overtones/droning

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Ok, I got the new studio blues, heres the deal, Im getting annoying overtones from my bass drum concentrated in the upper part of the gable directly behind my drum kit around 100hz, the bass guitar is generating a similar effect when played live, the wall is approx. 20' wide and 10' tall to the peak, the rest of the room seems for the most part to be managable, but this noise is ruining my recordings. Im thinking,
a) bass traps
b) diffusers
c) absorbtion
d) suggestions?
The room is 24' x 20' outside dimentions.
Need more info? By all means, just ask!
Any ideas or opinions would be grealy appreciated.
Thanks ya'll,
Jim
 
Down around 100Hz....

a. bass traps

However, once you take care of that problem I won't doubt you will need to address low mids - mids with slot resonators.

Check out John Sayers site http://johnlsayers.com/
 
Jim, sound PROOFing is just the beginning. Your heavy walls keep all the bass in, plus your dimensions (just ran 'em thru the grinder) cause some modes to be too close together around 111 to 116 hZ or so - I'm off to bed (up for work in about 4-1/2 hours) but I'll get you thru this part too, wouldn't wanna waste all that "quietness" in yer back yard, now would we??!?

Til I get a little time, you might try moving your kit to one side by about 8" at a time, see if it gets better or worse in 3-4 tries - Then find a beer and kick back a bit, we'll nail this thing before it's over... Steve
 
Amped,

You mentioned a gable. What exactly did you mean by that?

Darryl.....

p.s. Knightfly - dig the new avatar. Bearded men UNITE!!
 
Darryl - wish I still had the beard - that's a 20-year old shot of me at a Halloween gig, not too long before OSHA decided beards weren't safe for people who occasionally have to wear a respirator - (sigh) the GOOD news is, I'm gradually getting closer to LOSING the "DDJ" (Dreaded Day Job) and doing full-time acoustic consulting/audio forensics, etc...

If you'll check this thread -

http://www.homerecording.com/bbs/showthread.php?s=&threadid=88275

Your answer is in there somewhere - Jim used scissor trusses to gain some center height and more room volume, so there's a "vault" down the length of the room. Center of the ceiling is apparently 2 feet higher than the edges. At least I THINK that's what he's referring to... Steve
 
Hey Steve!
"Scissor trusses" thats exactly what Im refering to, the gable represents the upper angle on the short side wall which is approx. 2" taller than the 8" side walls, creating a triangle so to speak, as opposed to a flat ceiling at 8'.
I knew I was going to have to "tune" the room to some degree, since the room is new, Im just now figuring out exactly where and what approach is most effective for its personality.
By the way Steve, I have 703-705 available in my area, if you suggest incorperating this material as a potential resolution, please let me know if its advised to use with or without backing.
Ive also come to a decision on recording gear, right now Im using the protools free program and a cheapo soundcard with blah results, Ill be upgrading to a 3 gig system and protools 002 rackmount for starters.
Thanks a hundred million!
Jim
 
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Jim, did you try moving the kit to the side yet? If not, try centering the kick drum where your ceiling height is about 9.5 feet, or about 2-1/2 feet off center, and re-checking to see if your problem is as noticeable.

Glad you have access to 703/705, because your room dimensions are causing some modal problems that will need this.

After moving the kit around and trying a few different spots, it's time to buy some 703 - if you can find it, get at least 2" - 4" if possible. Start by just "catty-cornering" 3 pieces in each corner near the drum kit, one on top of the other, so you "box in" those two corners diagonally, up to about 6 feet (you can just stack full pieces to do this, no cutting - normal size for 703 is 2' x 4' pieces, so your front diagonal will be 4' wide, going up to 6 feet. No point in either covering or cutting the stuff initially, til you find out what works -

Next, if you can build a lightweight frame that will hold 6 pieces of the stuff (total size 6' x 8', build the frame so it holds 3 pieces the 2' dimension, and 2 pieces the 4' dimension, for a total size of 6 x 8 feet. If you make the frame so you can temporarily add plywood behind it, you can experiment with backed vs. unbacked absorbent - sometimes using backing works well if you angle it low at the wall, high away from the wall, so that it would reflect any sound (that's not absorbed ) to the other end of the room.

