Resilient Channel- Yes or No?

[fbhifi]

I will be building a listening room addition to an existing home we recently purchased. Three of the walls will be exterior walls, with one (short) wall essentially attaching to the existing structure. You will enter the room from the existing front porch. I have consulted briefly with a well known acoustical designer who recommended using steel studs spaced 24” on center, resilient channel and double layer drywall with a membrane between the drywall layers. He suggested a floating floor, I prefer a concrete slab floor and the general contractor I will be using prefers not to work with steel studs.
I’ve built a few dedicated rooms in the past and always thought that the more rigid the better for floor, walls and ceilings. My present room has wood framed 16” on center walls and double drywall with Green Glue between. The floor is suspended, but is built with flat trusses which are double spaced and exhibits virtually no deflection. I have a sealed very thick fire rated door to enter the room. I think it’s the best sounding room I’ve ever had.

The only objective I have for the new room is that it sounds good, I have had an acoustician analyze room modes for the approximate size room I would like and has determined good room dimensions, so that’s done And is arguably the most imp element of the entire exercise. The deal is that I have NO NEED for sound isolation, only good acoustical performance by the room itself.

With that in mind, will the 24” OC stud spacing and resilient channel enhance audio performance or would more conventional 16” OC framing with double drywall directly connected be preferential?

I believe the argument for 24” OC, resilient channel and floating floor is to allow all four surfaces to become much more diaphragmatic and, essentially allow the room absorb not reflect, primarily, bass energy.

 

[microstrip]

(...) I’ve built a few dedicated rooms in the past and always thought that the more rigid the better for floor, walls and ceilings. (...)

Not every time.

(...)
With that in mind, will the 24” OC stud spacing and resilient channel enhance audio performance or would more conventional 16” OC framing with double drywall directly connected be preferential?

It depends a lot on room dimensions and consequently the room eigentones. A problematic room will surely need more bass absorption. At this point you should discuss it the acoustical designer that helped you. Some people dislike the resilient channel technique others love it.

I believe the argument for 24” OC, resilient channel and floating floor is to allow all four surfaces to become much more diaphragmatic and, essentially allow the room absorb not reflect, primarily, bass energy.

Yes.

 

[MarkusBarkus]

...I think most of the performance modeling is done with steel studs, 24" OC. This may explain the acoustic person's recommendation. You might ask him for performance data with 16" OC wood studs as a comparison, if you have that relationship.

Another consideration is the installation aspect. It sounds like you already have a reluctant contractor re: your requirements. This is perhaps a bit of a flag (to me).

If you don't think it's off-putting to the contractor, perhaps ask if he has experience with Z-channel? (I had an old contractor doing my kitchen. Mama-mia, he had to do everything his way. He was good, but a PITA to communicate new ideas).

Because, it is easy to mis-install Z-clip walls. If you screw the drywall with screws that are too long, you make the wall more rigid than spec by (potentially) anchoring the drywall to the studs themselves or unifying the two horizontal planes of the Z.

Contractors may also short-circuit the desired spec by blocking the walls near the floor so they can screw in baseboard. Same prob as above.

Another practical consideration is hanging things on the walls. Theoretically, you would not want to screw through the layers and into the studs, which is needed for heavy stuff. Just a call-out. Excuse me if I am being jerky, but I wanted to call out a few things with the Z-clip/channel stuff in case it wasn't mentioned.

My walls are Z-clips with homesote, constrained layer, then drywall, because that was the solution 25 years ago. It works well/sounds good (to me), but I have not measured it.

BTW, the insulation is blown cellulose, walls and ceiling. I had a pipe chase that was a little boomy as the cellulose settled, so I added external treatments there.

My floor is slab (below grade) with vapor barrier and 3mm felt layer, typical for sound and moisture management. Engineered wood to finish it. No issues sonically, for me.

If I was making a new room, I would look seriously at an MLV application to really make those walls heavy/dense. In my limited experience with acoustic folks, they tend to like what they like, and what they know, which makes sense. They surprisingly may not know much about other solutions. It's natural, but may be a limitation, although you have to settle on something and move forward! Good Luck with your project. It's exciting to work out a new plan!

 

[fbhifi]

Markus- You went far beyond the call of audiophile duty in your response. I’ve done a fair amount of research and personal analysis on this type of build and I just want to Thank you for covering virtually all the important considerations. I think that the steel studs 24”OC are a critical element in a build with RC.
Going to wood studs, probably 16”OC, and having a concrete slab floor (my preference) most likely will screw up the formula and it would be best to go a more “rigid” direction. Considering how easy it is to screw up the installation of the drywall layers on top of the RC, without constant supervision which I will not be onsite to perform, I would always question if it was all done right.

What is an MLV application?

Franz

 

[MarkusBarkus]

Mass Loaded Vinyl. They can hang these heavy sheets to drape the studs. Used for soundproofing (not your target need), but for energy control too. Your acoustic person will have an opinion, I'm sure. The catch will be shipping, if no source near you: it is heavy! However you go, it'll be fun!