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Bass output through the hole in the wall.

Launagis

Launagis

Member
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Apr 1, 2020
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Vilnius, Lithuania
Hi all.

I've recently done subwoofer "crawl" and suprisingly, one of the good spots for low end was near the entrance to the storage room. Thing is, there is unused 125mm diameter hole in the wall, connecting listening room with the storage room. And this gave me and idea to put subwoofer in the storage room/behind the wall and somehow "feed" listening area with the bass through the hole.

The hole is round, 125mm in diameter and 160mm deep. Is there non-problematic way to output sound through that hole?

Because other option would be to enlarge the hole to accommodate the driver and put the box behind it. I just don't want the visual of the driver on my wall as the first option.

WallSub.png

There are some ready-made solutions which I'm not gonna buy since I have the drivers, it's just for illustration purposes:
1741606124508.png
 
Essentially, this can be made to work, with some caveats:

- The sub needs to be a closed sub, otherwise the reflex output will not go back into your room
- The sub woofer should be close to the hole, and the connection between hole and woofer should be airtight
- The woofer should not be too large vs the surface area of the hole. I guess you can get away with up to 1/3rd of the woofer SD for the surface of the hole. So in your case, that would accommodate about an 8" woofer.

Basically, you're creating an infinite baffe sub. You'll have more bass extention this way. You could even mount the woofer naked in the storage room and use the whole space. With the right kind of woofer, this will give you even more and lower output :eek:
 
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This reminds me of TRW-17 rotary subwoofer, learned of it few days ago thanks of ASR :

www.soundandvision.com

Eminent Technology TRW-17 Rotary Subwoofer

And now for something completely differenta subwoofer that looks like a fan and can reproduce frequencies down to 1Hz and below. Yep, you read that right1Hz and below. Developed by Bruce Thigpen and available from Eminent Technology, the Thigpen Rotary Woofer Model 17 (TRW-17) breaks entirely...
www.soundandvision.com www.soundandvision.com

1Hz-20Hz :facepalm:
 
dedobot said:
This reminds me of TRW-17 rotary subwoofer, learned of it few days ago thanks of ASR :

www.soundandvision.com

Eminent Technology TRW-17 Rotary Subwoofer

And now for something completely differenta subwoofer that looks like a fan and can reproduce frequencies down to 1Hz and below. Yep, you read that right1Hz and below. Developed by Bruce Thigpen and available from Eminent Technology, the Thigpen Rotary Woofer Model 17 (TRW-17) breaks entirely...
www.soundandvision.com www.soundandvision.com

1Hz-20Hz :facepalm:
Click to expand...
Can you really hear that low or is it that u feel those low notes?
 
voodooless said:
Essentially, this can be made to work, with some caveats:

- The sub needs to be a closed sub, otherwise the reflex output will not go back into your room
- The sub woofer should be close to the hole, and the connection between hole and woofer should be airtight
- The woofer should not be too large vs the surface area of the hole. I guess you can get away with up to 1/3rd of the woofer SD for the surface of the hole. So in your case, that would accommodate about an 8" woofer.

Basically, you're creating an infinite baffe sub. You'll have more bass extention this way. You could even mount the woofer naked in the storage room and use the whole space. With the right kind of woofer, this will give you even more and lower output :eek:
Click to expand...
That's effectively adding a small air volume and a port to the front of the sub, a bit like the bass of the KEF 104-2. I think it makes a bandpass response, but my memory on that is hazy. It would be worth modelling it to see what it does.
edit: which I now see @Flaesh has already done.
 
I think the hole is too small for a subwoofer. But with the right driver you don't need a box... Except maybe something for physical damage protection. The room on the other side becomes the box, essentially an infinite baffle. You could plug in the driver's Thiele-Small parameters into some speaker design software with a very large box to see how it behaves.
 
Launagis said:
one of the good spots for low end was near the entrance to the storage room
Click to expand...
A room suitable for an infinite baffle sub is a treasure and a gem, a happiness and a blessing :cool: for installing big, easy to drive drivers. The holes in the wall can be covered, for example, with a grill printed on fabric or something else. Do you have measurements? What drivers do you have?
Of course, a small box with a small driver attached to a small hole is also an option.

p.s.: Here is a grill for 4x21" drivers:
1741693662405.png
 
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Another option would be to build a 4th-order bandpass subwoofer, where the hole is the port. A 4th order bandpass isn't very tweakable, though, so it needs the right set of woofer parameters to get the most out of it. And then there is the fact that, generally, bandpass subs are seen as one-tone droning devices. Mostly this is due to poor design, I think.
 
Launagis said:
Hi all.

I've recently done subwoofer "crawl" and suprisingly, one of the good spots for low end was near the entrance to the storage room. Thing is, there is unused 125mm diameter hole in the wall, connecting listening room with the storage room. And this gave me and idea to put subwoofer in the storage room/behind the wall and somehow "feed" listening area with the bass through the hole.

The hole is round, 125mm in diameter and 160mm deep. Is there non-problematic way to output sound through that hole?

Because other option would be to enlarge the hole to accommodate the driver and put the box behind it. I just don't want the visual of the driver on my wall as the first option.