If all this helps but you're still noticing the specific frequencies you mentioned, we may need to design a slat absorber for at least one corner of the room, tuned to your specific problem frequencies... Steve
 
Steve,
Ill try moving the kit off center tomorrow at rehearsal, I hope the works, if not, Ill be lookin into the corner traps, I had already anticipated the possibility of this so it comes as no suprize. What about suspending a few pieces of 703-5 over the kit sloping the ridge and on the upper gable itself, thats where the noise is most noticable, I had my wife thump the bass drum wile I stood on a ladder and the tone was extremely concentrated in that area.
Ill be taking your advice, its beer time!
Thanks,
Jim
 
Yeah, that's what I had in mind when I mentioned the frame - that whole "cloud" would hang over the kit, with the end closest to the wall about 18" lower than the other end. With or without plywood backing, it's hard to say which will work better without trying it... STeve
 
Cool, at first I thought you were refering to the virtcal corners, this makes more sense, if in fact Im interpreting you correctly. Its very difficult at times to relate to information thru text alone.
Jim
 
First part WAS vertical corners, the frame part is a "cloud" you suspend from the ceiling, sloped but sorta horizontal - I'll do a couple drawings if I don't already have something close... Steve
 
Great! drawings would give me a much better grasp on exactly what I need to do. At your convenience of course. Man, I cant thank you enough for your help, again!
 
Kinda like this -
 

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Ahh, I see, that clears things up quite a bit. So the vertical traps should be approx. six feet high? And Im curious as to what the red line indicated in the side view drawing. (Im assuming the second layer of 703). And what about the orientation of the backing on the 703?
Thanks Steve,.
 
If you meant the red outlines around the drums, just contrast - if you meant the brown line behind the yellow slanted absorber, that was to illustrate backing the absorber with plywood. Backing a slanted 703 cloud like that would reflect lower frequencies to the other end of the room, not backing it would act more as a bass trap, using the area behind the absorbent to work on lower frequencies.

I only mentioned 6 feet as a suggested starting point - you may in fact want to completely enclose those corners floor to ceiling, as the floor and ceiling are tri-hedral corners and will concentrate more bass, so they would be the best places for traps.

The orientation on backing on 703? See the first paragraph above - if that's not what you're talking about, there IS NO backing on normal 703 - Owens Corning also make an FRK version of some of their products, which DOES have a facing. For bass trapping without losing highs, that facing should be toward the room. For more EVEN absorption, the facing should be AWAY from the room.

If you want to study more on these concepts, or if I'm not around soon enough, here's a good start -

http://johnlsayers.com/phpBB2/viewforum.php?f=3&sid=c212716dc414928698057c6ade706841

And here -

http://johnlsayers.com/phpBB2/viewforum.php?f=2

There's a few more illustrations floating around there as well... Steve
 
Im pretty sure what my dealer has is the FRK, with backing, Ill be getting ten pieces of 1-1/2 this weekend, First Ill try moving my kit to minimize the tones. I intend to fully enclose the two corners and hang three pieces above my kit as you outlined in the drawings, (do I have to build a frame?) I wont hang them permanently untill I dial in the most effective locations, then Ill probably cover them in some type of fabric for cosmetics.
Hows that sound?
Jim
 
No need for a frame for temp things, if you could get them to levitate magnetically, skyhook, duct tape, spit, whatever works. The FRK has better low end absorption because of the facing, but that also affects mids/highs - try it both ways, to see which side gives the best sound. One way will be deader in the highs.

Another thing that's been done - cover with those thin plastic dropcloths used for painting - leaves a bit more "sheen" on the high freq's than using cloth to cover the panels, and really works well to control the fiber shed. Remember, it's better to record slightly bright and have to turn DOWN the high EQ than to record kinda dull and have to BOOST the highs... Steve
 
Gotchya!
I have access to 2" 703 without the backing, would you recommend that over the FRK?
 
For the corners the FRK will do a better job of bass trapping - for the clouds, I've not tried it but straight 703 always works. I'd get the FRK first, try it both places, and if you're not happy with it overhead then get some straight 703 for your clouds. Odds are that if you've put more than one layer of gypsum on your inside wall leaf, you'll want the FRK for more bass trapping... Steve
 
Yup, two layers, 5/8" 1/2". Ill try the 2" FRK first. Im now wondering if trapping all four corners would be the way to go, I guess Ill see how it sounds this way first.
Thanks Steve.
 
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