Trapping Traps
#61
19th February 2012
Old 19th February 2012
  #61
Gear Head
 
MaximumAdams's Avatar
 

Hi guys, awesome topic! Thanks dandan for pointing me here.
Been through the thread and some of the designs reminded me of this article I found ages ago;

SAE Institute

This acoustic hanger idea looks like its working on a pretty similar principle to the "enhanced porous absorber" design. The article seems to be pretty dated, but I thought it might be of use somehow in regards to mounting options, or a different perspective.
I'm not sure if it's anything you guys haven't seen before, but I figure every little bit helps.
#62
19th February 2012
Old 19th February 2012
  #62
Lives for gear
 
latestflavor's Avatar
 

Quote:
Originally Posted by MaximumAdams View Post
This acoustic hanger idea looks like its working on a pretty similar principle to the "enhanced porous absorber" design.
The hangars only work in arrays and not the same in different parts of the room. Originally they were empirically developed by non-acousticians "in the wild". We shall see where they go as they become improved through reverse engineering, but they seem to take a lot of space though and work best in non-environment designs.
#63
20th February 2012
Old 20th February 2012
  #63
Gear Head
 
MaximumAdams's Avatar
 

I wasn't really thinking about the acoustical application as such, I was thinking more along the lines of the mounting method. By "similar principle" I meant that they're both resonating panels, but the metal plate design is an exponentially more effective and versatile evolution of the theory.
I suppose I should have said that "by a little dated" I really meant something along the lines of how apes are related to modern humans; they both have opposable thumbs and the like, but I couldn't see an ape being able to understand modern acoustic design.

Somewhat of an understatement you could say. Sorry, my bad.
#64
20th February 2012
Old 20th February 2012
  #64
Lives for gear
 
latestflavor's Avatar
 

The acoustic hangar is not a resonating panel. Conversely, a metal plate resonator ideally would not hang or rest on anything either. No biggie though, i'm not trying to shoot you down. They both look similar. An acoustic hangar is a bit hard to use if you're doing something other than a non-environment type of room because its so absorptive, if somewhat unpredictably so. A metal plate resonator, however, can be made either more or less absorptive, depending on how you desire the result. Also, a single metal VPR will attenuate LF if places where it is supposed to go (area of high pressure), a single acoustic hanger will not work at all (aside from the absorption that is hanging). So the only similarity is casually optical.

I wonder where G.E. stands with his testing, i subscribed to this thread with great anticipation! Hopefully its still alive!
NLP
#65
20th February 2012
Old 20th February 2012
  #65
NLP
Gear maniac
 
NLP's Avatar
 

... hangers can be different by structure, some use plywood, MDF (Newell)... hard core... some use like homosote cores (Hidley, Sayers)...
Hangers works best by waveguide effect, flexural vibration measuring with accelerometers, construction: 19mm chipboard and deadsheet of 3,5kg/m2 and both sides covered with 60kg/m3 cotton waste felt...is perhaps only 0,1% (AES E-Library ).
#66
23rd February 2012
Old 23rd February 2012
  #66
Gear Head
 
MaximumAdams's Avatar
 

Quote:
Originally Posted by NLP View Post
... hangers can be different by structure, some use plywood, MDF (Newell)... hard core... some use like homosote cores (Hidley, Sayers)...
Hangers works best by waveguide effect, flexural vibration measuring with accelerometers, construction: 19mm chipboard and deadsheet of 3,5kg/m2 and both sides covered with 60kg/m3 cotton waste felt...is perhaps only 0,1% (AES E-Library ).
Ahhh! So the boards in hangers aren't for absorption? The penny drops! I always just thought it was a mass principle that they rely on! Oh well a lesson learned the hard way is still a lesson learned. Thanks for the insight.
NLP
#67
23rd February 2012
Old 23rd February 2012
  #67
NLP
Gear maniac
 
NLP's Avatar
 

hmmm like I said:
"...hangers can be different by structure, some use plywood, MDF (Newell)... hard core... some use like homosote cores (Hidley, Sayers)..."
... softer "hard cores" can offer significant absorption and a bit of waveguide effect... and phases between...
G. E.
Thread Starter
#68
20th March 2012
Old 20th March 2012
  #68
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Moving Deadline

Quote:
Originally Posted by G. E. View Post
... Now that I have an empty room with different types of bass traps (see above) and a ready-to-go test setup available I kindly take your suggestions until the end of the year 2011 to compare different configurations directly for further public reference. ...
I'm giving this thread a restart: feel free to make your suggestion till April, 30th 2012.
G. E.
Thread Starter
#69
20th March 2012
Old 20th March 2012
  #69
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Listening Test Setup

