Diffusion/scattering specs of Alpha panels

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Mike-48

Diffusion/scattering specs of Alpha panels
« on: 7 Apr 2021, 02:11 am »
At what frequency range is there useful scattering from the Alpha panels? Can't find anything on the site.

JWL.GIK

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Re: Diffusion/scattering specs of Alpha panels
« Reply #1 on: 7 Apr 2021, 01:44 pm »
Binary-style diffusion like in the Alphas is trickier to pin down spec wise because there are many things happening, it's a gradual transition and blend of both absorption and diffusion. These are audible throughout the mids & highs, they just sound different than either absorption or diffusion alone. GIK has not had the diffusion performance tested, there aren't many places set up to test diffusion, but it could happen at some point.

One of the benefits of this is that the panel is inherently balanced, so you can treat an entire room with Alphas and it will sound wonderful. It also means the Alphas are a more broadband device than a dedicated diffusor, so even though they have less total diffusion than a QRD style diffusor, they are also improving things in other ways.


jriggy

Re: Diffusion/scattering specs of Alpha panels
« Reply #2 on: 7 Apr 2021, 02:27 pm »
I wish the attached panel for the diffusion properties was thinner to allow more of the bass absorption properties of the thicker offerings to stay as affective as without the attached diffusion panel.

emailtim

Re: Diffusion/scattering specs of Alpha panels
« Reply #3 on: 29 May 2021, 03:15 am »
Binary-style diffusion like in the Alphas is trickier to pin down spec wise because there are many things happening, it's a gradual transition and blend of both absorption and diffusion. These are audible throughout the mids & highs, they just sound different than either absorption or diffusion alone. GIK has not had the diffusion performance tested, there aren't many places set up to test diffusion, but it could happen at some point.

One of the benefits of this is that the panel is inherently balanced, so you can treat an entire room with Alphas and it will sound wonderful. It also means the Alphas are a more broadband device than a dedicated diffusor, so even though they have less total diffusion than a QRD style diffusor, they are also improving things in other ways.

Which Alpha scatter plate sonically performs the best (1D, 2D-a, 2D-b) ? 

Why would one choose one of the 3 versions of Alphas over the other versions (other than visual aesthetics) ?

Are any of the 3 targeted towards specific applications over the other versions ?  If so, what ?

Thanks much.

1D

2D-a

2D-b

« Last Edit: 29 May 2021, 05:24 pm by emailtim »

jriggy

Re: Diffusion/scattering specs of Alpha panels
« Reply #4 on: 29 May 2021, 01:44 pm »
When I got assistance from someone a GIK they recommended I go with either of the 2D options because of my high ceiling that goes from 9ft sloping up to over 14 feet. Said the 2D will scatter upward also and be good for the raised ceiling. I went with 2D(b) and unfortunately ended up not liking their affect almost everywhere. Maybe it’s just the choice of 2D(b) over the 2D(a), as the 2D(a) is what you see in most user pics around the web.

 But if you have standard 8 or 9 ft ceilings I’d go with the 1D, as I also have some panels with the 1D scatter plate option and they sound better (a more natural sounding presentation) in my space  :dunno:

emailtim

Re: Diffusion/scattering specs of Alpha panels
« Reply #5 on: 29 May 2021, 06:03 pm »
.... I went with 2D(b) and unfortunately ended up not liking their affect almost everywhere. Maybe it’s just the choice of 2D(b) over the 2D(a), as the 2D(a) is what you see in most user pics around the web.

 But if you have standard 8 or 9 ft ceilings I’d go with the 1D, as I also have some panels with the 1D scatter plate option and they sound better (a more natural sounding presentation) in my space  :dunno:

Thanks for the feedback.  I also noticed the 2D(b) doesn't get much air-time on the web.  I thought that it maybe in part due to its later arrival than the originally released 1D and 2D(a) models.

Hope some folks from GIK can chime in with some specifics.

RonP

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Re: Diffusion/scattering specs of Alpha panels
« Reply #6 on: 30 May 2021, 12:54 pm »
I recently ordered some 2Ds. I forget which pattern I have on order but I was told the 2D patterns are the same acoustically by GIK.

HTH


Desertpilot

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Re: Diffusion/scattering specs of Alpha panels
« Reply #7 on: 2 Jun 2021, 03:19 pm »
I have three 6A (6 inch) 2D-a (dots and dashes) panels along my front wall (behind L, C, R speakers).  I also have a vaulted ceiling.  I have the same question, what are these panels doing?  GIK website shows peak absorption at 200Hz and good absorption between 125Hz and 800Hz.  This is entirely mid range for my speakers (Spatial Audio X3).  Absorption drops off rapidly from 1,000Hz and higher.  I have to assume diffusion/scattering is happening in this area (AMT Driver, in my case).

