Real Acoustix GuD panels

[tjcinnamon]

Anyone have experience with these? I’m evaluating putting some diffusion on my sidewalls. I’m about 8’ away from them.

GuD Series — RealAcoustix LLC

www.realacoustixllc.com

Are they any… GuD?

 

[VinceHoffman]

While they certainly look neat (architecturally interesting), the ridiculously shallow 1" or 2" panel depth options are much too shallow to offer a useful operational bandwidth. The 250% efficiency bafflegab and lack of any accredited independant testing results in their product blurb are other major tells. Usefully designed QRD diffusers typically sport panel depths of 5" or greater.

 

[tjcinnamon]

While they certainly look neat (architecturally interesting), the ridiculously shallow 1" or 2" panel depth options are much too shallow to offer a useful operational bandwidth. The 250% efficiency bafflegab and lack of any accredited independant testing results in their product blurb are other major tells. Usefully designed QRD diffusers typically sport panel depths of 5" or greater.

I figured. That's why I asked. Seemed a bit too GuD to be true.

I'm looking at these:

1D diffuser: https://www.atsacoustics.com/square-acoustic-diffuser-qrd.html

Half circle things: https://www.gikacoustics.com/product/evolution-polyfusor-diffusor-absorber-bass-trap/

2D quadratic skyline: https://www.gikacoustics.com/product/gotham-n23-5-inch-quadratic-diffusors/

My seated position is about 9' away from the side walls and it's my first reflection point on the side walls. Thoughts on which one would be appropriate?

 

[tjcinnamon]

changing a bit. I'm going to go 1D or that half circle thingy. I need to measure my room and see if my RT60 is already too low in those ranges.

 

[VinceHoffman]

After nearly 30 years of small room acoustics experimentation, I'm not a fan of using diffusers at the first reflection points of the sidewalls nearest to the adjacent loudspeaker. In my experience a 5-6" deep broadband absorption panel there ALWAYS results in the widest, most solid image width and soundstage. I do like hybrid treatments, Binary Amplitude Diffusor panels (like the RPG BAD or GIK Alpha panels in a 5-6" depth), further back along the sidewalls where the primary reflection of the left speaker hits the right sidewall and visa-versa. I also like BAD panels on the front wall, provided your loudspeakers are placed well away from the front wall. In the pic below you see two 6' tall stacks of customized 8" deep RPG BAD ARC panels flanking a huge 8'x4'x8" DIY polydiffusor on my front wall.

In my experience where QRD diffusors do work well are on the rear wall provided the MLP is 5' or more off that wall. You do not want to be in the "nearfield" an acoustic phase grating (QRD or Primitive Root diffuser). These sorts of diffusors "sound weird" up close. QRD diffusors can also be beneficial on the ceiling towards the rear half of the room as well- just not at the ceiling first reflection points where pure absorption is the preferred choice.
The minimum distance requirement between a QRD and the listener's ears is 3 wavelengths of the diffusor's low frequency operational cut-off. For a 5-6" max well depth QRD, that translates to about 5 feet. Deeper diffuser designs will require greater minimum listener distances.

 

[tjcinnamon]

Thank you for the detailed response! Basically, I can't move my speakers nor my seated position so my options outside of EQ and Room Correction are room treatments. I'm fairly flexible with Treatment options. Here's a rough layout of my room and some hastily taken pictures.

 

[tjcinnamon]

After nearly 30 years of small room acoustics experimentation, I'm not a fan of using diffusers at the first reflection points of the sidewalls nearest to the adjacent loudspeaker. In my experience a 5-6" deep broadband absorption panel there ALWAYS results in the widest, most solid image width and soundstage. I do like hybrid treatments, Binary Amplitude Diffusor panels (like the RPG BAD or GIK Alpha panels in a 5-6" depth), further back along the sidewalls where the primary reflection of the left speaker hits the right sidewall and visa-versa. I also like BAD panels on the front wall, provided your loudspeakers are placed well away from the front wall. In the pic below you see two 6' tall stacks of customized 8" deep RPG BAD ARC panels flanking a huge 8'x4'x8" DIY polydiffusor on my front wall.
View attachment 57377
In my experience where QRD diffusors do work well are on the rear wall provided the MLP is 5' or more off that wall. You do not want to be in the "nearfield" an acoustic phase grating (QRD or Primitive Root diffuser). These sorts of diffusors "sound weird" up close. QRD diffusors can also be beneficial on the ceiling towards the rear half of the room as well- just not at the ceiling first reflection points where pure absorption is the preferred choice.
The minimum distance requirement between a QRD and the listener's ears is 3 wavelengths of the diffusor's low frequency operational cut-off. For a 5-6" max well depth QRD, that translates to about 5 feet. Deeper diffuser designs will require greater minimum listener distances.
View attachment 57378 View attachment 57382

I forgot to tag you. See my post above.

