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Knauf Acoustic Slab Ultimate - a couple questions
Old 16th January 2020
  #1
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Knauf Acoustic Slab Ultimate - a couple questions

Hi,

I am going to add some acoustic treatment to my home studio and have been suggested the following glass mineral wool slab by an acoustic consultant. I am basically going to make broadband absorption panels by buying two sets of the slabs (total 12 slabs, each 50 mmm thick) as follows:

Two 6" thick panels: one each for left and right side of the seating position
Two 4" thick panels: for front wall corners behind speakers
One 2" thick panel: for ceiling right above mixing desk
One 2" thick panel: for rear wall exactly behind my seating position

I will be making wooden frames and wrapping them with proper acoustic fabric.

https://www.knaufinsulation.ae/produ...-slab-ultimate

https://pim.knaufinsulation.com/file...984.1578991050

I have a couple of quick questions:

1. Does the above plan look correct? My room size is 13 ft. x 11.8 ft. x 9 ft. It has one single bed with mattress and a small shelf, apart from the typical home studio desk and stuff.

2. Is the above glass mineral wool by Knauf safe for home use? Any adverse effects on health in short and long term? I have a family with a young kid, so I want to take proper precautions. I am mainly worried about effects after installing the panels. Of course, I will not make the panels myself and will get help from a local carpenter.

I don't have much time and aim to make room even near-to-perfect and want to get it to sound better than it does now. It does not sound bad right now, but hopefully this treatment will strike the right balance between cost and performance.

Thank you so much for your help.

Last edited by LoveEnigma; 16th January 2020 at 06:22 AM.. Reason: typo
Old 16th January 2020
  #2
Old 16th January 2020
  #3
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Quote:
Originally Posted by Jens Eklund View Post
Sorry, but I don't know what to interpret here with respect to the questions I am asking.

I already have more than 3" for front and side walls, and thicker is usually better, so what's the point? Do you mean I should avoid the difference in thickness between side walls (6") and front corners (4")? Do you mean I should go more thicker for rear wall? Please clarify.

Also, I would appreciate an answer to the second question if anyone can. I am a bit more concerned about that.

Last edited by LoveEnigma; 16th January 2020 at 10:20 AM.. Reason: more clarity
Old 16th January 2020
  #4
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Quote:
Originally Posted by LoveEnigma View Post
Sorry, but I don't know what to interpret here with respect to the questions I am asking.

I already have more than 3" for front and side walls, and thicker is usually better, so what's the point? Do you mean I should avoid the difference in thickness between side walls (6") and front corners (4")? Do you mean I should go more t for rear wall? Please clarify.
In your post you wrote:

Quote:
One 2" thick panel: for ceiling right above mixing desk
One 2" thick panel: for rear wall exactly behind my seating position
Quote:
Also, I would appreciate an answer to the second question if anyone can. I am a bit more concerned about that.
It is safe.


Enjoy!
Old 16th January 2020
  #5
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Quote:
Originally Posted by avare View Post
In your post you wrote:



It is safe.


Enjoy!
Thank you for the confirmation.
Old 16th January 2020
  #6
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Quote:
One 2" thick panel: for ceiling right above mixing desk
One 2" thick panel: for rear wall exactly behind my seating position
Okay, so does that mean I should go with at least 3" or 4" thickness for even ceiling and rear wall? I am worried about the weight and mounting.
Old 16th January 2020
  #7
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Quote:
Originally Posted by LoveEnigma View Post
Okay, so does that mean I should go with at least 3" or 4" thickness for even ceiling and rear wall?
Did you read the post that Jens linked to? Especially the paragraph that starts:
Quote:
Originally Posted by Jens Eklund View Post
I always try to make the first order reflection panels at least about 8” but often 14-20” if possible.
At least 8" but 14-20" if possible is his way of saying that 2" is not enough. 2" is enough to treat higher frequencies but not low-mid and bass frequencies. Jens and avare are trying to steer you away from having a muffled, muddy sounding room.
Old 16th January 2020
  #8
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Quote:
Originally Posted by Starlight View Post
Did you read the post that Jens linked to? Especially the paragraph that starts:


At least 8" but 14-20" if possible is his way of saying that 2" is not enough. 2" is enough to treat higher frequencies but not low-mid and bass frequencies. Jens and avare are trying to steer you away from having a muffled, muddy sounding room.
Well put.
Old 16th January 2020
  #9
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Quote:
Originally Posted by LoveEnigma View Post
Okay, so does that mean I should go with at least 3" or 4" thickness for even ceiling and riear wall? I am worried about the weight and mounting.
Yes. What weight? 6 kilos? there are drywall fasteners rated for 25 kilos and they about the smallest sold. That is the weight for 6" deep panels.
Old 16th January 2020
  #10
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Quote:
Originally Posted by Starlight View Post
Did you read the post that Jens linked to? Especially the paragraph that starts:


At least 8" but 14-20" if possible is his way of saying that 2" is not enough. 2" is enough to treat higher frequencies but not low-mid and bass frequencies. Jens and avare are trying to steer you away from having a muffled, muddy sounding room.
Yes, I did read that, but the problem for me is will be beyond my budget to go for >= 8" panels everywhere.