Quote:
Originally Posted by latestflavor View Post
... I wonder where G.E. stands with his testing, ...
I used the room for testing some 1 hour listening setup with a 60cm [~2'] deep trap on the front wall. Deepest modes stayed in the 400ms range.
Attached Thumbnails
Trapping Traps-60cm.jpg   Trapping Traps-listening.jpg   Trapping Traps-burst_decay.jpg  
#70
21st March 2012
Old 21st March 2012
  #70
Gear maniac
 
BriHar's Avatar
 

Are those styrofoam blocks?
G. E.
Thread Starter
#71
21st March 2012
Old 21st March 2012
  #71
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Absorbent

Quote:
Originally Posted by BriHar View Post
Are those styrofoam blocks?
I used Caruso Iso Bond, a kind of non-woven polyester fabric.
G. E.
Thread Starter
#72
27th March 2012
Old 27th March 2012
  #72
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
EPA Real World Performance Example

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.

Setup included an almost square control room stuffed with a 32-channel console, some outboard, B&W 801 speakers, and minimal exisiting acoustic treatment with small porous absorbers.

Measured at the "client position" sofa 45cm [~1'6"] in front of the back wall window with both speakers driven, Red ... before (without EPAs), Blue ... after (with EPAs).

T60 for the lowest mode at 38Hz dropped from ~1400ms to ~600ms.
Attached Thumbnails
Trapping Traps-20120327_dual-gate_smoothed_fr.gif   Trapping Traps-20120327_burst_decay_before.gif   Trapping Traps-20120327_burst_decay_after.gif   Trapping Traps-20120327_waterfall_before.jpg   Trapping Traps-20120327_waterfall_after.jpg  

Trapping Traps-20120327_rt60_before.jpg   Trapping Traps-20120327_rt60_after.jpg  
G. E.
Thread Starter
#73
28th March 2012
Old 28th March 2012
  #73
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Measured vs. Caculated

Quote:
Originally Posted by G. E. View Post
... an almost square control room ... T60 for the lowest mode at 38Hz dropped from ~1400ms to ~600ms.
Here's length/width/height of this bedroom-sized studio space: 4,12m/3,96m/2,6m [~13'6"/12'12"/8'6"]

Using Bob Gold's "Room Mode calculator" gives a lowest mode at 41,8Hz. The lower measured figure of 38Hz could originate from the large window in the back or some coupling to the next room through the door. The room fails at some of the computed criteria.
Attached Thumbnails
Trapping Traps-20120327_bonello.gif  
#74
28th March 2012
Old 28th March 2012
  #74
Gear maniac
 
Prick Up UR Ears's Avatar
 

Quote:
Originally Posted by G. E. View Post
I used Caruso Iso Bond, a kind of non-woven polyester fabric.
to me those are just styrofoam blocks and those won't do a lot of trapping
#75
28th March 2012
Old 28th March 2012
  #75
Lives for gear
 
kasmira's Avatar
 

Holy hell GE, those results are extraordinary in that room! Superb!

Actually, I suppose its not extraordinary - that would imply that the results were unusual (but good). Instead, lets say that the results are superb.

I'm sure your client is ecstatic with the results. Why did you choose the front corner to trap?

Thanks so much for sharing this
G. E.
Thread Starter
#76
28th March 2012
Old 28th March 2012
  #76
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Reasoning

Quote:
Originally Posted by kasmira View Post
... Why did you choose the front corner to trap? ...
... in no particular order (fortunately no compromising necessary):
  • there is less sound pressure in the back of this room due to a large window and a door
  • the furniture left very little space in the back corners
  • EPAs in the front corner tend to "fill up" holes in the bass-range of the FR
bwo
#77
28th March 2012
Old 28th March 2012
  #77
bwo
Lives for gear
 

Great job G.E.!
May hire you one day.
#78
28th March 2012
Old 28th March 2012
  #78
Lives for gear
 
kasmira's Avatar
 

Quote:
Originally Posted by G. E. View Post
... some (hanging or self-standing) support from underneath:
Wow, I've read this thread multiple times, and have missed this post so many times. So simply, if you already had a cloud that, say was only hung from the sides - you could just slide a metal plate on top of it, throw some more insulation on top of it, and have an EPA? (Assuming the metal wouldn't be touching anything but the insulation above & below it)

This is really great news to some folk if so.
G. E.
Thread Starter
#79
28th March 2012
Old 28th March 2012
  #79
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Absorption Underneath the Listening Position

Quote:
Originally Posted by kasmira View Post
... So simply, if you already had a cloud that, say was only hung from the sides - you could just slide a metal plate on top of it, throw some more insulation on top of it, and have an EPA? ...
I would think so (the top layer touching the ceiling?!) but I haven't tried it yet. It's not the first thing I would do in a room because typically the height-mode is substantially higher than the deepest mode and therefor easier to tame.

