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OC 703 FRK... to foil or not to foil????
Old 31st October 2011
  #91
Gear Maniac
 

Dan - can you interpret?

Quote:
Originally Posted by DanDan View Post
Dan -- In posts referring to your waterfall test of FRK vs. no FRK, I believe you have indicated that the preferred FRK test result was first. (i.e. the top picture). Can you confirm if that's the case?

If so, I'm wondering if you can interpret your waterfall data for me (and perhaps others) who are new to interpreting the data. I would have chosen the 2nd (bottom) graphic as preferable.
I am noting more consistency on the 2nd graph in the following areas: 50-70Hz, 150-300 Hz -- I am referencing the "height", i.e. the frequency peaks. Also, from a depth standpoint, you've got a big gap between 40-50 Hz.

Presuming you are favoring the first graph -- can you explain WHY and WHERE it is preferable?

Thanks so much!

Craig (I'm brand new to REW this week)
Old 31st October 2011
  #92
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Quote:
Originally Posted by Craigster View Post
I'm wondering if you can interpret your waterfall data for me (and perhaps others) who are new to interpreting the data.
The idea behind waterfall graphs is to show frequency response over time, so you can see how much reverberation is happening at different frequencies. So the topmost lines are basically the dry response of the system (before resonances build and reflections start reaching the mic), and then the cascading lines (fading to cooler colors in this case) are after the source is silenced, showing mostly reverberating sound. The first graph shows considerably less reverberation in the bass region.
Old 1st November 2011
  #93
Gear Maniac
 

Thanks Frasier!

So, narrower mountains and lower reverb numbers are preferable.
Even when frequency response may have increased variation. (?)

I wonder if this could account for the difference of interpretation between DanDan (who's testing data prefers FRK added - due to lower reverb in the low, low bass region) and Glenn (who's experiential hearing preferred FRK removed - perhaps due to a smoother frequency response).

I don't know that all the back and forth has considered this perspective.
Old 1st November 2011
  #94
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avare's Avatar
 

Quote:
Originally Posted by Craigster View Post
I wonder if this could account for the difference of interpretation between DanDan (who's testing data prefers FRK added - due to lower reverb in the low, low bass region) and Glenn (who's experiential hearing preferred FRK removed - perhaps due to a smoother frequency response).
FRK covered, or uncovered posroud absorbers are one part of the system of a room's acoustics. You can not judge one component by itself.

Andre
Old 2nd November 2011
  #95
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Quote:
Originally Posted by Craigster View Post
So, narrower mountains and lower reverb numbers are preferable.
Even when frequency response may have increased variation. (?)
Narrower "mountains" are not preferable--in this case you're trading a bit of midbass smoothness for a reduction in lower bass resonance and a more even reverberation response overall (how far forward the mountains come). The two graphs are also on a slightly different vertical scale, which may be exaggerating some of the differences.
Old 2nd November 2011
  #96
Gear Maniac
 

Sorry: "waterfalls", not "mountains".

Can someone point me to a primer on interpreting waterfall data?

Perhaps this is simply not intuitive to me. My prioritization would normally be to achieve a fairly balanced frequency range (i.e. a typical small boost around 100-125 Hz, a small decline to 1K, flat from 1K-8K, and then a gentle downward slope beyond that) for effective mixing and desirable listening.

It seems that the waterfall test is prioritizing reducing the reverb resonance time of lower frequencies -- even if at the expense of a smoother, more balanced frequency range.

If these are simply tradeoffs -- by what criteria is it determined when reduced low bass resonance trumps or when a smoother linear frequency range in the mid-bass trumps? How is "better" determined by the graphs?

