Seeking help w/ soundproofing basement ceiling joists

[tubino]

I have an unfinished basement space, concrete floor and (mostly) cinderblock walls, about 18’ x 20’ that I want to turn into a serious two-channel audio room with HT potential. I will have to go somewhat slowly with the finishing, but it seems I should go in this sequence:

• Soundproof between ceiling joists to block sound from room above
• Install electrical in joist space under/between soundproofing, with at least two 20A circuits (one for audio, one for bench/workspace/second stereo) with normal height outlets
• Create wall to separate from rest of basement (open space is more like 18’ x 36’)
• Panel cinderblock walls and other walls with rigid fiberglass.
• Carpet floor, and maybe use vinyl damping sheets under carpet. Or build floating floor – but lose more height!


ALL SUGGESTIONS WELCOMED!
I’m looking specifically for advice on #1. I figure first worry about blocking sound, then use rigid fiberglass + foam to absorb. So on the blocking part, I’ve got the 16” spaced joists. How about I get ½” or 5/8” drywall, cut in 8’ strips to fit between joists, apply 3 or 6 lbs/square foot vinyl sheet on top, then nail into underside of flooring? If that’s reasonable, do I cut to leave ½” vinyl sheet on each side of the drywall, so that when I push it into place, the vinyl “seals” or isolates the drywall from the joists? Also, there are hundreds of nails sticking down from the flooring. So what if I use some kind of filler/spacer to avoid having to cope with all the nails, such as the rigid fiberglass instead of the vinyl?

Then if I want to go really crazy, I do a second layer of drywall plus the vinyl. I could use the resilient channel tricks to isolate from the joists, while adding a little air space between drywall layers. Or should I spend the extra attention on the naked joists instead?

Thanks for any pointers!

--tubino

 

[bpape]

IF your primary goal is to block sound from ENTERING the room from above, filling with insulation and double drywall should be plenty. If you're trying to keep sound from GETTING up stairs FROM the room, that's a different story.

Please clarify so we can help.

Bryan

 

[tubino]

If you're trying to keep sound from GETTING up stairs FROM the room, that's a different story.

I'm trying to keep sound from going into upstairs room FROM the HT/Hi-Fi room -- and I want to be able to turn it up. I know it's not going to be easy. I have Tannoy System 15 DMT II speakers, as well as a pair of Jensen Imperials, either of which can generate serious SPLs with low distortion -- which is one reason I like them so! (The dynamics is the other big reason...)

It just occurred to me that my chances for success go way up IF I decided to run the electrical around the wall in conduit, and completely avoid using the ceiling. There is almost no electrical, and zero plumbing or other in between the joists now, and if I don't have to worry about ACCESS, I could do a much better job of making an effective sound barrier... by stuffing the joist spaces, then using drywall, nailed to something isolated from the joists, and topped with the mass-loaded vinyl...

Then instead of finishing the drywall, I use sound-absorbent material on it, such as cloth-covered rigid fiberglass panels. But it seems a shame to put a reflective surface over those joists, when those deep hollows look like little bass traps waiting to be exploited...

 

[rikmeister]

instead of using sheetrock on the ceiling why not use the sheets they use in a

bathroom for using tile . that is waterproof then and i am sure there is probably a kitchen and a powder room above that ceiling if you ever get a leak you will wish you did not have sheetrock. Kilz will sometimes get rid of the water mark but not always and the sheet rock degrades if it gets wet. If you have the bucks you could then think of a ceramic ceiling that would reflect all the sound down not up. but it would be costly unless you are handy and can do it yourself.

 

[MacManNM]

Ok here's what I recomend:

The ceiling:
Fill the floor joists with something like R-13 insulation, and then you can just drywall over it. Your main concern isn't going to be the ceiling. It is going to be the walls transfering the sound. The walls have a much greater surface area. If you are worried about the transfer between the drywall and the floor joists, then you can place foam insulation in addition to the fiberglass.

The walls, fur the walls out with 2x4's and fill with insulation. You can do it 24" oc. You want to make sure you build the walls about 1" away from the concrete. This room will be really dead. I did this in my basement and am very pleased with the results.

As far as hearing sound from upstairs or downstairs, its the theory of reciprosity. The attenuation is the same from both directions.

 

[bpape]

When you fill the stud cavities with insulation and then cover with a single layer of drywall - they ARE little bass traps. If you double up the drywall, the rigidity helps with isolation but stops much of the absorbtion. A matter of priorities.

If you really want to stop the bass from going upstairs, as you said, don't use the ceiling for much of anything.

The optimal ceiling solution is:

Fill cavity with insulation
RSIC Clips and hat channel
Layer of Dryall
Green Glue
Layer of Dryall

Whether this is in the budget or not is unknown.

Also, if you REALLY want to isolate the room, the side walls should not touch the joists above. They should be mounted with appropriately designed RSIC clips (PAC International). You can do all you want with the ceiling but if the walls can still transmit vibrations through the structure, you're hindering the efficiency of the isolation.

 

[tubino]

The optimal ceiling solution is:

Fill cavity with insulation
RSIC Clips and hat channel
Layer of Dryall
Green Glue
Layer of Dryall

Thanks for help! This is taking shape...

Dryall is a typo for drywall, right? Sheet of 1/2" gypsum? But what is this Green Glue?

Agreed about the walls. I am lucky that two of the walls are cinder block/foundation. I don't think I need to worry about those. But once I turned up the Jensen Imperials with Chemical Brothers or similar playing, and it was quite obviously VIBRATING the bed TWO FLOORS UP. This was on less than 25 watts per channel (deHavilland 845 amps), BTW -- I estimate the sensitivity of the speakers at around 105 db.

So that had to be going through the floors and walls. That's why I know this isn't going to be easy. The false wall idea sounds just right to me. I can take some time to get this right -- doesn't have to be done this week! And I can do a fair amount of it myself, I think.

Thanks again for the ideas.

 

[bpape]

Yes. Should be DryWall - not Dryall. Can't believe I mistyped that twice!

Green Glue is a product by a company called Audio Alloy. One of the principals posts on several forums - his name is Brian Ravanas (I think that spelling is correct...) It is an elastomer type glue that is trowelled between layers but doesn't ever get totally hard. It's kind of like MLV but better. Any vibration in the first layer must make it through not getting coverted to heat by the Green Glue - then go through the second layer. Now mount all that on RSIC and hat channel and there is VERY little that will get through. This product is not for the faint of heart. It is messy and it is expensive (but less than MLV for the same area)

As for the cinder block walls - don't kid yourself. If you leave those walls and the ceiling just goes over to them, the sound will go RIGHT THROUGH that wall and upstairs through the airgaps in the concreate block. You'd be well served building a wall inside the cinder block and decoupled from the ceiling.