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OC 703 FRK... to foil or not to foil????
Old 18th July 2010
  #1
Gear Head
 

OC 703 FRK... to foil or not to foil????

OC 703 FRK... to foil or not to foil????
I have read for months now and have read Ethan Winer's FAQ. I am sooooo confused on whether to build my bass traps with the foil, without the foil completely, with the foil facing the room, with the foil facing the wall, facing the room on a bass trap... etc. etc. I'm so confused. Please someone help with some solid direction because I have read so many different ideas.

I'm building corner bass traps with two pcs. of 703 frk (2" thick x 2 = 4" thick and 2' x 4'). Two in each corner stacked as to fill the entire corner from floor to ceiling. Is it best for me to peel one off and place the one with the foil towards the room?

I'm also building some 2' x 4' (only 2" thick) pieces for hanging on the wall. All will have about a 2" gap because of the frame and wrapping material.

I'm tempted to pull all the foil off but I don't want to if I can use it to help in the room. I've read so much I'm just confused.
Old 18th July 2010
  #2
Gear Maniac
 
4 the Max's Avatar
 

FRK reflects highs

1. These are the related threads from this post:
2. I'd like to know if the paper or foil faces the room myself.

3. It's also possible to buy FRK and attach it to OC703 that doesn't have it using some kind of spray adhesive. Here's the email from customerservice:

Akiva,

Yes it is possible to put the FSK paper on the board after the fact, we laminate the boards in our shop, but I can cut the paper to 24" x 48" and mail it to you. You would have to spray glue it on. Each piece would be $1.50 and I can roll them up and ship them out to you. You might have to flatten them before applying to get the curl out of them. Let me know how many pieces you need.

Hope this helps,

Jim

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http://www.BuyInsulationProducts.com


How I built my bass traps...

====================================
Well on a 4x2 4" panel it would give you 50% more exposed area if the sides are open.. 6"? well, check my numbers but that would be 75% more exposed would it not?

Nice DYI dude! ... You may want to think about putting some FRK on the fronts. This will help with a little more low end and also keep the room from going "DEAD" on the high end.

Glenn
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====================================
RK/FSK is a scrim facing that comes on some insulation products. It's paper on one side, foil on the other, and has a reinforcing mesh in the middle.

The purpose is two-fold:

- act somewhat like a damped membrane increasing absorbtion at a specific band based on the density of the material behind it.

- reflect upper mids and highs so you can absorb the bottom without overdoing the top and making it too dead.

Bryan
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Bryan Pape
Lead Acoustical Designer
GIK Acoustic

====================================
If you want them to do mids and highs too, then don't use any FRK/FSK. The point of it is to be able to do more bass control without overdoing the highs.

Bryan
__________________
I am serious, and don't call me Shirley

Bryan Pape
Lead Acoustical Designer
GIK Acoustics
Old 18th July 2010
  #3
Gear Head
 

Question should the foil be completely removed on panels absorbing mids and highs...

Thanks 4TheMax...

Well, after reading another 4hrs. or so (retina's nearly burned, lol), I think I've got it. The foil should face the room if used on a bass trap... as long as the bass trap is not a direct reflecting point of one of the monitors.


You're right. It reflects mids and highs so if I don't want my room too dead, then I should alternate the 2" thick panels... or maybe just put a couple in with the foil facing the room.


I guess the only question I have left is... Should I leave the foil on all of my panels but simply face the foil towards the wall when using the panel to absorb the mids and highs or completely remove the foil for this purpose (as to not reflect the highs back into the room one they hit the foil facing the wall. I'm not sure because all of my panels will have that 1.5" gap from the wall due to the frame.

I'm building my frames so that the sides are exposed (to get greater coverage and absorption). The OC703 will lay against the small frame and will be covered with Muslin and colored cotton of nearly the same thread count.
Old 18th July 2010
  #4
Gear Guru
Careful

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
Old 18th July 2010
  #5
Gear Guru
 
Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by Mixed_Breed View Post
I think I've got it. The foil should face the room if used on a bass trap... as long as the bass trap is not a direct reflecting point of one of the monitors.
Exactly. Anything in the corners, out of the way, should have FRK. Any places where you need HF absorption, such as all reflection points and possibly other places on a low ceiling, should be fully absorbing.

