DIY MADD Sound Door Design - AVS Forum
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post #1 of 20 Old 04-30-2012, 09:52 PM - Thread Starter
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The door is the weakest link in the soundproofing efforts. I have dual walls but I couldn't sell the dual communicating doors idea to the Mrs. Here's a crazy design I came up with that involves only opening 1 door but still incorporates the 4 pillars of sound isolation:

M- Mass: Total of 2 door slabs and 1/2 MDF
A- Absorption: 3" of pink fiberglass between layers
D- Damping: Layer of green glue
D- Decoupling: Isolation clips and hat channel between layers

Could this work or am I kind of nuts....don't answer that. After some quick math this assembly should be well under 300lbs which is less than some other designs I have seen. It is kind of thick at 6.5" so would certainly need some type of custom handle assembly.
I am doing fabric walls so I would have fabric covering the inner door wrapping around to cover the gap between the inner and outer doors. The outer door would be finished to match the rest of the basement.


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post #2 of 20 Old 05-01-2012, 05:17 AM
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Basically, you've gone to a bunch of trouble to design what is effectively a communicating door. Structurally, that door isn't going to hold up, the latching, hinges, seals will be brutal to get right. Why not just do a communicating door? You can still add mass and Green Glue (except the Green Glue won't be as effective as it can due to the different flex characteristics of the two materials.

....and what is wrong with a 300+ lb door?

Disclosure...we manufacture sound isolation doors. Here's a 350lb door with an 11" plus jamb (to match wall depth at site) ready for crating at our shop. Damping, mass, and seals and it works.
LL

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post #3 of 20 Old 05-01-2012, 07:41 AM
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That door is really cool Dennis!

Just curious what is the thickness?

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post #4 of 20 Old 05-01-2012, 09:20 AM
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11"?

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post #5 of 20 Old 05-01-2012, 10:50 AM
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So the hinges would be mounted to the inner door, and the outer door would hang off the inner door? A solid core door, like you propose using for the inner door, isn't designed to take that much weight in that plane. You would end up with 1-3/8" of MDF trying to resist the bending forces exerted by the 100-lb weight of the inner door at the end of a 2" lever. Over time, I would expect the inner door to warp significantly. Even a little warpage would play havoc with the seals on both doors, and as the door continued to warp it would become more and more difficult just to get the door to latch.

I have a vague recollection that someone here rigged up a system of two communicating doors that opened and closed as one. Maybe you could play around with that concept.

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post #6 of 20 Old 05-01-2012, 01:16 PM
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They come in two depths .... 1.75" and 2.25". Well, they can be made to any custom depth but there is little need. The jamb was that deep due to the depth of the wall at the door's location.

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post #7 of 20 Old 05-01-2012, 01:18 PM
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Quote:
Originally Posted by Dennis Erskine View Post

They come in two depths .... 1.75" and 2.25". Well, they can be made to any custom depth but there is little need. The jamb was that deep due to the depth of the wall at the door's location.

1.75" and 350 lbs! Wow that is dense!

If you don't mind me asking what material are they made of? I don't think something like plywood would get you that kind of weight.

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post #8 of 20 Old 05-01-2012, 01:27 PM - Thread Starter
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Quote:
Originally Posted by dwightp View Post

So the hinges would be mounted to the inner door, and the outer door would hang off the inner door? A solid core door, like you propose using for the inner door, isn't designed to take that much weight in that plane. You would end up with 1-3/8" of MDF trying to resist the bending forces exerted by the 100-lb weight of the inner door at the end of a 2" lever. Over time, I would expect the inner door to warp significantly. Even a little warpage would play havoc with the seals on both doors, and as the door continued to warp it would become more and more difficult just to get the door to latch.

Thanks for the explanation Dwight.

Yes the plan was to have one set of hinges on the inner door so that the whole assembly could be opened at once. I can see what you're saying about the shearing forces causing warping to the inner door over time. Do you think there are alternatives to the inner solid core door that would resist warping under those kind of pressures? What about some type of heavier gauge steel door? Since that door will be covered with fabric maybe I can find a cheap industrial one from a salvage shop.
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post #9 of 20 Old 05-01-2012, 01:53 PM - Thread Starter
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Quote:
Originally Posted by Dennis Erskine View Post

Basically, you've gone to a bunch of trouble to design what is effectively a communicating door. Structurally, that door isn't going to hold up, the latching, hinges, seals will be brutal to get right. Why not just do a communicating door? You can still add mass and Green Glue (except the Green Glue won't be as effective as it can due to the different flex characteristics of the two materials.

....and what is wrong with a 300+ lb door?

Thanks Dennis. Has any consideration ever been given to what could happen to children's fingers (or adults for that matter) if they ever get caught in any of these very heavy doors . Any reasonable way to mitigate that risk?
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post #10 of 20 Old 05-01-2012, 01:56 PM
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Close the door slowly

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post #11 of 20 Old 05-01-2012, 02:09 PM
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Yeah, exactly what would happen when they get slammed into a car door.

