My control room

[pandamonk]

I've asked this before in another thread, but didn't get a response. So, Ethan, or someone who knows, will i need a cloud above my mixing position if the ceiling slants up to the back of my room, and the back is deadened? I'm guessing not, but need to make sure. Also, isn't it usually a problem to mount your speakers(ear height)on a desk? Is it because the reflections off the desk? What about if your desk slants? Thanks, Panda'

[Ethan Winer]

> will i need a cloud above my mixing position if the ceiling slants up <

The angle must be 35 degrees or more to avoid needing absorption at the first reflection points.

--Ethan

[pandamonk]

Don't think it's that much, but thats good to know. I'm going to be mixing in 5.1 surround, so obviously will need more acoustic treatment than the average person. Could you recommend where to put the broadband absorbers in my room. The room is a tiny 6'6" x 7'6".

[apl]

The old trick is to have some take a mirror and go around the walls and ceiling. Anyplace that you can see the monitors in the mirror, you put absorption. This creates a reflection free zone at your monitoring prosition.

Bass apsorption is different. You just need lots of it.

[pandamonk]

Yeah, heard that before, forgot it though. Will try it when the room is done.

[Ethan Winer]

> Could you recommend where to put the broadband absorbers in my room. <

APL gave you the right answer. Then add as many bass traps in corners as you can possibly manage.

--Ethan

[pandamonk]

Yeh, Only problem is that I doubt I'll be able to fit many bass traps. Should i do as your video on your site suggests and instead of mounting across the corners, mount on the door and wall at the corner? Does it matter if one side has more bass traps, or deeper absorbtion than the other? Because I've had a thought on how to build a really low frequency absorbing bass trap. I mentioned it a few months ago. Basically open the door and in the space put a broadband absorber. This makes the other room, the space behind the absorber making it absorb deeper bass. Someone said that for a 12' room, this trap would have peak absorbtion at 23Hz. Would it matter too much if i had this on one side, and just a standard bass trap across the corner on the other? What about the front wall? I wont be able to fit bass traps in those corners, but will be mounting broadband absorbers on the walls. If i spae them ouf from the wall slightly, will this suffice. I will be using Bondedlogic Ultratouch by the way. The absorbsion coefficients are:
Size Thickness 125 250 500 1000 2000 4000 NRC/STC
R-13 3.5” .95 1.30 1.19 1.08 1.02 1.00 NRC 1.15
So it already has reasonable bass absorbsion. I don't know what it's like below 125Hz though.

[apl]

It's the under 125 Hz part that's important and where the bass traps work their magic.

When the wavelengths start to get more than 1/3 or 1/4 the longest room dimension, the wave is trying to slosh the air, almost like pushing on a part of a balloon and the other part expanding. It's so everywhere at once in the room that you can put that absorption anywhere. The wave sort of leaks out of the room where the absorption is.

Another way to make bass traps (my personal fave for bang-buck-simplicity) is to take the 4 x 8 sheets of 703 and cut into triangles. Then, in the vertical corners you just stack them up. You can easily arrange them on the floor/wall corner, too, on their edges.

[Ethan Winer]

> Should i do as your video on your site suggests and instead of mounting across the corners, mount on the door and wall at the corner? <

Only after you've treated all the wall-ceiling corners.

> Does it matter if one side has more bass traps, or deeper absorbtion than the other? <

Not much.

> I've had a thought on how to build a really low frequency absorbing bass trap. <

Why do you think you need a bass trap for the really low frequencies? What matters most is from around 80 to 300 Hz. I'm not saying that trapping lower frequencies is not useful, but it's less important.

--Ethan

[pandamonk]

Honestly? I've been put under the impression that the lowest frequencies are what you wanna be trapping. Well the insulation i will using for absorbsion has a coefficient of .95 at 125Hz, so down at 80Hz it should absorb quite well. I'm not sure about wall-ceiling corners, 'cause my ceiling is very low. About 5'8" - 6'6"(I'm guessing) and I have doors and air vents to fit.I suppose i could have them at the mixing soition like the attached pics.

[apl]

Originally Posted by pandamonk

Well the insulation i will using for absorbsion has a coefficient of .95 at 125Hz, so down at 80Hz it should absorb quite well.

Nope. The absorption depends on the wavelength and that's proportional to 1/f. Those curves drop like a brick.

[pandamonk]

You've confussed me, please explain. I thought i knew about this stuff, but obviously not.

[emergencyexit]

Originally Posted by pandamonk

You've confussed me, please explain. I thought i knew about this stuff, but obviously not.

I'm not fully sure, but I think he is trying to tell you that just because your material is good at 125Hz doesn't mean its gonna be good at 80Hz unless it says its good there.

Ben

[pandamonk]

Yeh, that's what I thought. It doesn't say it's good there, but i thought if it's good at 125, it should at least be reasonable at 80, like .60 or sumthin

[apl]

Originally Posted by pandamonk

Yeh, that's what I thought. It doesn't say it's good there, but i thought if it's good at 125, it should at least be reasonable at 80, like .60 or sumthin

Probably way less than that.

