AudioGrotto Build Diary

lilith_envy · **Posted:** Mon Nov 02, 2009 11:26 am

how's your relationship with the judge?
Did you get the extra 20 dB reduction from the window?

bassman · **Posted:** Mon Nov 02, 2009 12:14 pm

Interesting you should mention that. I think we're doing pretty good. We had a halloween party last weekend with a DJ and he reported 51-52 dBC inside his house. I'd say we were pushing 100+ inside. That seems pretty good. The windows work great. If anything, the flanking through the eaves and from the front of the building are now the limiting factors.

As I can afford to do it, I will cover the rest of the windows with the same treatment as I want more isolation from the traffic noise on the other side of the church. Its an ongoing process I'd have to say... :horse:

Today we did some ethnic drums and percussion, including big "stomps" on the floor. No complaints. I keep him informed of things that might be loud so he knows to call me if there is an issue. That's reasonable to me and helps keep communication lines open!

-ashley

bassman · **Posted:** Thu Mar 25, 2010 12:45 pm

Hellooooooooooo

Just wanted to post back here with some follow ups on the studio outcome. We never hear from those builders once they're off and recording again do we??

Anyhow, a couple of things I would stress to other builders out there:

1. Acoustic caulk does NOT constitute a resilient connection.

We had a couple walls that had to be close to a non-isolated ceiling and we connected them with a large bead of acoustic caulk and backer rod. These connections transmit sound pretty well. Too damn well for my money. We had to pull out the caulk seams to get the transmission to stop. Foot fall noise from the space above was traveling into the control room and drum noise was of course going back up.

I would have, in hindsight, mounted the ceiling drywall on RC and made the HVAC runs in there on their own resilient mounts. This was hard to anticipate since the duct runs were added later. Proper building plans would have helped here. Be VERY careful when implementing firestopping in studio building. Even Rod's book has these caulk seams in the fire blocking diagrams. I'm not sure if I did something wrong but I just don't think the caulk has enough resilience to truly do a good job isolating between spaces.

2. Forget the green glue and go with another layer of rock if you have the space and structure to support it.

I went with three layers in the main control room and two layers everywhere else. They all have a layer of GG. And don't get me wrong, GG works, just for my money and given that I could hang that weight on the ceilings, I would have gone for three layers all around in every room with the money spent on GG. When space is at a premium and weight is an issue, GG baby, all the way.

If I desire, I can go back and put up another layer everywhere as the structure can handle it, but that is a last resort if isolation is not satisfactory. So far, it is minus the above caulk problem.

3. The more you treat a room, the more obvious the remaining problems become and the more difficult it is to fix those.

My control room is well damped but also has some RPG bad panels in the back so its not a 70's disco cave, but its nice and treated. The remaining acoustic issues become much clearer since most of the major ones have been dealt with. this makes the ones left more annoying to me. I have a couple modes that are so clear, I can move my head to a point where the frequency is totally out of phase in one position in the room. Its interesting.....

Just using a tone generator and an SPL meter, you can run through the low end in your room and see right away what's going on. I've been using a little corrective room EQ with great results. Don't underestimate the soffit bass effect! I love my bottom (and hers too) but too much is too much! Proper filters are needed to correct most speakers for soffit mounting.

OK. Back to messing with this kewl Federal compressor.....

-ashley

CNavas101 · **Joined:** Tue Jun 01, 2010 10:59 am **Posts:** 4

hey bassman,

check ure inbox =)

Sixstringer · **Posted:** Fri Mar 18, 2011 2:48 am

Those floors look amazing!

What did you do at the point where the floor meets the wall/drywall?

Pure L · **Posted:** Mon Mar 21, 2011 7:37 am

I dug the floors too.

Wasn't even considering doing that.......now I am.

Pure L · **Posted:** Mon Mar 21, 2011 7:50 am

bassman wrote:

Be VERY careful when implementing firestopping in studio building. Even Rod's book has these caulk seams in the fire blocking diagrams. I'm not sure if I did something wrong but I just don't think the caulk has enough resilience to truly do a good job isolating between spaces.

bassman,

What method did you use?

I'm under the assumption that, say, for fireblocking you want to use some sort of insulation as (very slightly compressed) "backer rod" and then go over that with some fire-rated caulking using a heavy amount of it.

I wanna say I read that the compression amount should be just enough to make sure it holds forever (i.e. it won't move it self out somehow) but no more.

Any expert wanna chime in here?

xSpace · **Posted:** Mon Mar 21, 2011 11:33 am

"Even Rod's book has these caulk seams in the fire blocking diagrams. I'm not sure if I did something wrong but I just don't think the caulk has enough resilience to truly do a good job isolating between spaces."

Rod presented what is going to keep you 1) code compliant and 2) healthy in the event of fire.

