C
Caiwyn
New member
Can someone explain to me what makes a membrane absorber better or worse than a 4" slab of OC 705-FRK? Assume that both are straddled across a corner. What difference should I expect?
B
bpape
Acoustic Designer - GIK
Well, you normally don't mount membranes across a corner - the Real Traps are an exception.
Wood membrane absorbers all you to tune into a narrower range to deal with specific issues. They also allow you to tune down pretty deep while maintaining relatively thin profiles (for a bass absorber). For instance, with a sealed wood membrane absorber you can center it down in the 50's pretty easily and stay < 6" thick.
Bryan
Wood membrane absorbers all you to tune into a narrower range to deal with specific issues. They also allow you to tune down pretty deep while maintaining relatively thin profiles (for a bass absorber). For instance, with a sealed wood membrane absorber you can center it down in the 50's pretty easily and stay < 6" thick.
Bryan
apl
Stand Up Comity
The membrane absorber can absorb more low frequency energy.
C
Caiwyn
New member
bpape said:
That doesn't make sense... if the point of a membrane absorber is to target bass frequencies, isn't the corner the optimal place to mount them? Why would you put it anywhere else?
RICK FITZPATRICK
New member
From what I understand, membrane absorbers re-introduce frequencies back into the room, due to resonances within the absorber. I'm certainly no expert though. Maybe Ethan can explain this phenomena. I read it a long time ago.
Actually, I was thinking of useing a very large(8'x8'x3' deep) membrane absorber on my back wall, as opposed to a very deep resistance absorber(703 or rockwool) because of the cost involved. Damn that shit is expensive. I was just quoted a price of a whopping $2.40 a square foot for Certainteed 4" thick rigid fiberglass. Crap, thats a whopping $800 just for a rear absorber!!! No fucking way. But I'm not mathamatically inclined enough to figure out the panel thickness, vs depth for what a membrane absorber that size will do? Anyone care to give it a shot?
I thought I might use this in conjunction with other devices or maybe a layer of 4" 703 in front of it. See my REAR WALL OPTIONS thread later today. I'll finish posting the drawings after my host server is reconfigered today.
Actually, I was thinking of useing a very large(8'x8'x3' deep) membrane absorber on my back wall, as opposed to a very deep resistance absorber(703 or rockwool) because of the cost involved. Damn that shit is expensive. I was just quoted a price of a whopping $2.40 a square foot for Certainteed 4" thick rigid fiberglass. Crap, thats a whopping $800 just for a rear absorber!!! No fucking way. But I'm not mathamatically inclined enough to figure out the panel thickness, vs depth for what a membrane absorber that size will do? Anyone care to give it a shot?
I thought I might use this in conjunction with other devices or maybe a layer of 4" 703 in front of it. See my REAR WALL OPTIONS thread later today. I'll finish posting the drawings after my host server is reconfigered today.
apl
Stand Up Comity
RICK FITZPATRICK said:From what I understand, membrane absorbers re-introduce frequencies back into the room, due to resonances within the absorber. I'm certainly no expert though. Maybe Ethan can explain this phenomena. I read it a long time ago.
Actually, I was thinking of useing a very large(8'x8'x3' deep) membrane absorber on my back wall, as opposed to a very deep resistance absorber(703 or rockwool) because of the cost involved. Damn that shit is expensive. I was just quoted a price of a whopping $2.40 a square foot for Certainteed 4" thick rigid fiberglass. Crap, thats a whopping $800 just for a rear absorber!!! No fucking way. But I'm not mathamatically inclined enough to figure out the panel thickness, vs depth for what a membrane absorber that size will do? Anyone care to give it a shot?
http://www.ethanwiner.com/basstrap.html
c7sus
Disenfranchised Member
When you say "membrane absorber" are you referring to wrapping 703 in painters' plastic or similar????
From what I understand the idea is to reflect a bit of high frequency energy.
Also, I wouldn't count slot resonators as membrane absorbers. Although you could combine the ideas.
From what I understand the idea is to reflect a bit of high frequency energy.
Also, I wouldn't count slot resonators as membrane absorbers. Although you could combine the ideas.
C
Caiwyn
New member
c7sus said:
I'm specifically referring to something like the RealTraps or GIK acoustic panels, where there is a limp mass membrane made of plastic or somesuch in front of rigid fiberglass or mineral wool, possibly with an air gap between.
c7sus said:
Doesn't the foil on the OC 705-FRK do this? I've heard this is the case but I've never seen any data backing it up.
eraos
Local Spiderman
RICK FITZPATRICK said:
I was under the impression that a membrane absorber was diaphragmatic absorber, which vibrates sympathetically.
