guide and help you.

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post #4 of 12 Old 07-09-2019, 06:29 AM
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Heyo,

For the sound quality I recommend two possible approaches:

1) Build the area oversize in case you ever want to upgrade, and stuff around the sub with fluffy insulation (like Owens Corning R30 or something, the pink stuff). This will reduce possible SBIR issues from the sub to the sides of the wall. Also reduce possible diffraction noise.

2) Build it just large enough to fit the sub, this will cause a large baffle wall effect.

Of those I'd go for option 1. Either shouldn't affect the sound terribly. Are you running an AVR with decent bass eq? If so it should be able to easily compensate for either option. It would be way worse if you were embedding speakers due to baffle step compensation, but even then manageable with EQ.

As for how to build, @BIGmouthinDC might have more ideas. Since you'll need to cut your wall studs for this you need to start worrying about structure. You're going to have to frame around it similar to what's done with windows. King stud, jack stud, sil plate, header, and cripple studs. You can google "window framing" to get an idea, but look up the code in your area. Also make sure you know where power cables are so you don't cut them. The usual safety precautions.

Is the theater soundproofed? If so you're going to have to build a fully decoupled backer box to go in the hole. If not, then a box out of 3/4 or thicker mdf, slid into the hole, should suffice. The thicker and more rigid the better. Then nail it to the studs and trim it out as you see fit.

Edit: For this you may get better feedback in the Dedicated Theater Design and Construction section of the forum.
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post #5 of 12 Old 07-09-2019, 06:35 AM
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Quote:
Originally Posted by Mocs123 View Post
I recommend looking into a DIY Infinite Baffle setup. I've never done one, but it seems like a great idea for those who have unfinished space surrounding their theater and want to get subs out of the floor - you seem like a perfect candidate.



My guess is you could sell your existing subs to cover the cost and end up with a better performing product then what you currently have without having any subs taking up floorspace in your room. Head one forum down (DIY) and start researching infinite baffle sub setups, the experts over there will guide and help you.
I agree, I just finished mine up and I love it. It wouldn't be any more work than what you plan on doing. I did four 18s, an NX6000D and all the materials for less than $2K. The extension is unbelievable. Here's a couple pics, let me know if you have any questions.


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post #6 of 12 Old 07-09-2019, 07:13 AM
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Quote:
Originally Posted by lloyd401 View Post
I agree, I just finished mine up and I love it. It wouldn't be any more work than what you plan on doing. I did four 18s, an NX6000D and all the materials for less than $2K. The extension is unbelievable. Here's a couple pics, let me know if you have any questions.


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looks great!. Do you get any vibrations through the framing?

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post #7 of 12 Old 07-09-2019, 07:19 AM
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Quote:
Originally Posted by John M Miller View Post
Hi all, before I start tearing into my walls, I was wondering if y’all could give me some opinions about building subs into walls. Currently I have 2 subs (SVS SB12-NSD) in a dedicated, enclosed home theater where each are located in the middle of the wall, on either side of the seating area. The room is about 2,300 sq ft—13’ x 18’ x 10’, rectangular shaped. While this is good for sound, it’s not good for foot traffic. There’s only about 8” of space between the subs and the chairs so you always have to step around the subs to get to the front row of seats.

I am considering cutting holes in each side of the theater and creating a recessed box that’s big enough to fit the subs (and maybe leaving extra room to accommodate future sub upgrades, like the Monoprice Monolith 12s that are currently on sale). I have plenty of room to expand the room outwards as each side of the theater is unfinished attic.

My question is: would having the subs in these recessed spaces audibly hurt sound quality? If only minimal loss of fidelity, how would y’all recommend I build that space out? Regularly spaced 2x4s and 2 layers of dry wall? Maybe stacked 2x4s to increase reflections inside the sub enclosure?

The room is used for 90% movies, 10% music. I’d love any opinions! Thanks!
I installed an in wall sub and still have it in play, but keep it turned down a bit. it rattled the walls when I turned it up. I suggest looking into techniques to isolate the enclosure from the framing. And along the lines as a previous suggestion re: insulation, I would look into "Mass Loaded Vinyl" there is a product called "acoustiblok" ( a specific brand of MLV). 1/8" of MLV is supposed to be equal to a 12" concrete wall for sound mitigation!

