Lots of freqs

[Thisguy]

Hey guys I'm new around here but I was browsing the forum and there is definitly a lot of knowledge to go around so I thought I'd stop in and see if I could get some help with my issues.

I converted a small bedroom into a tracking space. The room is 9'2"Lx9'4"Wx8'H. I built it with inside-out walls with two layer of 5/8" drywall seperated by green glue and the drywall was removed from the original wall so not to create a 3 leaf wall. The spacing between the the inner and outer walls, from drywall to drywall, is 5". On the inside of the room I have placed Bonded Logic Ultra Touch Cotton batts between each of the studs all the way around the room. On the ceiling I have Auralex 2" Wedgies fully covering the ceiling. The floor is laminate wood. There is no bass trapping in the corners... I know I know for shame.

So, last night I loaded the drumkit in the room and set up the only omni mic I have, a behringer measurement mic, and placed it directly above the snare and aimed at it with the mic about 1' from the ceiling. The resulting recording had some very obvious room resonance. I found that 130hz, 270hz, 390hz, 630hz and 980hz were really dominant.

My question is will adding bass traps help me get a handle on these frequencies or is this more or less just how it's going to be in this room?


edit: the mic was positioned approximately center in the room but 1' from the ceiling.

[Thisguy]

Ok after doing a little more research I think what I am experiencing is the build up of frequencies coming from the corners (no bass trapping). Here's how I arrived at this conclusion; The diagonal measurment from corner to corner is 13'1". I multiplied that by two and then divided 1130 (speed of sound) by that number which got me to a resonant frequency of 43hz. When I multiply that by 3 I arrive at 129hz which is very close to the 130hz problem I'm having. When I go further and continue multiplying 43hz I run into other frequencies that are also very close to where I was having issues.

Am I correct in my line of thinking or have I just made everyone a little more dumb for having read this?

[Soundman2020]

Hi there "Thisguy", and welcome to the forum!

I'm totally tied up on time right now, so I can't answer very completely (later!) but I happened to see your post so here's a link that might help get you on the right track:

http://www.bobgolds.com/Mode/RoomModes.htm

Plug in your room dimensions there, and it will tell you where all your room modes are. One problem: your room is nearly square.

Also, go to the Home Theater Shack web site, download the REW acoustic analysis program (its free!), follow the instructions in the manual, and run that on your room, then post the resulting data file here, so we can look at it.

I found that 130hz, 270hz, 390hz, 630hz and 980hz were really dominant.

Those are all a bit high to be modal issues (except maybe the first one). Probably something else. REW will reveal it.


- Stuart -

[Thisguy]

Thanks Soundman. I'll be sure to download REW.

The door to get into the room is a solid core pocket door but not completely sealed. There's about 1/4" space at the bottom of the door although I was able to seal it up everywhere else reasonably well. The room on just the other side of the door is a tiled dining room and is very live sounding. I suppose that when I did the test recording useing the drumkit that could have excited the neighboring room enough to have some of that sound leak back into the tracking room.

[Thisguy]

Out of curiosity I ended up taking some more Bonded Logic insulation and pinning it up in the corners of the room so it hangs freely down to the floor and did another quick recording with the mic in the same position and it has definitely rid me of some of the 130hz problem and to a lesser degree all of the other frequencies I was having issues with. It added a lot of clarity to the drums. The most significant problem I'm hearing now is at 380-390hz but I'm starting to suspect that it's more of an issue with the tuning of the snare than the room. Or perhaps a combination of the two.

I'm sure with my current method of assessment it's more or less guess work than science. After I get done with the session this weekend I'm going to give REW shot and see where I'm really at.