Trapping Traps
Old 29th May 2012
  #121
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Quote:
Originally Posted by DanDan View Post
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
If GE is not complaining about my posts then I don't understand why you are so upset and lost.
Old 29th May 2012
  #122
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Quote:
Originally Posted by Mctwins View Post
If GE is not complaining about my posts then I don't understand why you are so upset and lost.
Because this thread is not your private communication with G. E., but thread on the public forum, where we have many other people which will like to read what G. E. want to tell, including me.
Old 29th May 2012
  #123
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He is being extremely patient and polite.
Old 29th May 2012
  #124
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Quote:
Originally Posted by Mctwins View Post
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.
Thanks McTwins, I believe people should relax and understand if someone was not showing REW results the way we would view them, we would ask them to change the view (as you did) - I feel that is understandable.

Also, I do see quite a difference - it is pretty obvious to see in the Burst Decay (Not so much in the CSD) - and it is quite an extraordinary difference when its as simple as throwing a 'piece of metal with insulation glued' up (more or less)

There is obviously a very good product here, and this thread is for G.E. to compare different results of different mountings, sizes...other changing variables as G.E. sees. No problem to question his tests, but a PM might be more inviting than clogging up a page full of responses.
Old 30th May 2012
  #125
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Quote:
Originally Posted by Mctwins View Post
of course you don't have 42Hz mode, your response rolls of from -10dB from 60Hz.
This seems to be the origin of the misunderstanding/miscommunication. As others have pointed out, a 10 dB roll-off from 60 Hz still allows plenty of energy to excite a 42 Hz room-mode.

The other misunderstanding/miscommunication is about pressure. From my very basic understanding of acoustics, room-modes have areas of high-pressure/low-velocity and low-pressure/high-velocity but the decay is uniform. If you measure a 20 dB reduction in SPL from Y dB in X time it is the same as measuring that same SPL reduction from any other value of Y over the same amount of time X. I believe that is what G.E. was referring to while you were referring to zero pressure from the speakers to excite the mode in the first place (which has been addressed and isn't correct).

Now back to trapping traps...

Alistair
Old 30th May 2012
  #126
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Thread Starter
Driving modes

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. 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?
The decay time of a mode is a feature of the room and not of the speaker, not of the microphone, not of the (right) place, etc.. For example I can drive the 42Hz mode of my room with an Auratone successfully (quite a "high-pass" technically) and get results similar to those driven with a 15" subwoofer.
Old 30th May 2012
  #127
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Quote:
Originally Posted by G. E. View Post
The decay time of a mode is a feature of the room and not of the speaker, not of the microphone, not of the (right) place, etc.. For example I can drive the 42Hz mode of my room with an Auratone successfully (quite a "high-pass" technically) and get results similar to those driven with a 15" subwoofer.
Of course the decay time of a mode is a feature of the room. But you are wrong about the right place. You can have the mic at a suckout when you measure and it will give a wrong presentation of the decay time. The mic has to be moved around when measuring to see if the decay time is stable in the measurement and all over the room. In the measurments in post 103(yours) is, as I said, no pressure deviation and no improvment in the decay of CSD. Thats why I don't believe that your trap is working.

The other negative effect is that you are totally suckin out the energy in the room. To have a T30 from 150-8000 Hz at 0,1 s is for me a totally overdamped room, no place for music.

What I meant is that if you don't have the Auratone or 15" sub in the room and measure without these, could you show me how you can read the decay time in that measurement?

There has to be a difference from very low or close to 0 dB or 100 dB of SPL when measure.

That's all.........
Old 30th May 2012
  #128
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DanDan's Avatar
Ignorance

Quote:
You can have the mic at a suckout when you measure and it will give a wrong presentation of the decay time. The mic has to be moved around when measuring to see if the decay time is stable in the measurement and all over the room.
The mic is not moved in A/B Before/After tests.
But if a mic or speaker were place in a modal null, it would still show a CHANGE in decay before and after absorption at that frequency was introduced.
This is pretty fundamental basic stuff I am referring to.
DD
Old 30th May 2012
  #129
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Thread Starter
Details

Quote:
Originally Posted by Mctwins View Post
... In the measurments in post 103(yours) is, as I said, no pressure deviation and no improvment in the decay of CSD. Thats why I don't believe that your trap is working. ...
Its hard to see the obvious in the CSD -- thats the reason I prefer not to use the CSD.

Quote:
Originally Posted by Mctwins View Post
... The other negative effect is that you are totally suckin out the energy in the room. To have a T30 from 150-8000 Hz at 0,1 s is for me a totally overdamped room, no place for music. ...
This is a thread about bass traps so I searched for efficient ones. I agree with you that these traps suck out a lot of energy (I didn't care about mids & highs, you can easily control it with reflectors in front of the bass traps). Music in a room with T60<400ms down to 40Hz is hard to achieve but sounds very good to me.

