Soundproofing In-ceiling Rear Speakers

13134 Views 18 Replies 11 Participants Last post by CJO, May 18, 2007

mhallida

Discussion Starter · May 15, 2007

Due to house prices and no basements in California, my family room has to double up as my HT. I am placing Speakercraft AIM8 Three Rear in-ceiling speakers (no other choice really in terms of position.) For my front wall I've torn down all the drywall in order to route my many cables etc. I've managed to place the rear with mimimal impact on my drywall.

I tested the rears as front speakers on my regular two channel audiophile amp and they sound great (for inceiling speakers.) Only problem is..... the sound and vibrations in the bedroom above. There is no insulation between the floors. Sounds like that wouldn't do much anyway. I plan on putting green glue on my front wall as I have to redo the drywall.

I am curious as to what are my options for the inceiling speakers. I know as rears they have little of the soundtrack going through them so it might not be a problem. Or should I make enclosures for them (through the cutout) and place two layers of dry wall with green glue? If I do that I will have to cut multiple strips of drywall to get the pieces into the ceiling (I don't want to widen the access hole). Will that impact the sound proofing?

What are your throughts?

1 - 19 of 19 Posts

McCall

· #2 · May 15, 2007

If I were trying to make boxes to hold in ceiling speakers, [ugh] but that is what you have, I would use MDF with greenglue not drywall, would be a lot easier to work with and is very dense. I assume your speakers themselves have their own backboxes?

You might also want to decouple your ceiling as those speakers are not going to be our only transfer to bedroom problems.

Also greenglue and double drywall on only one wall will not do too much for you.

mhallida

Discussion Starter · #3 · May 15, 2007

Yeah I know green glue on one wall is not going to do a lot. Problem is I have an open plan house.... Short of knocking my house down and starting from scratch (not an option ;-)) I don't have much choice. I figured that seeing as the laundry room is on the other side I might as well try and block out something from that area. I am hoping it might deaden the sound in one direction.

Thanks for the pointers on using MDF, anyone else thing that would work better with the green glue?

The speakers are enclosed in their own plastic case, I've not bought an after market box of any kind. They are simply sitting in the cavity ontop of the drywall...

FreddyB

· #4 · May 15, 2007

Damping liquids such as Green Glue will not give you the noise reduction performance you are looking for.In theory, these materials must be sandwiched between two layers to create a sound isolation layer. Building enclosures with mdf and lining the exterior with a composite such as DuraBarrier or Ultrabarrier will do a better job at reducing both structural and airborne noise from emitting through the enclosure. You could also utilize an acoustical foam on the interior of the enclosure and mass loaded vinyl barrier on the outside.

Good old fashioned physics still apply today. You must add enough mass to overcome the sound energy.

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drin

· #5 · May 15, 2007

Quote:
Originally Posted by FreddyB /forum/post/0

Damping liquids such as Green Glue will not give you the noise reduction performance you are looking for.In theory, these materials must be sandwiched between two layers to create a sound isolation layer.

I believe McCall's post above recommnded just this approach. Build enclosures of double-layered MDF with Green Glue between them.

Quote:
You could also utilize an acoustical foam on the interior of the enclosure and mass loaded vinyl barrier on the outside.

MLV is generally thought of as a bad thing around here. Better off as McCall suggested, I think.

-drin

BIGmouthinDC

· #6 · May 15, 2007

I think I would try to do something simple and see if that mitigates your problem.

I looked up that speaker and looked at the specs. Ideally you want something you can fit up through those round holes you cut and when you press the speaker in to place will form a seal around the back and have some mass to contain the sound.

As I was thinking about this problem The first thought I had was a bag of something that you could fit up through the hole and when you put the speaker in place it would flow around the speaker and form a seal around the Speaker. I thought about sand. But that's too heavy. Then I thought about a bag of styrofoam beads (bean bag type) too light.

So something in between sand and styrofoam beads,

Must be getting close to dinner time because the thought of dried navy beans entered my head.

Maybe someone else has a suggestion of just exactly what to put in a plastic bag.

Of course after seeing your skills in that other thread you started You could always attack this problem from up above. Just roll back the carpet, remove a piece of the subfloor above, fit surround boxes. replace subfloor and unroll the carpet.

