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Acoustic Question...
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mquirk1
IsraTrance Full Member
Started Topics :
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384
Posted : Mar 26, 2009 13:09
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On 2007-10-03 18:27, subconsciousmind wrote:
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On 2007-10-03 18:05, Get-a-fix wrote:
Errr the bags are just to hold the rockwool! So the super sub bass bags would hold 6 inch thick rockwool, which IS good enough 
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6inch = 15cm
In THEORY, One quarter of the soundwave should be within the absorbing material to have full absorbing effect.
150Hz; Wavelength 2.2 meters (speed of sound/frequency) 330m/s / 150Hz = 2.2 meters (as for the units "Hz" is "1/s" )
so the material should have 50cm or more...
In PRACTICAL Its not that critical, but just to show, that theoreticaly for low frequency a lot of thickness is needed. as in corner traps etc.
But 6 inch, 15cm definitly is far from super sub bass.
the bag idea is great, I will do it myself next time. a little tailoring.. possible... 
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that depends heaps on the density and material used in the trap tho.. for example the traps on the real trap site, they're only 4 or 6 inches thick but they have absorbtion co-efficients of 0.5 at 50hz, better then any rockwool or whatever i've seen at twice/three times the thickness. 4-6 inch is fine if the material is dense enough |
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~d2~
Inactive User
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7
Posts :
751
Posted : Mar 26, 2009 13:31
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On 2007-10-04 14:11, subconsciousmind wrote:
One thing some may find wort to know.
A professional studio does NOT want 000 Refelections!!!
A pro studio wants EQUAL and mediocre reflection of soundwaves of all frequencies (whereas a little more in bass is tolerated).
Actually the prototype is a NORMAL LIVINGROOM, where the music will be played in.
The funny thing is, that a normal living room, with carpet, couch, table, curtains, furniture and all other kinds of funny obstacles results (due to its chaotic nature) in a very desired reflections behaviour. A living rooms diversity is optimal to "eat" all kinds of frequencies in an equal way, but still will not absorb them all, which would result in a "dead" sounding room.
The thing with accoustic treatment only comes into play when a room is very small or only dedicated to music, which obviously misses all the chaotic obstacles. only in that case (or when a also otherwise used room has hardfloor and few obstacles) we need to start optimising..
So before you jump on the absorbers train check if your room might not be quite optimal by its nature, cause also being your bedroom etc. etc.
Note, that small rooms are always a problem.
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Well a completely dead room is not much good, but, you have to understand that there is much difference between a pro control room and someone living room!!!
A good PRO control room will have background noise levels of below 20dBa (or NR20 or NC20). And will need to be deader than the recording space so one can hear the recording spaces natural reverb as opposed to the control rooms. The room will be designed to have a more even bass response (better spread of room modes) and will have any issues tuned out. There is a big difference between a pro control room and domestic room.
Of course there are thing we can do to make our rooms better.
1) Setting up your monitors and yourself listening position in the optimum position.
2) Dealing with Early reflection points.
3) Adequate corner bass trapping.
A cool little tool:
http://www.hometheatershack.com/roomeq/
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~d2~
Inactive User
Started Topics :
7
Posts :
751
Posted : Mar 26, 2009 13:42
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[quote]
On 2009-03-26 13:09, mquirk1 wrote:
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that depends heaps on the density and material used in the trap tho.. for example the traps on the real trap site, they're only 4 or 6 inches thick but they have absorbtion co-efficients of 0.5 at 50hz, better then any rockwool or whatever i've seen at twice/three times the thickness. 4-6 inch is fine if the material is dense enough
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Realtraps use Coeings 705 which is about 90 kg/m2.
Density is not actually the proper determining factor. Gas flow resistance is.
Finding exact specifications for this are hard. Also it very hard to test low frequencies, especially those very low ones.
The wavelength thing is quite right, however you have to consider the many angles of incidence. The overall size of the trap, not just the thickness or density. The air gap behind it is also important. And of course the placement.
Bass trapping I would recommend from 45kgm2 to 90kgms. 15cms thick. Usual slab dimensions for rock/mineral/fibre wool. cover as many corners as possible. Especially the 3 point ones. straddle the traps across the corners diagonally.
If you have more money then you could just make lots of corner super chunks. Apparently according TO Ethan Winner they are 16% more efficient, but do use up alot more material. |
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mquirk1
IsraTrance Full Member
Started Topics :
63
Posts :
384
Posted : Mar 27, 2009 06:10
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[quote]
On 2009-03-26 13:42, ~d2~ wrote:
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On 2009-03-26 13:09, mquirk1 wrote:
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that depends heaps on the density and material used in the trap tho.. for example the traps on the real trap site, they're only 4 or 6 inches thick but they have absorbtion co-efficients of 0.5 at 50hz, better then any rockwool or whatever i've seen at twice/three times the thickness. 4-6 inch is fine if the material is dense enough
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Realtraps use Coeings 705 which is about 90 kg/m2.
Density is not actually the proper determining factor. Gas flow resistance is.
Finding exact specifications for this are hard. Also it very hard to test low frequencies, especially those very low ones.
The wavelength thing is quite right, however you have to consider the many angles of incidence. The overall size of the trap, not just the thickness or density. The air gap behind it is also important. And of course the placement.
Bass trapping I would recommend from 45kgm2 to 90kgms. 15cms thick. Usual slab dimensions for rock/mineral/fibre wool. cover as many corners as possible. Especially the 3 point ones. straddle the traps across the corners diagonally.
If you have more money then you could just make lots of corner super chunks. Apparently according TO Ethan Winner they are 16% more efficient, but do use up alot more material.
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my point was that 6 inches of a dense material *can* easily absorb well into sub bass frequencies |
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