If you think about the ceiling in some rooms it's worth to think about the floor as well. Rooms with a height of about twice the typically listening position (lets say 1,2m [~4']) usually have a better measured frequency response if you move the mic up for 10cm-30cm [~4"-1']. One would need a platform to sit on that could incorporate a lying EPA underneath.
#80
28th March 2012
Old 28th March 2012
  #80
Lives for gear
 
kasmira's Avatar
 

Quote:
Originally Posted by G. E. View Post
I would think so (the top layer touching the ceiling?!) but I haven't tried it yet.
Well, what a perfect thread for this!

Could this be tested in your room? I propose checking the difference between the sandwich leaning against the wall (not corner) vs the sandwich laying on top of your cloud-box-thing.

I understand that it would mostly dampen the height mode, but considering how substantial clouds already are in a room, it may just work beautifully. Plus, there are so many studios that already have clouds (and some very large too) installed and a lot of people don't have room to put anything on the floor (or wall space may already be taken up from existing treatment), so this could be a simple addition to just beat down some modal ringing.
G. E.
Thread Starter
#81
28th March 2012
Old 28th March 2012
  #81
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Ceiling vs. Floor Measuremtn

Quote:
Originally Posted by kasmira View Post
... I propose checking the difference between the sandwich leaning against the wall (not corner) vs the sandwich laying on top of your cloud-box-thing. ...
I think results from floor testing would translate very well to the ceiling position.
#82
29th March 2012
Old 29th March 2012
  #82
Lives for gear
 
kasmira's Avatar
 

Quote:
Originally Posted by G. E. View Post
I think results from floor testing would translate very well to the ceiling position.
Good point. How far down does your cloud hanger sit from the ceiling? It could be nice to see the difference in effectiveness with an airgap vs filling the entire back with absorbent on something like this (be it on the wall or hanging)

I would assume airgaps with your EPA are not going to be similar to airgap on your typical bass trap, since you need the material to dampen the plate, correct? And air would not provide significant amounts of dampening..
G. E.
Thread Starter
#83
30th March 2012
Old 30th March 2012
  #83
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Distant Ceiling Mounting

Quote:
Originally Posted by kasmira View Post
... How far down does your cloud hanger sit from the ceiling? It could be nice to see the difference in effectiveness with an airgap vs filling the entire back with absorbent on something like this (be it on the wall or hanging) ...
The cloud height is variable.

Quote:
Originally Posted by kasmira View Post
... I would assume airgaps with your EPA are not going to be similar to airgap on your typical bass trap, since you need the material to dampen the plate, correct? And air would not provide significant amounts of dampening.
Yes, it's different from a standard porous absorber. Nevertheless the absorption (energy dissipation) comes from the porous absorber and it still needs (relative) velocity between air and absorber.

Therefor I think from all the mounting options so far the distant ceiling mounting is the most unpredictable so testing makes sense.
Attached Thumbnails
Trapping Traps-tt0038_distant-ceiling-mounting.jpg  
#84
30th March 2012
Old 30th March 2012
  #84
Lives for gear
 
gullfo's Avatar
 

G. E.
Thread Starter
#85
30th March 2012
Old 30th March 2012
  #85
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
Free Boundary Condition

Quote:
Originally Posted by gullfo View Post
... calculators for various DOF for plates - mainly displacement but interesting...
eFunda: Classical Plate Equation
... helpful resource though the link does not cover the rectangular plate under free boundary condition (in a mechanical sense, as is the case here).
#86
20th May 2012
Old 20th May 2012
  #86
Lives for gear
 
kasmira's Avatar
 

Quote:
Originally Posted by G. E. View Post
I'm giving this thread a restart: feel free to make your suggestion till April, 30th 2012.
Any updates / testing done, good sir?
#87
20th May 2012
Old 20th May 2012
  #87
Lives for gear
 
Mctwins's Avatar
 

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.

Setup included an almost square control room stuffed with a 32-channel console, some outboard, B&W 801 speakers, and minimal exisiting acoustic treatment with small porous absorbers.

