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OC 703 FRK... to foil or not to foil????
Old 27th July 2010
  #31
Gear Head
 

Quote:
Originally Posted by DanDan View Post
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!
DanDan.... How high are your ceilings? Mine are only 8ft. Would the result be the same?
Old 27th July 2010
  #32
Gear Guru
Yes

Same 8 Feet. My side walls are concrete as is the floor. If you have similar the results kinda have to be the same I guess.
DD
Old 27th July 2010
  #33
Gear Head
 

Quote:
Originally Posted by DanDan View Post
My side walls are concrete as is the floor. If you have similar the results kinda have to be the same I guess.
DD
My sides are thin sheetrock and the floor is carpet but will be laminated in the control room (maybe throw a rug down) and may keep carpet in vocal booth and put laminate down in other recording area for ambience of guitars, live instruments, etc.

My next question is... when placing absorbers on the wall, should I leave FRK on the back facing the wall or completely remove?
Old 27th July 2010
  #34
Gear Head
 

Quote:
Originally Posted by Glenn Kuras View Post
In fact I think you might be right, ....
Glenn,

So you agree with leaving the FRK on the RFZ and clouds but face towards the ceiling?

How far should they be from an 8ft ceiling when hanging?
Old 27th July 2010
  #35
Gear Head
 

Quote:
Originally Posted by Ethan Winer View Post
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,

If I'm trying to obtain a somewhat dead area for vocals, is there any benefit to leaving FRK on the back facing the wall?

Dead or "alive"... what is the benefit, if any, of leaving FRK on the back of 2" thick panels, foil facing the wall? Of 4" panels, foil facing the wall?

Can the highs travel through a 2" OC 703 board with absorbent facing the room and bounce off the FRK facing the wall? What about on 4" of OC703?

If I'm trying to fully absorb, will the FRK affect my absobency if it's facing the wall? Is it better to completely remove if I'm trying to fully absorb?
Old 28th July 2010
  #36
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Ethan Winer's Avatar
 

Lightbulb

When the foil/paper is against the wall it has no effect at all. But I wouldn't necessarily remove it since that's an extra step and might leave a ragged surface that's more difficult to glue to the wall (if you plan to use glue).

--Ethan

________________
The Acoustic Treatment Experts
Old 28th July 2010
  #37
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Glenn Kuras's Avatar
Quote:
Originally Posted by Mixed_Breed View Post
Glenn,

So you agree with leaving the FRK on the RFZ and clouds but face towards the ceiling?

How far should they be from an 8ft ceiling when hanging?
Yes and no. How is that for commitment!!
I think your safe if the panel is 4" thick, but I still would go ahead and remove it if 2" (we are talking about gaps. If there is not a gap then it does not matter as Ethan pointed out). As I pointed out on the first page, I did do a local studio here at one time that had 2" panels with the FRK (facing the wall) spaced off 2". After we removed the facing the response was better. I don't have the graphs, but that told me enough. Dan seems to be ok with 4" panels. If you want to make damn sure then I would buy it without the FRK, which will save you money anyway and has been proven to work in a lab. heh
Old 28th July 2010
  #38
Gear Head
 

Question

Quote:
Originally Posted by Glenn Kuras View Post
I did do a local studio here at one time that had 2" panels with the FRK (facing the wall) spaced off 2". After we removed the facing the response was better.
When you say the "response" was better, exactly what do you mean... More abosrbent? My frames make my panels about 1.5" from the wall and the eye hooks may add another inch.

Quote:
Originally Posted by Glenn Kuras View Post
If you want to make damn sure then I would buy it without the FRK, which will save you money anyway and has been proven to work in a lab. heh
I tried buying without FRK but my local SPI doesn't carry unfaced OC 703 or 705. Only ASJ or FRK. Bummer because I hate removing it for many reasons:

1. Messy
2. Loosens the fibers on that side and they are not smooth and rigid as the unfaced side.
3. Time consuming.
4. As you said, they cost more. Makes no sense if I have to remove.
5. Tears at least 1/8" to 1/4" of the rigid fiberglass away.

