Trapping Traps
Old 22nd May 2012
  #91
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Quote:
Originally Posted by G. E. View Post
I'm more into control room setups the last weeks, looking if the test results translate to this situation. Latest result shows that the 42Hz mode is totally gone.
This FR response looks good. I would like to see ARTA's waterfallplot(CSD) and not REW's.
Is the measurement taken from the LP?

Edit. of course you don't have 42Hz mode, your response rolls of from -10dB from 60Hz.
Old 23rd May 2012
  #92
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Arta & rew

Quote:
Originally Posted by Mctwins View Post
... Could you tell me where your mic was when these measurements was done. ...
The mic was at the back center of the room at the client couch position as I wrote in the EPA Real World Performance Example post.

Quote:
Originally Posted by Mctwins View Post
I have one Q?? Why the REW waterfall when you have ARTA, it has to come from the same impulse response envelope to be able to see some difference.
I have not yet got the ARTA waterfall display to the point where it is visually revealing for clients. Anyway the REW waterfall I've shown is calculated from ARTA's exported impulse response.
Old 23rd May 2012
  #93
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Roll-off

Quote:
Originally Posted by Mctwins View Post
... I would like to see ARTA's waterfallplot(CSD) and not REW's. Is the measurement taken from the LP?
Please, go ahead: ARTA's PIR-File is attached. The measurement is taken from a nearfield listening position after a 45min acoustic setup (starting with a naked room).

Quote:
Originally Posted by Mctwins View Post
... Edit. of course you don't have 42Hz mode, your response rolls of from -10dB from 60Hz.
I don't agree, the roll-off is mostly due to heavy bass-trapping -- the naked room has a T60 longer than 6 seconds. Furthermore the decay time of modes doesn't change that much with higher monitor roll-off.
Attached Files
File Type: zip 20120518 sv m32 S.zip (944.8 KB, 33 views)
Old 23rd May 2012
  #94
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Quote:
Originally Posted by G. E. View Post
Today I measured a control room before/after the installation of two Enhanced Porous Absorbers (both 2,8m x 1,0m [~9' x 4']) in the front corners.
flush on the walls (which?) or straddling corners?
Old 23rd May 2012
  #95
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Straddling

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Originally Posted by gigi View Post
flush on the walls (which?) or straddling corners?
... straddling both front corners (= behind the monitors).
Old 23rd May 2012
  #96
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G.E.: a question about EPA. I hope it's the right thread.
I have an old door in the middle of the rear wall I'm closing with Gypsum from the outside and I will leave it open from the CR side . It's 2,30x0,75m x0,30m deep. I'm toying with the idea of build an EPA inside it. I don't have many places to put such trap... One is inside the false ceiling, but it can't be taller than 70cm there (it can be very wide anyway), and the other is the right front corner. The room is 4,17x3,96m so it's square. Do you think is a good idea to build the EPA inside the door space or there will be little pressure to absorb there?
Old 23rd May 2012
  #97
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Door

Quote:
Originally Posted by gpiccolini View Post
G.E.: a question about EPA. I hope it's the right thread.
I have an old door in the middle of the rear wall I'm closing with Gypsum from the outside and I will leave it open from the CR side . It's 2,30x0,75m x0,30m deep. I'm toying with the idea of build an EPA inside it. I don't have many places to put such trap... One is inside the false ceiling, but it can't be taller than 70cm there (it can be very wide anyway), and the other is the right front corner. The room is 4,17x3,96m so it's square. Do you think is a good idea to build the EPA inside the door space or there will be little pressure to absorb there?
I would measure with sinus signals at the resonant frequencies and hear were pressure is high (that is where its loud for the human ear).

With the gypsum behind you already have a membrane so I'm not sure how this system reacts.
Old 24th May 2012
  #98
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Quote:
Originally Posted by G. E. View Post
Please, go ahead: ARTA's PIR-File is attached. The measurement is taken from a nearfield listening position after a 45min acoustic setup (starting with a naked room).



I don't agree, the roll-off is mostly due to heavy bass-trapping -- the naked room has a T60 longer than 6 seconds. Furthermore the decay time of modes doesn't change that much with higher monitor roll-off.
Hi

Let's see if I get this. The before, after and this last file is all coming from the same room?

Do you have a before measurerment from a nearfield LP from the same room? Naked off course.

To have a T60 of 6 sec can not be true in that room, maybe if in a church yes. This with heavy bass trapping I don't understand, can it be more explained what you mean. It is the room you have to treat not the loudspeaker. Proper treatment of modes/resonances in a room should not affect the loudspeaker.

Please do explain what you mean by "Furthermore the decay time of modes doesn't change that much with higher monitor roll-off".

And what additional treatment have been done in those 45 min besides of the VPR of yours. The last file shows a very dead room.

When I get the time I will post some waterfalls from your files here and from ARTA. if it is OK with you.
Old 24th May 2012
  #99
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Details

Quote:
Originally Posted by Mctwins View Post
... The before, after and this last file is all coming from the same room?
No, two different rooms. Before/after from the same room though.