If I do what I have mentioned, will it have a negative impact?

I read avare's suggestion somewhere that 2" is OK for ceiling (with 2" spacing).
Old 16th January 2020
  #11
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Quote:
Originally Posted by LoveEnigma View Post
If I do what I have mentioned, will it have a negative impact?

I read avare's suggestion somewhere that 2" is OK for ceiling (with 2" spacing).
Your room will be muddy as Starlight clearly wrote. I did not recommed 2" and 2" with 48 kg/m³ material which is what you linked.

Do not read thinggs out of context.
Old 16th January 2020
  #12
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Quote:
Originally Posted by avare View Post
Your room will be muddy as Starlight clearly wrote. I did not recommed 2" and 2" with 48 kg/m³ material which is what you linked.

Do not read thinggs out of context.

Okay, but what I read about 2" for ceiling seemed to be a general suggestion to me. Sorry if that caused any misunderstanding.


1. If I choose 4" thick, 48 kg/m3 or better density, for side walls, front corners, rear wall and ceiling, will that be a good idea? I do understand 8" is the preferred recommendation, but it won't fit my budget. And I can make a maximum of 6 panels and I want to strike the right balance with a decent performance.

2. Is Rockwool Roxul Safe N Silent a good alternative to Knauf one I have mentioned? The reason I am asking is because it is available cheaper, with higher density options and more slabs per pack. Not that I won't too much density as it would cause HF reflection, but I am targetting 40-60 Kg/m3. Also, Roxul mentions it to be safe, so just want to confirm if it is as safe or better than Knauf one.

Last edited by LoveEnigma; 16th January 2020 at 01:13 PM.. Reason: typo
Old 16th January 2020
  #13
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LoveEnigma, make as many 8" panels as you can afford. It will improve the sound a bit and these will be panels that you can add to when you can afford it rather than have to throw away and start again. Do what you can now and keep saving your pennies for the future!
Old 16th January 2020
  #14
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Quote:
Originally Posted by Starlight View Post
LoveEnigma, make as many 8" panels as you can afford. It will improve the sound a bit and these will be panels that you can add to when you can afford it rather than have to throw away and start again. Do what you can now and keep saving your pennies for the future!
Thank you for the suggestion.

I can definitely consider this suggestion, but what would be the most important points to treat in case I can go for:

2 x 8" panels (4 x 2 ft.): Side walls, right?
4 x 8" panels (4 x 2 ft.): Side walls + front corners, right?
6 x 8" panels (4 x 2 ft.): Side walls + front corners + rear wall + ceiling, right?

Does this sound correct?

Next question is if I only have side walls treated, will it help me with some modal issues? Not treating corners will not help with very low (~ 100 Hz) frequencies, right?
Old 16th January 2020
  #15
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I would suggest starting with 3 panels to cover the first reflection points: overhead and on the side walls. The rear wall can be a first reflection point zone, so there would be next in my book. Avare and Jens are both way more qualified than I to advise. After that I would aim to build corner traps to fill all four corners, floor to ceiling. I imagine this may be a number of steps for you, so build as many as you are able to and always think (left-right) symmetry, ie. match on the left what you have on the right. If you have an odd number of traps (after the three for first reflection points) you could place the odd one in the middle of the rear wall.

Because higher frequencies are directional, that is why we turn our monitors to face us, having the audio centre (usually a place between the tweeter and mid-range (if your monitors have 3 speakers apiece) or woofer (if they have two) at ear level. As frequencies get lower they cecome less directional, right down to bass frequencies being omnidirectional. That is why first reflection points mainly handle mid to high frequencies and bass traps can seemingly be everywhere. Any further (into the theory side of acoustics) and you will benefit by reading about room modes.
Old 16th January 2020
  #16
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Quote:
Originally Posted by LoveEnigma View Post
Yes, I did read that, but the problem for me is will be beyond my budget to go for >= 8" panels everywhere.
Do 4" and 4" with the linked material.
Old 16th January 2020
  #17
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I know nothing about Safe N Silent.
Old 16th January 2020
  #18
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Quote:
Originally Posted by Starlight View Post
I would suggest starting with 3 panels to cover the first reflection points: overhead and on the side walls. The rear wall can be a first reflection point zone, so there would be next in my book. Avare and Jens are both way more qualified than I to advise. After that I would aim to build corner traps to fill all four corners, floor to ceiling. I imagine this may be a number of steps for you, so build as many as you are able to and always think (left-right) symmetry, ie. match on the left what you have on the right. If you have an odd number of traps (after the three for first reflection points) you could place the odd one in the middle of the rear wall.