From the Master Handbook of Acoustics
.
Doesn't the fiberglass serve to increase the effective bandwidth of absorption?
apl
Stand Up Comity
eraos said:
Yep, that's what they do.
eraos
Local Spiderman
RICK FITZPATRICK said:
Another thing I just caught... which I think is more along the lines of what you're thinking here. The diaphragm pushes air into the cavity due to the vibrations. The fiberglass then will dampen that air flow (the frequency).
http://www.rpginc.com/products/modexcorner/index.htm
RICK FITZPATRICK
New member
Ok, this thread got me all interested in membrane absorbers again. So I did a search over at John Sayers Acoustics forum on membrane absorberw, and I'll do one over at Studiotits as well as Ethans site. Damn, gotta clean the snakeoil outa the acoustics medicine cabinet once and for all. 
Think I'll play around with the formula shit too. 
http://www.johnlsayers.com/phpBB2/search.php?mode=results
Even after reading the first few replys in the list, it became apparent to me that theremay be some contradictory replys. You know the net....NET FACT can really fuck with people. Thats why I wish the CEO of this BBS would allow some
GODDAMNED STICKIES!!!
Its threads like this that make you realize...there is NO ONE PLACE, that you can COUNT ON THE TRUTH. What we need here is a MEMBRANE ABSORBER...FACT vs FICTION sticky, with some actual ETF tests in a typical HR studio/control room, WITH AND WITHOUT various incarnations of membrane absorbers...and hey, HOW BOUT a RESISTANCE ABSORBER sticky too!!~ ....HEY! DAMN!...Thats it. I have an idea.....DAMN...ok guys. Thats it. My control room is gonna become a Guinea Pig!! Ha! Lets see, now to figure out some things....well, looks like I gotta start researching...hmmmmm, where did I file that info on Calibrated mics, oh, and ETF....damn, now I GOTTA finish the rear wall thread. It has all the different shit I've read about for years. Hmmmmm, maybe we can filter some of the hogwash outa this stuff, eh? 
Sheeeeesh, as if I don't have enough to do already...sigh 
Think I'll play around with the formula shit too. http://www.johnlsayers.com/phpBB2/search.php?mode=results
Even after reading the first few replys in the list, it became apparent to me that theremay be some contradictory replys. You know the net....NET FACT can really fuck with people. Thats why I wish the CEO of this BBS would allow some
GODDAMNED STICKIES!!!
Its threads like this that make you realize...there is NO ONE PLACE, that you can COUNT ON THE TRUTH. What we need here is a MEMBRANE ABSORBER...FACT vs FICTION sticky, with some actual ETF tests in a typical HR studio/control room, WITH AND WITHOUT various incarnations of membrane absorbers...and hey, HOW BOUT a RESISTANCE ABSORBER sticky too!!~ ....HEY! DAMN!...Thats it. I have an idea.....DAMN...ok guys. Thats it. My control room is gonna become a Guinea Pig!!
Ha! Lets see, now to figure out some things....well, looks like I gotta start researching...hmmmmm, where did I file that info on Calibrated mics, oh, and ETF....damn, now I GOTTA finish the rear wall thread. It has all the different shit I've read about for years. Hmmmmm, maybe we can filter some of the hogwash outa this stuff, eh? Sheeeeesh, as if I don't have enough to do already...sigh 
daav
Flailing up a storm.
Agreed!RICK FITZPATRICK said:Ok, this thread got me all interested in membrane absorbers again. So I did a search over at John Sayers Acoustics forum on membrane absorberw, and I'll do one over at Studiotits as well as Ethans site. Damn, gotta clean the snakeoil outa the acoustics medicine cabinet once and for all.
http://www.johnlsayers.com/phpBB2/search.php?mode=results
Even after reading the first few replys in the list, it became apparent to me that theremay be some contradictory replys. You know the net....NET FACT can really fuck with people. Thats why I wish the CEO of this BBS would allow some
GODDAMNED STICKIES!!!
Its threads like this that make you realize...there is NO ONE PLACE, that you can COUNT ON THE TRUTH. What we need here is a MEMBRANE ABSORBER...FACT vs FICTION sticky, with some actual ETF tests in a typical HR studio/control room, WITH AND WITHOUT various incarnations of membrane absorbers...and hey, HOW BOUT a RESISTANCE ABSORBER sticky too!!~ ....HEY! DAMN!...Thats it. I have an idea.....DAMN...ok guys. Thats it. My control room is gonna become a Guinea Pig!!
10 chars!
