[JLM]

You are fortunate to have 10 foot ceilings as ceiling height is typically the limiting factor in any residental listening room.  Looks like a good plan.  Don't forget to install a supply air diffuser and to use flexible duct.  Remember to account for the reduced airflow compared to sheetmetal ductwork.

We built our house with wooden floor trusses, if that's what you've got there's no problem.  If they are wooden I-beams, I'd check with the manufacturer to see how they'd recommend fastening to two layers of drywall to them (nailing/screwing a single layer using the RSIC clips shouldn't be a problem).

Depending on how cold it gets in the winter where you live and how well the foundation perimeter is insulated, a nice pad/carpet should do the trick.

I trust the double door is a CAD fluke (shouldn't be needed if an exterior grade door is used or if the hallway has another door).

Will you be surface mounting the wiring as suggested above?  Could hurt resale a bit. 

What's the water table like around the house.  Does the sump pump ever run?  Is the basement prone to moisture?  If it could be a problem I'd go with a large rug (carpets can have a finished border added), and replace the bottom few inches of drywall with foundation grade plywood and/or treated lumber.  Of course any framing in direct contact concrete should be treated lumber to start with.

[Daygloworange]

I trust the double door is a CAD fluke (shouldn't be needed if an exterior grade door is used or if the hallway has another door).

Double doors are a really good idea. Doors are typically the weakest links in lowering noise floor. Making sure they are some type of solid, or insulated door with sealing in the door jamb, and door stops is important too. Using an outdoor type jamb where the bottom of the door seals against a stop on the threshold is recommended.

Cheers

[ctviggen]

If you want to see a cool home theater (and house) check out the PDFs here, particularly Issue 07:

The "Optimum Performance" home

[bpape]

Bringing up HVAC is an excellent point.  This is the one thing that busts more isolation schemes than anything else.  There are a few rules to help:

- Make sure there are at least 2 90 degree bends between the time the duct enters the real room and the time it leaves the protected shell.  If there's no room for this, box the duct in MDF OUTSIDE the room until you can do that.

- Never use tin ductwork

- For sound performance, use high flow - low velocity vents.  Think like the long vents in commercial buildings.

Remember when I said something about building soffits after the room was already drywalled?  This is another reason for doing that.  The flex ducting can enter the room inside the soffiting and run the length of the room inside the soffit with a couple of bends and only enter the real room after that fact.  On the return side, you'll have 30' + between the duct and the exit of the room with no way for sound to enter anywhere else.

If you use normal 'in the joist' routing, the bass frequencies will go right up through that big hole and go through the flex duct and smack into the floor above like there's nothing there.  The rest of your soundproofing is wasted.

Bryan

[Papajin]

The Kinetics clips are OK - certainly better than nothing.  The PAC RSIC-1's are better - less contact, different resonances, etc.

As for the floor in a townhouse, yes - the slab will transmit sound pretty well.  Look at a product called Dri-Cor.  It's sold at Home Depot.  It only loses you 3/4" or so, gives you the warmth, the feel of a wood floor, and allows you to build walls on top of it for pretty good isolation at a reasonable price.

Bryan

Hey Bryan!

Great call on the DRICore.  That stuff looks great for use as a subfloor in a basement!

I would have thought the IsoMax clip would have been better since it's completely isolated by a rubber grommet/gasket from the hat channel (or whatever it's called) which of course is what the drywall will actually be attached to.  The RSIC-1 is metal on metal where the clip holds the hat channel isn't it?  Isn't there a possibility of noise where the 2 pieces of metal interface, or am I overthinking this?

[bpape]

With as much weight hanging on that channel, there will be no rattling - trust me.  The reason the RSIC-s work better is that there's less contact area.  For the solid rubber to be sturdy enough to do all the holding instead of metal, it necessarily transmits more sound.  That, coupled with MUCH more surface to surface contact makes them not perform quite as well.

As I said, they're certainly better than nothing.

Bryan

[mgalusha]

JLM,

Thanks for the feedback. Yes, the high ceilings are going to be very much appreciated. I haven't measured them yet but they were advertised as 10ft when we bought the house. The are pretty high and it doesn't feel like a basement.

I had planned on using a long, low velocity vent and putting in a couple of right angles between the outlet and the supply duct. I like Bryan's idea of building an MDF box for this as well. Easy enough to do and not expensive.

Water table seems to be low enough. I've never seen a drop of water in the sump but of course saying that will cause it to fill. Our community is on well water and there are 9 active wells feeding the distribution system so I'm hoping that keeps the water table from creeping up to high.

The double door isn't a CAD fluke, I saw this in the Green Glue literature where they show double walls and since I plan on using a double wall adding the second door won't add a huge amount to the cost of the room.

