Small mixing room initial measurements

Arsis

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Hi gang, I'm new here and new to REW. I'm setting up a small room for music mixing and thought I would share my quest and get some advice.
Here's my scenario. 12'6" x 11' with a 9' ceiling. The room is completely empty of furniture. The front corners have LenrD bass traps from floor almost to the ceiling. Live end/dead end with 2" thick foam tiles in the front end of the room and 1" thick tiles in the back of the room. The front wall is completely covered and the side walls are completely covered in the front and gradually thinning checkerboard pattern toward the back of the room.
The checkerboard pattern is offset so there are no opposing parallel surfaces. The highly technical clap test turns up no audible flutter echo.

The Hardware :
Mackie HR824 MK1
2 Polk Audio PSW 10 (these are more for fun than mixing)
MOTU M2 24/192 DAC
UMIK-1

I'm starting with a generic acoustic treatment and the subs are positioned at quarter length distance of each wall. Subs are spiked through carpet to a cement floor. The Mackies are on simple, plate steel and 1" square steel tubing stands and are sitting on top of the subs with 1.5" sorbothane isolation feet.

Measurements were taken from equilateral triangle with the speakers which is about 4' from the back wall.
Here they are.
30861
 

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Arsis

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I will be adding some more broad band bass traps ( foam corner variety ) to tame those modes.
I will eventually be replacing some of the 12x12 foam tiles with diffusion to get my RT60 up.

What inexpensive method have you guys employed to tidy that low, low mud sludge?
BTW, the back corners are doors, so no corner traps back there

The panoramic picture is kinda trippy but you can see what I have going on so far.
It's a bit of a vacuum right now but the imaging is beautiful.
30946
 
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Bruce Black

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Hi Arsis. I strongly recommend you that you use target, tuned low frequency absorbers instead of broad band bass traps, like Helmholtz resonators. It's much more effective to absorb the problem LF peaks than to just try to bring all the LF down with traps. That approach removes the good LF you really should keep for a smoother, flatter response, while the tuned resonators just reduce the peaks. You can find the peaks with the REW measurements.

I've attached a drawing of an easy-to-build Helmholtz resonator that I published in Recording Magazine a few years ago. When you install them, make sure the port faces the wall, and is an inch or two away from it. This ensures you get the best performance from it.

Also, try using REW's room simulator to find the best positions for your subs. I found that while JBL recommends 25% from the walls, I sometimes get better results at 20%.

Lastly, try to get some diffusion on your rear wall and ceiling - it helps create a better sense of space or "air". You can make very inexpensive polycylindrical diffusors by bending sheets of 1/8 in plywood or door skins and bending them into arcs.
 

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Arsis

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Hi Arsis. I strongly recommend you that you use target, tuned low frequency absorbers instead of broad band bass traps, like Helmholtz resonators. It's much more effective to absorb the problem LF peaks than to just try to bring all the LF down with traps. That approach removes the good LF you really should keep for a smoother, flatter response, while the tuned resonators just reduce the peaks. You can find the peaks with the REW measurements.

I've attached a drawing of an easy-to-build Helmholtz resonator that I published in Recording Magazine a few years ago. When you install them, make sure the port faces the wall, and is an inch or two away from it. This ensures you get the best performance from it.

Also, try using REW's room simulator to find the best positions for your subs. I found that while JBL recommends 25% from the walls, I sometimes get better results at 20%.

Lastly, try to get some diffusion on your rear wall and ceiling - it helps create a better sense of space or "air". You can make very inexpensive polycylindrical diffusors by bending sheets of 1/8 in plywood or door skins and bending them into arcs.
Thanks for the tips!
Let me reframe the situation a little bit. This room is being built for me by my wife. I'm in a wheelchair. So I'm wanting to keep it easy and simple. We had most all of the foam from a previous build. The room is certainly over dampened at this point. Right now I don't have anything to use as diffusers. Better over dampened than flutter echo. For now at least.
My first concern is the 60hZ and below. So what is a cheap easy way to deal with some of that?
 

Bruce Black

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If you have someone who can build some resonators, you can look at your REW waterfall data to determine what frequencies have peaks that sustain over time. Those are the most likely to cause issues for you. Have some resonators built to those frequencies, or close, and install them with the ports as near to the room's corners as possible. Expect the materials to cost around $65 to $70 per resonator. Don't put any absorptive material inside them.

As far as diffusion,I built two polycylindricals for around $40 ea. You take a sheet of 1/8 ply or door skin, bend it into an arc, and use 1 X 3 furring strips to hold it in the arc, and provide an easy way to mount it. (the drawing says 1 X 2, but 1 X 3 is much more secure). This is really light, so you can hang it from the ceiling to break up reflections from there. Be sure to secure the arc to the furring strips with both glue and screws.

Both the resonators and polys are designed to be simple to build, using materials easily sourced from pretty much any home center.
 

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Arsis

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If you have someone who can build some resonators, you can look at your REW waterfall data to determine what frequencies have peaks that sustain over time. Those are the most likely to cause issues for you. Have some resonators built to those frequencies, or close, and install them with the ports as near to the room's corners as possible. Expect the materials to cost around $65 to $70 per resonator. Don't put any absorptive material inside them.

As far as diffusion,I built two polycylindricals for around $40 ea. You take a sheet of 1/8 ply or door skin, bend it into an arc, and use 1 X 3 furring strips to hold it in the arc, and provide an easy way to mount it. (the drawing says 1 X 2, but 1 X 3 is much more secure). This is really light, so you can hang it from the ceiling to break up reflections from there. Be sure to secure the arc to the furring strips with both glue and screws.

Both the resonators and polys are designed to be simple to build, using materials easily sourced from pretty much any home center.
Do you have any suggestions for the frequencies below 60? I've mixed in worse rooms than this and as long as I am aware that there's a hump at 240, I can deal with that easier than the lower frequencies. So my first concern is putting a harness on the low end.
 
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