1st February 2013
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#1 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | A Ear Opener..
Panel Size :- 4'x2'
Material :- compressed fibreglass
Thickness :- 4 inch
Room Size :- 22ft x 16ft x 9.8ft
More than two years ago, I had made a few panels of the above mentioned specs, & they were installed as :-
Two in each front corner
One behind each speaker on FW
At Ceiling Reflection Points
At sidewall reflection points
Wall/Ceiling Junction of sidewalls
And one tri-corner trap at each ceiling corner...
Now in a quest to make the room response even better, I have made 20 more of the exact same specs, which are due to be finished this evening.
Last evening, I had to remove all the previous panels from the room to change their covering fabric to match that of the new ones. Though I had no intention of having a listening session after removing them, I reluctantly went for it. And I was stunned as to what I was hearing....
Apart from a little weaker bass & some room-sound, EVERYTHING else was substantially better. All those midrange peaks I had in Vocals & Pianos were far less fatiguing & clean. No rough-edges or grain either.
I'm still not able to recover from what had happened. And now, at this stage I have got 30++ of them at my disposal, ready (but reluctant) to be installed.
Why on earth does that happen???
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1st February 2013
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#2 | | Gear Guru
Joined: Jul 2005 Location: Atlanta, GA
Posts: 14,267
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You should test the room with the following program to see before and after. Room EQ Wizard Tutorial - GIK Acoustics | |
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1st February 2013
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#3 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by Glenn Kuras  | I've always tested using REW with the panels in the room. This was never expected. Now I guess it's about time I do that...
But how can such a thing happen ?
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1st February 2013
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#4 | | Gear Guru
Joined: Jul 2005 Location: Atlanta, GA
Posts: 14,267
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I am not in the room to know. Needless to say though you may want to build a slat design on the front of those panels to retain/scatter/diffuse as much upper energy you can.
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1st February 2013
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#5 | | Lives for gear
Joined: Feb 2007 Location: Belgrade, Serbia
Posts: 1,316
| Quote:
Originally Posted by Jolida I've always tested using REW with the panels in the room. This was never expected. Now I guess it's about time I do that...
But how can such a thing happen ? | This is expected if you mount only absorption panels at first reflection points (especially in the small room)
Beside your LF treatment, which is basic prerequisite to good frequency response, you also need a diffuse sound field above 1000Hz in your room for good mix translations.
When you remove your treatment which was probably only absorptive, you reveal specular reflections from your walls. If you like this, then you need some liveliness in your room (after LF treatment) to feel good in it (as all other people)
One simple method I apply in my designs to solve problems like yours, is mounting binary diffusers over existing panel absorbers, to bring back reflections in room after successfull LF treatment.
For binary diffusers, you can find more here: DIY Binary Amplitude Diffuser anyone?
Some examples of binary diffusers (1D and 2D) you can find here: Studio Music World, Belgrade, Serbia | Facebook Muzicki Atelje Radivojevic | Facebook Studio Marjanovic, August 24, 2011 | Facebook
More expensive, but much better method (especially on this topic) is discussed here (similar principle but much, much more diffuse): MyRoom Acoustic Design
hope I help you 
__________________
B. Petrovic MyRoom Acoustics -- "Religion is belief in someone else’s experience. Spirituality is having your own experience." (Deepak Chopra) | |
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1st February 2013
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#6 | | Lives for gear
Joined: Aug 2003 Location: Cork Ireland
Posts: 8,671
| Impetuous
Jolida, so your room was fine and then you decided to treat it, which made it worse. OR your room was a bit wild, you treated it, but didn't go all the way with the tuning, leading to a tough listening experience, then you removed the treatment and now find the room lovely, apart from weak bass.
Ahem, I presume the logical flaws are obvious.
I think you will find the weakness in the bass is caused by nulls. Thus the bass without treatment is probably very uneven.
Your room seems big so perhaps room tone is not a bad thing. Next time don't kill so much of it.
e.g. place most of your traps in the corners. All the corners including ceiling wall ones.
When rooms are treated, much of the midrange mush goes away. This leads to great clarity, which can be simply too much. Many of use roll off the HF to compensate tonally. This results in much better translation.
DD
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1st February 2013
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#7 | | Lives for gear
Joined: May 2012 Location: Texas
Posts: 733
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It would be interesting to see an ETC of treated vs not.
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2nd February 2013
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#8 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by boggy This is expected if you mount only absorption panels at first reflection points (especially in the small room)
Beside your LF treatment, which is basic prerequisite to good frequency response, you also need a diffuse sound field above 1000Hz in your room for good mix translations.
When you remove your treatment which was probably only absorptive, you reveal specular reflections from your walls. If you like this, then you need some liveliness in your room (after LF treatment) to feel good in it (as all other people)
One simple method I apply in my designs to solve problems like yours, is mounting binary diffusers over existing panel absorbers, to bring back reflections in room after successfull LF treatment.