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mhallida

Discussion Starter · #7 · May 15, 2007

You know I like your thinking. I must admit though I am a little nervous about removing subfloor etc. Maybe I shouldn't be... I would like to come up with something if possible without going that extreme. I am curious though realistically how much sound & bass would be coming out of the rear speakers on a 5.1? I don't remember the percentages off hand is it around 5-10% of the soundtrack at best? I know the majority comes through the center channel.

Maybe I will see what it sounds like once I'm done and the whole system is working as intended and then revisit this if it is still an issue. If there was a quick easy fix (is there every in life?) then I would do it know...

I like the idea of a bag of something.... or just making an MDF GG box. Getting it in will be a challenge but I think I'm up to it ;-)

ScottJ0007

· #8 · May 16, 2007

I have some in-ceiling speakers that I custom built using the double MDF with greenglue approach. I am very impressed with the results. However, I had full access to the ceiling before the drywall was installed. I understand you do not have this option.

As a simple alternative, I have an entirely different suggestion. When I was at CEDIA last year I saw a product by Dynamat that you might want to check out. It is called the DynaBox and it is specifically for the purpose you describe. Here is a link to the DynaBox . Basically, it is a heavy rubberized box that is collapsible. You can fold it up and stuff it into the hole you have already cut for your speakers. It then sits on top of your speaker and essentially creates an air-tight box (or nearly so).

In the demonstration hall at CEDIA, they had one of these in the DynaMat booth. With the box on top of the speaker, I could not hear the speaker at all. When I lifted the box off of the speaker, the speaker was playing at a pretty loud level. The main problem I see with them is they seem a bit pricey at $150 retail.

I have no idea how well this product will actually work in a ceiling, but you might want to give it a try before you start ripping out your ceiling or sub-floor.

- Scott

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HD STEVE

· #9 · May 16, 2007

I was in the same situation. My speakercraft AIM8 Fives were driving my wife crazy. I decided to have these speakercraft speaker boxes installed. They are a little costly and time consuming (drywall cut out and patch back) but it is well worth it.

http://www.avhifi.com/asp/product.as...chFor=&PT_ID=1

HD STEVE

mhallida

Discussion Starter · #10 · May 16, 2007

That Dynabox seems like a great idea if it will work. I would be interested in hearing if anyone has installed it and what the results where like. Do you know if you can have the hole where you want or does the speaker have to be center of the stud? I don't have mine centered as the studs are not in the place I want them to be! I don't know what these builders were thinking! I have a gas pipe going through the spot where I wanted a string of recessed lights... Now I am pactching up the the roof, very annoying.

I would also be interested in hearing if anyone can comment on how much sound really comes out of these speakers normally? I don't watch movies at crazy volumes... I only have these for the rears.

McCall

· #11 · May 16, 2007

Freddy B with your two posts where do you come from with all this technical information?

There are a lot of experts on here on these subjects and they don't seem to be saying the same thing you are so what is your background to give such info?

Dennis Erskine

· #12 · May 16, 2007

In-Ceiling/In-wall speakers which have integrated back boxes (not add-on or third party) are the only ones that should be used. By building a back box to a cheap, non-enclosed speaker will change the tonal characteristic of the speaker considerably. Speakers of this nature are available from many sources including Triad, Niles, Meridian and others.

I believe Freddy is making, as J-School would describe, a "glittering generality" which is not supported by specific cases or specific chemistry. I believe he'd prefer a more expensive, more difficult to install, less effective method such as MLV type products.

FreddyB

· #13 · May 17, 2007

It is funny you mention two posts... it appears that the latest has been deleted...Wonder why?

Well, the short answer would be 30 years in the design, production and marketing of many of the acoustic /sound reduction materials commonly referred to on these forums. Background also includes extensive R & D and commercialization of polymer based products including several patents for products and processes. I was playing with visco-elastic materials for sound reduction, vibration and other acoustic applications 20 years ago.

Like any material, it has place. Long term noise reduction applications are not one that favors damping glues, paints, spray-ons, etc.

Acoustics can be over complicated especially when you are discussing residential noise reduction or acoustic improvement. As time permits I will attempt to offer proven common sense advice to legitimate questions posted on this forum

Dennis Erskine

· #14 · May 17, 2007

Quote:
I was playing with visco-elastic materials for sound reduction, vibration and other acoustic applications 20 years ago.

