AVS Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
66 Posts
Discussion Starter #1
Hello,

I am at the very early stages of my home theater design/build and definately a newbie when it comes to this stuff.


This is my wife and my second house. In our last house we had a theater in the basement, but there was no sound isolation/absorbtion done. The thing I didn't like about it was, the sound could be heard throughout the house which i expected. The one thing I didn't think would happen was the amount of noise that would occure from vibrations in my ducting in the ceiling. This drove me crazy.


My first question is, what are some good common practicies for making sure that the ducting does not vibrate and rattle as it did int my last home? I have seen insulating, caulking, taping, etc done in some of the threads here. Should i tape the duct joints with some duct tape and then get some bats of unfaced r11 insulation and wrap it around the ducting? Or?


Second, If i were to fully insulate the walls and the ceiling in the theater would i notice much benefit if I don't build the room within a room, Green Glue and all of the other techniques? I want to isolate the sound as much as possible, and want to do those things that give me the most bang for my buck. (Master bedroom will be right above the HT. )


Finally, the room has a large opening on the one side where my door would go. We would like to be able to open this room up when entertaining so had thought about french doors or something of the sort. Is there a better door one could get that allows for a 6 foot opening?


If it would be easier I can provide some pictures if needed?


Looking for a small indoor project this weekend since it is going to be a high of -10 on Saturday. Yuk.


Love these forums and thanks for the assistance.
 

·
RETIRED theater builder
Joined
·
35,156 Posts
I'll tackle the HVAC part. (cut and paste from other threads)


If your house is like most of ours, you have large metal ducts called "trunks" that supply heated and cooled air and bring it back via returns. Off of these trunks you will have individual take off ducts that each supply an individual register somewhere in the house.


The worst cast scenario is you have metal take off ducts,


So you build a theater and it should have both supplies and returns. The most common technique is to just cut in a couple of supplies and returns and use metal ducts to connect up the theater.


If you or your contractor does this, it is nearly identical to cutting a hole in the ceiling to the room above from a sound containment perspective.


There are are number of solutions and generally the amount of sound isolation is dependent on how much you are willing to spend.


The cheapest solution is to not connect the theater with metal ducts. Instead use flexible Acoustical Ducts. or duct board. Include a few 90 degree bends so that the sound carrying capacity of the duct is reduced.


see the two products on the right of this chart:

http://www.flexmasterusa.com/pg/fdpp.php


I know they make in-line duct mufflers but they look like a small section of lined pipe:



http://www.espenergy.com/images/MuffPic.jpg



There are other solutions including zoning the theater, or installing a totally separate HVAC for the basement or theater.


Lastly you can construct baffle boxes for the supplies and returns.


While I'm not wild about the final product of the attached write up it shows you the concept of building a serpentine pathway lined with acoustically absorbent material. I think you can do it 3/4 plywood or MDF and linacoustic versus the authors choice of materials. You could build a baffle box inside the joist space.

http://paulmadison.com/baffle.html
 

·
Registered
Joined
·
66 Posts
Discussion Starter #3
Thanks for the reply.


I am pretty certain the trunk (thanks for the right term) is what would vibrate in my last home as it ran the length and smack down the middle of the room. How does one go about insulating that and and minimize this vibration?


Also, what makes the accoustical ducting better than the insulated ducting you can get at a home store?


Thanks again.
 

·
Registered
Joined
·
161 Posts
Using duct liner INSIDE will stop sound travel (works great), but packing mineral fiber around the outside of the metal ducts will do wonders to damp out rattles (which is what I did)


Interestingly, I think my system is now much more efficiant since less heat is lost to the steel ducts.


Gosh
 

·
Registered
Joined
·
66 Posts
Discussion Starter #5
When you say use duct liner "inside", do you mean placing some sort of liner on the inside of the trunk?


Mineral fiber, is this product similar to a rigid foam insulation? I am not really sure what mineral fiber is or where its normal application would be? How did you secure the mineral fiber to the ducting?
 

·
Registered
Joined
·
161 Posts

Quote:
Originally Posted by olson2334 /forum/post/12856131


When you say use duct liner "inside", do you mean placing some sort of liner on the inside of the trunk?