Daav
TexRoadkill
Audio Bum
I believe the bottom line is that membrane absorbers are more effective over a narrower frequency band. Plain fiberglass absorbers are less effective but absorb over a wider frequency band.
One of the main treatment challenges is that most rooms have too much energy in the low mids and as soon as you absorb any highs without equal low mid absorption you make this difference worse. The ultimate goal is to have a balanced or flat response and if you absorb the low mids without affecting the highs, by use of a thin membrane, you will get closer to flat cheaper and faster.
The use of very thin wood or plastic would reflect a broader range of higher frequencies then the foil alone.
One of the main treatment challenges is that most rooms have too much energy in the low mids and as soon as you absorb any highs without equal low mid absorption you make this difference worse. The ultimate goal is to have a balanced or flat response and if you absorb the low mids without affecting the highs, by use of a thin membrane, you will get closer to flat cheaper and faster.
The use of very thin wood or plastic would reflect a broader range of higher frequencies then the foil alone.
apl
Stand Up Comity
TexRoadkill said:
Diaphragms require way, way less thickness to get to a given low frequency.
c7sus
Disenfranchised Member
RPG® solved this problem by optimizing the absorption efficiency using a unique internally damped membrane absorber that provides ideal absorption in the modal frequency range.
How do they know the modal frequency needed for MY room???
It's only tuned by the volume of the cabinet.
In order to dial in a specific band you need more than those guys are giving you.
http://www.rpginc.com/products/modexcorner/modexcorner.pdf
This is great if your problem is at 500-625Hz. But if your problem is below 500Hz you're not getting all the absorbtion you could be getting with a tuned trap.
I did mine to center at 250Hz and extend an octave each way.
How do they know the modal frequency needed for MY room???
It's only tuned by the volume of the cabinet.
In order to dial in a specific band you need more than those guys are giving you.
http://www.rpginc.com/products/modexcorner/modexcorner.pdf
This is great if your problem is at 500-625Hz. But if your problem is below 500Hz you're not getting all the absorbtion you could be getting with a tuned trap.
I did mine to center at 250Hz and extend an octave each way.
RICK FITZPATRICK
New member
Hey Daav
I like it.
knightfly
GrouchyOldFartOnBatteries
One example of panel traps solving specific problems -
http://www.johnlsayers.com/phpBB2/viewtopic.php?p=6720
And note the comment about Dolby Certification in this thread on Wed Mar 22, 2006 -
http://www.johnlsayers.com/phpBB2/viewtopic.php?p=41118
However, if your room doesn't HAVE specific frequency problems (unlikely, but possible) then broadband trapping may be all you need - be advised, also, that you can't just put a panel trap ANYWHERE in the room and expect it to work - it needs to be at a high PRESSURE point for its particular frequency, not necessarily in a corner. Also, in some cases they will only work well on one SPECIFIC wall, depending on your room dimensions and modal energy.
IF you read through the entire text of the first link, it should help explain a few things about panel traps... Steve
http://www.johnlsayers.com/phpBB2/viewtopic.php?p=6720
And note the comment about Dolby Certification in this thread on Wed Mar 22, 2006 -
http://www.johnlsayers.com/phpBB2/viewtopic.php?p=41118
However, if your room doesn't HAVE specific frequency problems (unlikely, but possible) then broadband trapping may be all you need - be advised, also, that you can't just put a panel trap ANYWHERE in the room and expect it to work - it needs to be at a high PRESSURE point for its particular frequency, not necessarily in a corner. Also, in some cases they will only work well on one SPECIFIC wall, depending on your room dimensions and modal energy.
IF you read through the entire text of the first link, it should help explain a few things about panel traps... Steve
apl
Stand Up Comity
c7sus said:RPG® solved this problem by optimizing the absorption efficiency using a unique internally damped membrane absorber that provides ideal absorption in the modal frequency range.
How do they know the modal frequency needed for MY room???
It's only tuned by the volume of the cabinet.
In order to dial in a specific band you need more than those guys are giving you.
http://www.rpginc.com/products/modexcorner/modexcorner.pdf
This is great if your problem is at 500-625Hz. But if your problem is below 500Hz you're not getting all the absorbtion you could be getting with a tuned trap.
I did mine to center at 250Hz and extend an octave each way.
Theirs works well from 200 Hz on down, which is very difficult to do with resistive absorbers. Frequencies above that can be easily handled with 703 or foam.
RICK FITZPATRICK
New member
HOLY MOLY Steve! I was beginning to believe one of them thar gators got ya. Where ya been? Been meaning to email you but I guess I've been where you've been....overworked, overhoneydo'ed and overgatored I'll email ya today. Got news.