Sealed subwoofer in-wall?

[CLong]

Hi everyone,

Long time reader, first time poster. I was hoping you could help me with a question I have had trouble finding the answer to myself. Is it possible to use a sealed subwoofer behind a wall, firing into a room through a cutout? Would there be any significant acoustic drawbacks?

My current primary listening area is my family room, which is the lower level of a split-level home. Two of the four walls are just studs and drywall that border my utility room and crawlspace/storage. My wife's subtle murmurs about the "big black box" in the corner of the room have recently grown in frequency and amplitude, and it's got me thinking about potential solutions that won't result in me losing my low end for good.

I've played with the idea of buying a dedicated in-wall sub or IB setup, but honestly the lack of measurements for those products and the need for an external amplifier intimidate me. I'm still relatively inexperienced with this hobby and I figure the less variables the better. Plus, when compared to the plethora of budget sealed subwoofers on the market, it doesn't seem like a great bang for my buck. This brought me to the idea of placing one of those small sealed subwoofers (SVS, Monoprice, etc) between the studs in the utility room, and firing it through a cutout into the living space. I would have to DIY a way to seal the front baffle of the sub to the wall, stiffen the drywall to mitigate vibration (I assume?), and cover the cutout with speaker cloth. My AVR is already behind the wall in the utility room, so wiring wouldn't be a problem. Would this be a worth while alternative to traditional in-wall products? I suppose I could even use a front ported sub as long as it was small enough to fit between the studs.

I attached some rough drawings of the floorplan. In the second picture I outlined potential wall locations in red. Also note, I understand the limitations of permanent subwoofer placement with a project like this, but I don't anticipate us ever re-arranging the room and I would take measurements to find the flattest frequency response location(s) before proceeding.

Any advice on how that would affect the sound? Am I overlooking an obvious problem? Am I crazy? Thanks and let me know.

 

[Matthias McCready]

I am not an expert on this, and I am hoping someone more experienced than I am will chime in:

Subwoofers are working with some low frequencies, which can equate to some long wavelengths; think of a tractor-trailer in length.

In this light subwoofers do not always perform well in tight and enclosed spaces. This is not to say they cannot, I have seen it done, it just means some more consideration may be merited, potentially talking to an acoustician and getting their advice before getting to work would be a good idea.

It is my understanding, again not my area of expertise, that you would probably want a great deal of mass around the subwoofer (concrete or sand as an example), in order to create hard boundaries, this usually referred to a "subwoofer bunker."

This may be some helpful reading on a related subject.

 

[CLong]

That's an interesting point. I guess I had assumed the enclosure was a hard boundary and the sub would only produce energy outwards from the driver. Do they design subs to radiate from all sides? Or is that just how it works in reality when only using 3/4 or 1" MDF?

I suppose it wouldn't be the worst thing to have a little bass radiating in the utility room. It's not like the drywall is stopping that from happening anyway. But if that's the case, it may mess up the frequency response the sub is sending into the room and make the whole dang thing pointless.

Hmm. Thanks for the thought.

 

[Matthias McCready]

Subwoofers are almost inherently omni-directional, this has little to do with how thick the cabinet is, it does have a lot to do with the physical size of the cabinet though. Anytime a loudspeaker is producing frequencies that are larger than itself, those frequencies will be omni-directional, for example most bookshelf speakers are omni-directional below 200hz. The rub here being that a subwoofer will have the same volume in front of it, as behind it.

Extremely large subwoofers, such as a Meyer 1100LFC, are large enough that they are not completely omni-directional, and will measure about -1dB in the back compared to the front.

You can achieve directionality by creating subwoofer arrays, such as cardioid or end-fire. Granted subwoofer arrays require a LOT of space, so these are not methods used at home, usually. Specifically cardioid needs space and cannot work in a bunker or limited enclosure, as this would cause cancellation going forward (causing timing and magnitude issues).

----

The potential problem with bass is the utility room, is that it may reverberate in there which could sound weird, or it may not. I don't have enough experience to tell you for sure.
----

Idea: What about covering your subwoofer with something more attractive? A false wall made out of cloth comes to mind. It could look quite nice, and would not impede the low-end at all. Something has to be quite thick to start to absorb low-frequencies.

