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diy bass trap details... Dynamics Plugins
Old 12th September 2007
  #1
Gear Head
 

diy bass trap details...

Hi,

decided my hifi room at home needs acoustic help...

So started building some more bass trap and midband absorbers. I'm after some diy advice on finer design features. The latest thing was to put something behing my head (a stone/brick rear wall is quite close to my chair) to cut down on comb filtering effects.

{ Q. } I'm not sure if i've bought slabs that are too dense ? they are very rigid - i'll try to weight them tonight adn calculate their density. is too dense bad ?

the sheets are ~1" thick (60*120 cm)and i've placed them tight to the edges in a 3" deep wood frame with an internal 1" gap. the frame is ~6" from the wall on an integral stand. covered with a thin poly batting sheet stuck with double sided tape at the moment to the frame- seems to hold OK.

{ Q. } I wonder if the internal 1" gap will help absorption due to the cavity ? or does it not matter with bass having such huge wavelengths ?

my bass traps in the corners (only 2 corners) are very cheap and chearful - just unopened bags of tightly rolled fibreglass (used for loft insulation) that are about 2' diameter stacked in the corners floor to ceiling and covered with a 'nice' plain fabric to roughly match the wall colour.

{ Q. } I want to put some panels either side to cut the first reflections - would my very dense 1" fibreglass be enough for this ?

I've also read Ethan's (Mr realtrap) article on distribution of fibreglass panels which seems to show that covering floor to ceiling the four wall corners with 3" sheets was better that 1/2 as much 6" sheets (Rigid fiberglass density tests)

makes me think I should put more bass traps into the other two corners ?

{ Q. } anyone know what the structure of ethans real traps is ? there is mention of 'membranes' - i wonder if this is just faced fibreglass on the inside of two fibreglass panels that are face to face ?

I might try and put a floppy membrane in my cavity design panel so that I have two fibreglass panels about a sealed-ish cavity with the membrane not touching - the idea is that the pressure differentials inside and outside causes the air velocity inside the fibre panels to increase - thus increasing the absorption ?

not sure what to use as the membrane - possibly roof felt or rubber floor matting ?

sorry for the stream of ideas etc....

Gareth.
Old 12th September 2007
  #2
Gear Guru
 
Glenn Kuras's Avatar
Quote:
{ Q. } I'm not sure if i've bought slabs that are too dense ? they are very rigid - i'll try to weight them tonight adn calculate their density. is too dense bad ?
Up to about 8 to 10 pound for bass trapping should be fine.

Quote:
{ Q. } I wonder if the internal 1" gap will help absorption due to the cavity ? or does it not matter with bass having such huge wavelengths ?
I would not put any kind of air gap in the middle. Just make it 4" or more of solid fiberglass.

Quote:
{ Q. } I want to put some panels either side to cut the first reflections - would my very dense 1" fibreglass be enough for this ?
Up to 8 pound will be fine for early reflection panels.

Quote:
not sure what to use as the membrane - possibly roof felt or rubber floor matting ?
You want to use FRK on the face of the panel. NOTE ONLY ON THE FACE NOT INSIDE OF THE PANEL.

Hope that helps

Glenn
Old 12th September 2007
  #3
Gear Head
 

Studio SOS

this shows the high density stuff i can get.

hopefully OK for early reflection points.

BUT it's 2/3 the price to get the lower density slabs which are 10*50mm rather than 5*30mm - so for approx the same cash I get 150mm vs 30mm. SO, should i make my new panel bass traps from the lower densty material ?

it seems from the absorption data that 150 or 200 mm will always best 30mm irrespective of density ?
*Heavy Density Insulation vs medium Density Insulation

which should i try ?

i think these are 'rockwool' materials repackaged. but not sure !

G.
Old 12th September 2007
  #4
Lives for gear
 
Bob Ross's Avatar
 

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