For binary diffusers, you can find more here: DIY Binary Amplitude Diffuser anyone?
Some examples of binary diffusers (1D and 2D) you can find here: Studio Music World, Belgrade, Serbia | Facebook Muzicki Atelje Radivojevic | Facebook Studio Marjanovic, August 24, 2011 | Facebook
More expensive, but much better method (especially on this topic) is discussed here (similar principle but much, much more diffuse): MyRoom Acoustic Design
hope I help you | Great info. Thanks a lot
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2nd February 2013
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#9 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by DanDan Jolida, so your room was fine and then you decided to treat it, which made it worse. OR your room was a bit wild, you treated it, but didn't go all the way with the tuning, leading to a tough listening experience, then you removed the treatment and now find the room lovely, apart from weak bass.
Ahem, I presume the logical flaws are obvious.
I think you will find the weakness in the bass is caused by nulls. Thus the bass without treatment is probably very uneven.
Your room seems big so perhaps room tone is not a bad thing. Next time don't kill so much of it.
e.g. place most of your traps in the corners. All the corners including ceiling wall ones.
When rooms are treated, much of the midrange mush goes away. This leads to great clarity, which can be simply too much. Many of use roll off the HF to compensate tonally. This results in much better translation.
DD | Yes I think the panels had sucked out the overall ambience. Now since I have around 30++ of them ready to be fixed, I am bringing in two at a time & listening to the improvement (or screw-up) to decide. At the moment, I have brought in around ten of them, all on the wall/ceiling junctions, & it's great so far. Now for the cloud, I am installing three 4'x2' next to one another. Is it compulsory that all the three should be touching each other, or can there be say a 1.5 inch gap between them? This I ask because I already have hooks at those points installed on the ceiling. If all of them need to be next to one another without any gap, then I may have to re-drill new holes in the ceiling.. The cloud will be around 10 inches off the ceiling.
Edit :- pic in the next post..
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2nd February 2013
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#10 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | 
Three panels on the ceiling..
Haven't heard their effect yet. Intend to do this evening...
Is the gap between the panels best to avoid or does it make no difference ?
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2nd February 2013
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#11 | | Gear maniac
Joined: Sep 2010 Location: Los Angeles, California
Posts: 256
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It could be the fabric you are using for the panels. What fabric is that?
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2nd February 2013
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#12 | | Lives for gear
Joined: Sep 2011
Posts: 645
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This is happen when you are treating only with absorbtion.
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2nd February 2013
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#13 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by HermanV It could be the fabric you are using for the panels. What fabric is that? | The earlier panels that gave the above mentioned problems had porous Jute fabric. Now the fabric has been changed to Polyester & it's not as porous as the earlier one. So far, ten panels (using new fabric) in the room, & results are positive. Have yet to see what the remaining 20 do..
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2nd February 2013
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#14 | | Lives for gear
Joined: Feb 2007 Location: Belgrade, Serbia
Posts: 1,316
| Quote:
Originally Posted by Jolida The earlier panels that gave the above mentioned problems had porous Jute fabric. .... | I have good experiences with jute...
Mount wooden slats over front side of jute fabric panels, in random order, I already wrote above, and you will solve your problems.
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2nd February 2013
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#15 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter |
Too late 
Have already discarded the Jute fabric & swapped it with a polyester one. This one is around 50% less porous than the Jute. As of now, with the ten panels mounted, no suck-off is eminent ( may be due to the fact that all are mounted only in the wall/ceiling junctions). Will have to listen to the cloud mounted tonight to see how much benefit vs compromise it has brought. Since the new fabric is mostly reflective, I doubt if it would do what the previous one did (hopefully)..
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2nd February 2013
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#16 | | Lives for gear
Joined: Feb 2007 Location: Belgrade, Serbia
Posts: 1,316
| Quote:
Originally Posted by Jolida Too late
Have already discarded the Jute fabric & swapped it with a polyester one. This one is around 50% less porous than the Jute...... | This will lead your panels to weak membrane absorber functionality which will works in not as easy predictable way... (dependent of material itself, and stretching force too)
Slats over highly air transparent fabric, like juta is better solution, from my experience.
[I wrote this because other gs visitors... for you it is (possibly) "too late" as you said, but it depends of your new impressions too...] | |
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2nd February 2013
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#17 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by boggy This will lead your panels to weak membrane absorber functionality which will works in not as easy predictable way... (dependent of material itself, and stretching force too)
Slats over highly air transparent fabric, like juta is better solution, from my experience.
[I wrote this because other gs visitors... for you it is (possibly) "too late" as you said, but it depends of your new impressions too...] | You're right. The fabric is stretched very tight, & feels like a limp membrane when tapped...
