So after all this time, my acoustic treatment is doing ALMOST NOTHING??!
JLiRD808
Thread Starter
#1
5th January 2012
Old 5th January 2012
  #1
Lives for gear
 
JLiRD808's Avatar
 

Thread Starter
So after all this time, my acoustic treatment is doing ALMOST NOTHING??!

So I setup my RFZ before I got into REW. I made bass traps that are up to 6" thick at their center. I even built a 3" cloud over my head that hangs 12" from the ceiling. I read Mitch Gallaghers book on home studio acoustics and have been pretty active here on GS trying to soak up as much as I can and came up with this. Its nothing special, but its a huge step forward for me coming from a few auralex squares and rugs hastily thrown here n there.



But then, I was doing some REW testing today and decided to remove the corner traps to see what kinda effect they were having. I wanted to know how significant they were and how much MORE TRAPPING I should add.

REW results....NO EFFECT :(

Then I remove my side panels.....no REAL visible effects!! >:(

So after all this time, my acoustic treatment is doing ALMOST NOTHING??!-none-full.jpg

Aggravation, frustration, and confusion kicks in

Is this slight change normal? I usually see such a slight change when I run two exact tests back-to-back....and this graph shows with/without my LR and rear RFZ panels!!

2 theories so far:

-Wrong type of material/rigid fiberglass
-Not enough material/rigid fiberglass

The rigid fiberglass I used came from my uncle and his boss. They work for the school district and he is a drummer himself. He said there was no brand name on it and that it, supposedly, was manufactured by a company that OC forced to "cease and desist" for replicating their product. This is what it looks like:



I posted pics on here about a year ago that I had this stuff and ppl were like "looks like rigid fiberglass to me!". Ive never seen actual OC 703 or 705 and was skeptical myself. Ive since sold/given some away to studio veterans and they VOUCHED that it was most like OC705. One guy had like a $30k studio and I'm sure he would have told me if it wasn't legit. When I weighed some today it came in around 5 lbs/cu ft. And last but not least....its itchy and scratchy as f*ck and gets all over me when I have to handle it.

Theory Two:
These panels are only 1.5" thick, not 2" thick. I have them wrapped and set off the walls about 1/4" with the lil hooks theyre on. Are they too thin to have an effect??? I would think they would at least tame SOME highs/upper mids.

The other theory that I quickly abandonded was the material I have my panels wrapped with. Theyre ALL breathable.

Any ideas? Should I just double up these panels? Am I doing something wrong in testing? Is this SLIGHT difference normal?! Why go through all the trouble lol...I might as well put up posters!!!

Thanks!!
#2
5th January 2012
Old 5th January 2012
  #2
My guess is that your monitors look too close to the wall.

Also you need traps directly opposite of where your speakers are aimed. It's too hard to tell from the photo.

Can you upload a sketch of your layout?
JLiRD808
Thread Starter
#3
5th January 2012
Old 5th January 2012
  #3
Lives for gear
 
JLiRD808's Avatar
 

Thread Starter
Sure thing...this is what it looks like now. White/blue boxes are bass traps. Green/white are 1.5" panels.



This is what I'm gathering it SHOULD look like:



I pulled the traps out and tested cuz I was hoping it would show me a scope of what these 2'x'5'x6" corner traps are actually doing. Pretty bummed at the lack of change but I actually did notice a hump around 120hz after reexamining my results.