GIK says:  "...allows low frequency waves to pass through to the fiberglass panel for low end absorption".  What constitutes low frequency?  The mid range area 125Hz to 800Hz?  Or, lower than 125Hz?

GIK says:  "...behind dipole speakers to round off sharp reflections".  Good news for me as I own dipole speakers.

GIK says:  "...can be used on the front or back walls and rear sidewalls to keep the reverberation better mixed and the room lively".  I have mine on the front wall directly behind my speakers.  I see a lot of folks use this model 2D-a in their listening rooms.

I wish GIK provided more in depth information about what these panels are doing.

Marcus

youngho

Re: Diffusion/scattering specs of Alpha panels
« Reply #8 on: 2 Jun 2021, 04:20 pm »
Hi, I'm not speaking for GIK or their specific products, but there are products using similar concepts from other companies. See, for example:

https://kineticsnoise.com/interiors/tad.html
https://www.rpgacoustic.com/bad-panel/
https://www.realacoustixllc.com/fast-panel

There is some overlapping data:
https://www.rpgacoustic.com/documents/2016/08/bad-panel_data-sheet.pdf/
https://kineticsnoise.com/downloads/data-sheets/tad.pdf

One comparison: https://kineticsnoise.com/downloads/analysis/tad-panels.pdf
And commentary: https://www.realacoustixllc.com/blog-3/2016/12/1/the-gud-the-bad-and-the-fast

As you can see, the amount of scattering seems to be modest, so I thought the Real Acoustix comments that I linked were apropos.

With regards to Tim's question, I believe that the use of 1D vs 2D diffusion depends very much on placement and goals. For example, if you have significant absorption present on the front and back walls, but if the side walls are reflective, then you might want 1D on the ceiling to diffuse laterally towards to the reflective surfaces (discussed in Floyd Toole's book with respect to IACC), as opposed to 2D where a significant fraction gets absorbed. If you have an absorptive ceiling and floor, then again it's likely that 1D diffusion on the sidewalls would be preferred. Hope that makes sense,

Young-Ho

youngho

Re: Diffusion/scattering specs of Alpha panels
« Reply #9 on: 2 Jun 2021, 04:22 pm »
Oops, meant to modify my previous post, but I added a link from RPG showing comparisons between different thicknesses of their BAD product.

Young-Ho

Hi, I'm not speaking for GIK or their specific products, but there are products using similar concepts from other companies. See, for example:

https://kineticsnoise.com/interiors/tad.html
https://www.rpgacoustic.com/bad-panel/
https://www.realacoustixllc.com/fast-panel

There is some overlapping data:
https://www.rpgacoustic.com/documents/2016/08/bad-panel_data-sheet.pdf/ and https://www.rpgacoustic.com/documents/2017/06/bad-panel_acoustical-data.pdf/
https://kineticsnoise.com/downloads/data-sheets/tad.pdf

One comparison: https://kineticsnoise.com/downloads/analysis/tad-panels.pdf
And commentary: https://www.realacoustixllc.com/blog-3/2016/12/1/the-gud-the-bad-and-the-fast

As you can see, the amount of scattering seems to be modest, so I thought the Real Acoustix comments that I linked were apropos.

With regards to Tim's question, I believe that the use of 1D vs 2D diffusion depends very much on placement and goals. For example, if you have significant absorption present on the front and back walls, but if the side walls are reflective, then you might want 1D on the ceiling to diffuse laterally towards to the reflective surfaces (discussed in Floyd Toole's book with respect to IACC), as opposed to 2D where a significant fraction gets absorbed. If you have an absorptive ceiling and floor, then again it's likely that 1D diffusion on the sidewalls would be preferred. Hope that makes sense,

Young-Ho

Mike-48

Re: Diffusion/scattering specs of Alpha panels
« Reply #10 on: 2 Jun 2021, 07:28 pm »
Young-Ho,  Thanks for all that! I haven't read it all yet, but I will. It's surely quite pertinent to my question.

emailtim

Re: Diffusion/scattering specs of Alpha panels
« Reply #11 on: 2 Jun 2021, 07:40 pm »
Hi, I'm not speaking for GIK or their specific products, but there are products using similar concepts from other companies. See, for example:

https://kineticsnoise.com/interiors/tad.html
https://www.rpgacoustic.com/bad-panel/
https://www.realacoustixllc.com/fast-panel

There is some overlapping data:
https://www.rpgacoustic.com/documents/2016/08/bad-panel_data-sheet.pdf/
https://kineticsnoise.com/downloads/data-sheets/tad.pdf

One comparison: https://kineticsnoise.com/downloads/analysis/tad-panels.pdf
And commentary: https://www.realacoustixllc.com/blog-3/2016/12/1/the-gud-the-bad-and-the-fast

As you can see, the amount of scattering seems to be modest, so I thought the Real Acoustix comments that I linked were apropos.   ...