--Ethan

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Old 19th July 2010
  #6
Gear Maniac
 
4 the Max's Avatar
 

FRK with multiple 703 or 705

Owens Corning 705 FRK [oc705 FRK] - $139.99 : Ready Acoustics!, Hear - Sound - Better

According to this website:
Foil faces the room
only the front layer has foil if you are using more than one OC703 or 705 batt (e.g. 2 x 4 x 2")
Old 20th July 2010
  #7
Gear Head
 

Quote:
Originally Posted by Ethan Winer View Post
... and possibly other places on a low ceiling, should be fully absorbing.
Ethan, I thought the ceiling cloud should have the foil facing the ceiling (the gap)????
Old 20th July 2010
  #8
Gear Head
 

[QUOTE= only the front layer has foil if you are using more than one OC703 or 705 batt (e.g. 2 x 4 x 2")[/QUOTE]

So I should have the foil in the middle of the two 2" panels that I combine? If so, do the same "foil facing wall, foil facing room" principles apply????
Old 20th July 2010
  #9
Gear Maniac
 
4 the Max's Avatar
 

foil position

+----------- WALL -----------+

AIR SPACE

------- UNFACED REAR BATT --------

------ FRK FACED FRONT BATT ----- (FOIL SIDE FACING THE ROOM)


ROOM


This is my understanding of things from the above. But, I agree, the wording is confusing. I've broken it down as best I could. Other forum members please correct me if my conclusions are incorrect:

Quote:
-reflect upper mids and highs so you can absorb the bottom without overdoing the top and making it too dead.

If you want them to do mids and highs too, then don't use any FRK/FSK. The point of it is to be able to do more bass control without overdoing the highs. - Bryan Pape, GIK
FRK both "reflects mids and highs" AND "No FRK means you want them 'to do' mids and highs." "To do" must mean the bass trap relects mids and highs."

Quote:
Exactly. Anything in the corners, out of the way, should have FRK. Any places where you need HF absorption, such as all reflection points and possibly other places on a low ceiling, should be fully absorbing. - Ethan Winer, Realtraps
corners - reflects mids and highs, so it has FRK
reflection points, low ceiling - no FRK, so it absorbs LF and mids/highs ("fully absorbing" = everything = LF + MF + HF)

Quote:
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
DanDan seems to state the opposite: on clouds and reflection points, he likes foil on the backside. I think this increases the confusion beyond the wording above. But democratically, Bryan and Ethan agree on the FRK on the front (both commercial acoustical fabricators); Dan wants the FRK on the back (don't know his qualifications)

----------------
Quote:
corners
Though one cannot assume anything, it implies BOTH dihedral (wall-to-ceiling) and trihedral (wall-ceiling-wall) corners

Again, you experts out there - please clarify.
Old 20th July 2010
  #10
Gear Guru
Democracy

Quote:
DanDan seems to state the opposite: on clouds and reflection points, he likes foil on the backside. I think this increases the confusion beyond the wording above. But democratically, Bryan and Ethan agree on the FRK on the front (both commercial acoustical fabricators); Dan wants the FRK on the back (don't know his qualifications)
Tests
As published I tested my RFZ Cloud zone with FRK vs None on the rear of the panels. There were 8 Minitraps involved. The LF Frequency Response and Waterfalls were substantially better with FRK. I had to replace it all!

Theory
4 inch 705 FRK panel with a 4 inch airgap.
When the FRK is to the front it is double the distance from the boundary, likely to extend it's LF effect an octave plus HF Decay will be substantially increased. This brightens the room AND improves LF

FRK to rear, there is a still a useful, as tested, LF effect, but without the brightening.

This was not a LAB but better. An A/B test, same room before and after.
I don't think this forum allows me to publish the graph again. A search should easily find it.