I'm in Colorado so it can get cold but it doesn't get below 0*F too often. It averaged about 55*F in that room last winter but that is with bare concrete on all sides and no carpet. It's just a concrete bunker at the moment. The outside walls will all be full of insulation. In my HT at our old place it was basically the same, insulated perimeter walls in the basement and 8lb pad/carpet on the slab and it was very comfortable year round.

I'm not going with the surface mounted wiring. Since I'll be able to (I hope) ensure the outlet boxes are installed the way I want sealing the up well shouldn't be a problem.

mike

You are fortunate to have 10 foot ceilings as ceiling height is typically the limiting factor in any residental listening room.  Looks like a good plan.  Don't forget to install a supply air diffuser and to use flexible duct.  Remember to account for the reduced airflow compared to sheetmetal ductwork.

We built our house with wooden floor trusses, if that's what you've got there's no problem.  If they are wooden I-beams, I'd check with the manufacturer to see how they'd recommend fastening to two layers of drywall to them (nailing/screwing a single layer using the RSIC clips shouldn't be a problem).

Depending on how cold it gets in the winter where you live and how well the foundation perimeter is insulated, a nice pad/carpet should do the trick.

I trust the double door is a CAD fluke (shouldn't be needed if an exterior grade door is used or if the hallway has another door).

Will you be surface mounting the wiring as suggested above?  Could hurt resale a bit. 

What's the water table like around the house.  Does the sump pump ever run?  Is the basement prone to moisture?  If it could be a problem I'd go with a large rug (carpets can have a finished border added), and replace the bottom few inches of drywall with foundation grade plywood and/or treated lumber.  Of course any framing in direct contact concrete should be treated lumber to start with.

[bpape]

If you don't do the surface mount electrics, then plan on building an MDF box for the plastic box to sit inside.  Caulk where the romex enters the MDF.  This is a much better seal and much better isolation that expecting 1/16" of plastic (caulked or not) to stop bass passing through it.

Bryan

[JLM]

Mike,

If the walls of the room aren't interior, there shouldn't be a sound transmission problem (need for surface mounted wiring or double/staggered wall construction).  We used 1 inch foil faced (both sides) high density foam board with insulated 2x4 stud walls inside our cast in place concrete foundation walls and here in Michigan haven't had a problem with the cold.

Flexible/insulated ductwork would be much cheaper/easier than building MDF ductwork (which is probably a code violation anyway as supply air plenums aren't allowed).  The MDF can dry out and catch fire from months/years of dry warm air passing through it.

Whatever number of doors you use, make sure they are sealed and at least solid core.  Just using an insulated exterior fiberglass door is the easiest/cheapest way to go and something a residental contractor would be familiar with.

BTW, having potable water wells has nothing to do with ground water.

Do keep us posted.

[bpape]

The MDF box is not the duct.  The duct is still flex duct.  Building the MDF box around it is purely for sound isolation purposes.  I'll guarantee you it's not against code - I have customers do it all the time and inspectors pass it all the time.

Foundation walls do not need to be staggered stud I'll agree.  But if at all possible, make sure the insulation is fiberglass, mineral wool, or cotton.  The foam, while a great thermal barrier, is pretty much useless for sound isolation.  It's closed cell foam which has no sound absorbtive properties like open cell foam does (which is a lousy thermal insulator by the way).

Bryan

[MaxCast]

Mike, I think the angled walls is a good suggestion.
Have you gotten to the absorption stage yet?
Have you thought about building corner bass traping into the wall/interior design?

Looking forward to hearing about your journey.  I will be redoing a 16x30 room within a year.  Water and drywall are my first concerns.  I will be researching a double pump sump or something to that effect.

[Daygloworange]

Mike,


).  The MDF can dry out and catch fire from months/years of dry warm air passing through it.

I would never say it's impossible, but, I would find that hard to believe. Have you seen any reports of this? There are tons of fireplace surrounds for electric and gas fireplaces, and they are exposed to much higher temperatures.

Cheers

[bpape]

If you're going to do angled walls, just remember that you need at least 1" per foot on each wall to be really effective.  Since you have the luxury, I'd probably do the ceiling tapered before the walls since height related issues are the hardest to deal with. 

Bryan

[Papajin]

One thing I'm a little vague on is how to build soffits while maintaining isolation.  On the main part of the walls and ceiling, you can use the RSIC-1 or similar with hat channels to hang the drywall, but what about on a soffit where you may need a drop of less than 12" to get around the obstruction (I-Beam, Duct, etc.)?  It looks like one of the other RSIC products might do the job, but it's hard to tell without having one in hand which one might be right for something like that.  Any thoughts or experience?