Hanger Materials, Assembly, & Mounting

[Aaronw]

OK, thought I would post a topic here on trying to get specific details, diagrams, materials, and mounting techniques for hangers. In this case, let's start w/ hangers in bass traps.

I have a pretty good idea of what and how to assemble them, but would like to start a thread here for more details so everyone can understand how to construct them. Maybe at some point, make it another sticky.

Questions:

1. Do the hangers need to have a mass component such as plywood, pegboard, etc. in the center or on one side?

2. Should they or can they be something like 703 just hanging without a mass in the center.

3. If the center of the hanger is a mass material, should they have 703 on each side? Or should they just be wrapped with a material?

4. What type of material should be used to wrap around them? Batting? How thick? And best way to attach it?

5. Best way to attach or what type of hardware for hanging. Eye bolts or hooks? Then suspended by string, chain, etc.?

6. In the bass trap, let's say you have a drywall ceiling (2 layers 5/8" mounted on RC1), What's the best way to mount them here, without compromising the isolation and having flanking noise?

7. If there is a mass in the middle (eg: plywood) how thick? 1/4", 1/2", 5/8", 3/4", etc.?

Thanks again,

Aaron

[barefoot]

1. Do the hangers need to have a mass component such as plywood, pegboard, etc. in the center or on one side?
Yes, otherwise you're just filling the space with insulation. Personally, I think a dense, flexible material like linoleum yields the most effective damping.

2. Should they or can they be something like 703 just hanging without a mass in the center.
Not really. Like I said above, this wouldn't be a "hanger".

3. If the center of the hanger is a mass material, should they have 703 on each side? Or should they just be wrapped with a material?
Either way.

4. What type of material should be used to wrap around them? Batting? How thick? And best way to attach it?
703 is denser and yields higher absorption for a given volume, so it's a better choice in my opinion. I also like the idea of attaching the insulation only to the top of the hanger. This way the hanger and insulation are free to rub against one another, generating even more absorption through friction.

5. Best way to attach or what type of hardware for hanging. Eye bolts or hooks? Then suspended by string, chain, etc.?
Whichever, as long as it can hold the weight.

6. In the bass trap, let's say you have a drywall ceiling (2 layers 5/8" mounted on RC1), What's the best way to mount them here, without compromising the isolation and having flanking noise?
Usually the hangers are suspended from joists.

7. If there is a mass in the middle (eg: plywood) how thick? 1/4", 1/2", 5/8", 3/4", etc.?
I think most people use 1/4" masonite. As I side, I like dense flexible materials. Thin lead sheet would be outstanding, but not very environmentally friendly. Tin sheet would also be great, and safe, but it's very expensive. Linoleum or masonite are your best bets.

Thomas

[ollie]

I usually use 1" Dacron covering 1/2" Celotex or solid pink insulation, its very light but absorbtive. Masonite and pegboard also work but are heavy and more expensive.

What I do is fill the space with as many panels as possible, different sizes and shapes and at different angle. Trying to be as instrusive as possible to the sound.

Like this the following pics...

Of course I have trapped every air gap possible in the room, ceiling, corners etc. The pictures show the air space between my live room and the control room that house the flush mounted speakers.

I am quite astounded at how well it worked, in the top pic you can see the front wall sealed with 3/4" ply but not at the top, nor the bottom, the top will be inside the ceiling and I couldn't cover the sprinklers and the bottom will be covered with fabric covered 3/8" pegboard with helps smashs the lowend because of the holes. Pegboard rules.

I have many more pics to come... studio is almost complete.

sealedFront.jpg

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[ollie]

I usually use 1" Dacron covering 1/2" Celotex or solid pink insulation, its very light but absorbtive. Masonite and pegboard also work but are heavy and more expensive.

Am I allowed to change my mind??

Pegboard masonite is better that celotex, slightly more expensive but easier to hand and glue dacron on. I am using plastic zipper ties to hang them with.

o


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[Aaronw]

I don't know if you'd really want to use the plastic zip ties. Over time, they break. And for a permanent install in the wall, it's asking for trouble 2 years down the road. Especially with them being suspended.

