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genelec79
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16th September 2010
Old 16th September 2010
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Install bass traps

Hi everybody! If somedbody can help with advice i will be very thankfull. I have purchase 6 VPR(Modex plate) absorbers for low frequency treatment of my small small project studio room( HxWxL (2,45m;2,30m;4,40m) ). I wanted to find places in a room with highest modal activity to put absorbers there and i have place the speaker in one corner and the measuring mic in intersection all three boundary surfaces, two boundary surfaces. So basically is stupid but ,should i positioning absorbers according to results from measurement along the length of the room or according to measurement from my real speaker position (which is along the width of the room)!?????
Thanx and sorry for my bad English!
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16th September 2010
Old 16th September 2010
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Lightbulb VPR positioning

Quote:
Originally Posted by genelec79 View Post
... I have purchase 6 VPR(Modex plate) absorbers for low frequency treatment of my small small project studio room( HxWxL (2,45m;2,30m;4,40m) ). I wanted to find places in a room with highest modal activity to put absorbers there and i have place the speaker in one corner and the measuring mic in intersection all three boundary surfaces, two boundary surfaces ... should i positioning absorbers according to results from measurement along the length of the room or according to measurement from my real speaker position (which is along the width of the room)!???? ...
You always get the most modal activity in the corners where three boundary surfaces meet (8 of them in a cuboid). The VPRs (did you buy RPG products?) will reduce decay times of the deep nodes most propably regardless of the corner you mount them - just try to face all three room dimensions (two VPRs per dimension). Optimizing the speaker-/listening-position for a nice ETC and a smooth frequency response is yet another story. Post your setup/results!
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genelec79
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16th September 2010
Old 16th September 2010
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Hi Gernot! I was actually buy Fraunhofer Verbundplattenresonators-but most people know only RPG Modex Plate-(thats way i have put RPG sign). Can you explain this "just try to face all three room dimensions (two VPRs per dimension))?? Thanx
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16th September 2010
Old 16th September 2010
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Lightbulb Mode "directivity"

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Originally Posted by genelec79 View Post
... Can you explain this "just try to face all three room dimensions ...
Since the deepest modes are not "diffuse" but have a certain orientation (depending on the mode) you need to face all three dimensions of the room with any pressure based absober (that also has a prefered "orientation" perpendicular to its face) if you want to catch all of the modes efficiently.
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16th September 2010
Old 16th September 2010
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Quote:
Originally Posted by G. E. View Post
Since the deepest nodes [modes] are not "diffuse" but have a certain orientation (depending on the node [mode]) you need to face all three dimensions of the room with any pressure based absober (that also has a prefered "orientation" perpendicular to its face) if you want to catch all of the nodes [modes] efficiently.
Just to avoid confusion:

A node is a minimum pressure variation location of a room mode. I guess it was a typo in the post above.

Sincerely Jens Eklund
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16th September 2010
Old 16th September 2010
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Lightbulb Typo

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Originally Posted by Jens Eklund View Post
... A node is a minimum pressure variation location of a room mode. I guess it was a typo in the post above. ...
Thanks a lot, I've been "using" this typo for a long time - will correct anywhere...
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16th September 2010
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Quote:
Originally Posted by G. E. View Post
Thanks a lot, I've been "using" this typo for a long time - will correct anywhere...
Apparently easy to miss since I haven’t noticed until now ... One tends to read what one expects to read.

/Jens
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16th September 2010
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Guys thanks! But actuall problem with my room is that i have not enough space to instal absorbers in that way-see picture.
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16th September 2010
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Quote:
Originally Posted by genelec79 View Post
Guys thanks! But actuall problem with my room is that i have not enough space to instal absorbers in that way-see picture.
Then it will be difficult to tame modes that rely on the length dimension solely.
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17th September 2010
Old 17th September 2010
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thanx for the quick reply Jens! And what about absorber on the ceiling-between the doors and chimney-fill up almost all space on the ceiling and one more on the side wall directly to doors
??
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17th September 2010
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Quote:
Originally Posted by genelec79 View Post
thanx for the quick reply Jens! And what about absorber on the ceiling-between the doors and chimney-fill up almost all space on the ceiling and one more on the side wall directly to doors
??
Before anyone can give any specific advise, we first need some data (measurements) of your room.

Sincerely Jens Eklund
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18th September 2010
Old 18th September 2010
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genelec,

You have 12 corners in a rectangular room. Can you treat the wall/ceiling corners??

Treat the vertical corners where you can. The primary of the modes can be difficult to treat and you can end up with an over-absorbed room (dead). Usually 20% coverage is enough to bring the decay times down to manageable. If begins to sound too dead with all the trapping, you can cover the traps that are not in an area that will cause early reflections with thin plywood, paper or plastic to allow the mid and high frequencies to stay in the room a little longer.

Cheers,
John
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