 

[VinceHoffman]

Oh... You are firing across the narrow dimension of the room @tjcinnamon. Hmmm... Well I likely still wouldn't choose QRD's at the primary sidewall reflection points due to their typically quite limited operating bandwidth. Perhaps a couple more GIK Alpha Panels or some polycylindrical diffusers.
BTW, the broadband absorption panel directly behind the coach should be double the thickness you currently are using. Did GIK advise on your room treatment strategy when you purchased from them? 'Cuz they would normally have specced their 8" Monster Traps there...

 

[tjcinnamon]

Oh... You are firing across the narrow dimension of the room @tjcinnamon. Hmmm... Well I likely still wouldn't choose QRD's there due to their typically quite limited operating bandwidth. Perhaps a couple more GIK Alpha Panels or some polycylindrical diffusers.
BTW, the broadband absorption panel directly behind the coach should be double the thickness you currently are using. Did GIK advise on your room treatment strategy when you purchased from them? 'Cuz they would normally have specced their 8" Monster Traps there...

I actually built the ones that are behind my head and on the side walls. Whats the diffusion difference between the polycyndrical and the Alpha panels? I'm leaning polycyndrycal on those side walls.

I'll check to see the result of the 8" behind my head. Essentially, I could put the one above it right in front of it and it would be 8" but it would go right up to the back of my head. I suppose it wouldn't matter given my proximity to the back wall as it is. I think when they initially suggested it, I was uncertain I could do that. I had no treatments at that time and had some WAF to contend with.

 

[VinceHoffman]

I actually built the ones that are behind my head and on the side walls. Whats the diffusion difference between the polycyndrical and the Alpha panels? I'm leaning polycyndrycal on those side walls.

I'll check to see the result of the 8" behind my head. Essentially, I could put the one above it right in front of it and it would be 8" but it would go right up to the back of my head. I suppose it wouldn't matter given my proximity to the back wall as it is.

Well your GIK Alpha panels and my similar RPG BAD & DIY BAD panels are hybrids- part absorber and part diffuser. Below 1kHz the front mounted scatterplates are acoustically invisible. So pure absorption below 1kHz. The scatterplates will gradually transition the panel behavior from pure absorption to diffusive scattering between 1kHz and 5kHz. Above 5kHz a properly designed BAD panel should reflectively scatter between 50-70% of incident soundwaves. Flat Binary Amplitude Diffuser scatter plates are good. A curved BAD scatterplate like that found on RPG's BAD Arc panels offers even better diffusion performance. On the pic below you can see my modified RPG BAD Arc panels prior to being reupholstered.

Polycylindrical diffusors are simple geometric diffusers that do to incident soundwaves what a convex mirror does to light. It spreads the reflection out over a larger area but does so without messing around with phase. Your reflection in a vertically oriented convex funhouse mirror is still recognizably you, just much fatter and a little dimmer. Same goes for soundwaves colliding with a poly diffuser. This is very different than the way phase grating diffusers like QRDs work. A Poly will normally behave as a pure diffusor over its entire operating bandwidth. However for large polys like the one I constructed from a full 4'x8' sheet of 1/8" hardboard for my front wall, you can lightly stuff the airspace behind the curved panel with porous fiber (really low density fiberglass batting for example) to achieve some bonus mid-upper bass trapping. The collage below shows how I built my huge Poly including the breathable bulkheads and fabric grills on the endcaps which prevent the enclosed fluffy fiberglass fibers from escaping.

As for that big broadband absorber behind your head, the CAD pictogram you provided suggests there is an 18" gap between the wall and MLP. Based upon that, an 8" panel shouldn't be a problem.

