Considering Living Room In-Wall Subwoofers

[Peter Loeser]

We're getting ready to move into a new house (new construction) and while I wait for all of my HT gear to come out of storage I'm constructing our living room setup. This is where we will probably do the majority of our TV watching, so good audio is essential for me, but maximum WAF is also essential. There's a large cavity behind the fireplace stone which I'd like to use as an effective sub enclosure or IB.

Living Room TV

• Peter Loeser
• Aug 1, 2017

The fireplace is gas, so it really only takes up the space directly behind the opening you see. The rest is just a big cavity. There will be base cabinets on either side of the fire place, plus some shelving above them. My thought is to use the side walls (facing away from the fireplace) as baffles for a sub or subs (maybe one on each side) to keep things looking nice and clean. I guess my first question is, what type of driver should I go for? I have found a handful of in-wall specific subs, designed to secure themselves to a cutout in the sheetrock. Anyone have experience with those, and any thoughts on how close they would perform to a raw driver in a custom built baffle? I assume the purpose built in-wall subs are simplest to install, but I only want to do this once, and don't want to regret my choice once it's all put together.

Also, how much bracing should I plan to do behind the sheetrock to keep it from sounding overly boomy?

My goal in terms of performance is to get good depth and clarity, but I don't need max SPL capability. Looking for a solid foundation that blends well for casual listening/viewing, but has enough left in the tank when called upon to perform.

I guess I should add that I should be able to accomodate pretty much any driver size, though I'm not looking to put in a bunch of 18's or anything crazy. Budget is flexible but I'd like to keep it below $1000 including amplification.

 

[Peter Loeser]

So, a brief look at pricing tells me I can do this way cheaper by using raw drivers and constructing my own mounting/bracing. What's next? Is there any calculation to do for something like this or is the volume big enough that I can just pop the drivers in and add EQ to taste?

 

[Tonto]

You are in the ideal situation. You can build large box's which open into the room. I'm always partial to folding horn designs. So much bass for such little input. I can see you building 2 box's behind the fireplace & going into the attic and routing them to exit the ceiling on each side of the fireplace. It would rock!!!

 

[Peter Loeser]

That's one decision to make. Use the structure itself as the enclosure (probably easier) or build a separate enclosure inside the cavity of the walls (more challenging since I'd have to do it piece by piece and probably heavier to support). The space above is finished so I can't go up and over, and would prefer not to cut holes in the ceiling. I can have them exit the side walls though, and put grills over them. Once the shelving is up I'm thinking they'd barely be noticeable. Based on rough calculations the volume inside the walls is about 100 cu ft.

Anyone willing to model it for me? Let's say two Dayton 12" drivers with a Dayton SA1000. I'm certainly open to other suggestions in terms of woofers and/or amp. I think I have a partially damaged SA1000 though, which might be worth fixing if I can put it to use. I could back the sheetrock with MDF bracing, dynamat, pink fluffy, or something along those lines.

Now that I think about it, I have room to expand into the basement as well, since that will be the mechanical room, closed off from the finished portion of the basement.

The wheels are turning...

 

[Peter Loeser]

Ok, time for some sketches. The more I looked into mounting the drivers flush and using the wall as a baffle the more concerned I got about bracing and vibration. So now I'm thinking about doing a monifold with two opposed drivers to try to cancel as much of the vibration in the wall as possible. Here's a quick view from above. I think the spacing to the back wall would be tight enough that I'd need to have the basket inside the manifold, so I could potentially do a push-pull design. The manifold opening into the room would be about 12" wide by 18" tall. I would frame around the opening and add any bracing needed to support the weight of the sub. Thoughts?

IB Manifold

• Peter Loeser
• Aug 2, 2017

Additional questions... do I need to choose a driver design specifically for IB application? What parameter values should I be looking at?

 

[Peter Loeser]

Starting a list of possible drivers, and contiuing to search. I'm looking at 12" for size/weight/cost. I'd like to keep the cost per driver at about $200 or less, especially if I end up with 4 of them. I can't find many IB specific drivers outside automotive applications. I guess I'm generally looking for low Fs with Xmax over 11mm or so. I've read conflicting info regarding Qts for an IB sub. Some say 0.7 or higher, others say it doesn't matter much. I can add some EQ/boost if needed but again, I'm not looking to go crazy in this room. Yet, at least...

