Building bass traps above floated ceiling, need expertise

DRob · Post by **DRob** » Fri Dec 10, 2004 4:50 am

I have calculated the room modes for my tracking room and determined problematic frequencies, now I am building some resonating bass traps to put above my ceiling. I have read parts of Everest's Master Handbook of Acoustics, but when it comes to instructions on building these resonators, he only specifys the depth (that it should be a quarter wavelenght deep). What I am curious about is the length and width. I have been told that the larger the length and width, the more dB of reduction the resonator will offer. Therefore, my idea is to construct the width of my resonators to be approximately two feet or so, and the length to be the entire length of the room itself. Being that each of these resonators are only about two feet wide or so, and the room is 16.8' x 22.8', I will be able to add somewhere around 7-8 resonators tuned to specific problematic frequencies. It seems like a good idea to me, but I don't have much practical experience. If anyone has a word of advice, it would be greatly appreciated.

giles117 · Post by **giles117** » Fri Dec 10, 2004 11:20 am

What is the ht of your raw ceiling???

DRob · Post by **DRob** » Fri Dec 10, 2004 12:38 pm

The floated ceiling is 12 feet, the raw ceiling is 20, so there should be plenty of room.

Paul Woodlock · Post by **Paul Woodlock** » Tue Dec 28, 2004 3:38 am

Greetings Drob

Why not just use broadband absorption? It saves messing around trying to tune narrowband absorbers.

Simply put as much mineral wool semi-rigid slabs in the void above the false ceiling as you can.

Paul

DRob · Post by **DRob** » Sat Jan 01, 2005 3:32 am

okay, but after I treat the room for broadband absorption I'm still going to have those specific problematic frequencies that any room has. What type of absorption, if any, do you recommend that I use to treat these problematic modes? I thought tuned resonators would be the way to go since I had already calculated the room's modes. I know there are many options, maybe you can suggest a few that I haven't thought of.

Paul Woodlock · Post by **Paul Woodlock** » Sat Jan 01, 2005 4:48 am

DRob wrote:okay, but after I treat the room for broadband absorption I'm still going to have those specific problematic frequencies that any room has. ....

Well NO absoprtion solution is perfect and no room can be made perfectly flat, but how do you know you're going still have those problems at those freqeuncies after broadband absorption?

Paul

Jon Best · Post by **Jon Best** » Fri Jan 07, 2005 12:23 pm

Yow, you've got eight feet up there to play with. I'd load up the (soft, hopefully) drop ceiling with loose fiberglass, and maybe hang some additional fiberglass at fairly random heights above it. Hang 'em from both ends so they make big U's of different depths.

I doubt you're going to have any additional low end problems based on the floor-to-ceiling modes after that.

If you've got further low end issues relating to the length and width of the room afterwards, a bunch of extra crap up on the ceiling's not going to do much. That's when you start looking at a combination of Ethan's panel traps on the walls, at least near corners, and rigid absorption a few inches to a foot off the walls and/or across the corners.