Quote:
Originally Posted by Mctwins View Post
... There has to be a difference from very low or close to 0 dB or 100 dB of SPL when measure. ...
I never talked about 0dB. The main difference is the noise floor that may come in the way at very low sound pressure and might flaw the measurement. Apart from that the decay doesn't care about the dBs ...
Old 30th May 2012
  #130
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DanDan's Avatar
Noise

I seem to remember hearing that the Waterfall CSD in ARTA is not well done.
I presume ARTA can Export IR's as WAV?
Perhaps you would consider in future posting Zipped WAV IR's so that those of us on REW or FuzzMeasure and others, can view in our own familiar ways.
Again, warm thanks for your hard work and sharing.

Best, DD
Old 30th May 2012
  #131
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Thread Starter
Impulse Response

Quote:
Originally Posted by G. E. View Post
Please, go ahead: ARTA's PIR-File is attached. ...
Attached is ARTA's exported impulse response.
Attached Files
File Type: zip 20120518_sv_m32_S_IR.zip (136.1 KB, 28 views)
Old 30th May 2012
  #132
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Thread Starter
Impulse Response of an Empty Room

Quote:
Originally Posted by G. E. View Post
... 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. ...
Attached is ARTA's impulse response.
Attached Files
File Type: zip 20120326_sv_m01_IR.zip (303.3 KB, 36 views)
Old 30th May 2012
  #133
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Thread Starter
Real World Impulse Responses

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.
Attached are ARTA's impulse responses.

EDIT: The filenames are wrong in the ZIP-file below ("before" and "after" are swapped unintentionally)! In the meantime I've posted the correctly renamed files.
Attached Files
File Type: zip 20120327_IRs.zip (602.7 KB, 31 views)
Old 30th May 2012
  #134
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Thanks for those files G.E.

I will be popping them in REW later today when I get home and scope them out!
Old 30th May 2012
  #135
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DanDan's Avatar
Reversed

Gernot, are those WAVs reversed, i.e. Before is After?

DD
Old 30th May 2012
  #136
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Quote:
Originally Posted by DanDan View Post
Gernot, are those WAVs reversed, i.e. Before is After?
I was wondering that too: Before looks better.
Old 31st May 2012
  #137
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Thread Starter
Correction

Quote:
Originally Posted by DanDan View Post
Gernot, are those WAVs reversed, i.e. Before is After? ...
Yes, they are wrong in the original post and I'm sorry about that.

Attached are the correctly named files. Thanks for catching this.
Attached Files
File Type: zip 20120327_IRs_CORRECTED.zip (602.7 KB, 52 views)
Old 18th June 2012
  #138
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Quote:
Originally Posted by Tikka Masala View Post
From the thread DIY Diffusors to the Max on 26th Feb 2009

Hi G.E.

I'm upgrading the acoustic of my studio since a few months now (making bass-traps, polycylindrical diffusers, and frames for Auralex foams in a modular way)

I was linked to this thread at the begining of my project and i've decided to move to a rubber membrane for my bass-traps instead of ply-wood.

The design of mines seems to be similar to yours:
-30 cm depth
-frame made of 18 mm pine wood
-back made of 12 mm MDF (quite rigid, according to me)
-membrane made of 4 mm Rubber (SBR, density of 1.55, Shore A about 60/70)
-membrane dimension 60 cm*120 cm

I've made 2 of this type (should resonate at 44Hz without damping, 37Hz with damping)
I've also made 4 with 20 cm depth and 3 mm rubber membrane (should resonate at 62Hz without damping, 52Hz with damping)

According to the dimensions of my room, I've got modes at 42.5Hz, 48Hz and 64Hz. When I designed the bass Traps, I only had the formula without damping so they might be tuned 1.2* to low but according to your experience, they should work pretty well if they where designed like yours !

But they don't ! No need of ARTA to tell you that I still have a 120 dB null (at least, no kidding ) at 64Hz at listening position ! (quite the same at others modes)

What's wrong with mines ?
-Are your membranes made of 4mm rubber (or 6mm) ?
-Did you joint and sealed everything (mines are not, but yet fermly and precisely fixed)
-What did you use for damping (I've used Auralex foam, thinking it was Hi-Density Foam, but I've found that you can buy 3 to 4 times more dense foam, since Auralex is about 20 Kg per cubic meter)

Please, let me know about that precisely tweeked after long long research and all the controverse about velocity/pressure, Hi-density or not, rigidity or not, big or little air flow resistivity performance of porous absorbers, and especially when used in bass-traps !!!
Here is the question that I've posted in the "DIY Diffusors to the Max" thread.
I've posted it there because you're talking about membrane absorbers that you've built on page 12: DIY Diffusors to the Max

