How to de-couple subwoofer box - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 15 Old 11-25-2019, 08:25 PM - Thread Starter
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How to de-couple subwoofer box

Hi folks, I'm looking for some help on my custom entertainment center/subwoofer box build...

I am incorporating a UM18 sub in a ported box. My flooring is hardwood on a suspended I-Joist floor. I want the box to retain it's built-in look so I don't want to use a visible isolation pad (i.e. SubDude) to raise it off the floor. Also, the box will be butted against the rear wall and the equipment rack on one side, and a stone base on the other.

Will rubber feet (< inch tall) suffice? Also, should I put some kind of rubber matting between the back of the box and the wall. As shown in the picture, the top of the subwoofer will be covered in granite. In the picture, the box is the portion of the lower section that is veneered in wood. I am incorporating a center channel cavity in the center of it. The sub will be behind the right hand side grill cover and the port behind the left side. Everything but the subwoofer box itself has already been built so modifications to the surrounding entertainment center itself are not possible at this point.

Any suggestions would be appreciated.

Thanks
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post #2 of 15 Old 11-25-2019, 09:22 PM
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https://www.isolateit.com/


I've used the hemispheres and sheets with great results.
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post #3 of 15 Old 11-25-2019, 11:54 PM
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Is transfer to neighboring rooms a concern? I specifically put my system in a second-floor room to achieve easy floor rumble. I'd rather couple than decouple. YMMV.

If you do need to decouple and you do wish to use sorbothane, make sure to follow the directions on the website for choosing the proper thickness and durometer ratings. They're going to need to be pretty beefy to handle the sub and not squish so much that they lose their decoupling ability.
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post #4 of 15 Old 11-26-2019, 04:12 AM
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Quote:
Originally Posted by Soulburner View Post
Is transfer to neighboring rooms a concern? I specifically put my system in a second-floor room to achieve easy floor rumble. I'd rather couple than decouple. YMMV.

If you do need to decouple and you do wish to use sorbothane, make sure to follow the directions on the website for choosing the proper thickness and durometer ratings. They're going to need to be pretty beefy to handle the sub and not squish so much that they lose their decoupling ability.

Good advice. When I had my JTR Cap 2400, I had eight 1.75 inch rated @ 50 on their scale. Worked great over the years, but when I sold it, I noticed a couple were smushed and cracked from the weight of that beast. I should have went with the 70 on their scale.
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post #5 of 15 Old 11-26-2019, 06:31 AM
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Don’t forget, with sorbothane the weight you use in the calculation is the total weight of the speaker/sub divided by the number of isolators you’re using. So, a 200 lb sub using four isolators would mean you need isolators rated to 50 lbs. Weight rating charts:

https://www.sorbothane.com/Data/Site...othane-SPG.pdf

Personally, I use sorbothane to isolate between speakers and stands. I’m using a subdude on a hsu sub in my family room and it solved a problem for me.

https://www.auralex.com/product/subdude-ht/

SPEAKERS: 3 x DIYSG 1099's LCR; DIYSG HTM 6's and 8's surround; 4 x RSL C34E's atmos.
SUBS: 4 x UM18-22 Mini Marty's and 2 x 21DS114-4 Devastators
SIGNAL CHAIN: Denon X4400; Minidsp 2x4 HD; 2 x Jensen Iso Sub 2RX; 3 x NX6000d.
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post #6 of 15 Old 11-26-2019, 08:34 AM
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holy crap those are expensive!

Just looked down and was thinking...What about keyboard rests? But obviously weight would be a problem I guess.
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post #7 of 15 Old 11-26-2019, 09:53 AM
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I'd take a look at the isolators the guys are using for BOSS platforms.

https://www.amazon.com/gp/product/B079SV39KW/

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post #8 of 15 Old 11-26-2019, 10:33 AM
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these work well:
https://www.svsound.com/products/sou...olation-system

also, the keyboard rest/mouse pads work pretty well actually... and are cheap and easy to try... you could even double up the mouse pads if you are worried about the crush factor...

https://www.bestblanks.com/blank-mou...25x775x25.html

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post #9 of 15 Old 11-26-2019, 11:25 AM
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Since this is the DIY forum …

https://www.avsforum.com/forum/113-s...ion-riser.html

https://www.avsforum.com/forum/113-s...platforms.html

https://www.avsforum.com/forum/155-d...-pad-subs.html

SPEAKERS: 3 x DIYSG 1099's LCR; DIYSG HTM 6's and 8's surround; 4 x RSL C34E's atmos.
SUBS: 4 x UM18-22 Mini Marty's and 2 x 21DS114-4 Devastators
SIGNAL CHAIN: Denon X4400; Minidsp 2x4 HD; 2 x Jensen Iso Sub 2RX; 3 x NX6000d.
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post #10 of 15 Old 12-01-2019, 04:53 PM - Thread Starter
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Quote:
Originally Posted by Soulburner View Post
Is transfer to neighboring rooms a concern? I specifically put my system in a second-floor room to achieve easy floor rumble. I'd rather couple than decouple. YMMV.