Thanks!
Old 2nd November 2011
  #97
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Quote:
Originally Posted by Craigster View Post
My prioritization would normally be to achieve a fairly balanced frequency range. It seems that the waterfall test is prioritizing reducing the reverb resonance time of lower frequencies -- even if at the expense of a smoother, more balanced frequency range.
Waterfall graphs can be used for different things, but here we're using them to compare bass traps, whose function is to absorb bass energy to reduce reverberation in the bass range. So reverberation is what we're comparing here--we're not asking which system has a better frequency response, we're asking which one has less bass reverberation. Which one is better overall is a subjective matter, but it shows that foil facing the gap can improve low end absorption. Midbass could probably be smoothed (and overall absorption improved) by using thicker RFG, and perhaps varying the air gap. Frequency response in general can be manipulated with EQ, crossover, speakers, etc., but there's only one way to take care of resonance and reverberation--room treatment.
Old 3rd November 2011
  #98
Gear Maniac
 

Quote:
Originally Posted by Frasier View Post
Waterfall graphs can be used for different things, but here we're using them to compare bass traps, whose function is to absorb bass energy to reduce reverberation in the bass range. So reverberation is what we're comparing here
Thanks Frasier. That's really helpful!

Usually the range for this purpose is about 30Hz-300Hz?

RFG?
Old 4th November 2011
  #99
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Quote:
Originally Posted by Craigster View Post
Usually the range for this purpose is about 30Hz-300Hz?

RFG?
Yes, bass occupies approximately those frequencies, sometimes extending to 20Hz as in these graphs. RFG = rigid fiberglass, the usual material of choice for sound absorption.
Old 20th March 2012
  #100
Gear Guru
Honest

I had some lingering doubts about my 'conclusion' preference.
The difference between the Waterfalls is small enough, and debatable.
So out of curiousity I took a look at a few other graphic views of the same data. Then thought I may as well share them.
RED is with FRK
OC 703 FRK... to foil or not to foil????-frk.jpg
OC 703 FRK... to foil or not to foil????-no-frk.jpg
OC 703 FRK... to foil or not to foil????-fretc.jpg

A little surprising IMHO.
DD
Old 14th February 2013
  #101
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hi everyone,

I know this frk subject has been beat up to death but i have a slightly different question. I know and understand the effects of having frk on bass traps in the corners but is it ok to have bass traps with frk on the back wall?

specifically in my current room i have a mixture of real traps and gik traps (mini traps, 244 and tri traps and 1 monster bass trap)...and the corners are covered. i've got a dip around 4k- 8k that is significant so i'd like to brighten up the room a bit. all of the frequencies below that are fairly even. would me swapping out a few panels on the back wall with 703 frk help with this or am i going in the wrong direction and should start thinking diffusion?

thanks,

ej
Old 14th February 2013
  #102
Gear Guru
Dip

I reckon you would be best served finding out what is really causing that dip.
Are you measuring with two speakers running?
I would be slow to have FRK facing me, even from behind. It has a plasticky ping to my ear. If you do want to try it back there, how about angling it send the bounce along a longer path and not directly at the back of your head.
DD
Old 14th February 2013
  #103
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yes i am measuring with 2 speakers...should i only use 1?

also in my room the backwall i very long so the frk panels wont be directly behind me per se.

i do know what you mean about the ping of frk though.

ej
Old 14th February 2013
  #104
Gear Guru
One

The HF from the two tweeters will cancel unless the distances from tweet to mic are very very precisely the same and the room is perfectly the same on each side.
https://www.gearslutz.com/board/4217370-post13.html
Testing with one speaker is the norm.

Since the back wall is a long way back why not try the FRK. Unless there are lot of panels you will probably not hear any difference. I kinda think that sheets of aluminium clad plastic have no place in a listening room, and I think I hear the ping when there are lots of such traps, but this could be all in my mind...

DD
Old 14th February 2013
  #105
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Quote:
Originally Posted by DanDan View Post
The HF from the two tweeters will cancel unless the distances from tweet to mic are very very precisely the same and the room is perfectly the same on each side.