Measured at the "client position" sofa 45cm [~1'6"] in front of the back wall window with both speakers driven, Red ... before (without EPAs), Blue ... after (with EPAs).

T60 for the lowest mode at 38Hz dropped from ~1400ms to ~600ms.
The yellow line from 20-50Hz schoulden't be there, if you have this and according to ARTA "denotes frequency region where the time-bandwith requirement is not fulfilled", read "System Analysis from Impulse Response"

and

The burst decay graph, is it mesured in sweep, sequence lenght 256 or what?
Can you show? Burstdecay, Mode Waterfall_F

Nevertheless, there is a huge suckout and there is no changes before and after. Just saying.
G. E.
Thread Starter
#88
21st May 2012
Old 21st May 2012
  #88
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
42Hz Gone

Quote:
Originally Posted by kasmira View Post
Any updates / testing done, good sir?
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.
Attached Thumbnails
Trapping Traps-20120518-sv-m32-s.jpg   Trapping Traps-20120518-sv-m32-s-2fr.jpg  
G. E.
Thread Starter
#89
22nd May 2012
Old 22nd May 2012
  #89
Lives for gear
 
G. E.'s Avatar
 

Thread Starter
PIRs

Quote:
Originally Posted by Mctwins View Post
The yellow line from 20-50Hz schoulden't be there, if you have this and according to ARTA "denotes frequency region where the time-bandwith requirement is not fulfilled", read "System Analysis from Impulse Response"

and

The burst decay graph, is it mesured in sweep, sequence lenght 256 or what?
Can you show? Burstdecay, Mode Waterfall_F

Nevertheless, there is a huge suckout and there is no changes before and after. Just saying.
Thanks for pointing me to the yellow line, I've never noticed that before.

I can't remember if the measurement was made with ARTA's sweep or periodic noise but I'm quite sure that I've used maximum (256k) sequence length.

Feel free to make your own conclusions with the attached PIR-files (before/after).

The measurement was made to show the reduced decay time of the lowest mode. I agree with you that the FR at this position has major flaws.
Attached Files
File Type: zip 20120327_ARTA-PIRs.zip (1.85 MB, 31 views)
#90
22nd May 2012
Old 22nd May 2012
  #90
Lives for gear
 
Mctwins's Avatar
 

Quote:
Originally Posted by G. E. View Post
Thanks for pointing me to the yellow line, I've never noticed that before.

I can't remember if the measurement was made with ARTA's sweep or periodic noise but I'm quite sure that I've used maximum (256k) sequence length.

Feel free to make your own conclusions with the attached PIR-files (before/after).

The measurement was made to show the reduced decay time of the lowest mode. I agree with you that the FR at this position has major flaws.
Hi
Thanks for the file...

About the yellow line, it depends if you push the button Smoothed FR or Dual-gate Smoothed FR. In Dual-gate Smoothed FR the yellow line comes up but not in Smoothed FR if you have the Gate1 and Gate2 set in the default value (20ms and 200ms). The Y line can accure in Smoothed FR if you set the yellow curser line and red marker line in the Impulse Response Envelope.

Via Setup and Analysis parameters one can set a fix value or default value for the Y-line only for Dual-gate Smoothed FR but if you use yellow curser line and red marker line in the Impulse Response Envelope you are changing both Smoothed FR and in Dual-gate Smoothed FR despite the fixed or the default value.

I am always lokking at Smoothed FR or Unsmoothed FR(DFT)

The only thing I can see from your before and after measurements in ARTA's Burst decay is a slight differense in the resonance but it is not as effective as it schould be, maybe you need alot of your basstrapps to be effective. There schould also be a pressure change in that region as well. According to Smoothed FR there is no changes before and after.

Could you tell me where your mic was when these measurements was done. It is also important that the mic is not moved from it's position when doing before and after measurements, but I think you know this.

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.
New Reply Submit Thread to Facebook Facebook  Submit Thread to Twitter Twitter  Submit Thread to LinkedIn LinkedIn  Submit Thread to Google+ Google+ 
 
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
Cojo / Bass traps, acoustic panels, foam etc
1268
Red Mastering / Bass traps, acoustic panels, foam etc
15
Ydope / Low End Theory
34
JohnPaulJones / So much gear, so little time!
16
fatgaz / Low End Theory
64

Forum Jump
 
Register FAQ Search Today's Posts Mark Forums Read

SEO by vBSEO ©2011, Crawlability, Inc.