Young-Ho

Thanks for the links.  I will read the ones that I haven't yet. 

The designer of the patented RPG BAD panel did a rebuttal paper to the one published by Kinetics comparing the performance of both products.  It can be download from here.  The gist of the rebuttal appears to be how even the power distribution is between the 2 design patterns.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiax6rw0_nwAhXWrZ4KHdNyAkoQFjAAegQIBBAD&url=https%3A%2F%2Fwww.gearslutz.com%2Fboard%2Fattachments%2Fbass-traps-acoustic-panels-foam-etc%2F169439d1272032980-rpg-bad-panel-detailed-plans-kinetics_absorber_diffuser_panel-vs-bad.pdf&usg=AOvVaw2ubw10eHt3DdT7ldp9OXqr

Here is a multi-layer absorber / reflection calculator for those that are interested.  Modeling the "Perforated Panel" layer over the "Porous Absorbent" layer gives you an idea of what is going on between a straight absorber panel and a scatter plate panel, but doesn't give much indication as to the scatter qualities. 

Adding a scatter plate appears to be akin to adding a LOW PASS filter to the panel's absorption creating an inverse relationship between the absorption and reflection curves. 

Varying the hole size appears to control where the absorption peak occurs moving the peak slightly higher or lower in frequency.  I tried entering the BAD hole diameter/spacing pattern using 12mm, 9mm and 6mm holes.  Using smaller holes moves the absorption peak lower in frequency while lowering the low pass filter according to the model.

Increasing depth of absorbent extends the bass absorption based on the flow resistivity of the absorbent used.

From playing with the calculator, it appears that adding an equal thickness layer of less dense absorbent in front of a denser absorbent (e.g. pink fluffy over OC703) pushes the absorption peak lower under the perforated panel (changes the shape of the top of the curve) as well as extends bass absorption.  Doubling the higher density absorbent tends to leave the absorption peak higher in frequency according to the calculator.  I would assume a lower frequency absorption peak would be more desirable to make a more consistent HF rolloff curve.

How well the calculator represents reality is TBD and it doesn't give any indications about scatter, just reflection.

http://www.acousticmodelling.com/multi.php





Desertpilot

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Re: Diffusion/scattering specs of Alpha panels
« Reply #12 on: 2 Jun 2021, 09:28 pm »
I read through the articles.  Very interesting.  It seems that the concept of these panels is to absorb mid range frequencies.  GIK claims 125Hz up to 1,000Hz.  And diffuse/scatter above 1,000Hz.  That would work for me.  The articles also go on to claim that competitor scattering may not begin until 2,500Hz or maybe even 6,500Hz.  Thus, we don't know about GIK panels unless they provide data.  I own them so I use them on the front wall behind my speakers.  My room does not sound dead so I will assume they are working as intended.  Real data would be nice, though.

Marcus

emailtim

Re: Diffusion/scattering specs of Alpha panels
« Reply #13 on: 2 Jun 2021, 09:47 pm »
...  GIK claims 125Hz up to 1,000Hz.  And diffuse/scatter above 1,000Hz.  ...

That tends to correspond with the 1/4" hole model from above. 

Maximum absorption (absorption coefficient 0.6 and above) is centered on the decade from [100-1,000]Hz and the 0.6 reflection coefficient increases from 1kHz upwards.  If the frequency is absorbed, it can't be scattered so scattering has to take place in the reflection region of the curve.

RonP

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Re: Diffusion/scattering specs of Alpha panels
« Reply #14 on: 3 Jun 2021, 01:36 pm »
I have three 6A (6 inch) 2D-a (dots and dashes) panels along my front wall (behind L, C, R speakers).  I also have a vaulted ceiling.  I have the same question, what are these panels doing?  GIK website shows peak absorption at 200Hz and good absorption between 125Hz and 800Hz.  This is entirely mid range for my speakers (Spatial Audio X3).  Absorption drops off rapidly from 1,000Hz and higher.  I have to assume diffusion/scattering is happening in this area (AMT Driver, in my case).

I wish GIK provided more in depth information about what these panels are doing.

Marcus

If in doubt, contact GIK directly. They will spend the time to answer you questions. I've had great phone and email replies from Mike over there.

ps. I have my eye on some X3s as well.