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Post by mahdes on Feb 17, 2019 20:58:12 GMT
Hi!
I made very thick triangles from rockwool. I filled all four corners (wall to wall) from floor to the ceiling. Triangles are of course touching the walls - no airgap at all.
But today I found this on Ethan's page
"Likewise, fiberglass placed exactly at a rigid boundary does nothing because the air particles are not moving there. And since there's no velocity, the fiberglass has very little effect. As fiberglass is spaced further from the wall, the air particles passing through it have greater velocity. They are slowed down as they pass through the fiberglass, which converts the sound energy into heat therefore absorbing some of the sound."
Is it same with the rockwool? Should I move my triangle towers of rockwool away from the wall? If yes, How many centimeters ?
Thank you!
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Post by rock on Feb 18, 2019 4:41:35 GMT
At the exact point of the boundary there is precisely 0.00... velocity, but... as you move ANY distance from the boundary the velocity will increase. By moving your traps away from the wall, you gain absorbing higher velocity "waves" that and you can space your very thick triangles away from the wall to optimize their efficacy. This is the point where you may want to take acoustic measurements because the dimensions and modes of your room will come into play with your bass trap positioning. As you experiment with different distances from the wall, you should find the optimum spacing.
The only caveat with spacing is that if you go too far (like more then double the thickness of the absorber) you will get "holes" or losses in the frequency range you will effectively absorb (that's usually a bad thing). As said before, testing will show you the way.
All that said, most who build super chunks like you did often place them directly in the corner. There is nothing wrong with that either...but if you have the room to move them out, experiment and take measurements if you want to know for sure!
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Post by Ethan Winer on Feb 18, 2019 15:59:55 GMT
Thanks Rock.  |
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Post by Hexspa on Feb 18, 2019 19:26:07 GMT
Rock said it well. I will add that I do gap my super chunks and probably because I've measured them to perform better that way. As I recall, this was a contentious point at the time but measurements don't lie. For what it's worth, my front super chunks have an angled rigid panel behind them. Sometimes it pays to double wrap it, so to speak.
My front two chunks are spaced 24"x20" off the walls. I have a rear chunk spaced 7" and another spaced 24"x42". These are 2'-half fluffy chunks. The reasons I have one spaced 42" is due to my hall partly bisecting my room in addition to the modal issue which it causes.
So, start by stuffing them in the corner then inch them out until you find what works best.
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ths61
New Member
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Post by ths61 on Nov 24, 2019 21:23:04 GMT
... The only caveat with spacing is that if you go too far (like more then double the thickness of the absorber) you will get "holes" or losses in the frequency range you will effectively absorb (that's usually a bad thing). As said before, testing will show you the way. ...
What air gap depth do you optimally use when straddling a corner (maximum depth of corner, average depth of corner or something else)?
The normal commercial 2'x4'x4" deep rectangle traps that straddle corners have a maximum air gap depth of 12" in the center (which is 3X that of a 4" thick trap, 4X that of a 3" thick trap) and an average air gap depth of 6" (which is 1.5X that of a 4" thick trap, 2X that of a 3" thick trap).
If the outside edges of the rectangular traps are tapered to countersink the trap into the corners, then the maximum air gap depth is 8" (which is 2X that of a 4" thick trap) and the average air gap depth is 4" (which is 1X that of a 4" thick trap).
I would like to use this information in conjunction with the 1/4 wavelength rule to determine the optimal air gap and to determine lowest frequency for a given trap thickness (e.g. 8" thick corner traps) without creating "holes/losses".
TIA
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Post by Ethan Winer on Nov 25, 2019 17:22:21 GMT
When straddling a corner the gap size is whatever it is, based on the panel width. Bit I wouldn't obsess over matching gaps and frequencies. A typical 2x4 foot 4- or 6-inch thick panel straddling a corner works very well.
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Post by Hexspa on Nov 26, 2019 19:42:23 GMT
Ethan is right. In addition, if using panels on a parallel surface, about a 1x gap is optimum for the ideal bass extension-to-no midrange holes ratio. You may also angle the panels vertically, i.e. 'lean them against the wall' which worked best in my case for my side walls.
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ths61
New Member
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Post by ths61 on Nov 27, 2019 6:23:35 GMT
When straddling a corner the gap size is whatever it is, based on the panel width. Bit I wouldn't obsess over matching gaps and frequencies. A typical 2x4 foot 4- or 6-inch thick panel straddling a corner works very wel
I am limited on wall space, so ...
I was considering making floor to ceiling corner bass traps (GREEN) that tie into soffit traps at the top for extra bass trapping coverage around the room. Wall-to-Wall corners and Wall-to-Ceiling corners (including all 8 - 3 plane corers: Wall-to-Wall-to-Ceiling and Wall-to-Wall-to-Floor).
The basic (yellow) and CounterSunk (orange) or SuperChunk (brown) traps won't mate up well with the soffit traps.
Knowing the 1/4 wavelength rules and corner air gap depth ratio can help optimize the amount of material usage as well as predict lowest frequency. It would be helpful to know if the custom green trap could be half as thick as what is pictured (e.g. a reversed counter sunk profile), or if a "double-counter sunk" thickness profile is required (or something else).
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ths61
New Member
Posts: 22
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Post by ths61 on Nov 27, 2019 7:18:13 GMT
Ethan is right. In addition, if using panels on a parallel surface, about a 1x gap is optimum for the ideal bass extension-to-no midrange holes ratio. You may also angle the panels vertically, i.e. 'lean them against the wall' which worked best in my case for my side walls. Thanks, my 3" and 4" thick wall traps are spaced at 1". Will try spacing them at 1X thickness. |
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Post by Hexspa on Nov 27, 2019 17:39:10 GMT
Try to go a minimum of 4" wherever possible for rigid, up to 8" which is ideal in terms of frequency cutoff.
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