Because higher frequencies are directional, that is why we turn our monitors to face us, having the audio centre (usually a place between the tweeter and mid-range (if your monitors have 3 speakers apiece) or woofer (if they have two) at ear level. As frequencies get lower they cecome less directional, right down to bass frequencies being omnidirectional. That is why first reflection points mainly handle mid to high frequencies and bass traps can seemingly be everywhere. Any further (into the theory side of acoustics) and you will benefit by reading about room modes.
Thank you for your detailed reply.

I will consider the order of preference and symmetry. But I wonder why front corners are not as important as side walls and ceiling. Aren't these the corners that would cause more low frequency problems? This was my assumption and so I was considering 4 panels with 2 for sides and 2 for corners and just ignored the ceiling and rear wall.

And the thing with me about acoustics is that I know some decent, surface level stuff, mainly by reading online material and forums like this, but I never really feel like going too deep in it. I know it helps to know, but I want to produce music after all. That's the main goal for me. I don't want to get too possessive about these things, but I know I am being right now. I just want to move on and get some decent treatment done in my current non-treated room so that is sounds significantly better.
Old 16th January 2020
  #19
Gear Head
 

Quote:
Originally Posted by avare View Post
Do 4" and 4" with the linked material.
Sorry, but what's linked material?
Will 6" be better than the above combination in case I cannot manage it?

If I get 2 Knauf kits, I get 12 slabs, each 2" thick. If I do 6" thick panels, I can make 4 of them, of which 2 can go on sides, one on ceiling and one on rear wall. Front corners would be left out in that case. Will this be a good starting point and an acceptable alternative to 8" inch panels?

One more potential concern for me is on the left wall there is a window and the first reflection point of this wall lies between exactly where the window starts and 1 foot away from it.

Attached is a rough mock up of the room.
Attached Thumbnails
Knauf Acoustic Slab Ultimate - a couple questions-studio-room.png  
Old 16th January 2020
  #20
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Quote:
Originally Posted by LoveEnigma View Post
Sorry, but what's linked material?
Will 6" be better than the above combination in case I cannot manage it?

If I get 2 Knauf kits, I get 12 slabs, each 2" thick. If I do 6" thick panels, I can make 4 of them, of which 2 can go on sides, one on ceiling and one on rear wall. Front corners would be left out in that case. Will this be a good starting point and an acceptable alternative to 8" inch panels?

One more potential concern for me is on the left wall there is a window and the first reflection point of this wall lies between exactly where the window starts and 1 foot away from it.

Attached is a rough mock up of the room.
The links you put in the first post. 4" and 4" is just as good as less dense material.
n
The first reflection points, including the ceiling, are the first to do. They will absorb down to the modal range. Plus you probably already have bass traps as in membrane absorbers in your walls. It is called drywall.

No figs were attached.
Old 16th January 2020
  #21
Gear Head
 

Quote:
Originally Posted by avare View Post
The links you put in the first post. 4" and 4" is just as good as less dense material.
n
The first reflection points, including the ceiling, are the first to do. They will absorb down to the modal range. Plus you probably already have bass traps as in membrane absorbers in your walls. It is called drywall.

No figs were attached.
Oh, silly me. Thanks again. By 4" and 4" do you mean 4" panel thickness plus 4" air gap? Why not 6" plus 2" gap?

Okay, that's what I was not knowing. I felt corner traps would be absorbing the lows (when done appropriately, of course). So, I will focus on 1st reflection points now.

Sorry, but I can see the attached image. I just attached it directly to the post as attachment.
Old 16th January 2020
  #22
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Quote:
Originally Posted by LoveEnigma View Post
Oh, silly me. Thanks again. By 4" and 4" do you mean 4" panel thickness plus 4" air gap? Why not 6" plus 2" gap?

Okay, that's what I was not knowing. I felt corner traps would be absorbing the lows (when done appropriately, of course). So, I will focus on 1st reflection points now.
The material has the right gas flow resistance at 4". Are you trying to get an acoustics course surreptitously?

They both absorb low frequencies. Corner absorbers are more efficient.
Old 17th January 2020
  #23
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Quote:
Originally Posted by avare View Post
The material has the right gas flow resistance at 4".