If we consider there are three components in this configuration, fire rated caulk/rockwool or comparable gas impeding material/fire rated caulk it should be easy enough to determine that the fire rated caulk doesn't create a bridge if there is not something between the two caulk joints to continue this bridge.

If the rockwool is over compressed...there's your trouble:) it isn't the caulk joint. And in an assembly like this, fire rated caulking (which is a whole nother animal from your basic run of the mill latex/silicone/butyl caulk) has a higher tolerance to heat, much like any type of sealant used on a motor engine where heat is constantly in the materials/environment and that is why it has to be a fire rated (usually red in color) caulk designed specifically for these purposes.

It isn't (fire rated caulk) acoustical in nature...much of what goes on in construction of theses rooms in general isn't...methods and procedure...but by and large you are attempting to build to a higher degree of isolation since everything around you, residential and commercial is designed to some level of isolation.

What we all attempt is to get past that minimum level of isolation and shoot for a higher level.

bassman · **Posted:** Mon Mar 21, 2011 11:00 pm

I had a nice big reply all typed up for this but had to re-login and lost the darn thing.... Curses! :evil:

Anyhow, I was not required to use fire-rated caulk for the assembly. I had to have drywall across the gap and caulked at the seams. I also had some walls where we had to extend drywall up to the ceiling to prevent smoke/fire from going into the ceiling cavity between floors.

The issue that I am sensing is that the caulk used on these seams has hardened too much. Compressed rockwool is not the problem here. A small caulk seam that isn't super squishy will transmit lower frequencies. We're talking 1/2 to 3/4" caulk seams here. There is simply not enough deflection to stop 40hz. One reason for my thought is that footfall noise from upstairs has increased over time (about two years from initial drywall). This leads me to believe the caulk's resiliency has failed during that time. Also, I do have access to some of the caulk joints and they are fairly hard in spots. All it takes is one small area to get really hard and blammo, you have coupling of structures.

The second issue has to do with stiffness and mass. On the larger ceilings, the membrane resonates easier and at lower frequencies. I would over-engineer the ceiling framing for stiffness whenever possible and in my case would have opted for another layer of drywall for that reason, 3 layers total. I would have traded the green glue layer for a third drywall layer as the cost is almost the same. My conclusion is that unless you cannot isolate your framing, bag the GG and go for more drywall layers. When framing must touch, GG is the best solution though.

Where the floor meets the wall, I have a plastic edge strip for a very simply and clean finish. It also forced the drywallers to take the sheet as close to the floor as possible which helped in isolation.

-ashley

xSpace · **Posted:** Tue Mar 22, 2011 11:11 am

"I had to have drywall across the gap and caulked at the seams. I also had some walls where we had to extend drywall up to the ceiling to prevent smoke/fire from going into the ceiling cavity between floors."

That is a fire stop area. It is also a more rigid connection than what Rod suggested. I understand that you have to work in side of the environment that your particular area governs, these things happen

Pure L · **Posted:** Tue Mar 22, 2011 1:49 pm

Quote:

When framing must touch, GG is the best solution though.

I'd bet that GG doesn't have the fire-retardant property that a fire-approved caulk would.

Actually, I'm not quite sure what you mean there....

Just out of curiosity, what is the consistency of fire-approved caulk? Anyone?

It would make most sense that it was one of those caulks that "dry" creamier than the average sound sealant.

As hard as the osi is that's already on my first leaf, I'd be reluctant to use it to connect anything as well. It turns to rock.

I haven't seen it in the summer time though.

bassman · **Posted:** Tue Mar 22, 2011 2:51 pm

RE: Green Glue, I was talking about the difference between using GG inbetween two layers versus going for three layers of 5/8" rock. If I could do it again, I would go for the third layer as the cost is almost the same. Not the same issue as the fire-blocking.

I would have LOVED to use rockwool for fireblocking, but its not allowed and in Rod's book, it showed clearly that drywall was used across fire-blocking chases and sealed with caulk. I'd have to go back to double-check but I pained over that issue for a while and had to get an architect friend in on the case to get an assembly approved by code enforcement.

Make that gap BIG and use a lot of caulk!

-ashley

HOOK · **Posted:** Tue Mar 29, 2011 2:17 am

Oh, I´m green with envy!!

Very nice build, indeed....

HOOK

bassman · **Posted:** Tue Mar 29, 2011 2:04 pm

Thanks, HOOK. Session in the green room then for you sir.... I need to see Sweden in my lifetime...

-ashley

Sixstringer · **Posted:** Tue Mar 29, 2011 9:38 pm

Ashley,

I am very much considering staining my concrete floors as opposed to hard wood. Now that you've been in your studio a while, how do you like the sound? Can you tell any tonal differences from the concrete (as opposed to hardwood)? Any regrets at all from going with the concrete floors?

Thanks

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