[pandamonk]

How come? Could you please explain how to calculate roughly what it will be like. I've compared it to others with roughly the same coefficients but that show deeper absorbsion than 125 and it doesn't seem too bad. I know every types different, but surely it wont be .95 to .35 in 45Hz

[apl]

Originally Posted by pandamonk

How come? Could you please explain how to calculate roughly what it will be like. I've compared it to others with roughly the same coefficients but that show deeper absorbsion than 125 and it doesn't seem too bad. I know every types different, but surely it wont be .95 to .35 in 45Hz

I'm having trouble finding something to link to, but if you go to Ethan's acoustics page you can see how fast the absorption coeffecients drop off when you get beyond their useable range. And, frankly, I don't believe 4" of fiberglass is going to do much at 125Hz and I am suspricious of the specifications.

[cincy_kid]

Originally Posted by apl

It's the under 125 Hz part that's important and where the bass traps work their magic.

When the wavelengths start to get more than 1/3 or 1/4 the longest room dimension, the wave is trying to slosh the air, almost like pushing on a part of a balloon and the other part expanding. It's so everywhere at once in the room that you can put that absorption anywhere. The wave sort of leaks out of the room where the absorption is.

Another way to make bass traps (my personal fave for bang-buck-simplicity) is to take the 4 x 8 sheets of 703 and cut into triangles. Then, in the vertical corners you just stack them up. You can easily arrange them on the floor/wall corner, too, on their edges.

Not to try and hi-jack the thread, but APL I have seen you say this before about the triangle bass traps and I was going to attempt this with my left over 703. After I cut the triangles, stack them 3-4 high (2" thick 703), cover it with fabric, then just put them on the floor/wall/wall tricorners? Does that sound accurate and also should I mount them on ceiling/wall/wall tricorners too? And lastly, does it matter if the bass traps touch my broadband absorbers? Like in the ceiling corner here

Thanks in advance -

Looks like cool setup btw Panda (im jealous)

[apl]

Originally Posted by cincy_kid

Not to try and hi-jack the thread, but APL I have seen you say this before about the triangle bass traps and I was going to attempt this with my left over 703. After I cut the triangles, stack them 3-4 high (2" thick 703), cover it with fabric, then just put them on the floor/wall/wall tricorners? Does that sound accurate and also should I mount them on ceiling/wall/wall tricorners too? And lastly, does it matter if the bass traps touch my broadband absorbers? Like in the ceiling corner here

Thanks in advance -

Looks like cool setup btw Panda (im jealous)

My recommendations, in order:

1. RealTraps. I haven't talked these up enough lately.

2. The triangles of 703, stacked in the corners from floor to ceiling and along the wall floor corners, too.

3. 703 straddling corners.

4. Stack rolls of pink in the corners up to the ceiling.

[cincy_kid]

1) Yea, Realtraps are quite the product, but out of my budget and overkill for me in my small space atm.

2) Oh, so the entire height of the wall in the corner? Interesting...I was thinking of putting fabric around the triangles and making them look similar to this shape

3) I have no space to straddle (small space as it is)

4) I have this extra 703 I will use and try your stacking method.

[apl]

Originally Posted by cincy_kid

1) Yea, Realtraps are quite the product, but out of my budget and overkill for me in my small space atm.

2) Oh, so the entire height of the wall in the corner? Interesting...I was thinking of putting fabric around the triangles and making them look similar to this shape

3) I have no space to straddle (small space as it is)

4) I have this extra 703 I will use and try your stacking method.

Well, it's not my method. But 2 and 3 take up basically the same amount of space.

[pandamonk]

Originally Posted by apl

I'm having trouble finding something to link to, but if you go to Ethan's acoustics page you can see how fast the absorption coeffecients drop off when you get beyond their useable range. And, frankly, I don't believe 4" of fiberglass is going to do much at 125Hz and I am suspricious of the specifications.

I've read through that page a couple of times before. On a very quick skim i just had there i didn't see any coefficients that went below 125Hz. It's actually not 4" rigid fiberglass, but 3.5" natural cotton fiber insulation. BondedLogic Ultratouch. I understand that you don't trust the spcs, but they are all we have to go on before we buy the product really, aren't they. Either that or word of mouth. But this seems like a relatively new product, so most probably haven't even heard of it yet, nevermind used it and tested it.

[apl]

Originally Posted by pandamonk

I understand that you don't trust the spcs, but they are all we have to go on before we buy the product really, aren't they. Either that or word of mouth. But this seems like a relatively new product, so most probably haven't even heard of it yet, nevermind used it and tested it.

Or physics.

[pandamonk]

That too, do you know how to calculate it?

[apl]

Originally Posted by pandamonk

That too, do you know how to calculate it?

Absorptive acoustic materials work by converting the air molecules' kinetic energy to heat. As the wave is reflected from the wall, the velocity at the wall is zero, and the maximum velocity is at the 1/4 wavelength. For 125 Hz, the 1/4 wavelength is around 24" from the wall. So when the acoustics experts build anechoic chambers, they use 24" thick treatment and rate it down to 125 Hz. They're being extemely precise about it, though. That said, there is so little molecular movement of a 125 Hz wave 4" from the wall that no absorber can do much about it.