They both absorb low frequencies. Corner absorbers are more efficient.
Okay, thanks. So, ideally corner traps/panels are also needed.

Quote:
Are you trying to get an acoustics course surreptitously?
Haha, not at all. Is it even possible? I am just trying to get some help, implement the suggestions, be grateful of everyone who helped and wish them best, and then move on. As I said before, I don't want to get too deep into acoustics. I want to focus on producing music and want to get the room treatment sorted at the earliest.
Old 17th January 2020
  #24
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I am thinking about the following approach from cost and effectiveness point of view and based on my understanding of suggestions:

Material: Knauf Acoustic Ultimate, 48 Kg/m3, total 12 slabs, each 4 ft. x 2 ft., 2" thick. I can make total 6, 4" panels.

4" panels with 4" air gap for each: side walls, front wall to wall corners (45 deg.), ceiling above mix position, and rear wall directly behind the mix position.

Could anyone please suggest if this sounds like a reasonable compromise and I would not do more harm than good by doing this?

The reason is I want to finish this task in one go, as I am not sure later I would be able to do it or save up for it. Music is not my profession, and responsibilities are increasing on personal front - just like for anyone.

Thank you.

EDIT: I am not disrespecting any suggestion here, especially the 8" panels one, but trying to strike a good compromise.

Last edited by LoveEnigma; 17th January 2020 at 06:44 AM.. Reason: in EDIT
Old 17th January 2020
  #25
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Quote:
Originally Posted by LoveEnigma View Post
Okay, thanks. So, ideally corner traps/panels are also needed.
Ideally yes,but you are not in an ideal situation. The wall and ceiling absorbers will provide low end absorption. There are people who have put absorbers in all eight corners. You are not one of them.
Old 17th January 2020
  #26
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Quote:
Originally Posted by avare View Post
The wall and ceiling absorbers will provide low end absorption.
Okay, but you also said that corner absorbers will be more efficient, so I thought if I should consider installing them too as a priority.
Old 17th January 2020
  #27
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Quote:
Originally Posted by LoveEnigma View Post
Okay, but you also said that corner absorbers will be more efficient, so I thought if I should consider installing them too as a priority.
You already have some low end absorption. You have nothing for ISD.

You want to think abbout making half the traps 1´wideo. You then can have 4 sets of absorbers 3´by 4´.

2 side walls
1 ceiling
1 back wall

I do not know your construction budget. If you want to increase the back wall absorption make smaller absorbers and spread them out. Eg. 12 1´ by 1´ absorbers in a checkerboard pattern,
Old 17th January 2020
  #28
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Quote:
Originally Posted by avare View Post
You already have some low end absorption. You have nothing for ISD.

You want to think abbout making half the traps 1´wideo. You then can have 4 sets of absorbers 3´by 4´.

2 side walls
1 ceiling
1 back wall

I do not know your construction budget. If you want to increase the back wall absorption make smaller absorbers and spread them out. Eg. 12 1´ by 1´ absorbers in a checkerboard pattern,
Thank you. I am getting lost in the wide variety of possibilities to be honest.

I think this is the best possibility for me right now: 6 panels, 4" thick panels with 4" airgap, at the following positions. I will make panels such that I can stuff more (4") material later.

1. Side walls
2. Front wall-wall corners (mid way only, not completely from ground to ceiling)
3. Ceiling
4. Rear Wall

So, please suggest if this would be a reasonable compromise. My room would sound much better with the above, right?

Last edited by LoveEnigma; 17th January 2020 at 11:12 AM.. Reason: updated the proposal
Old 17th January 2020
  #29
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Quote:
Originally Posted by LoveEnigma View Post
Thank you. Let me see if I can do that. I am getting lost in the wide variety of possibilities to be honest.

If I were to do 6" OR 8" thick, 4 x 2 ft. panels for each of the following positions, would it be the end of the story?

1. Side walls
2. Front wall-wall corners (mid way only, not completely from ground to ceiling)
3. Ceiling
4. Rear Wall

If I go with 6", I can save some cost by getting only 3 x Knauf Acoustic Ultimate slab boxes. For 8", I would need 4 x Knauf Acoustic Ultimate Slab.

So, please suggest.
FORGET THE CORNER ABSORBERS! The 3" material does not have the proper GFR for use in 6" total depth absorbers. With 6" absorbers you still need 4" thick insulation.
Old 17th January 2020
  #30
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Quote:
Originally Posted by avare View Post
FORGET THE CORNER ABSORBERS! The 3" material does not have the proper GFR for use in 6" total depth absorbers. With 6" absorbers you still need 4" thick insulation.
Thanks for your reply, but I edited the post, apparently after you quoted me. Could you please check my previous post again? I appreciate your help.
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