Maybe some type of a nylon or polyester string/cord or small chain w/ hooks?

By the way, here's some drawings and info that Steve posted on my other thread under construction...

http://johnlsayers.com/phpBB2/viewtopic ... &start=190

Aaron

[ollie]

The way I am doing baffles is quite a bit lighter than the method in your thread.

I am using sheets of Sonopan (green acoustic fibreboard) cut into different lengths and widths and then I use I strong spray adhesive to attach 1" Dacron wool on either side. Then I hang them with 3 - 4 heavy duty wire tie wraps.

They seem to work great.

cheers,
o


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[ollie]

I just noticed that I have used 3 different materials in the "cheese" part of the dacron sandwich.

They all seem to work great.

Celotex - cheap light and great if you have lots and lots of hangers in odd spots and sizes. About $3.00 usd for a 2' x 8' sheet.

Pegboard - not that cheap not that light but easy to hang in large spaces and large sizes. About $8.00 usd for a 1/8" x 4' x 8' sheet.

Sonopan - Panels made from wood fiber and recycled paper, great acoustic properties. About $14.00 usd for a 4' x 8' sheet.

o


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[Aaronw]

For as many thousands of $$$ I've already spent (especially with current costs of materials) a few extra bucks to have a better material at this point isn't a concern anymore. If I've got to have, I've got to have it. I'd rather do things right the first time if I can, rather than the "I wish I had" and have it cost me more in the long run, or a bad or inacurate sounding room.

[barefoot]

Yeah, I don't think these lightweight materials will be as affective at low frequencies as the heavier ones. The point of hangers is to create an absorptive tortuous path for the sound waves to traverse. Low frequencies will just pass by the light panels like an ocean wave passes a floating swimmer.

The perfect suspension material in my opinion is "plummer's tape", or sometimes called "pipe strapping". It's strong, cheap, and very easy to use.

Thomas

[Aaronw]

Great, I've already got a roll at the house.

[lex]

I had some questions about hangers and thought I'd ask here instead of starting a new thread. What is the ideal length and spacing of hangers? I read that they work best when they are different lengths in specific relation to each other. If so what is this relationship? What is the ideal spacing? Why is it the ideal spacing? I understand the materials to use and how to mount them, but the details are obscure.

[knightfly]

Typically you'll be putting hangers in non-square spaces, so length is usually as long as you can get and still have them NOT touching the floor, or the ceiling if they're in a false ceiling cavity.

Spacing - just far enough apart so they don't touch at rest is fine - a bass wave becomes a pressure change within the cavity, so it tries to get through the hanger - the hanger moves slightly, damping some of the bass energy.

more is damped with the wrapped insulation around the hanger. If the hanger itself is relatively limp, like linoleum, more damping happens.

If the hangers are hung in a sort of herringbone pattern, it makes the path through them even more tortuous and more losses occur. Then, when the same wave tries to get BACK it has to pass through all the same interference going the other way, and more losses occur.

Considering that typical bass waves have a wavelength of 10 to 35 FEET, spacing between the hangers will have little or nothing to do with wavelength of the affectied frequencies... Steve

[lex]

Thanks, you've always got great advice.

[lex]

So as long as the ceiling doesn't have resilient channels, the standard procedure is to drill holes for the hooks in the ceiling joists, and then hang the hangers with chains?

Or should I build a cage like in your soffit example, 'hanger hanger' within the area? Or is this just done for soffits?

[knightfly]

If isolation is a serious concern, then any solid coupling of hangers to your inner leaf of mass will cause a loss of isolation by exciting the inner panels more than they would otherwise be. Under those conditions, I would NOT directly connect any hanging method to the frame that's supporting your inner containment leaf in a mass-air-mass envelope. That's where the "hanger hanger" cage would help.

If, however, isolation is LESS of a concern, you need maximum bass trapping (generally true), and don't want to use more materials, then finding the joists and running screws up into them can be done. It will make LESS isolation loss if the above ceiling is well-insulated and damped, but there will still be a few dB of isolation lost by doing this; I have no concrete numbers, but likely anywhere from 2-6 dB, depending on about 20 different variables... Steve