So u say the corners that my speakers point into should be trapped primarily (first)? I figured since the port holes on the back of my HS80's pointed into those back corners I'd grab them there (though Ive since plugged my ports with some spare scrunched up Auralex which did reduce the boominess below 80hz). Also, regarding the proximity to the rear wall, the speakers are about 13" away. I COULD move further back but I'd have to move the couch too and it'd probably feel a lil close to the TV at that point lol. I'll think about it though...or try it and test again

Another thought...what if I set these 1.5" panels 1.5" off the wall?
#4
5th January 2012
Old 5th January 2012
  #4
Gear maniac
 

Quote:
Originally Posted by JLiRD808 View Post
Theory Two:
These panels are only 1.5" thick, not 2" thick. I have them wrapped and set off the walls about 1/4" with the lil hooks theyre on. Are they too thin to have an effect??? I would think they would at least tame SOME highs/upper mids.
First and foremost, you're using fibreglass, which causes the itchness and is also not really optimal for your health. Most Fibreglass should work as broadband absorbers, though others might be better on that topic than I am.

1,5" thickness (about 3,8cm) of the absorbtive material should in theory take care of everything above 900Hz. If it counts anything, your reverberation time should be reduced at least.

Basstrap wise you definitely need to stack or have thicker absorbtive material. 4" (about 10cm) at least.


Regarding the speaker placement - looks fine to me, also the frequency response (I've seen worse), and I wouldn't say that bass traps need to be on the oposite side of the speakers. Bass up until 250-300Hz is omnidirectional, so it doesn't matter where they are, as long as they take care of the absorbtion. More important are the first reflection points (e.g. the "Mirror Trick").

Also, your ceiling seems to be very high, so I'd lower the clouds a bit above the rig (if possible).


You can't do much about it for the time being (IMO!) other than rebuilding your room (which is mostly not possible), or using a room correction device on top of your already built absorbers. This could help a bit more if you really want to go "level" other than adding more absorbtive material.
#5
5th January 2012
Old 5th January 2012
  #5
Lives for gear
 
Jens Eklund's Avatar
 

#6
5th January 2012
Old 5th January 2012
  #6
Gear Guru
 
Glenn Kuras's Avatar
 

Quote:
I made bass traps that are up to 6" thick at their center.
This part I am a little confused about. Are they 6" thick panels that are 2'x4'? And how much corner area have you covered?

Also noting that when you straddle corners it really is not going to do much to the frequency response itself (for the most part), but it will help A LOT with the ringing (VERY important as this is where the clarity/tightness on the low end comes from) . For this you want to view the waterfall graph to see how much it improved and where it improved. For frequency response you will need to either have them REALLY thick or something tuned flat on the wall where the problem is coming from.

BTW below is a 17x13x8 lab/test room I built to do tests here at the plant. The following is the room empty vs 8 Monster traps. As you can see it decreased ringing as low as 40hz which is what I was looking for. In no way am I saying this is all this room would need to make it to my liking, but just showing you what to look for.



#7
5th January 2012
Old 5th January 2012
  #7
Lives for gear
 
amishsixstringe's Avatar
 

Quote:
Originally Posted by Mister Fox View Post
Bass up until 250-300Hz is omnidirectional, so it doesn't matter where they are, as long as they take care of the absorbtion.

Be careful with this statement. It is partially true, but partially misleading. Sound below the Shroeder frequency (this varies based on geometry of the room iteslf, but 250-350hz is close usually), but that does not mean that basstraps can just go wherever. Bass trap placement is quite important. Moving them even an inch can result in huge differences.

Neil
#8
6th January 2012
Old 6th January 2012
  #8
Lives for gear
 
Jens Eklund's Avatar
 

Quote:
Originally Posted by amishsixstringe View Post
Be careful with this statement. It is partially true, but partially misleading. Sound below the Shroeder frequency (this varies based on geometry of the room iteslf, but 250-350hz is close usually), but that does not mean that basstraps can just go wherever. Bass trap placement is quite important.
+1 !

I completely missed that statement.

Placement of bass absorbers is paramount in order for them to work. It is crucial to know about the modal distribution of the offending frequencies in order to treat the successfully. Placing a bass absorber in a node or other area where the pressure variation is limited will render the absorber more or less useless (assuming pressure based type, the opposite is true more or less for velocity based types). I strongly advise the OP to read up on room modes (and perhaps SBIR as well) and different bass absorbing techniques in order to effectively deal with the problem (assuming bass related, modal or SBIR). For the frequency range above Schroeder; read up on some different control room design concepts, pick one, and learn how to use the ETC and start making measurements.
#9
6th January 2012
Old 6th January 2012
  #9
Moderator
 
narcoman's Avatar
 

take that stuff out of your room!