 

[Prana Ferox]

A sealed sub in the wall doesn't have differing resonance issues than a sealed sub outside the wall. Your main problems are going to be:

- Having the sub entirely in the wall greatly limits volume, which is why dedicated in-walls tend to be anemic. The common fixes to this are to have an IB setup that uses a neighboring room as the enclosure (with obvious downsides) or to have the sub enclosure actually in the attic or underneath the floor. In your case an IB setup using the utility room might be feasible, you may want to google more on this. Alternately you may be able to dedicate a chunk of your crawlspace to enclosure (this may be what you meant originally.) If I was going to that effort for something out of sight I'd make it a big 'ole box with a big 'ole driver and not some tiny thing. But even then:

- Subs tend to be sensitive to placement, hence the near-necessity for putting the sub in the MLP and doing a 'sub crawl' before deciding on final placement. Unfortunately the best places for the sub are usually not the most out-of-the-way ones (like in the corner where you have it in your pic.) If you build-in a sub in your walls (or floor etc) then if the location turns out to be not optimal, you're out of luck. At the least, you want to put your existing sub as close as you can to the spot and see if there are vicious dropouts at MLP.

- If the baffle of the sub isn't the surface of your wall, i.e. you have the sub basically firing into a tube, it's going to act as a horn. You can calculate what that's going to do with something like hornresp, if it's relatively shallow it won't matter much but if it's a big long tube it may do weird things to frequency response.

Have you considered something like disguising the sub as part of the coffee table or other furniture? Will it go behind the couch? Can you get two subs that are smaller and easier to blend in? Your drawing makes your existing sub look small enough you could throw a nice cloth on it and hide it, but maybe that's wishful thinking.

 

[CLong]

Just for clarification the sub can stick into the utility room and/or crawl space. It doesn't need to be the same depth as the studs like a traditional in-wall product. A 12" sealed sub would be fine. Also, neither the utility room or crawl space have dry wall on there side, so the "horn" would only be 5/8" thick through the face of the family room (plus whatever "gasket" I use). Either way, it wouldn't be more than 2" at most.

Also as I said in the OP, I would move my current sub around the room (or microphone) and take measurements to determine the best wall location before doing this.

 

[NiagaraPete]

Maybe look here

5041A redirect - Genelec.com

www.genelec.com

 

[CLong]

Maybe look here

5041A redirect - Genelec.com

www.genelec.com

I appreciate the recommendation but something tells me that's out of my price range.

 

[Matthias McCready]

I appreciate the recommendation but something tells me that's out of my price range.

Your "spider-senses" might be correct on that one!

 

[Matthias McCready]

I have been curious about this subwoofer. It could fit nicely behind a couch or something.

Their subwoofers that I have encountered in the wild were nothing to sneeze at.

 

[Prana Ferox]

Just for clarification the sub can stick into the utility room and/or crawl space. It doesn't need to be the same depth as the studs like a traditional in-wall product. A 12" sealed sub would be fine. Also, neither the utility room or crawl space have dry wall on there side, so the "horn" would only be 5/8" thick through the face of the family room (plus whatever "gasket" I use). Either way, it wouldn't be more than 2" at most.

Also as I said in the OP, I would move my current sub around the room (or microphone) and take measurements to determine the best wall location before doing this.

Yeah, that'll have negligible horn effect.

I'm just saying, generally people go with little sealed subs because they're tight on space. If you're using crawlspace that would normally be empty, and it's out of sight and out of mind, you can go a little bigger.

Might need to step up the amp a bit to match.

 

[CLong]

Yeah, that'll have negligible horn effect.

I'm just saying, generally people go with little sealed subs because they're tight on space. If you're using crawlspace that would normally be empty, and it's out of sight and out of mind, you can go a little bigger.

View attachment 224665

Might need to step up the amp a bit to match.

Man, I wish! I definitely went down an infinite baffel rabbit hole a couple weeks ago. I'm just trying to be realistic about my budget, time, and technical abilities.

 

[Matthias McCready]

View attachment 224665

That looks like a hernia in progress sort of situation to me!