Planning for Garage Studio - Acoustics of Carriage Doors?

masterofnone
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Trying to make sounds sound better

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Planning for Garage Studio - Acoustics of Carriage Doors? Jun 18, 2018 17:07:16 GMT

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Post by masterofnone on Jun 18, 2018 17:07:16 GMT

Hi!

Long time lurker. I've thrown up a couple early reflection panels by my monitors and read a bunch over the years. In general I do grasp these concepts and truly appreciate them!

I'm starting the planning stage of converting my brick free-standing garage into a treated recording/listening space. It has three brick walls, two windows on the back wall, and hanging wooden sliding doors (old carriage house style) at the front. Interior dimensions are approximately 16' (sliding doors take up this entire wall on one side) by 18'.

My question is mostly around how bass frequencies might react to this space (assume speakers pointing from back of garage towards carriage doors). I know bass travels through thinner materials, and my assumption is that this thin hanging-wood rear wall will let bass frequencies pass out of the space into the alley and prevent buildup of lower frequencies in the room itself. I'm actually considering trying to use this to my advantage and just attach some insulation directly to the doors to insulate against higher frequencies bouncing off the wood as well as from coming in from outside (and also keep the space warm/cool as needed).

I'm also open to other general suggestions - I'm not 100% sure how I'll approach the renovation yet. Options range from a minimal 'patching holes and throwing up some panels' to a full on 'room in a room' setup with floating walls/floor. I live in DC and I'm hoping to have a nice flexible space I can use to do some recording, mixing/mastering, as well as just general use as a home office space.

Thanks!

Michael Lawrence
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Planning for Garage Studio - Acoustics of Carriage Doors? Jun 18, 2018 17:21:33 GMT

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Post by Michael Lawrence on Jun 18, 2018 17:21:33 GMT

Masterofnone-
Welcome. Glad you finally decided to step out of the shadows.
Imagine these two circumstances:
1) No garage doors. Open to the world. All the energy leaves. (Absorption coefficient: 1)
2) No garage doors. Rigid wall. All the energy stays. (Absorption coefficient: 0)

Your situation is somewhere in between. (Isn't it always?)

Remember that these are wavelength-dependent, and therefore frequency-dependent, effects.
If you want a better answer than that, I would recommend the following:

Set up your subwoofer in the far corner of the room. Put your measurement mic very very close to the inside of the (closed) door. Within a few inches will keep you in the pressure zone at the frequencies in question. Run an REW sweep. Then open the door, touch nothing else, and run the sweep again. The door closed sweep will be artificially high because of the boundary effects of being near the closed door, so you can offset the sweep in software by 6dB if you like. We're looking at differences over frequency here, and the door's TL will not be flat.

Subtract the traces in REW. This will show you how much energy is bouncing back into the room from the door.

If you want to make a fun experiment out of it, repeat those tests with the mic outside. This will measure the Transmission Loss (TL) of the door over frequency, which would be interesting to see.

You can set REW to run a few sweeps with averaging to increase the signal to noise ratio due to background noise, traffic, complaining neighbors, etc. Doubling the number of sweeps increases SNR by very close to 3dB.

Let us know how it turns out.

Last Edit: Jun 18, 2018 17:24:28 GMT by Michael Lawrence

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masterofnone
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Trying to make sounds sound better

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Planning for Garage Studio - Acoustics of Carriage Doors? Jun 18, 2018 17:40:53 GMT

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Post by masterofnone on Jun 18, 2018 17:40:53 GMT

Hi Michael, thanks for the detailed reply and suggestions!

I wish I could leave them open, but it wouldn't be the safest choice in the city

(I get that it was a mental experiment not a literal suggestion - maybe I could put up a security fence?)

I think you're probably right that the best place to start would be testing the room as is. I'll definitely report back! Unfortunately I probably won't be able to test too soon, as the garage first needs to be cleaned out as they all do. Not too bad but the acoustics will certainly change when the old car is removed...

Awesome idea to measure outside to see how much sound is escaping - that's a great way to quantify, literally, how much bass is escaping! Fortunately There's not much noise coming from the alley typically - although as cars pass through the alley it might be a problem if I'm tracking something quiet and low rumbles creep in. Maybe it'll be ok if the room is also treated internally. Happily I can be as loud as I want - no neighboring houses are too close to the garage door.

-m

rock
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Planning for Garage Studio - Acoustics of Carriage Doors? Jun 20, 2018 1:11:27 GMT

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Post by rock on Jun 20, 2018 1:11:27 GMT

Jun 18, 2018 17:07:16 GMT masterofnone said:

I'm also open to other general suggestions - I'm not 100% sure how I'll approach the renovation yet. Options range from a minimal 'patching holes and throwing up some panels' to a full on 'room in a room' setup with floating walls/floor. I live in DC and I'm hoping to have a nice flexible space I can use to do some recording, mixing/mastering, as well as just general use as a home office space.

Regarding the "room in a room" approach, since it's will only be necessary for tracking low level instruments, I would imagine that in your case it would be a luxury and might take up a fair amount of otherwise useable real estate to implement. The weak link is your carriage doors. If you need isolation there, you might consider a double wall by building a partition wall in front of the carriage doors. Rod Gervais' book on "building studios like the pros" gives details.

If you do build a partition wall, you can simply treat the room as you normally would. The back wall is a good candidate for full coverage with FG, mineral wool etc.

You did not mention the ceiling/roof isolation so that may be a weak area too.

I had a garage in Chicago with walls three bricks thick and poured and reinforced concrete ceiling/roof. it was quiet except for the garage doors and at the time I did not know a fraction of what Ethan's site offers so we just put layers of old carpet on the back doors. For the service doors, we simply added another door for a double door. For a garage practice space it worked pretty good.