# Unique HT insulation situation..and question



## dogmatix (Nov 18, 2008)

I have a area (9'x30') in my finished basement I plan to use for HT. This area opens up to the rest of the basement, but I am considering a wall with a door to enclose it completely. The ceiling, which I am in the process of updating, is suspension, and only 7' high. There is not much I can do about the height because of very extensive duct network lying below the floor joists. The exterior wall was insulated with polystyrene sheets, glued to the concrete wall, then drywalled over it. The front wall adjoins the utility room, so I can treat that wall and the ceiling, if necessary, with insulation, but can't do much more to the exterior walls without ripping out drywall or building on, neither of which is an option to me.

Is there anyway I can go about it to maximize my return (of decent HT sound) on getting the best out of my situation? 

Thanks for your input.


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## ScruffyHT (Sep 23, 2008)

Are you trying to sound proof the room or improving the acoustics of the room ?


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## bpape (Sep 14, 2006)

I'll second that question and add a couple of comments.

First of all, if you wall off the area, seriously consider reducing the length. at 30', you'd be over 3x the width which isn't good.

If you have a drop ceiling, the actual acoustic height of the room for modal purposes will be the subfloor above. Fill that cavity with insulation the best you can for a variety of reasons.

With a 9' width, any side wall internal treatment will need to be 1" to save space. Plan on thicker in the front and on the rear.

Bryan


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## dogmatix (Nov 18, 2008)

My objective is to soundproof the room as much as I can. 

The base from my SVS Ultra travels to the first and second floors, even at less than 30% volume output (can't recall the dB).
I also erred on the width, although I suspect Brian's recommedndation would still stand: The room is 12 feet wide.
Thanks.


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## bpape (Sep 14, 2006)

With a drop ceiling, there's no way you're going to provide isolation. The best you can do is fill the joists with insulation and loosely hang mass loaded vinyl from the joists to block a little of it. This might gain you 10db or a little more reduction in bass transmission.

Also, you'll want to pay attention to HVAC ducting which is a huge noise transmission path.

Bryan


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## dogmatix (Nov 18, 2008)

Thank you, Brian. The HVAC lines may be the culprit because there is a lot of it, and most aren't even wrapped. The subfloor itself was insulated, I assumed because the main floor above is ceramic tiled. I thought of laying additional R38 insulation on top of the ceiling panels as I install them in the grid.
Is this worth it?


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## ScruffyHT (Sep 23, 2008)

If you are serious about stopping bass from travelling out of the room and into the rest of the house then you need to revisit the ceiling, walls, hvac and door

ceiling - I understand the height limitation here so best case would be with clips/channel + DD & GG ... if you cant sacrifice the height then do the DD & GG ( DD & GG = Double 5/8 drywall with Green Glue in between - 1 to 2 tubes per sheet ) at a minimum and loose bat insulation in the joist space

Foundation Walls - the exterior walls need to be decoupled from the foundation or you will get flanking paths around your new ceiling ... take the drywall down and frame a 2 X 4 wall 1" away from the foundation wall ... loose batt insulation between joists ... vapour barrier and then DD & GG

Interior walls - staggered stud construction with DD & GG

HVAC - use flexible ducting and build mufflers and dead vents

Door - use a solid core door with proper weatherstripping and threshold

for more detailed info on soundproofing techniques visit www.soundproofingcompany.com and read the library articles ... John and Ted will be happy to answer any questions and of course they supply the products you need as well like GG, clips etc


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## bpape (Sep 14, 2006)

dogmatix said:


> Thank you, Brian. The HVAC lines may be the culprit because there is a lot of it, and most aren't even wrapped. The subfloor itself was insulated, I assumed because the main floor above is ceramic tiled. I thought of laying additional R38 insulation on top of the ceiling panels as I install them in the grid.
> Is this worth it?


Tin ducts are the worst. Replacing with flex will at least keep them from amplifying the noise. 

Filling the joist cavities will help more with upper bass through highs rather than the low to midbass. That just requires mass like the MLV hung loosely from the joist bottoms.

Bryan


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## dogmatix (Nov 18, 2008)

Oy vey!

Thanks Steve. The ceiling I can do something about, but since this is a pre-existing home, and budget is an issue, and the wife and daughter do not think it HT sound should demand such attention, I am going to have to have to do what I can and settle with reading about other guys set up.


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## ScruffyHT (Sep 23, 2008)

dogmatix said:


> the wife and daughter do not think it HT sound should demand such attention,


Just get a MONSTER sized sub and they will get the point why a few bucks spent on sound isolation is a good thing ... that is unless whenever you watch movies you are all together so no one else is disturbed

There is another point to consider when thinking about sound isolation for a theater

Due to the fact that alot of them are built in basements there is alot of "basement noise" that can be disturbing especially when movies are in quiet scenes ... stuff like HVAC, water running in pipes, people walking around upstairs, sounds from the neighbourhood etc etc

replacing drywall and framing some walls is not that costly anyway ... if you change the roomsize to something like 9 X 20 that is only about 28 sheets of 8' drywall & 5 sheets of 9' ( for ceiling ) if you do 2 layers of 5/8" ... anywhere from $6 - $10/sheet so under $300 probably ... framing is cheap and so is R13 insulation ... you can use 1 tube of GG per sheet and still get 70% effectiveness so a couple cases should do ya


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## dogmatix (Nov 18, 2008)

When I picked up the SVS Ultra, it scared me. And when the seller told me he was building a couple of monstrous sonotubes (for his rental apartment!) I had to get out of there fast, after he helped me load the 150 lb sub.The drywall and green glue I will do when I build a front wall to recess my speakers and components.
I will put R13 insulation over the ceiling tiles as well, because the complaints is that the house just seem to vibrate all the way to higher floors, and after this discussion, I am convinced the ductwork is the main cause for the sound transmission.
Thanks again for your advice in the matter.


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## ScruffyHT (Sep 23, 2008)

dogmatix said:


> I am convinced the ductwork is the main cause for the sound transmission.
> Thanks again for your advice in the matter.


Well the HVAC is one cause :innocent: ... but not the only cause LOL

At least you have a gameplan should you decide to go ahead and soundproof the room.

Cheers


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