And yes I like Foil on the backside, who doesn't? heh

DD
Old 20th July 2010
  #11
Here for the gear
 

Quote:
Originally Posted by DanDan View Post
This was not a LAB but better. An A/B test, same room before and after.
I don't think this forum allows me to publish the graph again. A search should easily find it.
I wasn't able to find the graph, which thread was it in?
Old 20th July 2010
  #12
Gear Guru
FRIK

OC 703 FRK... to foil or not to foil????-picture-1.jpg
OC 703 FRK... to foil or not to foil????-picture-2.jpg

Last edited by DanDan; 20th July 2010 at 03:35 PM.. Reason: Disbelievers!
Old 20th July 2010
  #13
Gear Guru
 
Glenn Kuras's Avatar
We may test this in the lab next time we go. I have mixed feelings about it but can see the benefits too.
Old 20th July 2010
  #14
Gear Guru
 
Glenn Kuras's Avatar
Dan,
I don't have the graphs but around 3 years ago I redid a local studio that had 2" panels with facing on the back and air gap. There room was a mess and after we removed the facing things looked much better. My point is before I recommend this way of doing it I really want to see some lab reports.
Old 21st July 2010
  #15
Gear Guru
Test

Hi Glenn, the more tests the better. Due to the variability of Lab tests and their arguable unsuitability for our purposes, I tend to favour this A/B-same -room- same conditions type of test. Logically it seems to stand up.
Ethan has made this point more eloquently here. RealTraps - Alternative Test Methods
FRK has been shown to enhance LF absorption at the expense of some linearity.
FRK out as opposed to FRK in is a tiny distance in terms of LF and there is little directional about LF. This suggests to me that the 'benefit' of FRK should be there out or in.

If this is true, I can't see how Lab tests would not pick it up so I would love to see them done.
Or just ask Frank, he has stated that 'Dan is always right' heh

DD
Old 21st July 2010
  #16
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Due to the variability of Lab tests and their arguable unsuitability for our purposes
I don't want to go off subject, but I would do a lot more research on lab testing before thinking like that. Lab testing is very reliable. Give me a call anytime and I would be more then happy to explain it in more depth.
Old 21st July 2010
  #17
Gear Guru
Research

Hi Glenn, I hear you. However the studies I have briefly looked at indicate test uncertainties of up to 26% at LF in particular.
This is not just Lab testing it is all sound testing. I don't have the quote to hand but it goes something like this.
'We can measure the light out put of a single candle three miles away with accuracy of several decimal points. However with sound we can only achieve at best a 3% accuracy and this is in a controlled room"
Not an exact quote, nor numbers, but I am sure you get my drift.
Incidentally, the practical side of my Diploma was all done in the Anechoic and Reverb Rooms at Liverpool university.
DD
Old 21st July 2010
  #18
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Originally Posted by DanDan View Post
Hi Glenn, I hear you. However the studies I have briefly looked at indicate test uncertainties of up to 26% at LF in particular.
This is not just Lab testing it is all sound testing. I don't have the quote to hand but it goes something like this.
'We can measure the light out put of a single candle three miles away with accuracy of several decimal points. However with sound we can only achieve at best a 3% accuracy and this is in a controlled room"
Not an exact quote, nor numbers, but I am sure you get my drift.
Incidentally, the practical side of my Diploma was all done in the Anechoic and Reverb Rooms at Liverpool university.
DD
That 26% has really no meaning as you have to understand what part it is talking about. The good news is labs can tell you this where testing in a normal room you would never know what the uncertainties are. The point is uncertainty is not a negative but a positive. If you look at our 244 and Monster test numbers you will see they follow each other pretty close as one is 4" and the other is 6" and both where tested on different days. If labs where that unreliable it would have shown here. As a test when we tested the Tri Trap we pushed the button twice (testing) just to see what would happen. Guess what? They looked the same. mmmmmmm Are we just lucky this has happened ever time for us??? I don't think so. I do agree though that a larger test room would be great some day.
Old 21st July 2010
  #19
Gear Guru
Statistics

98% of Statistic are wrong!

I would have to pull the papers etc. but the uncertainty I refer to is the same test, same materials, performed to extremely tight defined standards with calibrated equipment, was done in different Labs. They came up with a very varied results. Comparative tests done in the same Lab, same equipment, same day, are intrinsically reliable.
Comparative tests done in the same room are likewise, intrinsically reliable.
DD
Old 21st July 2010
  #20
Gear Guru
 
Glenn Kuras's Avatar
Well we have done our own test twice, so........................
Old 21st July 2010
  #21
Glen, how much is the improvement with FKR? comparing with 2" regular OC 703.