You've already reply to me that you've never built a rubber membrane absorber.
In fact, that's the question: can you tell me more about those membrane absorbers wich seems to be efficient over 2 octaves above theirs resonance frequency and despite the fact that they're tuned 1 octave lower than they were expected to be !
Old 18th June 2012
  #139
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Thread Starter
Closed Tuned Absorber

Quote:
Originally Posted by Tikka Masala View Post
Here is the question that I've posted in the "DIY Diffusors to the Max" thread.
I've posted it there because you're talking about membrane absorbers that you've built on page 12: DIY Diffusors to the Max

You've already reply to me that you've never built a rubber membrane absorber.
In fact, that's the question: can you tell me more about those membrane absorbers wich seems to be efficient over 2 octaves above theirs resonance frequency and despite the fact that they're tuned 1 octave lower than they were expected to be !
I see that you are really interested but I don't build these closed tuned membrane absorbers anymore, they work narrowband and they are hard to predict.
Old 11th July 2012
  #140
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Hello again G.E.
I had read the thread again as I'm quite interested in it: I have a quite similar room (square, 4x4m) and some similar problems so I think the EPA would help.
I'd like to know if you managed to test it on the floor (and how it worked) as I have plenty space for them on the ceiling (what a logic! ). Also curious about the possibility to use them as doors.
regards
G
Old 12th July 2012
  #141
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Mounting

Quote:
Originally Posted by gpiccolini View Post
... I'd like to know if you managed to test it on the floor (and how it worked) as I have plenty space for them on the ceiling (what a logic! ). Also curious about the possibility to use them as doors.
regards ...
I've tested various VPRs on the floor and the results showed less efficiency than what I call an EPA. I'd be interesting to see how it works on the ceiling. To use a VPR as a door has never come to my mind, probably because of the mounting, how would you do that?
Old 12th July 2012
  #142
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thanks for the reply.
I have an acoustic door that needs to be rebuilt. It's located in a corner (well... a slated wall if that's the correct word in english). My plan is to copy your EPA and put a hard back and a frame around it to hold the steel in place leaving it as free as possible. Maybe somme rubber at the bottom. Solid enough to keep acting as a door.

Regarding the ceiling: I have all my ceiling built as a big cloud, so it seems pretty easy to sandwich some steel plates between the Rockwool (60kg/m3). I'm interested to know if the ┬Ěless efficiency" when compared floor vs corner is extreme or it can be overcome by using more EPAs. I never saw a waterfall from a VPR on the floor vs corner.
Old 12th July 2012
  #143
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DOH

I am a bit lost. What is the difference between a VPR and an EPA?

DD
Old 12th July 2012
  #144
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Enhanced Porous Absorber.

I believe it's as simple as the absorbent being on both sides
Old 12th July 2012
  #145
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Quote:
Originally Posted by johndykstra View Post
Enhanced Porous Absorber.
...
Yup, it's Gernot invention (Patent pending...)
Old 19th July 2012
  #146
Gear interested
 

I found a product in the US called PolyMax. It seems to be a dense polyester fiber batt material. Listed as 7.5 pcf density. I want to DIY some VPR/Enhanced porous absorbers, but iso-bond is hard to source in the US. Does anybody think this might be an alternative to iso-bond?

http://www.acousticalsurfaces.com/ac...ll-panels.html
Old 20th July 2012
  #147
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Quote:
Originally Posted by visa.the.dog View Post
I found a product in the US called PolyMax. It seems to be a dense polyester fiber batt material. Listed as 7.5 pcf density. I want to DIY some VPR/Enhanced porous absorbers, but iso-bond is hard to source in the US. Does anybody think this might be an alternative to iso-bond?

Sound Control Wall Panels
The product in the page you linked to appears to only come in a 1" thickness. You need 4" to build a VPR. The mechanics of stacking and bonding the fibrous panels to achieve the required thickness makes this product a poor choice before any other questions about it's suitability are asked.

Happy Trails!
MTB Vince
Old 20th July 2012
  #148
Gear interested
 

Vince, thanks for the reply. What are you DIY people in the US using for an absorbent material? That stuff is hard to find!
Old 20th July 2012
  #149
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Quote:
Originally Posted by visa.the.dog View Post
Vince, thanks for the reply. What are you DIY people in the US using for an absorbent material? That stuff is hard to find!
Contact a local insulation supplier and tell them what you need. They should.be able to find it. In talking with a sales rep for EnGuard (polyester insulation in the US) I discovered they have their products at multiple (but not all) IDI Distributors locations. IDI is in a lot of States so look em up and see if there's one near you. There is also another national chain that sells insulation though I don't remember their name - you can find it on John Sayers forum.

If you do contact IDI they may be able to special order EnGuard, I'd look into it.

Sent from my ADR6425LVW using Gearslutz App
Old 20th July 2012
  #150
Gear interested
 

Kasmira I was interested to hear any results you had with the EnGuard. You mentioned earlier that the company was sending you some. Have you checked it out yet?
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