It's not healthy (lung damage, eyes and skin ) and won't do much acoustically. It's not dense enough OR thick enough to work at any of the lower or low mid frequencies.
#10
6th January 2012
Old 6th January 2012
  #10
Lives for gear
 
Jens Eklund's Avatar
 

#11
6th January 2012
Old 6th January 2012
  #11
Moderator
 
narcoman's Avatar
 

JLiRD808
Thread Starter
#12
6th January 2012
Old 6th January 2012
  #12
Lives for gear
 
JLiRD808's Avatar
 

Thread Starter
Quote:
Originally Posted by Jens Eklund View Post
Placement of bass absorbers is paramount in order for them to work. It is crucial to know about the modal distribution of the offending frequencies in order to treat the successfully. Placing a bass absorber in a node or other area where the pressure variation is limited will render the absorber more or less useless (assuming pressure based type, the opposite is true more or less for velocity based types). I strongly advise the OP to read up on room modes (and perhaps SBIR as well) and different bass absorbing techniques in order to effectively deal with the problem (assuming bass related, modal or SBIR). For the frequency range above Schroeder; read up on some different control room design concepts, pick one, and learn how to use the ETC and start making measurements.
Thanks for all the tips everyone!!

Any suggested readings on the room nodes? Alls I've heard is that I can play sine waves and listen for the loudest corners but that's about it.

I would def feel like an idiot if I built a couple more (bigger) bass traps and got minimal results again bcz Im not putting them in the right place. I've always just heard "corners" but I'm kinda limited on WHICH corners I can use. I rent so I cant mount much anything else on the ceiling so I cant use ceiling/wall corners :(
JLiRD808
Thread Starter
#13
6th January 2012
Old 6th January 2012
  #13
Lives for gear
 
JLiRD808's Avatar
 

Thread Starter
Quote:
Originally Posted by Glenn Kuras View Post
This part I am a little confused about. Are they 6" thick panels that are 2'x4'? And how much corner area have you covered?
They're actually about 5'x2' but yes, they are only 6" in the center as they are kinda pyramiding down in size. The outermost panel is 2' wide, 2nd is 18", 3rd is 12", 4th is 6". At 1.5" thick, the thickness of the four panels in the middle is 6" lol. It sounds ghetto but I originally just had them setup as 3" thick, then had some extra slivers laying around that I basically installed on the back of them

I guess these are the mistakes u make when u dont measure first
#14
6th January 2012
Old 6th January 2012
  #14
Gear addict
 

Basic tip 1 = Dont confuse time domain problems with frequency domain.

Basic tip 2 = Understand difference between pressure and velocity.

Basic tip 3 = Understand how velocity absorption works.

Basic tip 4 = Understand SBIR (Speaker Boundary Interface Response)

Carefully read the Acoustics Primer

Your posts indicate you still have some misconceptions which you need to resolve before you'll fully understand why your current solution isnt working optimally.

Sean
#15
6th January 2012
Old 6th January 2012
  #15
Gear maniac
 

Quote:
Originally Posted by Jens Eklund View Post
Like I said, others might have better knowledge on this end.
It's surprising to me that the much loved (standard) fibreglass actually "reflects" rather than absorbs compared to rockwool/ownens corner. This was new to me. Good that I didn't go that route while doing my drywall reconstruction and rather went for rockwool.


I also stand corrected on the bass absorber end. I didn't take into consideration the different frequencies/reflection points. So indeed placing both speakers and absorbers different can have a huge impact. If that is not possible, I think(!) only tuned absorbers can help.