Quote:
Originally Posted by Mctwins View Post
... Do you have a before measurerment from a nearfield LP from the same room? Naked off course. ...
Sorry, no. It has been a ~90min job all in all to put up two straddling traps including measurement.

Quote:
Originally Posted by Mctwins View Post
... To have a T60 of 6 sec can not be true in that room, maybe if in a church yes. ...
This room is all solid concrete and the 42Hz mode is caclulated by REW with more than 6 seconds (see image below). In fact ARTA was not able to find the 300 sample starting point (see PIR-File) from the measurement so the result may be a flawed. Standing in the room you can hear the mode decaying for a few seconds so I guess the impulse response is not much off because of the starting point. As soon as you start using bass traps the T60 goes down to 3-4s.

Quote:
Originally Posted by Mctwins View Post
... Please do explain what you mean by "Furthermore the decay time of modes doesn't change that much with higher monitor roll-off". ...
The decay time is basically independent from the pressure level.

Quote:
Originally Posted by Mctwins View Post
... And what additional treatment have been done in those 45 min besides of the VPR of yours. The last file shows a very dead room. ...
Please note that I am talking about two different rooms!
Attached Thumbnails
Trapping Traps-20120524_rew.gif  
Attached Files
File Type: zip 20120326 sv m01.zip (932.1 KB, 21 views)
Old 24th May 2012
  #100
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Treatment

Quote:
Originally Posted by Mctwins View Post
... This with heavy bass trapping I don't understand, can it be more explained what you mean. ...
See the room situation at measurement time of "42Hz Gone". There're 4 plates of steel included that you don't see in the drawing, placed near the corners in between the absorbent.
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Trapping Traps-20120518_sv_m32_s.gif  
Old 25th May 2012
  #101
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Correction

Quote:
Originally Posted by G. E. View Post
See the room situation at measurement time of "42Hz Gone". ...
I just revisited the room and saw that the cloud is closer to the front than shown in the initial drawing.

BTW: yes, the room is very dry, I didn't care about mids and highs this time. It was all about the bass ...
Attached Thumbnails
Trapping Traps-20120518_sv_m32_s_corrected.gif  
Old 25th May 2012
  #102
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Great

Nothing to add but encouragement. Carry on, thanks, well done.

DD
Old 28th May 2012
  #103
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Hi
Here is before and after measurements from your ARTA file. CSD and Burst decay...

Before:





After:





As I see it, there is a slight difference but not much. The decay time in CSD hasen't changed below 100Hz. I have no problem to see resonances in ARTA.

Last edited by Mctwins; 29th May 2012 at 05:53 AM..
Old 28th May 2012
  #104
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Quote:
Originally Posted by G. E. View Post

The decay time is basically independent from the pressure level.
So you mean, when there is a zero pressure in the room you still have decay time? Could you please explain it a bit further.
Old 28th May 2012
  #105
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Quote:
Originally Posted by Mctwins View Post
So you mean, when there is a zero pressure in the room you still have decay time?
Yes.
Quote:
Originally Posted by Mctwins View Post
Could you please explain it a bit further.
Decay time is characteristic of room, which we presume as linear system, so it is constant regardless of pressure level.

EDIT: We need sound pressure to measure decay, but he (decay) exist regardless of this excitation.
Old 28th May 2012
  #106
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Quote:
Originally Posted by boggy View Post
Yes.

Decay time is characteristic of room, which we presume as linear system, so it is constant regardless of pressure level.

EDIT: We need sound pressure to measure decay, but he (decay) exist regardless of this excitation.
Yes, I understand know if it is explained in this way, then I agree. But one need a pressure to measure. If I have highpass filter at 100 Hz then I will never be able to see if there is a decaytime or not under 100 Hz.
Old 28th May 2012
  #107
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OT

McT, I tune into this thread now and again as I am very interested in the Topic of VPR, CBA, Metal Panel resonant trapping.
I have difficulty in seeing the relevance of your recent posts to this topic.
I see ARTA results and a picture of a room. Are they from that room or are they G.E.'s ?
If they are from another room with no VPR's, what the hell are they doing here?
Frankly I am lost.

DD
Old 28th May 2012
  #108
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Quote:
Originally Posted by DanDan View Post
McT, I tune into this thread now and again as I am very interested in the Topic of VPR, CBA, Metal Panel resonant trapping.
I have difficulty in seeing the relevance of your recent posts to this topic.
I see ARTA results and a picture of a room. Are they from that room or are they G.E.'s ?
If they are from another room with no VPR's, what the hell are they doing here?
Frankly I am lost.

DD
The four first graphs is GE before and after, I just wanted to show that one can see resonances in ARTA.
Old 28th May 2012
  #109
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Quote:
Originally Posted by Mctwins View Post
Yes, I understand know if it is explained in this way, then I agree. But one need a pressure to measure. If I have highpass filter at 100 Hz then I will never be able to see if there is a decaytime or not under 100 Hz.
Whatever, decay time is independent from sound pressure level, as G. E. said
Old 28th May 2012
  #110
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Back to earlier post:
Quote:
Originally Posted by Mctwins View Post
.........
Edit. of course you don't have 42Hz mode, your response rolls of from -10dB from 60Hz.
Wrong conclusion, he still have enough energy to measure decay time and characteristic of room mode, regardless of filter roll-off.
-10dB (or even -20dB) of SPL doesn't mean that sound pressure was dissapear (especially for measurements).