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2nd February 2013
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#18 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | 
With the cloud & corner traps (floor to ceiling) installed, the performance is the worst I have heard in my room ever. Nothing but dry & coarse Mids & Mid-bass. No stage, No ambience, No detail. Oh Damn !!! Seems like the bass is looking this bad because of the other parameters going down in spl...
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2nd February 2013
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#19 | | Lives for gear
Joined: Aug 2003 Location: Cork Ireland
Posts: 8,671
| Gaps
I see no problem with the gaps. I often include six inch gaps.
If you are getting reflections (visible on ETC) from your fabric, a simple angle will solve that. I use plastic cable ties to hang traps. Easily adjustable.
DD
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2nd February 2013
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#20 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by DanDan I see no problem with the gaps. I often include six inch gaps.
If you are getting reflections (visible on ETC) from your fabric, a simple angle will solve that. I use plastic cable ties to hang traps. Easily adjustable.
DD | :( terrible performance
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4th February 2013
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#21 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by Glenn Kuras | If due to excess absorption, I have to install Slats, as suggested by u, is there any specific thickness & spacing between them to follow, or is it just random..??
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4th February 2013
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#22 | | Gear Guru
Joined: Jul 2005 Location: Atlanta, GA
Posts: 14,267
| Quote:
Originally Posted by Jolida If due to excess absorption, I have to install Slats, as suggested by u, is there any specific thickness & spacing between them to follow, or is it just random..?? | DIY Binary Amplitude Diffuser anyone? | |
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4th February 2013
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#23 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by Glenn Kuras | Are these Slats as well..??  | |
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4th February 2013
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#24 | | Gear Guru
Joined: Jul 2005 Location: Atlanta, GA
Posts: 14,267
| Quote:
Originally Posted by Jolida | Hard to say without being in the room, but kind of looks like them. Here is a commercial brand, but talks about the over all concept. GIK Acoustics Scatter Plate Product Video | |
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4th February 2013
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#25 | | Lives for gear
Joined: Feb 2007 Location: Belgrade, Serbia
Posts: 1,316
| Quote:
Originally Posted by Jolida | Yes, they are, but not random as binary diffuser.  | |
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4th February 2013
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#26 | | Gear addict
Joined: Jun 2011
Posts: 310
Thread Starter | Quote:
Originally Posted by boggy Yes, they are, but not random as binary diffuser. | Agreed. But in a binary diffusor, the Math is involved. Unlike the pic I posted. That being said, since the main focus at this moment on my side is to retain sufficient amount of HF energy in the room due to over-absorption, will the design I pictured be sufficient in my case???
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4th February 2013
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#27 | | Gear addict
Joined: Nov 2010
Posts: 306
| Quote:
Originally Posted by boggy Yes, they are, but not random as binary diffuser. | I'm interestd on this subject. So it's better to add some slats in a complete random fashion or maybe use some sequences that you can find on acoustic books?
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4th February 2013
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#28 | | Lives for gear
Joined: Feb 2007 Location: Belgrade, Serbia
Posts: 1,316
| Quote:
Originally Posted by Jolida Agreed. But in a binary diffusor, the Math is involved. Unlike the pic I posted. That being said, since the main focus at this moment on my side is to retain sufficient amount of HF energy in the room due to over-absorption, will the design I pictured be sufficient in my case??? | Periodic slats cause other interfernces, which also may be unacceptable for you. Quote:
Originally Posted by blizt I'm interestd on this subject. So it's better to add some slats in a complete random fashion or maybe use some sequences that you can find on acoustic books? | There is a gs thread, listed above, where you can find more informations about making binary diffuser, than in common "acoustics books".
Sent from my ST18i using Tapatalk
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4th February 2013
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#29 | | Lives for gear
Joined: Aug 2003 Location: Cork Ireland
Posts: 8,671
| Random
blitz and Jol, the patterns show by boggy are attempts at being random, but reliably so, by using maths.
You could try random by eye also, there is really very little chance of not achieving your goal. A client of mine has created scattering surfaces using 'wany edged' wood. Rough wood from the sawmill. Not mathematical but it certainly looks random.
The big plus of boggy's sequences are that they use just one size of lath.
The much simpler Newell 543 sequence requires three different sizes.
But remember this is scalable within reason. You might be able to buy finished laths 100, 80, 60, mm. Recording Studio Design - Philip Newell - Google Books
EDIT, boggy that's a lovely looking room. Bright and welcoming visually. What is the sequence in use there?
DD
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4th February 2013
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#30 | | Lives for gear
Joined: Feb 2007 Location: Belgrade, Serbia
Posts: 1,316
| Quote:
Originally Posted by DanDan .........
EDIT, boggy that's a lovely looking room. Bright and welcoming visually. | Thank you very much Dan. Quote:
Originally Posted by DanDan What is the sequence in use there?
.... | Maximum Length Sequence. It is the same sequence as I give to gearslutz members long ago...  | |
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