Summary:
I'd say get rid of the fibreglass and rather get proper acoustic foam (here the thing with 4cm = absorb +900Hz should work), or a different more dense absorbtive material (rockwool/703/etc).

The rest was covered by the acoustic gurus.
#16
6th January 2012
Old 6th January 2012
  #16
Lives for gear
 
Jens Eklund's Avatar
 

Quote:
Originally Posted by Mister Fox View Post
It's surprising to me that the much loved (standard) fibreglass actually "reflects" rather than absorbs compared to rockwool/ownens corner.

...

Summary:
I'd say get rid of the fibreglass and rather get proper acoustic foam (here the thing with 4cm = absorb +900Hz should work), or a different more dense absorbtive material (rockwool/703/etc).
Hold our horses ...

How about downloading the PAC (Porous Absorber Calculator) and learn about the relationship between flow resistivity, thickness and absorption efficiency for velocity based absorbers at various frequencies before jumping to conclusions.
Quote
1
#17
6th January 2012
Old 6th January 2012
  #17
Gear Guru
 
Glenn Kuras's Avatar
 

Quote:
Originally Posted by JLiRD808 View Post
They're actually about 5'x2' but yes, they are only 6" in the center as they are kinda pyramiding down in size. The outermost panel is 2' wide, 2nd is 18", 3rd is 12", 4th is 6". At 1.5" thick, the thickness of the four panels in the middle is 6" lol. It sounds ghetto but I originally just had them setup as 3" thick, then had some extra slivers laying around that I basically installed on the back of them

I guess these are the mistakes u make when u dont measure first
Oh that is way to small. If you are going to straddle panels then make the over all panel 6" deep.

Last edited by Glenn Kuras; 6th January 2012 at 04:59 PM.. Reason: typo BIG TIME
#18
6th January 2012
Old 6th January 2012
  #18
Gear maniac
 

Quote:
Originally Posted by Jens Eklund View Post
Hold our horses ...

How about downloading the PAC (Porous Absorber Calculator) and learn about the relationship between flow resistivity, thickness and absorption efficiency for velocity based absorbers at various frequencies before jumping to conclusions.
Don't get me wrong here, sir. I'm just going my numbers/math I once learned with ideal values. I don't have my ring binder at hand where I resided all my projects and handwritten stuff, but I remember that I created a frequency/thickness relation list years ago just for personal reference.

Of course the PAC is more accurate, but you need more coefficients than just the wavelength of a certain frequency and the thickness (in mm) of the planned material, which in turn gives you a better info what will be absorbed, and what reflected.

Again... I only go my numbers that I remember - I'm mainly an audio engineer, no acoustician.
#19
6th January 2012
Old 6th January 2012
  #19
Lives for gear
 
amishsixstringe's Avatar
 

Quote:
Originally Posted by Mister Fox View Post

Again... I only go my numbers that I remember - I'm mainly an audio engineer, no acoustician.
Yes, you've made the pretty obvious...however, Jens IS an 'acoustician'.

You told the guy to get rid of the fiberglass and replace it with 703...which IS fiberglass. Also, thickness of an absorber in relation to wavelength is only one of many vectors that are considered when deciding absorption coefficients.

I'm not trying to rip on you or anything, I just don't want misinformation to be spread around the net.
Jens is a pro. It's usually not too easy to argue with him.

Neil
#20
6th January 2012
Old 6th January 2012
  #20
Lives for gear
 
Jens Eklund's Avatar
 

Quote:
Originally Posted by amishsixstringe View Post
I just don't want misinformation to be spread around the net.
+1 !
#21
7th January 2012
Old 7th January 2012
  #21
Gear maniac
 

Quote:
Originally Posted by amishsixstringe View Post
You told the guy to get rid of the fiberglass and replace it with 703...which IS fiberglass.
But it should be a more dense fibreglass compared to what the OP is using, no?


