AudioGrotto Build Diary

I dug the floors too. Wasn't even considering doing that.......now I 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?

"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.

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

"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 :)

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.

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

Oh, I´m green with envy!! Very nice build, indeed.... 8) :thu: HOOK

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

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

The only tonal diff I can imagine is that with new hardwood over concrete you would have to use a thin foam layer as a base before the wood. We did this in another room and it was not good for TL as the pad and floor acted as a resonator in the midrange. The concrete sounds great and you can always throw a rug down if you need it. Plus, when the drummer barfs, its an easy clean!!!! :shot: -ashley

Can you comment on the price for the concrete compared to hardwood by chance? p.s. Strange. It may just show my inexperience in studio design, but I always thought that the bass player was the one to barf more often. :blah:

Well, I am the bass player and I try to retain my dignity in these matters..... pass the buck to the drummer. They always need a shower.... Concrete finishing was around $4/sq ft. if I remember. Not cheap, but its a VERY durable floor. It will need a re-sealing at some point but never another grinding in my lifetime. I get a lot of compliments on the floors. They have really helped with the vibe in the place. Plus, my chair rolls effortlessly.... -Ashley

I joined this site just to be able to comment on how awesome this studio looks. What a great design! Congrats

thanks, lowemae. If you're ever down this way, shoot me a note and stop by. Ft. Wayne ain't that far.... This summer has been the busiest yet for me, getting the B room running with other engineers coming in. It finally feels like what I had imagined so many years ago when we bought the place. Again, my thanks to all here at John Sayers site for the help and support. It made a great deal of difference in the end. Actually, I have an acoustic consultation tomorrow with a condo builder as a result of the studio..... go figure :shot: -Ashley

Hi Bassman, I'm digging through the site here to find info on how best to setup my PMC AB1 monitors in my control room now that I'm rebuilding my (small) studio. I've worked on flush mounted systems before and I love it, so I would love to have mine flush mounted as well. But I haven't been able to find anyone else who has exeprience with these particular monitors until now. And here you are! :yahoo: I'm sure you love the AB1's as much as I do. I hope it's ok to ask you a few questions specifically about those monitors flush mounted like you have them. I would absolutely love to drop by for a quick listen (and see your beautiful rooms of course), but Kentucky's quite a long way away from Denmark. I'm curious to hear if you have experienced any problems? ...a need to tilt/filter the low end or anything? Your wall construction seems pretty simple. Aren't there any problems with vibrations transferred to the front wall? Have you done anything to prevent that specifically? In return, I can offer a little tip for you. I have always thought that the AB1's are awesome...yet they do have a little high mid/low treble sting that I would rather do without. So I tested a few different tweeters and I found one that is absolutely spot on for them. It has the same level of detail (I wouldn't compromise that) and character, but with that "sting" eliminated. Same price range as the original Vifa D27TG35 tweeter. It's a ScanSpeak R2604/832000 tweeter. Here's a photo for reference. It's large so I'm not attaching it here in the thread. Note that it's 4Ω instead of the originals 6Ω. If you're bi-amping then just drop it in, but if not, then you'll need a resistor in series with the tweeter. Also you'll need to "adjust" the hole behind the tweeter a bit + mount it with 5 (new) screws instead of the 4. All this is well worth the effort in my opinion. My ears are more relaxed now that the slightly fatiguing sting is gone. Also, I think that when bi-amping, the woofers and tweeters are way more easily balanced to perfection. If you experience the same stingy thing with your AB1's, then you should just go ahead and get these replacements. You'll love it.

Hey Luny Tune, I use DSP EQ on the speakers to compensate for the low end gain of the soffits and other anomalies. I had Wes Lachot help me design the soffit wall and we placed bags of sand underneath the boxes to help deaden them and minimize vibration of the soffit wall. I know what you mean about the 'sting' and prefer those tweeters to be off-axis. With the soffits angled in, that can be an issue. I have built these soffits to accept the larger IB2S when the budget allows. Also, I will be adding absorption to the front wall later this year when I get a break from working so much! That will change a lot. The speakers have been great for so many years. I am looking forward to fixing the front wall up a bit more and adding some more bass trapping to the room, plus rebuilding my console to accommodate the Nuage units I've had for a while. Time for the upgrade... :horse: -Ashley

Alright. Thanks! :) I'll have a little chat with myself about whether or not to make it a firm or soft front wall, then...