JL Audio 12W1v3
Size 12 -inch
Impedance 2 ohms
Cone Material Mica-filled polypropylene
Surround Material Rubber
Ideal Sealed Box Volume (cubic feet) 1.152
Ideal Ported Box Volume (cubic feet) 1.652
Port diameter (inches) N/A
Port length (inches) N/A
Free-Air No
Dual Voice Coil No
Sensitivity 85.9 dB at 1 watt
Frequency Response 22 - 200 Hz
RMS Power Range (Watts) 75-300
Peak Power Handling (Watts) 600
Top Mount Depth (inches) 5 7/16
Bottom Mount Depth (inches) N/A
Cutout Diameter or Length (inches) 10 15/16
Vas (liters) 72.04
Fs (Hz) 26.55
Qts 0.521
Xmax (millimeters) 11.4


Dayton RSS315HFA
Nominal Diameter12"
Power Handling (RMS)400 Watts
Power Handling (max)700 Watts
Impedance8 ohms
Frequency Response25 to 1,500 Hz
Sensitivity85.7 dB 2.83V/1m
Voice Coil Diameter2.58"
Thiele-Small Parameters
Resonant Frequency (Fs)22.2 Hz
DC Resistance (Re)6.5 ohms
Voice Coil Inductance (Le)1.56 mH
Mechanical Q (Qms)2.50
Electromagnetic Q (Qes)0.54
Total Q (Qts)0.45
Compliance Equivalent Volume (Vas)3.43 ft.³
Mechanical Compliance of Suspension (Cms)0.27 mm/N
BL Product (BL)18 Tm
Diaphragm Mass Inc. Airload (Mms)194g
Maximum Linear Excursion (Xmax)14.3 mm
Surface Area of Cone (Sd)506.7 cm²

Eminence Lab 12C
Nominal Diameter12"
Power Handling (RMS)500 Watts
Power Handling (max)1000 Watts
Impedance4 ohms
Frequency Response25 to 120 Hz
Sensitivity88.9 dB 1W/1m
Voice Coil Diameter2.5"
Magnet Weight160 oz.
Thiele-Small Parameters
Resonant Frequency (Fs)23 Hz
DC Resistance (Re)3.11 ohms
Voice Coil Inductance (Le)1.09 mH
Mechanical Q (Qms)11.70
Electromagnetic Q (Qes)0.34
Total Q (Qts)0.33
Compliance Equivalent Volume (Vas)4.53 ft.³
Mechanical Compliance of Suspension (Cms)0.36 mm/N
BL Product (BL)13.36 Tm
Diaphragm Mass Inc. Airload (Mms)136g
Maximum Linear Excursion (Xmax)13 mm
Surface Area of Cone (Sd)506.7 cm²

JBL S3-1224
Size 12 -inch
Impedance 2 ohms
Cone Material Polypropylene
Surround Material NBR
Ideal Sealed Box Volume (cubic feet) 0.75
Ideal Ported Box Volume (cubic feet) 2.5
Port diameter (inches) 4
Port length (inches) 11.7
Free-Air Yes
Dual Voice Coil No
Sensitivity 92 dB at 2.83 volts
Frequency Response 25 - 175 Hz
RMS Power Range (Watts) ---
Peak Power Handling (Watts) 1500
Top Mount Depth (inches) 7 1/16
Bottom Mount Depth (inches) N/A
Cutout Diameter or Length (inches) 11 1/16
Vas (liters) 54.65
Fs (Hz) 28.84
Qts 0.47
Xmax (millimeters) 12

 

[Peter Loeser]

Looks like I've been nominated the guinea pig so I'll take a bit of a shot in the dark and hopefully we all learn something. I just pulled the trigger on two Dayton Ultimax 12" subs. Low Fs, lots of linear travel, good power handling, and the price is right.

We're moving into the house this weekend and my to-do list seems to grow daily, but I may try to do some bracing behind the wall this weekend.

 

[Tonto]

Man I wish I'd come back to this thread! It occurred that Electrodynamic should be having his summer sale...

http://stereointegrity.com/product/hs24-24-subwoofer/

1 of these in an IB set up would be all you needed! He has cheaper solutions as well. And a great person to talk to about subs in general. We should see about getting him on the forum.

 

[Todd Anderson]

Peter - Wish I had some wisdom to dish in this realm... but I don't.

Your wife must love you... in-wall subs in the living room!

Congrats on the new house!!

 

[Peter Loeser]

She trusts me when it comes to electronics so she's been very compliant. She's an amazing decorator so the rest of the house is in very good hands.