EDIT: You can find about ARTA Burst Decay analysis here: http://www.artalabs.hr/download/ARTA-user-manual.pdf (pg. 103)
Old 29th May 2012
  #111
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Quote:
The four first graphs is GE before and after, I just wanted to show that one can see resonances in ARTA.

I just show my room and my graph just for comparison.
Please leave it to Gernot to present the results of his own greatly appreciated work.

If you wish to brag about your own room, and why not, it's impressive, please start a thread, ideally showing the results of treatment and without, and anything you have in between.
That would be interesting in it's own right.
Here it and comparisons to the technique this thread is about, is simply way Off Topic.

DD
Old 29th May 2012
  #112
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Quote:
Originally Posted by DanDan View Post
Please leave it to Gernot to present the results of his own greatly appreciated work.

If you wish to brag about your own room, and why not, it's impressive, please start a thread, ideally showing the results of treatment and without, and anything you have in between.
That would be interesting in it's own right.
Here it and comparisons to the technique this thread is about, is simply way Off Topic.

DD
He has made a thread for his room. I think it would be easier for us, McTwins, to have you post a link to your room or to posts of your measurements instead of posting them in this thread.
Old 29th May 2012
  #113
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I have removed my graphs in post 103.

Those four measurements from that post is from GE file. He had some problem to show and interpent the graphs in ARTA. I was only trying to help him out.
Old 29th May 2012
  #114
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Quote:
Originally Posted by DanDan View Post
Please leave it to Gernot to present the results of his own greatly appreciated work.
But GE didn't know how to present the data from ARTA.
Old 29th May 2012
  #115
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Quote:
Originally Posted by boggy View Post
Back to earlier post:

Wrong conclusion, he still have enough energy to measure decay time and characteristic of room mode, regardless of filter roll-off.
-10dB (or even -20dB) of SPL doesn't mean that sound pressure was dissapear (especially for measurements).

EDIT: You can find about ARTA Burst Decay analysis here: http://www.artalabs.hr/download/ARTA-user-manual.pdf (pg. 103)
Don't tell me about the manual, tell it to GE.
Old 29th May 2012
  #116
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ARTA Settings

Quote:
Originally Posted by Mctwins View Post
... As I see it, there is a slight difference but not much. The decay time in CSD hasen't changed below 100Hz. I have no problem to see resonances in ARTA.
I get your "waterfall"-like view with the Burst Decay yet I don't agree that the difference is "slight", I call it substantial and it can be seen in the Burst Decay (not so much in the CSD). The point is: the difference in the room was unquestionable.

BTW: the posted CSDs and BDs are from the room of "EPA Real World Performance Example"
Old 29th May 2012
  #117
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Decay

Quote:
Originally Posted by Mctwins View Post
So you mean, when there is a zero pressure in the room you still have decay time? Could you please explain it a bit further.
From my understanding a "zero pressure" is measured at certain places in the room but the "decay" at this frequency is basically independent from the place and can be measured elsewhere in the room.
Old 29th May 2012
  #118
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Quote:
Originally Posted by G. E. View Post
From my understanding a "zero pressure" is measured at certain places in the room but the "decay" at this frequency is basically independent from the place and can be measured elsewhere in the room.
My definition of "zero pressure" is 0(null) Pascal like when you don't have any loudspeaker(no sound) in the room when you measure.

So again, I am asking the same queastion. Can you see in the measurement the decaytime if you have highpass filtered at 100Hz. You can't measure the decaytime when there is no energy present below 100Hz. Do you understand now??

From your understanding, how do you know that you are in the right place when you measure and what frequency do you mean?
Old 29th May 2012
  #119
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Quote:
Originally Posted by Mctwins View Post
...
So again, I am asking the same queastion. Can you see in the measurement the decaytime if you have highpass filtered at 100Hz.
Yes.
Quote:
Originally Posted by Mctwins View Post
You can't measure the decaytime when there is no energy present below 100Hz. Do you understand now??
Applying (ordinary) 100Hz HP filter does not means that you have "no energy" below 100Hz. It is dependent of the filter slope, but all ordinary HP filters (2nd an 4th order), does not rolloff so fast to "kill" all energy below 100Hz. Only brick-wall HP filter (200dB/dec or more) may illustrate your idea, but this is not a case here.
Old 29th May 2012
  #120
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Topic

McT, Gernot over a long period of time Gernot has experimented with many different types of LF Traps. In the quest for the best.
I can assure you he knows have to construct and how to test and how to show results. But aside from that, this is not a thread discussing ARTA or its use, or Measurement techniques, or the weather for that matter. It is about DIY experiments with a Metal Panel Damped Resonator Trap.
If you have queries regarding extraneous matters please use PM.
Your are currently polluting the IMHO single best thread on GS, with dubious nonsense.

DD
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