But hey, @ 1.03 per square foot, I won't complain.
Old 28th July 2010
  #39
Gear Head
 

Question

Quote:
Originally Posted by Ethan Winer View Post
When the foil/paper is against the wall it has no effect at all. But I wouldn't necessarily remove it since that's an extra step and might leave a ragged surface that's more difficult to glue to the wall (if you plan to use glue).
Mine will be placed on frames that allow all sides of the rigid fiberglass to be exposed (no wood blocking them). Not glued to wall and have about 1.5" - 2" gap from the wall (please see my original thread at the start).

So is there any pros or cons for leaving the foil on the back of my standard 2" or 4" absorbent panels?

What I'm really asking is .... If I'm looking to build a fully absorbent 2" panel, will leaving the foil on the back facing the wall (with the small 1.5" - 2" gap due to frame and harware) have a negative effect on the absorbency? What about on a 4" panel the same way? What effect, if any, will it have?
Old 28th July 2010
  #40
Gear Head
 

Question

Quote:
Originally Posted by Glenn Kuras View Post
There is no number I can give you, but enough to recommend it.
Glenn,

So are you saying you recommend the foil on the back of panels used to absorb MF and HF?????????????
Old 29th July 2010
  #41
Gear Guru
Certainty

There is division of opinions on the matter. Quite normal when there are not enough tests, or if they are not public.
Plse take a look again at my Waterfalls.
That is 4 inch gap, 4 inch 705 traps with FRK and without. If you think one Waterfall looks better than the other, then go for it. It is a subtle enough difference. Nobody will die if you make the wrong choice.
FWIW, I chose to reinstate the FRK.
Now, I have also seen a Lab report, with a very similar setup.
The result is exactly as expected. FRK seems to increase the LF absorption in a slightly resonant manner at the expense of linearity.
As luck would have it the peak is pretty much where one would normally want it. I reckon possibly the dimensions of the room (relative to panel area), but certainly the thickness of the panel, and the size of the gap will all go towards delivering a better or worse overall response with Foil.

From my test, with 4 inch panels and 4 inch or larger gaps I would certainly recommend FRK. Whatever about the relatively small extent of the LF improvement in the Waterfalls, I found no downside whatsoever.

There is no public evidence to suggest that this still applies to different thickness of panel and trap.
There similarly no test info to the opposite except for Glenn's story. He has suggested that the result may be room dependent, i.e. different results in different rooms. (Thus my inclusion of room size relative to panel area or even total panel area)
As he says we have plenty of Lab and real world tests and experience to show what fibre with FRK will do. Thus a safe bet.

DD

Last edited by DanDan; 29th July 2010 at 02:28 AM.. Reason: Tidying up convoluted thoughts.
Old 29th July 2010
  #42
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Glenn Kuras's Avatar
Quote:
There is no public evidence to suggest that this still applies to different thickness of panel and trap.
There similarly no test info to the opposite except for Glenn's story. He has suggested that the result may be room dependent, i.e. different results in different rooms. (Thus my inclusion of room size relative to panel area or even total panel area)
wow Dan I almost find this a bit insulting. Story??? Lets please try to help instead of trying to just look smart, OK???

The fact of the matter is you did one tests in your room, so for your room it worked fine and for 4" I can see why. 2" on the other hand is not 4".

Quote:
Glenn,

So are you saying you recommend the foil on the back of panels used to absorb MF and HF?????????????
I was answering a question that was about foil to the front, which I DO recommend.

Quote:
When you say the "response" was better, exactly what do you mean... More abosrbent? My frames make my panels about 1.5" from the wall and the eye hooks may add another inch.
It was a number of years ago, but the over all response seemed to be much smoother, if I remember right, between 125hz and 500hz and did not change below that. The bottom line is (as I have said) as it has been proven A TON of times that not using foil on the back works and Dan might be totally right about his method, but I can't take one test in someones room and start to recommend it all the time. It would be very unprofessional of me (btw that is nothing against Dan as I have a lot of respect for me).

