John Sayers' Recording Studio Design Forum Archive

hey RJ, thanks for stopping by .

Here's the long aswer as far as I understand it.....I've got a single skin brick building with a tin roof. The tin roof is obviously very light on in the mass department, and nigh impossible to hermetically seal. So the theory is to put a 'middle leaf' on the bottem chord of the trusses, mounted on resilient mounts, and seal this against the brick work which will create my air-tight shell.

The GG is going in between the two layers of 16mm drywall for the middle leaf to try and give it the highest trasmission loss as possible without having to hang more than two layers of drywall, which would put a lot of extra weight on the truss assembly. I'm not exactly sure how it compares with a brickwall in TL terms, but i'm hoping it's at least close.

If I were to use GG on the ceiling for the internal rooms (two layers 16mm also) I would also have to use it on all the walls (two layers 16mm) to make the whole internal structure perform to the same level. That's a whole heap more GG (around 3 times as much).

The short answer.....Beefing up the middle leaf with GG is an attempt to compensate for not having built a heavy enough roof to start with . But as you build, so you learn.

Stuart might have a more straight forward way of describing this concept, but I hope I've made some sense.

So here's the floor plan i'm looking to use.
I've only drawn in bass traps for the rooms to keep the drawing simple at this stage. Inside-out construction for the walls and ceilings as suggested by John, so there'll be plenty of room for acoustic treatment once i've done some analysis of the finished rooms.

HVAC for both rooms will be handled by Daikins new whizz-bang AC's that also do air exchange. One for each room.

Treatment for the back wall of the control room will be tricky as the entry/exit door is there. Possibly a removable section for the back of the door that can be moved whe not mixing.

green gluing in progress. and a calibrated galaxy cm140 is getting shipped to me in the next couple of weeks. Hopefully that will yield some more solid results on the TL and also be used for REW analysis when the time comes.

Unfortunately i'll only have the iphone spl results to go on till then, by which time the GG and 2nd layer of gyprock will be on. Any comparison between TL for different stages of the build will therefore be a bit biased unless the galaxy agrees with the iphone 100%, which sounds doubtful

halfway through the second layer of gyprock and green glue. sealing the perimeter and sheet joins as I go. I'm really impressed by the quality of the green glue acoustic caulk, not that i've got experience with any other acoustic caulk, but it certainly stays elastic and rubbery when it dries.

sore shoulders, but progress is being made

Hey there, Steve. Just one word: Brick. I see bricks. With mortar in between (not very well laid, either). Don't forget to SEAL that entire wall, to ensure that you get good isolation! Brick and mortar are both porous, to a certain extent, meaning air can penetrate. So they do need to be sealed, especially considering the "quality" of that brick-laying job.


- Stuart -

sealed as in 'rendered' or sealed as in 'painted' Stuart? (or sealed as in 'some other kind of sealed')

thanks for the tip.

Paint is fine. Any good quality masonry sealant will work, and some of the IRC documents even suggest plain old latex. The idea is just to seal the porous surface, so air (and therefore sound) cannot penetrate.

Of course, if you really wanted to you could render it, with a nice thick layer of plaster / stucco / mortar / whatever you happen to call it, and that would have the added benefit of increasing the mass of the wall, and ensuring that all those gaps in the bricks and mortar really are closed up. But that would add expense and delays that you might not have budgeted for. As long as the entire surface is carefully sealed, that's all you really need.

thanks for the tip.

That's why posting photos and comments on what you are doing is so important! It gives you several extra pairs of eyes, looking over your shoulder and hopefully spotting things that can be improved. I wish everyone would post photos regularly, like you are doing!


- Stuart -

Soundman2020 wrote:Of course, if you really wanted to you could render it, with a nice thick layer of plaster / stucco / mortar / whatever you happen to call it, and that would have the added benefit of increasing the mass of the wall, and ensuring that all those gaps in the bricks and mortar really are closed up. But that would add expense and delays that you might not have budgeted for. As long as the entire surface is carefully sealed, that's all you really need.

Ahhh, expense and delays. There's rarely a building/construction project of any description that I know of, or have been involved in, that doesn't encounter some amount of expense and delays But at the end of day, like I said in my first post:

"I’m hoping I can get it constructed for $20-$25K (not inc gear) but I won’t set that as a hard limit as I’d rather have a better sounding room than a cheap one."

I'll most likely go for a render with a bonding agent like Bond-crete and some plasticizer to really get it to squeeze into any gaps and stick. It makes sense to really seal the brick up nice and tight while i've got the oppurtunity, as this is the one and only time i'll be able to access the walls before the rest of the build.

So it looks like the good ship 'Dog & Bear' is moving on to an unschedueld, but necessary stop, at the rendering port after a couple of days of 'finishing-the-second-layer-of-gyprock-and-green-glue' is complete

I'll most likely go for a render with a bonding agent like Bond-crete and some plasticizer to really get it to squeeze into any gaps and stick. It makes sense to really seal the brick up nice and tight while i've got the oppurtunity, as this is the one and only time i'll be able to access the walls before the rest of the build.

Smart move! Very smart.

Hope your ship and crew have a nice "vacation" in the render port! It seems to be a very popular destination, too! Vacations in that port have been known to extend a bit beyond the originally planned stay...


- Stuart -

cheers Stuart

i'm calling in the troops given the amount of rendering to be done. Hopefully the old 'beer-and-BBQ' option will get a few takers for a fun-filled afternoon of rendering madness. most of them are muso's who'll probably be happy to trade some rendering hours for rec time once we're done

on another note, the second layer of gyprock is up for the middle leaf, and i'm not sorry to see the end of it. screwing in ceiling plaster is pretty tough on the neck!!!

here's the ceiling detail for the internal rooms. Basically John's design from the manual, but with thicker insulation in the cavity. Walls will be a similar inside out contruction.

rendering begins, and it's actually a resonably swift process. sponge finished to make sure any small holes are sealed over.
there's a 20mm-30mm cavity between the brick and the slab rebate at the bottem which is hard to see in this photo. It'll be filled with concrete and then the small amounts of brickwork at the bottem that haven't been rendered will be seen to.

so we're about 90% rendered and the rest is getting done tomorrow. Now it might just be my imagination, but I'd have to say that the room has a lot more natural reverb as the rendering progresses. The green glue curing might have something to do with it as well.

Looking good! The better sound might have something to do with the better sealed surface and the increased mass, too, as well as the GG on the ceiling. Have you done any isolation testing, to see how much you are getting now that the outer leaf is done? From the way it looks, you should be getting something quite reasonable already.

- Stuart -

I'd still be using an I-phone app for testing at the moment Stuart. I'm waiting on a calibrated meter (galaxy cm 140) to arrive. Hopefully won't be too long. Looking forward to posting up some more definite results

Using my own calibrated meters (ie: ears) it sounds like there's a significant amount of TL going on.