Thanks!
Old 21st July 2010
  #22
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Originally Posted by AMIEL View Post
Glen, how much is the improvement with FKR? comparing with 2" regular OC 703.

Thanks!
There is no number I can give you, but enough to recommend it.
Old 21st July 2010
  #23
Lives for gear
 
Weasel9992's Avatar
 

Quote:
Originally Posted by DanDan View Post
98% of Statistic are wrong!

I would have to pull the papers etc. but the uncertainty I refer to is the same test, same materials, performed to extremely tight defined standards with calibrated equipment, was done in different Labs. They came up with a very varied results. Comparative tests done in the same Lab, same equipment, same day, are intrinsically reliable.
Comparative tests done in the same room are likewise, intrinsically reliable.
DD
Dan, you're over stating your point a little.

First, it's nothing like a 26% variance. Down to 50Hz it's something like 10-15% at the most. That information comes directly from the lab itself...we're not making it up. Secondly, Glenn makes a really important point about the consistency we see in the test numbers for the 244 and the Monster Bass Trap. Two different panels measured on two different days. That tells us a couple of things: one, that the testing methodology is consistent and accurate, and two, that we are in fact seeing results that are a measurement of reality and not figment of statistical variation. Now, if the results varied widely then we could question both of those things, but they don't.

On the topic of room testing being more accurate that a lab, I'll just say this: There’s a lot of value in testing your room…no doubt about it. There are about a million things that have an affect on the overall acoustics in an enclosed space: doors, windows, furniture, etc. Testing your room before treatment will provide a baseline for further comparison as you place each panel where it’s supposed to go. If you test as you go along you’ll be able to tell whether you’re headed in the right direction or not. However, relevance of those results is limited to your room or another space exactly like it. A lab on the other hand is an acoustically neutral space. In other words, it doesn’t add its acoustic thumbprint to the results like another type of space would, so lab results are applicable across a much wider sector, and are not limited to the testing environment. Plus, a lab like Riverbanks can boast an error range as small as 6% down to 100Hz. From there it gets higher, but not wildly so: up to 10% or so down to 63Hz and up to 15% down to 50Hz. Those are tough numbers for even the best room-testing enthusiast to match for all the reasons laid out above.

Furthermore, Room tests are usually conducted with a single omni directional measurement microphone using a neutral preamp and measurement software. The mic is placed at the listening position, and then a full-range sweep (20Hz-20Khz or higher) is played through the mains (one at a time and/or both simultaneously). The results are calculated by the software, and then interpreted by the user. The effectiveness of the testing is, of course limited by the skill of the person conducting the tests, his/her attention to detail, the type of preamp being used, the speakers, their placement and, of course, the room and everything in it. A lab has none of those potential pitfalls. Highly skilled, experienced personnel conduct the tests with proven, calibrated equipment using time-tested methodology with a long history behind it.

Honestly, here's it doesn't seem to be that there is sufficient reason to doubt the results of lab testing since good methodology is always followed and disciplined testing protocols observed.
Old 21st July 2010
  #24
Gear Guru
Overstated?

The ASTM, ISO, and other methods are rigorous. They bend over backwards to eliminate individual anomalies from the tests. They have employed all sorts of electronic, acoustic, and statistical minds.
I can's show it here but an actual survey shows variance between Labs of
-37 to +25% in the 125Hz band. Same test, same materials. Real Labs, USA, proper survey.
Ron Sauros work on the edge effect seriously challenges the viability of the standard tests, even in terms of their real goals.
The harbingers of good scientific test are Reproducability and Repeatability. In the same room, same equipment etc., you get or should Repeatability. In neither Labs nor real rooms do you get Reproducability.
The science of sound ain't great yet. In light or other studies those parameters are much better satisfied.
Comparative tests are very believable if they repeat in the same room, as Frank has said. If the comparative result can be reproduced in another room, everything different, I believe then we have a slam dunk, both Harbingers looking good. IMHO this beats the Lab.
This is standard Test philosophy. Not sure it's On Topic here.

