Standing Wave Treatment
Mike.C
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#1
28th February 2013
Old 28th February 2013
  #1
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Standing Wave Treatment

Hey guys! This will be my first post I'm an acoustics noob so please bare with me.

My mix position seems to be in the peak of a standing wave at around 130Hz. If I play a 131Hz sine wave while sitting, it's quite a bit louder compared to other frequencies (C notes stick out like a sore thumb) and when I stand up it almost disappears. If I stand on my toes I can hear it again. It's because of this I've come to the conclusion that it's an axial mode between my floor and ceiling. My ceiling is roughly 2.5m high and the width of the room is roughly 4m.

I don't have any bass trapping in my room at the moment (other than a queen sized bed in the back corner and 2 small couches if that counts) and I'm thinking of building two panel bass traps from rock wool and hanging one from the ceiling above the mix position and one closer to the front wall at an angle.

Am I in any way going about this the right way? If so how thick is thick enough and how much space between the trap and the ceiling is space enough?

Thanks in advance to any replies
#2
28th February 2013
Old 28th February 2013
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Ceiling will help...
Use rockwool....as deep as you can...
don't take the fluffy one use higher density...
#3
28th February 2013
Old 28th February 2013
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Jens Eklund's Avatar
 
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First; identify the areas related to your modal issue:

Need help to tune my control room. (First Measures Included)

Your initial guess is probably correct, but why not dubble check. If tangential or oblique mode; you might find more or better areas to treat.


Then treat relevant areas using appropriate treatment options (pressure based or velocity based depending on if the area in question is an early reflection point or not and depending on the acoustic response desired) effective in the same frequency range as the modal frequency of interest.
#4
28th February 2013
Old 28th February 2013
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Jens Eklund's Avatar
 
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Quote:
Originally Posted by burnhard View Post
Ceiling will help...
Use rockwool....as deep as you can...
don't take the fluffy one use higher density...
First of all; density alone says little or nothing about the acoustic properties of a porous material. Secondly, the opposite is often true depending on thickness of the panel:

Acoustic Panel Stand
Low kg/m3 is worthless.
Mike.C
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28th February 2013
Old 28th February 2013
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Thread Starter
Quote:
Originally Posted by Jens Eklund View Post
First; identify the areas related to your modal issue:

Need help to tune my control room. (First Measures Included)

Your initial guess is probably correct, but why not dubble check. If tangential or oblique mode; you might find more or better areas to treat.


Then treat relevant areas using appropriate treatment options (pressure based or velocity based depending on if the area in question is an early reflection point or not and depending on the acoustic response desired) effective in the same frequency range as the modal frequency of interest.
Thanks for the information and the great post! It's a lot to take in but I'll definitely give it some thought.
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28th February 2013
Old 28th February 2013
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#7
15th March 2013
Old 15th March 2013
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Quote:
Originally Posted by burnhard View Post
Ceiling will help...
Use rockwool....as deep as you can...
don't take the fluffy one use higher density...
If you use the Porous Absorber Calculator you will see that it's not that simple.
Pink fluffy R13 or R11 can be fine, depending on lots of things.
#8
15th March 2013
Old 15th March 2013
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Calculation vs Reality

Welcome Mike. You do have a typical 130Hz vertical mode.
I am not sure that you want to go making an overhead frame to hold fluffy or crumbly insulation over your head. In which case you could do what the commercial manufacturers do. Use rigid fibre panels. Fibreglass tends to be more rigid per weight, although Roxul gives full choices in this regard. The calculators do not take account of placement in corners or the damped panel drum head effect exhibited by rigid panels.
100mm 100KG Rock or Glass Wool should work fine for you. I wouldn't consider less than four for the cloud. Be sure to include a 100-300 mm airgap. You could include Space Couplers under the cloud.
It can be well worth doing another four or two in the ceiling wall corners, say between you and the speakers, over the side RFZ traps. This is a very simple ingenious frame design Best DIY Trap EVER
DD
#9
17th March 2013
Old 17th March 2013
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Gdupproductions's Avatar
 
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Quote:
Originally Posted by burnhard View Post
don't take the fluffy one use higher density...
Fluff has usually gasflow resistivety of 5000 rayls which absorbs way deeper !.
@ 350mm thickness you already have aborbtion coefficients that go equal with each band bellow 100hz.
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