...you put a catch on the door that stops it from closing until the pin is moved out of the way.

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post #12 of 20 Old 05-01-2012, 02:10 PM
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Quote:
Originally Posted by 235 View Post

Thanks Dennis. Has any consideration ever been given to what could happen to children's fingers (or adults for that matter) if they ever get caught in any of these very heavy doors . Any reasonable way to mitigate that risk?

Put sharp edges and rubbing alcohol all the around the jamb so it does a clean slice of the finger. Keep your sewing kit handy too.

In all seriousness, Lowe's and other big box stores sell products to help heavy door's slow down as they close.
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post #13 of 20 Old 05-01-2012, 02:14 PM
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Quote:
If you don't mind me asking what material are they made of?

Ha! In your dreams. "Product of seven years patient research at the University of Padua" --Bertold Brecht
Here's how you find out ... buy one. Get a very powerful table saw (diamond blade is suggested) and cut it up. Would you like to meet our IP attorney?


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post #14 of 20 Old 05-01-2012, 02:27 PM
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Quote:
Originally Posted by Dennis Erskine View Post

Ha! In your dreams. "Product of seven years patient research at the University of Padua" --Bertold Brecht
Here's how you find out ... buy one. Get a very powerful table saw (diamond blade is suggested) and cut it up. Would you like to meet our IP attorney?


Haha Dennis! Don't worry I understand.

And if I bought one the last thing that I'd want to do is cut it up!

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post #15 of 20 Old 05-01-2012, 03:16 PM
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Quote:
Originally Posted by 235 View Post

I can see what you're saying about the shearing forces causing warping to the inner door over time. Do you think there are alternatives to the inner solid core door that would resist warping under those kind of pressures? What about some type of heavier gauge steel door? Since that door will be covered with fabric maybe I can find a cheap industrial one from a salvage shop.

I have never seen an off-the-shelf door that would be a good candidate for resisting this kind of shearing force. The steel doors I'm familiar with are thin steel around a foam core -- no help in this situation.

I'm speculating, here, but it seems possible that one could build a torsion box door that would be stiff enough to resist the shear force we're talking about. Here's an image that shows the basic construction of a torsion box:


Building a torsion box to function as a door would require some woodworking skill and tools capable of a fair degree of precision. For sound control purposes, you would have to find a way to fill the voids in the web with mass -- maybe pieces of MDF cut to fit precisely. Overall, a difficult, fiddly job that might or might not yield good results. If you had to pay a woodworker to make one, it would be expensive.

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post #16 of 20 Old 05-01-2012, 06:06 PM
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I thought about this a bit and had two different ideas.

One, a sheet of 1/2" plate steel green glued between two sheets of 1/2" MDF. You would have to cut the plate narrower and work some magic with the MDF to give yourself some wood to screw into and bore a lockset. That would easily get you the mass. How effective.. I dunno.

Another idea I though about was creating a door filled with sand. Then I thought that would probably be a bad idea.. but it's kinda like the riser idea, only vertical. Glass bead would probably be a better substrate.. but still. I could imagine springing a leak

In the end.. I'm just gonna buy a Jeld-Wen fire-resistance rated door. Not for the fire rating, but the additional mass... and it will match the rest of the doors in my house.

I don't think the OP idea will work, but there are plenty of innovative ideas and I hope we get to try one out!

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post #17 of 20 Old 05-01-2012, 06:52 PM
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I know that jelloslug filled a hollow core door with sand for his home theater.

Edit: Here you go. (Post #54)

http://www.avsforum.com/avs-vb/showt...6#post17476436

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post #18 of 20 Old 05-01-2012, 10:26 PM - Thread Starter
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Thanks for the suggestions everyone. The only major flaw I see at this point is with the probable warping of the inner door caused by having to support the weight (approx 70lbs) of the outer door. Need more stiffness....maybe Pfizer has something . The torsion box idea sounds interesting or maybe replacing the inner door with something like steel?

Has anyone ever designed and built a single door assembly that incorporates decoupling and absorption? It seems to me something like this could rival the performance of communicating doors without the hassle of constantly opening and closing two doors. My goal was to do this in an affordable manner with commonly used construction materials and techniques. Keep the ideas coming, I haven't given up just yet.
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post #19 of 20 Old 05-02-2012, 10:30 AM
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Quote:
Originally Posted by Dennis Erskine View Post

They come in two depths .... 1.75" and 2.25". Well, they can be made to any custom depth but there is little need. The jamb was that deep due to the depth of the wall at the door's location.

What's the price for the 1.75 door in a 30" x 80" size? Do the door come complete with everything?
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post #20 of 20 Old 05-02-2012, 10:46 AM
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You can PM me. Prices are no no on the forum. The doors are pre-hung with all the seals, threshold, etc. You have to supply your own latch set. They can come pre-finished (stained & sealed, painted) or not as you wish.

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