So was I...but 35 years ago. They're still working.

aaron_hinni

· #15 · May 17, 2007

Quote:
Originally Posted by Dennis Erskine /forum/post/0

In-Ceiling/In-wall speakers which have integrated back boxes (not add-on or third party) are the only ones that should be used. By building a back box to a cheap, non-enclosed speaker will change the tonal characteristic of the speaker considerably. Speakers of this nature are available from many sources including Triad, Niles, Meridian and others.

If one were to use one of the in-wall/ceiling speakers with the integrated back boxes, would it still be desirable to mount them inside of another box for sound isolation purposes?

krasmuzik

· #16 · May 17, 2007

Quote:
Originally Posted by FreddyB /forum/post/0

Damping liquids such as Green Glue will not give you the noise reduction performance you are looking for.In theory, these materials must be sandwiched between two layers to create a sound isolation layer. Building enclosures with mdf and lining the exterior with a composite such as DuraBarrier or Ultrabarrier will do a better job at reducing both structural and airborne noise from emitting through the enclosure. You could also utilize an acoustical foam on the interior of the enclosure and mass loaded vinyl barrier on the outside.

Good old fashioned physics still apply today. You must add enough mass to overcome the sound energy.

Seems you should list your affiliations before you say one product does not work - yet other products do - it would appear you are affiliated somehow with these products - since you mentioned no other competing products. Later you mentioned you are involved in industry - I would assume as the mentioned products manufacturer/distributor?

There is a big difference on here between educating about acoustics and promoting your products - something you will learn from the mods whenever you cross that line. We have enough attempts at that on this forum already. Nobody here likes to read free advertising from those who do not support the forum. Mentioning your products in your first forum post - is not a good start.

And if you do have products to sell - this forum likes to see them tested in accredited non-affiliated standardized labs to back up performance claims. Generally we want more than single numbers - we want the lab reports that gives the performance across frequency, how it was installed, etc. There are a number of acoustic engineers on this forum that can see right thru marketing hype.

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mhallida

Discussion Starter · #17 · May 18, 2007

Quote:
Originally Posted by Dennis Erskine /forum/post/0

In-Ceiling/In-wall speakers which have integrated back boxes (not add-on or third party) are the only ones that should be used. By building a back box to a cheap, non-enclosed speaker will change the tonal characteristic of the speaker considerably. Speakers of this nature are available from many sources including Triad, Niles, Meridian and others.

Dennis,

Actually you make a lot of sense. Of course changing the speaker shape in affect would alter the characteristics of the speaker. I am convinced my AIM8 Threes sound different than in th store. Well they have a different ceiling space etc. I have nice long hollow sections which are terrible if you ask me. How much would some enclosed Ceiling speakers have set me back? Are you able to install them without tearing out your drywall?

Seem this posting is generating a lot of heat. ;-)

Dennis Erskine

· #18 · May 18, 2007

(I am not a speaker designer.) Among the criteria affecting the response of a speaker is the volume of it's enclosure. For an in-wall/ceiling speaker, the shape has far less an impact than volumetrics. Thus, an open back speaker's response will vary based upon the actual volume of the wall cavity and if that cavity has insulation or not.

Further, an in-wall/ceiling mount should damp the speaker cabinet's points of attachment to the wall/ceiling itself. There is energy transfer from the cabinet to the drywall causing resonance in the wall material itself.

A fully enclosed in-wall/ceiling speaker design will not have its response characteristics changed by wall cavity volume. If sound isolation is an issue for the room in question, then yes, I'd put the inwall in a "dog house" built into the wall cavity.

CJO

· #19 · May 18, 2007

Quote:
Originally Posted by HD STEVE /forum/post/0

I was in the same situation. My speakercraft AIM8 Fives were driving my wife crazy. I decided to have these speakercraft speaker boxes installed. They are a little costly and time consuming (drywall cut out and patch back) but it is well worth it.

http://www.avhifi.com/asp/product.as...chFor=&PT_ID=1

HD STEVE

Why not just get the Speakercraft back boxes to which HD Steve linked? I've used them before with good results.

CJ

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