How Stupid is this ?

vestast

vestast

Gassy Member
After reading through all the great info here and at Ethan's FAQ page I decided to try and find OC to build myself some wall treatments. After calling several local suppliers from the list that I received from OC themselves I was pretty frustrated to find out that no one even knew what OC703 or 705 was. So figuring I had no other choice and I went ahead and purchased a room kit from Primacoustic.

The room kit from primacoustic works pretty well, but I still think I have a bass build up in my room. I decided to go back to Ethan's FAQ and discovered that I had missed some alternatives to OC703. One of the alternatives is Ottawa Fibre.

This is the stupid part. I live in Ottawa ! :(

After 2 phone calls I know have 2 packages of 2" OFI 48 waiting for me.

The reason I'm posting this is that I need some ideas. I already have the primacoustic kit which I think is doing a good job with freq over 500hz. Using MODCALC I know I have some issues at around 300hz (but of course I'd like to try and treat below that as well) I have foam bass traps in the corners which I would like to leave there if I can. So what I was hoping to do is place the fibreglass on my walls and ceiling with some space behind them.

Any ideas for hanging from the ceiling ? Should they be angled so that the end closest to the speakers are lower ? Any ideas for building frames for both the wall units and ceiling units ?

Sorry for the long rant/story.

Hopefully you guys can help me out.

Dave
 
here's your paradox.

If the foam in the corners was doing an adaquate job then you wouldn't have a buildup at 300 hz, now would you? But you want to keep the foam in place because well, tearing it down would make you feel even more stupid.

So you want to put the good stuff in a less optimal place because the optimal place is taken up with the not-so-good stuff.

Figure out which is the best place to put the Ottawa Fibre stuff and put a nice thick layer of it IN FRONT of the foam. Then you can still think that the money you spent on the foam is not being completely wasted.
 
Innovations said:
here's your paradox.

If the foam in the corners was doing an adaquate job then you wouldn't have a buildup at 300 hz, now would you? But you want to keep the foam in place because well, tearing it down would make you feel even more stupid.
Click to expand...

Ya that pretty much hit it on the head. :)

I'm considering doing what you suggested. One more question though. Everything I've read says more air behind the fibreglass the better. Can you think of any issues that would come up from having the foam behind the fibreglass ?

Thanks for the reply.

Edit - OK I lied 2 more questions - Why do you consider putting it on walls and ceilings as not optimal ? I've seen Ethan's products used on ceilings and walls, could it not work for me as well ?

I'm asking not to be a pita, but because I want to understand if using it there will not provide the same low frequency absorption.

Thanks again !
 
Tell me your secret!

vestast said:
After 2 phone calls I know have 2 packages of 2" OFI 48 waiting for me.
Click to expand...
Hey, Dave, do you have an inside man at OFI? If so, can you put me in touch with him? When I called OFI last week they referred me to their U.S. salesguy, but he's not returning my calls. (See my pathetic cry for help in the "Foam Facts" thread.)

Also, how much OFI 48 is in each of the packages you ordered? And did you buy two packages because that was their minimum order or because that was the amount you needed?

Finally, I'm curious why you bought OFI 48 instead of the higher density OFI 64. Was there a big price difference, or are you concerned that the higher density fiberglass will be too sound-deadening for your purposes?
 
Hey Hapi - The people at OFI put me in touch with a local supplier here in Ottawa. The bundles came with 6 panels each.

The reason I went with the 2 " OFI 48 is because I figured I could experiment using a frame with one panel in it and then a frame with 2 panels for a total of 4" fiberglass in it. Not sure why I went with the 48 instead of the 64 but I think looking at the numbers the 48 seems pretty close to the OC stuff. They would have sold me any amount as I drove to the warehouse.

I found this link that has all kinds of numbers for different products


http://www.bobgolds.com/AbsorptionCoefficients.htm

I'm still experimenting with placement in the room with them but so far it really seems to work as advertised.

Good luck

Dave
 
"I'm considering doing what you suggested. One more question though. Everything I've read says more air behind the fibreglass the better. Can you think of any issues that would come up from having the foam behind the fibreglass ?" -

"air" doesn't have to mean AIR - the foam, even though it's less dense than rigid fiberglass or rockwool, still absorbs - a corner that is FULL of absorbent works even better than one with 4" absorbent ACROSS the corner, because the longer wavelength sounds get more absorption than they would by just passing through 4" material, continuing to the wall, coming back, and once again passing through 4" material.

As to wall and ceiling placement, it's not that it isn't good; it's just that it's not QUITE as important as doing all the corners. You will still need (for a mix room, anyway) first reflection points absorbed; these can be found using the "mirror trick", where you have a helper hold a mirror flat against any and all surfaces of the room while you sit facing your speakers; anywhere (including the ceiling) that you can see either speaker in the mirror, you need absorption.

This doesn't apply to reflection paths that are longer than around 25 feet, because these are long enough that the reflected sound won't be integrated by your ears, but will rather be heard as a distinct echo. You may still not want it, but you won't think it's part of the direct sound so you can at least identify it.

Generally, for smaller rooms (less than about 20 x 25 feet or so, with tall ceilings) the first thing to do is absorb the corners, then first reflection points including the ceiling, then broadband trapping at the rear wall.

HTH... Steve
 
OMG..

I've been concentrating on the front mix position where I have most of my absorption in place. I just stuck some panels in the rear corners over the existing "traps" and what a freaking difference.

Wow - Thanks again guys.
 
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