I'm in the planning phase of my 1 room (plus amp iso closets) studio, and am looking for some suggestions on where to place traps. My listening position when the room is set up for mixdown is well locatated and offers a balance between the first few axial harmonics in the long axis of the room, but naturally I'm placed dead center in the width of the room, and would like to place some traps specifically tuned to addressing the null from the width axial modes.
If I decide to go with some kind of Helmholtz absorber...either slat, or perforated panel, where should they be placed for maximm effect on the width modes. Should they go on the side walls, where the modes terminate, and have high pressure, but no velocity, or should they go on the ceiling at the peaks and/or null locations? Does a Helmholtz trap work on pressure or velocity?
What about panel traps? Same question.....but I figure it's a little less important since the panel will have lower Q than a purpose built Helmholtz..
Any other bass traps I should be considering?
Cheers,
Kris
Trap type and placement suggestions....
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drfrankencopter
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- Location: Ottawa, Canada
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knightfly
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Kris, a Helmholtz is (externally, at least) predominantly a pressure device; the slot width, absorbent against the rear of slots, and depth of cavity act like a "tank" circuit in electronics. The narrower the gap between boards, the slower it "charges" - the shallower the depth behind the boards, the quicker it will "peak out" and quit "charging", and the higher the acoustic "resistance" (cloth and insulation against the rear of the slats) the more the "R" factor, which would lower the "Q" of the trap.
Some "R" is necessary, because the slats need to be damped or they will ring at their own physical resonance AND at the resonance point defined by trap dimensions - Generally about 2" of absorbent should be minimum, up to about half the total trap depth maximum.
Deeper insulation will (I believe) broaden the Q of the trap, which considering the difficulty of getting ANY trap like this exact, would be a GOOD thing.
If your room is rectangular, placing 1 or 2 4-foot wide ANGLED slat absorbers along the side walls will kill flutter, keep more highs, and work on your axials (L-R dimension) all at the same time; if you use the median depth of a slat absorber whose slats are angled by at LEAST 6 degrees as your value to plug into the Helmholtz calculator on THIS SITE, then adjust slat width/depth and slot width to achieve your axial frequency, that should be all you need to get your "sideways" axials tamed.
Reason I emphasized using this sites calculator is that nearly all other sites still have the erroneous equation so prevalent on the net.
Here's an example of placement - (bottom of the page)
http://www.johnlsayers.com/HR/index1.htm
Note the orientation of the dotted lines in the side absorbers; this will re-direct higher frequency early reflections away from the mix position (as well as control flutter)
It's my theory that one 4-foot wide unit beats two 2-foot wide ones, based on the longer wavelengths involved - otherwise ( I think) they would tend to "average" -
HTH... Steve
Some "R" is necessary, because the slats need to be damped or they will ring at their own physical resonance AND at the resonance point defined by trap dimensions - Generally about 2" of absorbent should be minimum, up to about half the total trap depth maximum.
Deeper insulation will (I believe) broaden the Q of the trap, which considering the difficulty of getting ANY trap like this exact, would be a GOOD thing.
If your room is rectangular, placing 1 or 2 4-foot wide ANGLED slat absorbers along the side walls will kill flutter, keep more highs, and work on your axials (L-R dimension) all at the same time; if you use the median depth of a slat absorber whose slats are angled by at LEAST 6 degrees as your value to plug into the Helmholtz calculator on THIS SITE, then adjust slat width/depth and slot width to achieve your axial frequency, that should be all you need to get your "sideways" axials tamed.
Reason I emphasized using this sites calculator is that nearly all other sites still have the erroneous equation so prevalent on the net.
Here's an example of placement - (bottom of the page)
http://www.johnlsayers.com/HR/index1.htm
Note the orientation of the dotted lines in the side absorbers; this will re-direct higher frequency early reflections away from the mix position (as well as control flutter)
It's my theory that one 4-foot wide unit beats two 2-foot wide ones, based on the longer wavelengths involved - otherwise ( I think) they would tend to "average" -
HTH... Steve
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drfrankencopter
- Posts: 186
- Joined: Sun Apr 03, 2005 1:09 am
- Location: Ottawa, Canada
Thanks for the advice...
I'll probably end up with a couple angled slat absorbers up near the front of the room to tame the bass modes at the mix position, and combat flutter echo (without killing the reverb of the room for recording purposes). I like the idea of having a 4 foot wide slat as opposed to two 2 foot wide slats. Seems like it'd be a little easier to construct (less cutting required).
Also, I'll likely do broadband absorbtion right at the front of the room, and go with 2" 703 on the ceiling (furred out 1", and FWIW the floor is hardwood). I'd like to put corner traps on the wall/ceiling junctions to kill corner reflections and absorb bass where it builds up most! The rear wall will be diffuse (it's 17 feet from the listening position so I figure diffusion would be good there), should help it out for working as a tracking room too.
Cheers,
kris
I'll probably end up with a couple angled slat absorbers up near the front of the room to tame the bass modes at the mix position, and combat flutter echo (without killing the reverb of the room for recording purposes). I like the idea of having a 4 foot wide slat as opposed to two 2 foot wide slats. Seems like it'd be a little easier to construct (less cutting required).
Also, I'll likely do broadband absorbtion right at the front of the room, and go with 2" 703 on the ceiling (furred out 1", and FWIW the floor is hardwood). I'd like to put corner traps on the wall/ceiling junctions to kill corner reflections and absorb bass where it builds up most! The rear wall will be diffuse (it's 17 feet from the listening position so I figure diffusion would be good there), should help it out for working as a tracking room too.
Cheers,
kris