Quote:
Originally Posted by amishsixstringe View Post
Jens is a pro. It's usually not too easy to argue with him.
I agree on the false info part, so sorry from my side. Never intended to argue with an acoustician. No harm done, no harm taken.
#22
7th January 2012
Old 7th January 2012
  #22
Lives for gear
 
Jens Eklund's Avatar
 

Quote:
Originally Posted by Mister Fox View Post
But it should be a more dense fibreglass compared to what the OP is using, no?
The optimum flow resistivity (loosely related to density) of the porous material depends on the thickness of the panel. If thicker (always better than thinner); lower flowresistivity is better. Download the PAC and explore for yourself.

The conviction that denser wool (higher flowresistivity) is better, is one of the most common misconceptions. Usable FR values for velocity based absorbers is about 5 - 15 kPa*s/m² depending on thickness. If very thin, perhaps higher but a thin panel will never absorb anything but midrange and treble and this is seldom useful in studio design.
#23
7th January 2012
Old 7th January 2012
  #23
Gear Guru
 
Glenn Kuras's Avatar
 

Quote:
Originally Posted by Mister Fox View Post
But it should be a more dense fibreglass compared to what the OP is using, no?




I agree on the false info part, so sorry from my side. Never intended to argue with an acoustician. No harm done, no harm taken.
See the following
Rigid fiberglass density tests
#24
8th January 2012
Old 8th January 2012
  #24
Lives for gear
 
JulianFernandez's Avatar
 

So, let´s say that you can´t find FR values in your area (f*cking ISOVER branding), is it safer to just go with deep superchunks made of regular fluffy stuff? Thanks!
#25
8th January 2012
Old 8th January 2012
  #25
Lives for gear
 
amishsixstringe's Avatar
 

Quote:
Originally Posted by JulianFernandez View Post
So, let´s say that you can´t find FR values in your area (f*cking ISOVER branding), is it safer to just go with deep superchunks made of regular fluffy stuff? Thanks!
Safer for your health, or do you mean more effective acoustically?

Neil
#26
8th January 2012
Old 8th January 2012
  #26
Lives for gear
 
JulianFernandez's Avatar
 

Quote:
Originally Posted by amishsixstringe View Post
Safer for your health, or do you mean more effective acoustically?

Neil
Both!
JLiRD808
Thread Starter
#27
9th January 2012
Old 9th January 2012
  #27
Lives for gear
 
JLiRD808's Avatar
 

Thread Starter
Ok...Im gonna build some traps in the coming weeks...def at least 6" thick maybe up to 12".

Regarding the RFZ though, which test or measurement would show differences in a room with/without a well-treated RFZ? I always just thought it was the freq response. Is it waterfall? I thought waterfalls were only for low end. RT60? IR lol?

I just dont see a difference in freq response when I pull these panels down/put em back up. Thats what had me freaked out, like these panels were some bologna mystery fiberglass....half tempted to just buy "official" ones.

Thanks again!
#28
9th January 2012
Old 9th January 2012
  #28
Lives for gear
 

Quote:
Theory Two:
These panels are only 1.5" thick, not 2" thick. I have them wrapped and set off the walls about 1/4" with the lil hooks theyre on. Are they too thin to have an effect??? I would think they would at least tame SOME highs/upper mids.
hmmm .... if these are the wall 'broadband' absorbers ?? then there are a couple of issues that should be looked at.

1. The panel thickness.

Most every comment on this, is that, panels should be [at least] 4" thick.

2. Spaced off wall.

Again ... much guidance given on this, that the panel should be spaced EQUAL to the panel thickness.

so ... with 4" thick panels, there should be 4" of space between the wall surface and the back of the panel.

NOW !!!

I am NOT an acoustician ... I've been trying to learn this with regards to my current build.

I've raised this point so that the PROs can confirm/correct.