 

[tripplej]

Always great to have an understanding wife.. You are one lucky guy.

 

[Peter Loeser]

Ultimax 12"

• Peter Loeser
• Aug 8, 2017

 

[tesseract]

Let the fun begin!

 

[DrDyna]

If that was my room, I would build two subs that occupied most of that area on each side. As far as IB, you need loooots of space on the back side of the driver, and usually many multiples are needed to reach comparable output with a standard bass reflex type. 2 12" drivers in an IB would most likely be...underwhelming.

 

[tesseract]

The Dr. is correct. You'd just be getting started with four of those twelves in a manifold. Eight would be better and eight 15" drivers would rule.

 

[Peter Loeser]

Both sides of the fireplace will have cabinets with built-in shelving above. The function of the space also requires that any sub be completely invisible, and I'm thinking IB manifold makes the most sense. The floor behind the stone can be cut out on either side of the actual fire place, so the volume on the back side of the drivers extends down into the basement.

We'll do mostly casual viewing/listening in this room and therefore don't require a system with super high performance. The goal of the subs is to fill in the bottom end for a passive LCR soundbar. I plan to construct these in a way that I could accomodate 8 12" drivers if I decided I needed that much thump, but I don't expect to. Maybe I do find that a number of 15" drivers makes more sense. I think the structure can accomodate that too, and I've certainly got other places I could use the 12s. My point is, the performance benchmark for these is pretty low compared to what it would be for a dedicated theater space.

Another option that is certainly a possibility is to build a sealed or ported enclusure within the fireplace cavity with the driver baffle flush to the wall where I currently plan to have the manifold exit. It wouldn't really change much. I'm not dead set on IB, honestly I've just been curious to build one and see how I liked it. I figured this was a good opportunity to learn.

And trust me, I'm all for eight or more 15" drivers, but if I do a big scale IB it will be in the dedicated theater downstairs, and probably consist of 8-12 18" drivers.

I appreciate the feedback. I've had to take a break from "my" projects and help get boxes unpacked and make the living spaces functional, so it might be a couple weeks yet by the time I have any results.

 

[DrDyna]

Hah, sounds good!

Just wanted to make sure that you manage your expectations with IB. Not trying to talk you into anything crazy, just that output level and extension from IB typically needs lots of big woofers. You'd probably need 4 15s in IB to get the same output level as those 12s will give you in a relatively small vented enclosure.

I tried an IB with TC Sounds epic 12s, and it only took me about 30 minutes before the drivers were back out of the wall and I was patching holes.

 

[Peter Loeser]

I'm starting to lean toward a plan B, along the lines of what some have suggested. By the time I build a manifold and sure up the wall I'm wondering if it wouldn't be easier to get a flat pack cabinet for the 12" driver and mount it between the studs against the inside of the wall. I think it would be relatively easy to brace the back side as well so the weight of the enclosure isn't hanging on the wall itself. That eliminates the mystery of what kind of performance I'll get from the IB setup and makes construction simpler overall.

 

[Tonto]

And external bracing is so much easier to do. And you can place as much as you like without affecting the internal volume.

 

[Peter Loeser]

Well it's been a crazy few weeks to say the least, but I'm gradually picking away at a long list of house projects. I ordered to flat pack sub enclousres for the 12" drivers. My plan is to basically mount them to the studs with supports at the back end, and integrate the baffles into the walls. Basically when I'm done all you'll see is a round grill cover between two shelves on each wall. Looking forward to the look on my wife's face when I cut giant holes in our recently constructed/painted living room walls...(but the real test will be the look on my face the first time I fire up a movie with these bad boys connected) I'll try to post some photos of the demo/construction along the way. Should be fun.

 

[Peter Loeser]

No turning back!

Fireplace 01

• Peter Loeser
• Sep 23, 2017

Who cuts a giant hole in a perfectly good wall anyway?

 

[DrDyna]

There's enough room back there for some 18s...

 

[Peter Loeser]

There's enough room back there for some 18s...

I'd say you're right though the 12s are already paid for. And don't forget I've still got a full theater build to start. Plenty of room for big subs in there if I really get the itch!

 

[Peter Loeser]

Support bracing in place and one flat pack ready for glue.

Fireplace 02

• Peter Loeser
• Sep 23, 2017

Fireplace 03

• Peter Loeser
• Sep 23, 2017

 

[phillihp23]

Congrats on the House. Watching your sub build.