BTW I totally am up for being wrong on this. I have no horse in this race. heh
Old 29th July 2010
  #43
Gear Guru
Steady

Glenn,

If you re-read my post you should find what I said is very similar to what you are saying. Either that or we both need to study English as a foreign language!

4 gap, eight x 4 inch panels was tested in one room, test presented. You reckon it is not safe to extrapolate and apply this to all rooms, with good reason. I agree.

The good reason is that you found the opposite with two inch in one room, and I trust your word on this.

Now in balance, surely this observation can not be applied to all other rooms by exactly the same logic. i.e. One test in one room is not enough.

The addition of Safe Bet, and Lab and all that is just innuendo. There is no proper testing to show benefit or not of Foil on back, universally. Lack of Lab testing does not prove anything.
(Personally I am even less convinced about the 'benefit' of Foil on the front.)

I think it quite reasonable, and you have previously agreed that it is, for me to recommend foil in situations similar to my test. i.e On the back of panels 4+4 small mostly concrete room.

I think it quite unreasonable for you to warn against using Foil backing on the basis of on room's experience.

There is an elephant in the room.
The presence of such membranes on highly successful commercial products is an innuendo that I take seriously. There are tons of these high end products in use every day for years.
They go to 1 inch.

Lastly, please calm done and edit your post to take out those ugly unworthy comments.

Respect, DD
Old 29th July 2010
  #44
Gear Guru
 
Glenn Kuras's Avatar
Dan I was not being ugly at all. I think it is best just to agree to disagree (is that the saying??). As I said though I totally welcome you being right about your findings. Not just in your room but every room that treated. I would just like more research/testing in the matter before making it a "standard" recommendation. Considering the other is a standard and has been used in thousands of rooms with great success.
Old 29th July 2010
  #45
Gear Guru
Ugly

Quote:
Lets please try to help instead of trying to just look smart, OK???
I find that ugly Glenn, that should be enough for you to remove it , please do.
Also the suggestion that I 'almost insulted' I didn't. Read my post again, without anger blindness. It agrees with all your stated views, as you have previously agreed with mine. If there is something of substance in error or disagreement, state it. You will not find that possible.
What is going on here? Please do remove the rancour and I will remove all ripostes to it.

Your single room experience can hardly be used to 'Warn' against foil in all other rooms. This just doesn't make sense.

Quote:
it worked fine and for 4" I can see why
If you have a theory please do share, that would be helpful.

The TONS, Standard, and Thousands, is hardly an argument against presented test and undisputed factual statements.

As I said there are thousands of rooms using TONs of a particular high end commercial product which has foil on the back and goes down to one inch.
I suggest that it was very likely thoroughly tested.

The differences are subtle enough. One might include foil in a room modally strong (concrete). In a sheetrock or TnG room, LF absorbent, one might chose bare panels, which are more linear, as stated by both of us.
These things have a 'sound'. I chose which to use on that basis.

DD
Old 29th July 2010
  #46
Gear Guru
 
Glenn Kuras's Avatar
lol... I can't believe we are writing back and forth about something as dumb as this. If you thought I was being ugly then sorry. Lets move forward as it seems as you and I might not be as far apart on the issue as we both think.

Moving on. thumbsup

Quote:
If you have a theory please do share, that would be helpful.
I would think the thickness of the 703 alone would reach frequencies of importance where the 2" might not. At that point the foil would then come into action.
Old 14th August 2010
  #47
Gear Head
 

Question

Quote:
Originally Posted by Glenn Kuras View Post

I was answering a question that was about foil to the front, which I DO recommend. heh

Glenn,

When using the foil facing the front for bass traps... should this method be the same on the bass traps placed/straddled on the "flat wall to ceiling" meeting points?