Hope this helps!
#29
9th January 2012
Old 9th January 2012
  #29
Lives for gear
 
Jens Eklund's Avatar
 

Quote:
Originally Posted by JLiRD808 View Post
Ok...Im gonna build some traps in the coming weeks...def at least 6" thick maybe up to 12".

Regarding the RFZ though, which test or measurement would show differences in a room with/without a well-treated RFZ? I always just thought it was the freq response. Is it waterfall? I thought waterfalls were only for low end. RT60? IR lol?

I just dont see a difference in freq response when I pull these panels down/put em back up. Thats what had me freaked out, like these panels were some bologna mystery fiberglass....half tempted to just buy "official" ones.

Thanks again!
So after all this time, my acoustic treatment is doing ALMOST NOTHING??!
#30
9th January 2012
Old 9th January 2012
  #30
Gear maniac
 

Hm.... this is a bit... strange and... dissapointing? I don't know where and how to put it elseway. Maybe it's due to the fact that I'm not as skilled in the building-studios section.


I did take a look at PAC again. Thankfully I found the flow resistance coefficient of SONOROCK (the rockwool material I'm using to build traps), which is ? 6 kPa ? s/m² (DIN EN ISO 29053). It turns out that the 10cm bass traps without spacing are best efficient (aka 1) at 800Hz and the 4cm wall traps I initially designed are best at 2,1kHz and up.

Porous Absorber Calculator - Results


If I add 6cm in terms of "airspace" (10cm deep frame mount for 4cm rockwool) for absorber or clouds, it looks a bit different, same with the bass traps (15cm deep frame, 10cm Sonorock). But it's still not what I expected, calculated back in the day.

Porous Absorber Calculator - Results


And here I added a cloud with 10cm spacing from the ceiling:

Porous Absorber Calculator - Results
Less spacing between the cloud and the ceiling produces better coefficients, but the ceiling is made of reed, gypsum and ingrain wallpaper (it's an old building).


Looks like I have to rethink everything as well. Unless acoustic foam produce better results. Then again... what about (e.g.) the "RealTraps" (MiniTraps) that Ethan Winer supports? According to the page presentation, they go as low as 80Hz? Then again, they're 3 1/4" in terms of thickness.


Am I on a wrong track here?
The drywall I built (standard 12,5mm, space between walls: 20cm, each inside wall treated with 4cm rockwool => airpocket of 12cm between rockwool sheets) is fairly "soundproof". And from crawling through the net, I always thought spacers are adding to absorbtion even with not as thick material (like 2" = 5cm, 4" = 10cm).

The frames are planned through already, and I think 10cm deep (with an inside size of the Sonorock pannels of 100cm x 62,5cm) with 1,8cm thick plywood framing should work. But do I really have to fill all of them with 10cm/4" sonorock wrapped in fabric? This is not how I initially planned it.



Here's another plot, this time with an added GOBO with 100mm porous material and 100mm airpocked "closest to rigid backing" (like the BBC designs). Though I think in this equation "rigid" means "solid walls" rather than 5mm MDF as absorber backing/membrane.

Porous Absorber Calculator - Results

To make things worse, here with the cloud 30cm away from the ceiling.

Porous Absorber Calculator - Results



Then again, I don't want to "soundproof" a room, I want to tune it and reduce the reflections (RT). I plan to add IKM ARC as final touch anyway.

New Reply Submit Thread to Facebook Facebook  Submit Thread to Twitter Twitter  Submit Thread to LinkedIn LinkedIn  Submit Thread to Google+ Google+ 
 
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
Flying_Dutchman / So much gear, so little time!
9
hey_mavis / So much gear, so little time!
0
Dr. Cuso / Remote Possibilities in Acoustic Music & Location Recording
17
Nick96 / Bass traps, acoustic panels, foam etc
4
Nevelicious / So much gear, so little time!
5

Forum Jump
 
Register FAQ Search Today's Posts Mark Forums Read

SEO by vBSEO ©2011, Crawlability, Inc.