If you do need to decouple and you do wish to use sorbothane, make sure to follow the directions on the website for choosing the proper thickness and durometer ratings. They're going to need to be pretty beefy to handle the sub and not squish so much that they lose their decoupling ability.
I mainly am worried about things rattling around the house more than I am how much transfer I am going to have to other rooms. I don't have kids so its just me and the wife, but I still would go nuts if everything on my walls, dishes in the kitchen cabinets, etc. were rattling constantly.

I wish I knew how much the box was going to weigh went it was done. I'm in a kind of a catch 22. If I go with the sorbothane feet I want them to be short as possible because the taller I go, the smaller (less internal volume) the box is going to have to be as the height of the granite over top of it cannot be raised. So without knowing the weight of the completed box, I don't know which how tall of feet I am going to have to buy to get the properly sized weight/ratio. In other words, if I deduct say 1/2" off the height of my box to allow for 1/2" feet, will the 1/2" feet be with the weight rating that my box winds up at. I can always try and use more/less of the feet as necessary to get the equation right, but its still kind of a guessing game at this point if it is going to work out properly.

Should I also some sorbothane pads between the back of the subwoofer box and the drywall?
"
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post #11 of 15 Old 12-01-2019, 05:35 PM
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3cm granite weighs 20lbs a sq ft. Enclosure weight should be easy to calculate plus driver. I bought a lot or Sorbothane 50duro. I can send you 4 and if you like them you can buy them if not send them back. I think it was 6.50 per, so that plus shipping.
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post #12 of 15 Old 12-01-2019, 08:31 PM
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Quote:
Originally Posted by TStubb View Post
I mainly am worried about things rattling around the house more than I am how much transfer I am going to have to other rooms. I don't have kids so its just me and the wife, but I still would go nuts if everything on my walls, dishes in the kitchen cabinets, etc. were rattling constantly.

I wish I knew how much the box was going to weigh went it was done. I'm in a kind of a catch 22. If I go with the sorbothane feet I want them to be short as possible because the taller I go, the smaller (less internal volume) the box is going to have to be as the height of the granite over top of it cannot be raised. So without knowing the weight of the completed box, I don't know which how tall of feet I am going to have to buy to get the properly sized weight/ratio. In other words, if I deduct say 1/2" off the height of my box to allow for 1/2" feet, will the 1/2" feet be with the weight rating that my box winds up at. I can always try and use more/less of the feet as necessary to get the equation right, but its still kind of a guessing game at this point if it is going to work out properly.

Should I also some sorbothane pads between the back of the subwoofer box and the drywall?
"

Loud low bass will couple to the floor, the walls and shake your dishes, appliances and furniture regardless if you place the enclosure on a foam pad or compliant feet. It comes with the territory.
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post #13 of 15 Old 12-02-2019, 07:07 PM - Thread Starter
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Quote:
Originally Posted by michael hurd View Post
Loud low bass will couple to the floor, the walls and shake your dishes, appliances and furniture regardless if you place the enclosure on a foam pad or compliant feet. It comes with the territory.
Is your comment based on your thought of not subscribing to the decoupling theory, or are you pointing out that the sound waves itself will cause shaking?

I understand that with loud enough volume that the sound wave themselves will move objects, but for me there is a desire that any movement is not coming from displaced energy through coupling of objects.
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post #14 of 15 Old 12-04-2019, 07:20 AM
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If the subwoofer box is properly built the box itself should not rattle nor transfer energy. It is the sound wave itself that shakes the house
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post #15 of 15 Old 12-04-2019, 10:26 AM
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Quote:
Originally Posted by TStubb View Post
Is your comment based on your thought of not subscribing to the decoupling theory, or are you pointing out that the sound waves itself will cause shaking?

I understand that with loud enough volume that the sound wave themselves will move objects, but for me there is a desire that any movement is not coming from displaced energy through coupling of objects.

The sound itself will set your walls, floor, ceiling, windows and all manner of items into vibration, when the amplitude becomes high enough.

Ask your doctor if DIY is right for you. Side effects of DIY may include anxiety, elevated blood pressure, lightheadedness, rapid heartbeat, skeletal muscle flaccidity, euphoria, psychological dependence, insomnia, confusion, blurred vision, impulsivity, uncontrolled or repeated movements.
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