I put a layer of MLV around my in wall sub and it helped a bit, but not enough to be my only sub. The reason I still have it in the system is that I don't want to hassle with repairing the drywall.

Main: Sony XBR75900E, Denon AVR-x4400, Denon POA-5200 (L/R(a) Goldenear supersat 60, (b)FW Boston acoustic Bravo 2. C Goldenear supersat 60C,
SSR DIYSG Volt 6v2. RSS Volt 6, Atmos(.4) Boston acoustics soundware XS
HSU research ULS -15, Episode ES-IW-Dual 8 / Monitor audio IWA 250 amp 2nd Rm: Visio E55, Denon avr730H, Boston Acoustics CR8, cr400 sub.
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post #8 of 12 Old 07-09-2019, 08:11 AM
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looks great!. Do you get any vibrations through the framing?
Of course but only when it's really cranked up. The manifold does a good job of cancelling some of the vibrations but it's still 4 high excursion 18s. I keep my expectations in check.
I do plan on adding some support to the structure this fall when it cools off some.

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post #9 of 12 Old 07-09-2019, 11:41 AM
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Originally Posted by mushroommunk View Post
1) Build the area oversize in case you ever want to upgrade, and stuff around the sub with fluffy insulation (like Owens Corning R30 or something, the pink stuff). This will reduce possible SBIR issues from the sub to the sides of the wall. Also reduce possible diffraction noise.

2) Build it just large enough to fit the sub, this will cause a large baffle wall effect.
Neither of those phenomena are going to affect a subwoofer. The wavelengths are way too long.
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post #10 of 12 Old 07-09-2019, 11:54 AM
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Quote:
Originally Posted by John M Miller View Post
My question is: would having the subs in these recessed spaces audibly hurt sound quality? If only minimal loss of fidelity, how would y’all recommend I build that space out? Regularly spaced 2x4s and 2 layers of dry wall? Maybe stacked 2x4s to increase reflections inside the sub enclosure?
It shouldn't have an appreciable negligible effect on sound quality. Build the recessed spaces the same way the rest of the wall is built.
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post #11 of 12 Old 07-09-2019, 12:51 PM
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If you are shoving a powered sub into a wall box, be sure there is a way for the heat to escape. Otherwise, it'll be toast the first time you crank it up for any length of time. IB makes a lot more sense to me, with a rack-mounted amp.

It's a VIRTUAL channel unless stated otherwise.

Last edited by RayGuy; 07-09-2019 at 08:09 PM.
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post #12 of 12 Old 07-10-2019, 06:57 AM - Thread Starter
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Originally Posted by lloyd401 View Post
I agree, I just finished mine up and I love it. It wouldn't be any more work than what you plan on doing. I did four 18s, an NX6000D and all the materials for less than $2K. The extension is unbelievable. Here's a couple pics, let me know if you have any questions.


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Thanks for all the replies, this was all very helpful!

I had heard of open baffle speakers before, but not IB subs, so that was eye-opening to say the least. I spent quite a few hours investigating this option, and I think that’s my new plan of action. According to my calculations, it’ll cost $300 less to do two 18” Fi IB3 v2 subs (with amp and supplies) in a single manifold than it would cost to buy two boxed Monolith 12s. And that’s for 18” subs instead of 12” subs, a massive difference.

I only have one concern, and that is losing the benefits of dual subs. Or at least I’m assuming that’s the case because the 18s would be in a single manifold. Would I lose the even room response (fewer nulls) with two boxed subs on different sides of the room by having the IB subs in one location? Unfortunately, if I’m going to do IB subs I have to keep them both on the left side of my theater as my son’s bedroom is on the other side of the attic on the right side of the theater.

Another question I have is which amp I should use. In my research Behringer DSP amps seem like a popular choice because they have DSP. I’m looking at the Behringer iNuke NU3000DSP. Any other suggestions?

Finally, are there quick and dirty ways of dialing this sub in? Is buying a high quality microphone and running REW necessary? I have a Denon X4300H receiver which obviously has Audyssey, but how low/accurately can Audyssey calibrate? It seems as though calibration under 20Hz is less important than above that threshold so maybe I’m fine with just running Audyssey? Would I also have to buy an equalizer in addition to a DSP amp? If so, which one would I need?

Thanks again! This forum is awesome!
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