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PostPosted: Wed Feb 23, 2011 3:38 pm 
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Joined: Thu Nov 26, 2009 2:33 pm
Posts: 34
Location: Findlay, Ohio
HVAC silencer Boxes design: (see drawing below).
Box material: outer shell is 5/8 drywall, inner shell is 1/4" osb with 1" OC703 on all faces

Duct coming in to the box is metal 6" round, path through the box is 6" square with 3 baffles also covered with 1" OC703 on both sides, exits out a 8" round metal duct register vent into the room.

My questions:
1. Does this seem like a good plan?
2. I have heard some people wrap the 703... Do you wrap it? ...and if so, what is the best way?
Attachment:
silencer1.jpg


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PostPosted: Thu Feb 24, 2011 3:35 am 
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Joined: Wed Jul 13, 2005 3:55 am
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Location: Old Tappan, NJ USA
i prefer duct liner instead of 703 as its designed for the this purpose. if i use insulation, i wrap it in plastic. as a general approach, making the box 2x the area of the inlet (or the return) will reduce the air flow velocity which can reduce air movement noise - usually more critical in places where you use microphones. you also want the flow to be balanced in the CR so any noise is evenly dispersed.

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PostPosted: Thu Feb 24, 2011 4:49 am 
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Location: Findlay, Ohio
A few questions:

Considering my 6" metal duct currently installed into my space - should my design have 12" path through them instead of a 6"? Or does just the register opening that needs to be 2X greater (12")?

Why do you prefer duct liner over Fiberglass?

My biggest concern is damping the sound transfer through the ducts to the rest of the house not necessarily air flow noise.

Here are some other options I have considered:

1. Wrapping the current 6" metal duct with the duct liner or MLV & fiberglass only at the register end to dampen/reduce the sound from filter in to the remaining duct?

2. Using insulated/flexible ducts.


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PostPosted: Thu Feb 24, 2011 6:02 am 
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Location: Old Tappan, NJ USA
the duct liner has binder built into it to prevent particle release. the entire path would be larger. another option if you don't want to (or cannot) go with the larger path, is to work on the fans driving the air flow to get them to push as slow as possible.

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PostPosted: Sun Aug 28, 2011 8:50 am 
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Joined: Thu Nov 26, 2009 2:33 pm
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Location: Findlay, Ohio
Well, I have finally finished up construction (all be finishing trim) and need to address some problems with the room. The room is extremely bright. I think it has to do with the low ceiling from the soffit over the speakers (6'8 1/2" *See photos) - It kind of sounds like it is creating a bullhorn effect. I also have some serious slap back - maybe between the floor and the ceiling. The rest of the ceiling ended up being 7'6".

Attachment:
photo-5.jpg


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photo-6.jpg


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photo-6.jpg


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photo-7.jpg


Attachment:
photo-8.jpg


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photo-9.jpg


Here is the front false wall before they were filled with OC703 and covered with plastic and black felt.

Front wall cavity:

Attachment:
photo-11.jpg




Back Wall Cavity.

Notice the 3 Baffles in place on each side of the back wall. the rest of the wall was filled with OC703 and covered with plastic and black felt.

Attachment:
photo-10.jpg


I have downloaded REW and took a measurement to see what is going on. Not really sure how to read or what measurement to make in REW.

Here is the first attempt.

Attachment:
image 1.jpg



Any thoughts on where to go from here would be greatly appreciated.

Thanks

Greg


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