DD
???
Old 14th February 2013
  #106
Gear Guru
Ignorant

I used the word cancel loosely of course. More pedantically I might say, partly cancel at particular frequencies, but I did provide link to a whole thread which I started on this particular topic. I can see no reason for confusion or multiple meaningless question marks.

DD
Old 14th February 2013
  #107
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Quote:
Originally Posted by DanDan View Post
I used the word cancel loosely of course.
it's confusing when you use such terms "loosely".

Quote:
Originally Posted by DanDan View Post
I can see no reason for confusion or multiple meaningless question marks.

DD
i wouldn't expect the person making the confusing statement to see a reason for confusion. you probably know what you mean, but your communication and choice of vocabulary do create confusion. we are not mind readers!

clear communication on complex topics is imperative!
Old 14th February 2013
  #108
Gear Guru
Orders

Hmmm, imperative, and an ex colony won't blend well local.....;-)
I wrote quickly and cancel is descriptive enough IMO. More importantly I provided a link to the substantial stuff.

DD
Old 15th April 2015
  #109
Here for the gear
 

Quote:
Originally Posted by DanDan View Post
Foil bonded to semi rigid insulation batts increases the LF absorption.
It is however, somewhat resonant, bare traps are more linear.
Foil facing the room definitely increase HF decay time.
Not necessarily a good thing in my opinion. I don't particularly like the ping of aluminium or plastic.
Foil on the back of traps, where there is an airgap, still has that enhanced but slightly resonant LF absorption boost. On clouds and RFZ panels it helps diminish peaks and nulls due to the height and width modes.
DD
I know I'm resurrecting a very old thread, but I'm about to install a drop ceiling in my home theater. I'm using CertainTeed Theater Black 5/8 as the room facing tile, and just orded several cases of 2" 703 FRK to install above the tiles.

The drop is 7", and is under an existing sheetrock ceiling which is itself installed on resilient channels 2x10 joists above which are filled with pink insulation.

So would it be best to face to foil away from the room (toward the ceiling, since there will be about 5" of air gap between the panel the the sheetrock, or lay the foil face downward on top of the Certainteed tiles, facing the room? Looking to maximize LF trapping. In some areas, such as the corners, I was going to layer two 2" panels to increase trapping.

Thanks
Old 16th April 2015
  #110
Gear Guru
 
Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by thrang View Post
So would it be best to face to foil away from the room (toward the ceiling
Probably, though it might not make much difference. If you're up for some extra work you could try both ways and measure the response and ringing. But I'll guess it won't matter much.

--Ethan

The Acoustic Treatment Experts
Old 16th April 2015
  #111
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Quote:
Originally Posted by Ethan Winer View Post
Probably, though it might not make much difference. If you're up for some extra work you could try both ways and measure the response and ringing. But I'll guess it won't matter much.

--Ethan

The Acoustic Treatment Experts
Thanks Ethan - in principal, it is worth doing this, correct, in terms of some LF trapping, especially if I load the corners with double layers...?
Old 16th April 2015
  #112
Gear Guru
 
Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by thrang View Post
Thanks Ethan - in principal, it is worth doing this, correct, in terms of some LF trapping, especially if I load the corners with double layers...?
Worth adding rigid fiberglass above the ceiling tiles? Yes, absolutely.

--Ethan
Old 16th April 2015
  #113
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Quote:
Originally Posted by Ethan Winer View Post
Quote:
Originally Posted by thrang View Post
Thanks Ethan - in principal, it is worth doing this, correct, in terms of some LF trapping, especially if I load the corners with double layers...?
Worth adding rigid fiberglass above the ceiling tiles? Yes, absolutely.

--Ethan
Thanks - might be worth facing foils down in the rear of the room presuming some hf gets through the 5/8 certain teed tile to add some liveliness in the rear soundstage. Also am trying some Auralex T fusors to create some scatter off the ceiling, at the side and rear speaker first ceiling reflection points...does this make sense, and/or should I do t fusors for the first reflection points for the LCR?