Mineral fiber, is this product similar to a rigid foam insulation? I am not really sure what mineral fiber is or where its normal application would be? How did you secure the mineral fiber to the ducting?

linacoustic is ment to line the inside of a duct (see the manufact app notes.)

Like this... http://www.avsforum.com/avs-vb/showthread.php?t=946354

Go down the thread and you will see me ripping my ducts open to put in the liner. (My methods were a little hairy)



As for mineral fiber, Roxal at home depot... commonly available I think.

In my thread you will see some cases of my packing the mineral fiber above the ducts and inbetween them. but you will need framing to hold the insulation under the ducts, or even use long screws and tabs/plates/big washers/chunks of wood/bits of plastic or whatever to keep the screw from pulling through the insulation.



Perhaps I should be posting more info on my thread.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #7
Excellent. I see how it works now.

Are you going to fill the space between the joists with the mineral fiber as well?
 

·
Registered
Joined
·
161 Posts

Quote:
Originally Posted by olson2334 /forum/post/12857550


Excellent. I see how it works now.

Are you going to fill the space between the joists with the mineral fiber as well?

Yep... ( the joist spaces hidden above the ducts are completly filled now)
 

·
Registered
Joined
·
4,367 Posts

Quote:
Originally Posted by Goshwin /forum/post/12855569


Using duct liner INSIDE will stop sound travel (works great), but packing mineral fiber around the outside of the metal ducts will do wonders to damp out rattles (which is what I did)


Interestingly, I think my system is now much more efficiant since less heat is lost to the steel ducts.


Gosh

I have an issue with sound from my theater room going throughout the ductwork in my house -- particularly into my son's bedroom.


The two main HVAC supply trunks go through the theater room ceiling. Right above the ceiling tiles.


Would duct liner inside those trunk lines really stop sound (100%) from being heard at other vents in other rooms in the house?


If so, what exactly is the type of duct liner to be used?


And can duct liner be put in existing duct work?
 

·
Registered
Joined
·
161 Posts

Quote:
Originally Posted by caesar1 /forum/post/12880220


I have an issue with sound from my theater room going throughout the ductwork in my house -- particularly into my son's bedroom.


The two main HVAC supply trunks go through the theater room ceiling. Right above the ceiling tiles.


Would duct liner inside those trunk lines really stop sound (100%) from being heard at other vents in other rooms in the house?


If so, what exactly is the type of duct liner to be used?


And can duct liner be put in existing duct work?

100%? thats hard to say.


Linacoustic cuts the sound that will reflect along a duct but its a function of distance and if there are any bends in the duct.Two feet of liner won't do much, but 10 feet and a right angle bend will remove alot. (it worked well for me)


Gosh.
 

·
Registered
Joined
·
4,367 Posts

Quote:
Originally Posted by Goshwin /forum/post/12881394


100%? thats hard to say.


Linacoustic cuts the sound that will reflect along a duct but its a function of distance and if there are any bends in the duct.Two feet of liner won't do much, but 10 feet and a right angle bend will remove alot. (it worked well for me)


Gosh.

The ductwork that I assume will get the liner applied is a straight shot through the ceiling of the theater room. Since that room is 20 feet long, then it would be 20 feet of liner.


Here is a picture of the ductwork -- the middle trunk line in the picture is the one that feeds the bedroom level in my house:




My question is, would lining the duct in that room (20 feet of liner) really stop sounds from the speakers in the theater room going through duct work into a bedroom -- two stories above the theater room?


Right now, you can hear what is being played through the speakers, come through the supply vent in my son's bedroom (and other bedrooms).


My concern is that it will be costly, since they would have to take down this 20 feet of ductwork, put in the liner, then put it back up.


My other concern is that duct liner is really for cutting down HVAC noise (i.e, the noise of air going through the duct work) -- not hearing voices or sounds from one room getting into the ducts, and coming out in another room. My belief is that the speaker sounds from my theater room are getting into the trunk lines, by the sound going up through the acoustic ceiling tiles and then into the supply duct trunks themselves.


So I dont' want to do it unless it wil be pretty likely to work.


Also, what exactly is the right type of liner to use? Brand names, etc.?
 
1 - 11 of 11 Posts
Top