Question # 2: If I choose to place the bass traps perpendicular in the corners (not straddled but flat on each both walls at the corner meeting place), is it still best to leave the foil on these (just as in the case of the straddled corner bass trap????
Old 16th August 2010
  #48
Gear Guru
 
Glenn Kuras's Avatar
Quote:
When using the foil facing the front for bass traps... should this method be the same on the bass traps placed/straddled on the "flat wall to ceiling" meeting points?
Yes.

Quote:
Question # 2: If I choose to place the bass traps perpendicular in the corners (not straddled but flat on each both walls at the corner meeting place), is it still best to leave the foil on these (just as in the case of the straddled corner bass trap????
Yes

Both of the questions are yes because the foil will help absorb a bit more low end and keep the highs a bit more alive.
Old 17th August 2010
  #49
Gear Head
 

Question

Quote:
Originally Posted by Glenn Kuras View Post
...the foil will help absorb a bit more low end and keep the highs a bit more alive.
Thanks Glenn.

One more question:

If I place the bass traps flat on the wall, do they need some type of gap behind them? Right now they are attached to 2" strips which actually gives them about 1.5" of a gap. However, the wood will be nearly flat against the wall (no sound or air can get behind except for whatever gap is behind once the hanging hardware is attached... wire and/or D-hooks or both) so I'm not sure if this qualifies as a gap.

Oh yeah, just so you know... I decided to go your route of taking the foil off the backs of the panels used just for absorbers. I took your advice on the room you found treated with the foil on the backs and once you removed it, it improved the room drastically.
Old 17th August 2010
  #50
Gear Guru
 
Glenn Kuras's Avatar
Quote:
If I place the bass traps flat on the wall, do they need some type of gap behind them? Right now they are attached to 2" strips which actually gives them about 1.5" of a gap. However, the wood will be nearly flat against the wall (no sound or air can get behind except for whatever gap is behind once the hanging hardware is attached... wire and/or D-hooks or both) so I'm not sure if this qualifies as a gap.
You should be fine with a gap like that. If you want you can gap it a bit more which will help with absorbing low end, but not sure if you would really notice much of a difference to your ears.
Old 18th August 2010
  #51
Gear Head
 

Question

[ATTACH][/ATTACH]
Quote:
Originally Posted by Glenn Kuras View Post
You should be fine with a gap like that.
Glenn,

I'm not sure if I worded the question right. I don't want you to think I have the bass traps on "strips". They are actually attached to the wood frames. I have included a picture of the back so that you have a visual reference.

The picture is without any hardware because I am still building the total needed for the control room and a recording room I'm currently building.

I plan on using D-hooks and wire OR.. just the D-hooks hooked to screws/hooks that I may screw in the wall for those I will be attaching to the wall (I will use eyebolts and rope for the clouds above hanging from the ceiling).

To clear up my question: Once I attach the hardware and hang the trap(s), the wood frame of the trap will pretty much make the trap flush with the wall(s). Will the 1.5" gap provided by the wood itself be enough (between the wood and the back of the trap)?

I'm guess I'm wondering if I need to provide an additional gap to the entire trap that lifts the wood from the wall so the trap is not flush... so that air/sound can get behind it to the back of the fiberglass back of trap???? Or am I thinking the wrong idea here??
Attached Thumbnails
OC 703 FRK... to foil or not to foil????-image_186.jpg  
Old 18th August 2010
  #52
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Glenn Kuras's Avatar
I understood your question. My answer is still the same.
Old 18th August 2010
  #53
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Weasel9992's Avatar
 

Quote:
Originally Posted by Mixed_Breed View Post
Will the 1.5" gap provided by the wood itself be enough (between the wood and the back of the trap)?