View attachment 435027
There are some ready-made solutions which I'm not gonna buy since I have the drivers, it's just for illustration purposes:
View attachment 435028
Click to expand...
@Launagis is that a product or a DIY thing?
 
Hi,

put your system playing some low tone and walk around in your house. I bet you hear the bass in any room regardless there is holes or not. In my house most impressive bass is in the toilet on the hallway, while the system is playing in the livingroom. So, depends, just stick the sub anywhere it sounds good and is not on your way.

You could use REW to further figure out how the system works, and listen whether the sound is even and impactful, or not, and well balanced. System tuning is very important, but it's also about how much you care about it and be able to differentiate what sounds good or bad, so, anything thats good to you is fine, improve as you go.

Have fun!:)
 
Launagis said:
Hi all.

I've recently done subwoofer "crawl" and suprisingly, one of the good spots for low end was near the entrance to the storage room. Thing is, there is unused 125mm diameter hole in the wall, connecting listening room with the storage room. And this gave me and idea to put subwoofer in the storage room/behind the wall and somehow "feed" listening area with the bass through the hole.

The hole is round, 125mm in diameter and 160mm deep. Is there non-problematic way to output sound through that hole?

Because other option would be to enlarge the hole to accommodate the driver and put the box behind it. I just don't want the visual of the driver on my wall as the first option.

View attachment 435027
There are some ready-made solutions which I'm not gonna buy since I have the drivers, it's just for illustration purposes:
View attachment 435028
Click to expand...
Hi

You just stumbled on a most interesting way to build a subwoofer. And a very powerful at that:
This can be an infinite baffle subwoofer. One of the easiest subwoofer built around... yet, one of the more performant subwoofer out here. With the right dimensions you can have a subwoofer capable of extremely clean, low distortion Bass system, capable of house destructing output from below 10 Hz (Yes) to 200 Hz... with THD in the <10%.. Few if any commercial subwoofer are able to reach that low so cleanly and with such massive output...:
You just mount the drivers on a baffle and make of the storage room the drivers cabinet. It is that easy.

There are however some requirements.
Drivers with low Qts <0.6
Good displacement , this is expressed in the Vas parameter, > 7 cubic feet.
Good Power handling capacity around 500 Watts per driver.
A good , sturdy and powerful amplifier, something like the cheap but good Behringer NX3000 Power Amplifier...
The volume of the "cabinet" needs to be at least 6 times the combined Vas of the driver. The Vas is one of the Thiele-Small parameter of a driver. It is part of its specifications. It is expressed in the US in cubic feet.

Now a concrete example:
Assuming a storage room with the following dimensions: 4 x 3 x 2 meters (L x W x H) 24 cubic meters or about 900 cubic feet...
You acquire 2 drivers with good specs say the Dayton Audio RSS390HF-4 15" Reference Series HF Subwoofer 4 Ohm
You mont 2 of these in a baffle ( the current place where there is the current hole, for exemple properly reinforced and sealed so that there is no leaks)
You use an amp such as the Behringer NX-3000

My WinISD is misbehaving, so on a hunch: In a sizable living room say up to 40 squared meter... you would hit 10 Hz digits at 95 dB ... perhaps more. Of course this sub needs to be EQ for best results...

A good place for great information about Infinite Baffle subwoofers:

The Cult of The Infinitely Baffled

I am surprised that these are not more popular with audiophiles. Not always possible but .. I did try it once and was pleased by the measured performance. I can't build one in my current abode, I have neighbors now ... and rather close, in a suburban setting. Else ...


Peace.
 
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Hi again and thank you all for the replays!

I really like the idea of an infinite baffle, it's just I can't do that - the storage room has an hvac airflow throught it, it's just not throught the hole, but throught the gap under the door. The hole just being there and being shut/unused gave me the idea for the subwoofer in the storage room in the first place.

Other two options - some sort of bandpass or in-wall subwoofer with a box behind it are doable. I'm just a bit scared of the complexity/unexpected consequences with bandpass stuff.

I think the least complicated thing to do for me would be to mount the driver to the wall with a box behind it. And to leave the driver visible or to cover it with something to hide it, as was suggested. Coupling or decoupling is still a headscratcher, the wall is sandwich of plywood/plasterboard/rockwool and plasterboard/plywood again. Might be sturdy enough, might be not.

The drivers are SB Acoustics SW26DBAC76-4 and I have four of them. As far as the driver looks go, those are on the more "pretty" side for me and I have no wish to buy something new. Those model well in sealed 30-40ltr boxes.

As for REW and measurements, I have done hundreds of them, sadly after putting subwoofers in hidden locations. In the process of building my room, I, without research, chose convenient, but poor locations for my four subs. To get good bass in the seating position, I have to crank up the output so much, that the floor just resonates annoying me a lot. Finally, I built "test" sub from cheap spare 10" driver, did a crawl thing, found the good spots (near the hole was on of them), put the mentioned "test" sub in one of the good spots and now alone it sounds more pleasing than the other four subs. So I'm determinded to reuse SW26DBAC76-4 in proper locations.
 
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