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#1 of 6 OFFLINE   Shane_M

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Posted April 10 2003 - 06:45 PM

Hi all.

I'm about to embark on building my first HT room. I've got a room that's rougly 12x20 give or take a few inches and I have few questions I'd like to ask the HT pros around here.

[1] First of all the ceiling, that was a finished drop ceiling, is unfinished. I want to block as much sound as possible from travelling through the floor into the living room right above it. What is the best route to dampen or block the most of noise that will travel that route. I've read so much here and there and everyone says something different. I cannot find sound board anywhere around here, so that kind of eliminates that option. The only thing I've been able to find is sound reduction insulation. It's 1" think stuff.

Here's what I was considering doing. I was thinking of putting that insulation between the truses right against the roof/floor and then packing in regular pink insulation. The installing drywall. Think that'll work?

[2] I'm not sure if I should run the speaker wire behind the wall or along the floor and hide behind the baseboards. Any thoughts on this?

[3] What kind of paint should I use or not use? I know that I should avoid glossy paints because you want to reduce the amount of reflection.

[4] What's the best way to sound proof doors that are already installed? I believe they are hallow doors.

I think those are all the questions I have presently. I'm starting work on it on Wednesday next week - I have 10 days off. w00t!
Shane
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#2 of 6 OFFLINE   Dave Milne

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Posted April 11 2003 - 07:43 AM

Shane,
Ten days off should give you a good start on your theater. Let the chips fly...

1) I'm not sure what you're talking about regarding "sound reduction insulation". Is this a rigid material? If so, putting it between the rafters sounds like a lot of work (cutting/fitting) and probably won't be too effective (inevitable gaps). I had the same goal on a wall adjoining the rest of the house. I filled the cavities with pink insulation, laid Celotex SoundStop board over the studs first, then two layers of drywall (making sure the joints didn't line up). Note that attaching the top layer of drywall required long screws. Overall this worked pretty well... probably in the STC 52 range. You might want to look into resilient channel for some extra attenuation.

2. I put speaker wire in the wall (mostly in the soffits, actually...and then down the walls). There's no way I was going to be able to hide ten runs of 12ga speaker wire (seven audio channels and three subs) behind a baseboard. While some codes require "in-wall rated" wire, I just used plain old HomeDepot 12ga and the inspectors had no problem with it.

3. You're right about glossy --not a good idea because of annoying visual reflections (there's no difference between flat and glossy as far as sonic reflections). Are you planning a front projection system? If so, then paint color can make a difference. Darker is usually better --to keep reflected light from the screen from washing out the image. The purists use black or "18% gray" (I think) because the reflected light is color-neutral. I just used a pleasant dark gray.

4. Hollow doors are really bad acoustically. I'd replace with a solid door. I used a 1-3/4 exterior solid door (about 100lb) with a threshold and gasket all the way around. This is very important. An air gap at the bottom of the door will completely destroy all of your other soundproofing efforts. My door is probably in the STC 35-40 range). If you want better, or you don't like the idea of a threshold, you'll have to buy a true acoustic door with drop seal (think $$$).

Don't forget about HVAC: When you seal up the room acoustically, this usually means a pretty airtight package. You will need to address cooling and ventilating (a bunch of gear and viewers can be a substantial heat load). Accomplishing this without compromising the acoustic isolation is not trivial. I put in extra length of flexible duct with several bends and two acoustically-treated plenum boxes.

Do a search on soundproofing on this forum as well as the Net. You should get lots of info...

Best of luck,
Dave

#3 of 6 OFFLINE   Shane_M

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Posted April 11 2003 - 12:50 PM

Dave thanks for the info - the insulation I'm referring to looks almost like carpet underlay, yet it's much thicker. It's already designed to fit inbetween the floor struts. The only cuts I'll have to make are in width of the room.

I'm going to have search harder to try and find sound stop board. I haven't been able to find anywhere around here - that includes home depot.

Quote:
then two layers of drywall (making sure the joints didn't line up).

I guess you mean that you overlapped the board and the two layers of drywall.

I don't think I'm going front projection in this house. When we move or build our next place I'm going to work the cost of a projector into the home.

Quote:
Don't forget about HVAC: When you seal up the room acoustically, this usually means a pretty airtight package. You will need to address cooling and ventilating (a bunch of gear and viewers can be a substantial heat load). Accomplishing this without compromising the acoustic isolation is not trivial. I put in extra length of flexible duct with several bends and two acoustically-treated plenum boxes.

Huh? I have three heating ducts in this room. One of them feeds upstairs while the other two feed this room. Should I wrap them with something. What are acoustically-treated plenum boxes?

Thanks for the info thus far. I'm already a step in the right direction.
Shane
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#4 of 6 OFFLINE   Dave Milne

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Posted April 13 2003 - 01:16 AM

Quote:
Huh? I have three heating ducts in this room. One of them feeds upstairs while the other two feed this room. Should I wrap them with something. What are acoustically-treated plenum boxes?
If your ducts are already built into the house and you don't plan on making any substantial structural changes, there's not much you can do. The bedroom I expanded had the original A/C duct exiting right above the entrance door. Since this duct provided a "straight shot" down the hall to other rooms, I decided to add ductwork and have it exit about halfway across the theater. This was easy because the theater has soffits I could hide the ductwork in. I built plenum boxes to interface between the existing rectangular sheet metal duct and the new flexible round ductwork...and then back to a rectangular opening to mount the grill on. I'm sure there are pre-fab sheet metal connectors to do this, but I figured I could build something faster than searching all over town for the right size. I built them out of MDF and lined them with convoluted foam.

Wrapping the exterior of your ducts won't help acoustically (but it might improve the heater efficiency).

#5 of 6 OFFLINE   carl_lunenfeld

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Posted April 22 2003 - 12:03 PM

Dave,

Are you saying that I don't have to worry about paint color if I have an RPTV, 53 inch Pioneer? I was about to ask some detailed questions regarding this topic.

Thanks,

Carl


Quote:
3. You're right about glossy --not a good idea because of annoying visual reflections (there's no difference between flat and glossy as far as sonic reflections). Are you planning a front projection system? If so, then paint color can make a difference. Darker is usually better --to keep reflected light from the screen from washing out the image. The purists use black or "18% gray" (I think) because the reflected light is color-neutral. I just used a pleasant dark gray.


#6 of 6 OFFLINE   Dave Milne

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Posted April 22 2003 - 02:42 PM

Carl,
I don't think it makes as much of a difference with RPTV, but dark, color-neutral paint couldn't hurt. Never having owned an RPTV, I'm probably not an expert here. I can tell you that stray light deteriorates the contrast in an FP system in a hurry.


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