I'm guess I'm wondering if I need to provide an additional gap to the entire trap that lifts the wood from the wall so the trap is not flush... so that air/sound can get behind it to the back of the fiberglass back of trap???? Or am I thinking the wrong idea here??
1.5" is great. Add another couple of inches if you can, but don't sweat it if you can't. I think that's what Glenn was saying more or less.
Old 18th August 2010
  #54
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Originally Posted by Weasel9992 View Post
1.5" is great. Add another couple of inches if you can, but don't sweat it if you can't. I think that's what Glenn was saying more or less.
thumbsup
Old 18th August 2010
  #55
Gear Guru
Men

To be fair it might be worth asking the same question of a female.
i.e. Does a couple of inches extra matter?

DD
Old 19th August 2010
  #56
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Weasel9992's Avatar
 

Quote:
Originally Posted by DanDan View Post
To be fair it might be worth asking the same question of a female.
i.e. Does a couple of inches extra matter?

DD
That's what she...no, wait....
Old 31st August 2010
  #57
Gear Head
 

Question

Quote:
Originally Posted by Glenn Kuras View Post
I understood your question. My answer is still the same.
Cool, Thanks alot Glenn.

I have couple more questions... going by Ethan Winer's "covering more area is better than a smaller area with thicker material".... If I were to place the bass traps perpendicular (as opposed to straddling the 4" thick traps), can I use 2" thick traps (four 2" thick traps, 2 stacked on each wall at the corner meeting place so that the floor to the ceiling is covered, entire 8ft)? If so, would these still absorb as much low end as the 4" thick traps straddled (2 covering from floor to ceiling)? More, less?


If I lay them perpendicular or straddled, will it aid to place a trap at the ceiling? I would think "no" since there is no adjacent wall to reflect sound (b/c bass trap is there).
Old 1st September 2010
  #58
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Originally Posted by Mixed_Breed View Post
Cool, Thanks alot Glenn.

I have couple more questions... going by Ethan Winer's "covering more area is better than a smaller area with thicker material".... If I were to place the bass traps perpendicular (as opposed to straddling the 4" thick traps), can I use 2" thick traps (four 2" thick traps, 2 stacked on each wall at the corner meeting place so that the floor to the ceiling is covered, entire 8ft)? If so, would these still absorb as much low end as the 4" thick traps straddled (2 covering from floor to ceiling)? More, less?

).
For a broad band bass trap to be effective in the corner it should be no less then 4" thick and straddle the corner. That would be the starting point to "cover more area vs thicker panel". You can put 2 4" panels flat in each corner but I believe that would be about as good as 1 panel straddled.
Old 2nd September 2010
  #59
Gear Head
 

Quote:
Originally Posted by Glenn Kuras View Post
For a broad band bass trap to be effective in the corner it should be no less then 4" thick and straddle the corner.
Is 6" OC 703 ideal here (of course I know that thicker is better)?

Quote:
Originally Posted by Glenn Kuras View Post
You can put 2 4" panels flat in each corner but I believe that would be about as good as 1 panel straddled.
Yep, I searched before I wrote this and come up empty but searched after (later that night) and found some of your responses on what you recommend due to what you have tested which is "straddling the corner". Also found the .pdf from your site about getting started that stated the same thing. Other sites also recommend straddling as well.

Straddling the corner will definitely save me from building 2 extra frames and the extra materials to cover since it would take 4 frames to lay the bass traps flat against the wall (floor to ceiling, 8'). Not to mention, to lay the 4" thick OC 703 bass traps flat, it would also take twice the 703 panels (8 x 2" panels as opposed to only 4 x 2" panels). I too agree that straddling is better... especially after viewing many of the test results. There's not enough difference to make me use all the extra materials just to lay them flat.

I'll also get that extra space behind them too. I have read many places that it's best to gap atleast the same distance as the panel is thick.

Thanks so much Glenn... for your patience, guidance and knowledge. Thanks for sharing!
Old 3rd September 2010
  #60
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Weasel9992's Avatar
 

Quote:
Originally Posted by Mixed_Breed View Post
Is 6" OC 703 ideal here (of course I know that thicker is better)?
6" traps would be great for corner straddling.
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