DD

Last edited by DanDan; 21st July 2010 at 04:41 PM.. Reason: Typso
Old 21st July 2010
  #25
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I'd say that that's true, but the purpose for testing of this sort is to prove that the panels will do what we say they will do. For that purpose lab testing is not only entirely reliable, but preferable due to the neutrality of the testing space. That's the only point I'm making here.

I do have a couple of things to say about the variance discussion. First, I think that much to much is made of the variances between labs. The variance numbers are presented in a way that doesn't reflect the reality they imply.

Secondly, a variance between one lab and another doesn't necessarily say anything whatever about any one of those labs' accuracy in and of itself. In other words, you can start with a premise that says "there are variances from lab to lab" and jump to the conclusion, "therefore all lab results are unreliable". It simply doesn't follow.
Old 21st July 2010
  #26
Gear Guru
 
Glenn Kuras's Avatar
Quote:
I can's show it here but an actual survey shows variance between Labs of
-37 to +25% in the 125Hz band. Same test, same materials. Real Labs, USA, proper survey.
Your talking about the round robin which is not what we are talking about in the same lab. Yes there was a test and guess what they found a difference from one lab to the next lab. The good news is Riverbank, who we and most larger acoustic companies use fell right in the middle. Meaning it was not to high or not to low. In fact you can use them as a base line which makes them 0%. heh
Old 21st July 2010
  #27
Gear Guru
Too much

Quote:
Your talking about the round robin which is not what we are talking about in the same lab.
Glenn, yes and surely the same can be said of the same test in the same room?
If an A/B in any room is repeated with a similar comparative result in another, it seems to me proven. I think we are agreed here.

Frank, I would riposte that there is too much assumption made. Labs are hopefully neutral. Everything is randomised as best we can.
Small rooms are the opposite in every sense. Specific dominant modes. Specific single speaker locations. And most importantly specific location of treatment to address specific issues. Traps at hot spots, not a random distribution.

To Topic, my two Waterfalls, would ye accept that one of these situations is 'better'? Would ye also accept that it is most likely that the same will hold true of the same comparison in any other small room?

I am trying to compare FRK and no FRK from published Lab results here.
Unfortunately there is no airgap in one test, and a huge gap but no FRK in another. Finally the one test which might matter, FRK, no FRK, up down, same gap, I can't show you. I may be able to extrapolate and hint though.
That,with the fact that Frank said 'Dan is always right' should do it heh
Leave it with me. I may be able to save the cost of a Lab test....
DD

Last edited by DanDan; 21st July 2010 at 05:08 PM.. Reason: Question
Old 21st July 2010
  #28
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Glenn, yes and surely the same can be said of the same test in the same room?
If an A/B in any room is repeated with a similar comparative result in another, it seems to me proven. I think we are agreed here
I want you to run a test 100 times and report back how many where the same and how many where different. I have my money on more (if not all) of the tests where different then the same. heh

BTW I want to make clear I have nothing against room testing, I just believe lab testing is needed and can be trusted.
Old 26th July 2010
  #29
Gear Guru
Foiled!

I did try to make comparisons between various published data on OC and FRK.
Quite inconclusive. So all I have is my test. FRK vs None same room, carefully tested, mic spots marked and all that. To me the LF improvements look worthwhile so I will stick with my recommendations of including Foil on the back of RFZ and Cloud Traps. I wouldn't be shouting it too loud though ;-)
DD
Old 27th July 2010
  #30
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Originally Posted by DanDan View Post
I did try to make comparisons between various published data on OC and FRK.
Quite inconclusive. So all I have is my test. FRK vs None same room, carefully tested, mic spots marked and all that. To me the LF improvements look worthwhile so I will stick with my recommendations of including Foil on the back of RFZ and Cloud Traps. I wouldn't be shouting it too loud though ;-)
DD
Your fine recommending that in my book. In fact I think you might be right, but my only point is when someone recommends something that is not of the norm I just question it and recommend what is proven. No harm in what you are doing though, as it does work in YOUR room.
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