Garage studio - questions

Hello, I was hoping to get some clarification regarding insulation. I was planning on using Roxul mineral wool R13, 3.5" thick with a density of 2 lb/ft3 for each wall frame (exterior and interior). I read that preferred density for mineral wool is 50 kg/m3 (which is about 3.1 lb/sq3) and 30 kg/m3 for fiberglass. The store does not carry the Roxul so I would have to order it. They do, however, carry UltraTouch denim insulation, same thickness (3.5") and density of 1.2 lbs/sq3. I also read that lower density may be better at absorbing low frequencies. Do you think recycled denim insulation is a good alternative with these specs? How does it compare to mineral wool and fiberglass in terms of density? I'm trying to yield good sound isolation and low frequency absorption. As always, thank you for your input.

Quick answers to looong outstanding questions! :

My HVAC guy said he could run the copper pipe through the ceiling (between the inner/outer frames) across the room to then connect it to the outside unit. Will this be ok?

That's fine, as long as all holes are sealed very well. Also, the condensation line should have a constant downwards angle, for obvious reasons: no uphill, as it's gravity that does the work, and you don't want water puddling in the middle of the line. The other option is to use a pump on that line, if you have to go uphill.

I've been reviewing the various silencer box designs. The question I have is how to calculate the size? Is there a formula?

Not really formula: just rules of thumb. After you figure out your flow rate (CFM) and flow velocity (fpm), then you'll know what size duct you need to use. Figure out the cross sectional area of the duct, and make sure that the cross sectional area inside your silencer is at least twice that, and that the transition at both ends is sudden: the duct enters and immediately the box is twice as big. No slow transitions. The reason is that the impedance mismatch helps you a lot with the isolation. You also want at least two baffles in the silencer, so it has to be long enough so that you can do that while still retaining the cross sectional area. Three baffles would be better: the more the merrier, but the box can get very long if you have lots... The silencer box also also needs to be lined completely with proper 1" duct liner.

Once the box is built and installed, do I need a fan to push the air into the room?

If you are going with a mini-split plus a separate duct system, then yes. Put the fan as far away as you can, on the end of the duct that exhausts stale air from the room where that exits to the outside world. Second best is to put it at the entry point, where the other duct sucks in the fresh air from the outside world. The fan needs to be sized to move the amount of air that you need (CFM) at the velocity you need (fpm) at the static pressure that your duct system will impose on it. Some people put fans on both ducts, but that isn't really necessary if the system is done right, and the doors are always closed. One suitably sized fan on the exhaust duct outlet is enough.

if I'm mounting this box on a wall, should it be attached to the outside frame? or inside frame?

For maximum isolation, use one box on each leaf penetration. In other words, on teh supply duct, one box where it goes through the outer leaf, then another box where it goes through the inner-leaf, and ditto for the exhaust duct. If you don't need so much isolation, then you can get by with just one box on each duct, in which case I prefer to put it on the outer leaf, then have a decoupled "sleeve" on it that penetrates through the inner leaf, then carries on for as far as possible before reaching the register.

I was planning on using Roxul mineral wool R13, 3.5" thick with a density of 2 lb/ft3 for each wall frame (exterior and interior).

That would be fine. It's a little on the light side, but if that's all you can get, it will work OK. Put as much as you can in the cavity, filling it completely if possible, but without compressing it (no forcing it in). - Stuart -

Awesome, thanks a lot Stuart! I understand the silencer box concept much better now and I think I'll go with the UltraTouch denim insulation for the walls. I'll update soon, thanks again!

here's a quick update, insulation is done and drywall started today... getting closer!

Any update on this? I have enjoyed following this thread.

79_Limited wrote:

Any update on this? I have enjoyed following this thread.

Sorry it's been forever since the last update, I've been super busy lately, the good news is the studio is completed! It's been completed since May actually, I just haven't gotten around taking pictures and posting updates although I plan on doing so very soon...

Hey guys! the studio was completed around this time last year... everything worked as planned. I've been upgrading some of the treatment so it looks a little different but these pictures are pretty much a good example of how it turned out. The live room sounds great, definitely bigger than what it is. The control room is accurate, I feel really comfortable mixing there, mixes translate very well. Sound isolation is perfect, no low end build up in either room. The AC units are super quiet, I can even run them while tracking with no issues. They're heat pumps too so just as comfortable in the winter. The studio glass was probably the toughest thing to assemble and mount, it took all night! The electrical was done up to spec, with separate circuits for each zone (AC, outlets, lights, etc). We made some bass traps and corner traps for the rooms, filled with different absorptive materials. They control the sound in a very pleasant way, without drying out the room too much. I found an IKEA hack online to make panels from bookshelves. Super cheap and effective! I'll try to record a sample and upload it here soon, hopefully it won't take me another year! LOL - A million thanks for all the advice and helpful resources in this site, it really made this process a lot easier to understand. :D

It looks pretty darn nice, Felipe! Congratulations! You are now on the list of "recently completed studio"... www.johnlsayers.com/phpBB2/viewtopic.php?f=10&t=5842 (#2 on the list). It would be great if you could do a couple of tests in your control room using REW, and post the results here! - Stuart -

Which AC units did you end up installing? I need to purchase a few like yours in the coming months.

79_Limited wrote:

Which AC units did you end up installing? I need to purchase a few like yours in the coming months.

I have Fujitsu's Halcyon units, 9000BTU. They are super quiet and provide heating as well. The coolest thing about them is that they don't have a separate drain line so it's only 1 small hole to run the pipes out to the condenser. Even the outside units are super quiet. I measured less than 30db outside for both of them. I've always ran them low and never had to push them too hard. For the room size 900BTU is perfect. In the winter, the gear in the control room makes it pretty toasty so I can even run the unit on fan only and it's pretty comfortable, unless the temperature drops below 20 degrees outside. They were installed with a "kill switch" to be up to code here in Englewood, so if anything goes wrong I can easily cut the power. Also helps if you need to troubleshoot the electrical connections or anything like that. They have timers and an "economy" mode which saves energy. I can't say enough good things about these units, they rule! I don't remember correctly but I think a 20amp breaker is needed to provide power.

Felipe, Thanks for the info. I will look into the units for sure. Do you have any problems getting fresh air into your finished room?

79_Limited wrote:

Felipe, Thanks for the info. I will look into the units for sure. Do you have any problems getting fresh air into your finished room?

No problem! There's a hallway adjacent to each room with a big window. Before/after a session, or during breaks, I'd open the doors and window to let the air flow. It was strategically placed so each room gets a good amount of air. That in addition to running the mini split fans to push the air out, and maybe a little fan to help on a hot day, takes care of the ventilation for me. Cheers!