Thanks
Old 17th April 2015
  #114
Gear Guru
 
Ethan Winer's Avatar
 

You need absorption at reflection points.

--Ethan
Old 26th April 2015
  #115
Gear Guru
Foiled

I am not at all sure what foil will do in the various scenarios mentioned.
But I would be pretty sure it would be best to remove it when doubling the 703 depth. If there is 7 inches of space up there I would fill it with light cheap insulation and keep the semirigid 703 for other jobs.
DD
Old 14th October 2015
  #116
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moonkhatri's Avatar
Hello Everyone,
Hope everyone is well. I am currently setting up my first control room with acoustics. The only form of insulation available here in Karachi, Pakistan at the moment is Oc 703 (48kg density m3) with aluminum Foil on one side.( the kind used in construction and buildings for thermal insulation)
A lot has been discussed in the past on gearslutz regarding my query but I need further clarification.
My concerns are of course if the Foil alters glass wool's acoustic properties when doubled or facing the room or walls.

(Acoustic Panels details)
I have a huge intended cloud being designed for the ceiling area above my monitors. (cloud size 6.5 feet length, 7 feet width, cloud panel depth about 4 inches)
Bass trap panels sizes are
24 inch triangular ones for the four ceiling corners of the room
a few 2 by 4 feet rectangular panels for other corners (depth 4 inches)
2 more panels, sizes of a square meter ( each one intended for hanging right adjacent to the monitors for immediate absorption)
Also 2 feet high solid wood fractal diffuser for the rare wall for even better results.

Questions:
1) Should i remove the foil from all the Batts/Sheets i have?
2) Will 50mm batts/sheets of glass wool be enough for the cloud of the aforementioned size? or the cloud needs doubling too just like the bass traps?
3) Height of the room being used is 9 feet. How can I battle the standing wave phenomenon as someone who doesn't know acoustics and cant afford one either.
A response to these questions will make my life so much better.
Help me out if you can.

regards
Shamoon Khatri*
Cell:*+92 324 3206244
Composer*and*Producer
http://www.shamoonkhatri.com

Last edited by moonkhatri; 19th October 2015 at 07:27 PM.. Reason: corrections
Old 14th October 2015
  #117
Gear Maniac
 
doodlebug's Avatar
Quote:
Originally Posted by moonkhatri View Post
Hello everyone,

Questions:
1)Should the foil be sandwiched in between when doubling the 50 mm batts/sheets for the Bass traps?
2) Will 50mm batts/sheets of glasswool be enough for the cloud of the aforementioned size? or the cloud needs doubling too ?
3) when using one single batt/sheet with one side foiled, should the glasswool face the sound/room or the ceiling?
4) Height of the room being used is 9 feet. How can I battle the standing wave phenomenon as someone who doesn't know
acosutics and cant afford one either.

A response to these questions will make my life so much better.
regards
Shamoon Khatri
Shamoon Khatri
1) Usually no. Remove the foil.
2) I'd go thicker. 200mm minimum(even thicker would be better) and no foil in the RFZ. If using high density batts, 100mm with 100mm air gap should be ok or if using low density, use 200mm with no gap.
3) as above...no foil in the RFZ.
4) 9' ceiling? Luxury compared to my 8' ceiling. Go at least 300mm for the cloud. I'm planning on (at this stage) 375mm of low density with a 175mm airgap, making 525mm. I think you could easily get away with something like this.

Regards,

Harry
Old 20th October 2015
  #118
Gear Guru
 
Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by moonkhatri View Post
Questions:
I got your PM, but Harry already gave you all the answers.

Usually it's better to start a new thread rather than ask a new round of questions about a new room in an existing thread. That might be why you didn't get more replies. Again, you already got good answers, but you're welcome to ask any follow-up questions as needed, here or in a new thread.

--Ethan

The Acoustic Treatment Experts
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