 

[tjcinnamon]

Well your GIK Alpha panels and my similar RPG BAD & DIY BAD panels are hybrids- part absorber and part diffuser. Below 1kHz the front mounted scatterplates are acoustically invisible. So pure absorption below 1kHz. The scatterplates will gradually transition the panel behavior from pure absorption to diffusive scattering between 1kHz and 5kHz. Above 5kHz a properly designed BAD panel should reflectively scatter between 50-70% of incident soundwaves. Flat Binary Amplitude Diffuser scatter plates are good. A curved BAD scatterplate like that found on RPG's BAD Arc panels offers even better diffusion performance. On the pic below you can see my modified RPG BAD Arc panels prior to being reupholstered.
View attachment 57390


Polycylindrical diffusors are simple geometric diffusers that do to incident soundwaves what a convex mirror does to light. It spreads the reflection out over a larger area but does so without messing around with phase. Your reflection in a vertically oriented convex funhouse mirror is still recognizably you, just much fatter and a little dimmer. Same goes for soundwaves colliding with a poly diffuser. This is very different than the way phase grating diffusers like QRDs work. A Poly will normally behave as a pure diffusor over its entire operating bandwidth. However for large polys like the one I constructed from a full 4'x8' sheet of 1/8" hardboard for my front wall, you can lightly stuff the airspace behind the curved panel with porous fiber (really low density fiberglass batting for example) to achieve some bonus mid-upper bass trapping. The collage below shows how I built my huge Poly including the breathable bulkheads and fabric grills on the endcaps which prevent the enclosed fluffy fiberglass fibers from escaping.
View attachment 57389

As for that big broadband absorber behind your head, the CAD pictogram you provided suggests there is an 18" gap between the wall and MLP. Based upon that, an 8" panel shouldn't be a problem.

Wow! Thats fantastic. For the 1/8th inch did you just wrap that around the frame? That’s awesome!

I think I’m gonna go with the PolyDiffuser likely on the side walls. They seem to be remarkably similar to yours. Thin wood shell with fill.

“transitions as a bass trap from 80Hz, to upper-bass/lower-mid scattering device, to diffusor. Starts diffusing at 600Hz.

Thin wood poly diffuser lets low frequency waves in for low end absorption”

Evolution PolyFusor © - Sound Diffuser / Absorber Combination

The GIK Acoustics Evolution PolyFusor© is a combination of a polycylindrical diffuser AND an absorber merged into a single unit. Polyfusors offer a wider band of spatial diffusion than a typical quadratic residue diffuser, but do not affect the phase of the incident sound.

www.gikacoustics.com

 

[tjcinnamon]

Well your GIK Alpha panels and my similar RPG BAD & DIY BAD panels are hybrids- part absorber and part diffuser. Below 1kHz the front mounted scatterplates are acoustically invisible. So pure absorption below 1kHz. The scatterplates will gradually transition the panel behavior from pure absorption to diffusive scattering between 1kHz and 5kHz. Above 5kHz a properly designed BAD panel should reflectively scatter between 50-70% of incident soundwaves. Flat Binary Amplitude Diffuser scatter plates are good. A curved BAD scatterplate like that found on RPG's BAD Arc panels offers even better diffusion performance. On the pic below you can see my modified RPG BAD Arc panels prior to being reupholstered.
View attachment 57390


Polycylindrical diffusors are simple geometric diffusers that do to incident soundwaves what a convex mirror does to light. It spreads the reflection out over a larger area but does so without messing around with phase. Your reflection in a vertically oriented convex funhouse mirror is still recognizably you, just much fatter and a little dimmer. Same goes for soundwaves colliding with a poly diffuser. This is very different than the way phase grating diffusers like QRDs work. A Poly will normally behave as a pure diffusor over its entire operating bandwidth. However for large polys like the one I constructed from a full 4'x8' sheet of 1/8" hardboard for my front wall, you can lightly stuff the airspace behind the curved panel with porous fiber (really low density fiberglass batting for example) to achieve some bonus mid-upper bass trapping. The collage below shows how I built my huge Poly including the breathable bulkheads and fabric grills on the endcaps which prevent the enclosed fluffy fiberglass fibers from escaping.
View attachment 57389

As for that big broadband absorber behind your head, the CAD pictogram you provided suggests there is an 18" gap between the wall and MLP. Based upon that, an 8" panel shouldn't be a problem.

I forgot! After some measurements, I may go for a Scopus Membrane Trap with an Alpha on it. I had a tail between 50 and 60 hz. The newest version of REW has frequency dependent windowing. I also have a 2 subs I can move around. Once I flatten that response and measure my room, I'll run some sweeps and see if there's any modes in places where I could fit a membrane trap.

Who am I kidding!?!? I'll probably get both!

 

[VinceHoffman]

I forgot! After some measurements, I may go for a Scopus Membrane Trap with an Alpha on it...

Other than perhaps an aesthetic choice, I see no point to paying the premium to affix a GIK Alpha scatterplate to a Scopus trap. Behind the decorative fabric upholstery, the outward facing resonant "membrane" of the Scopus is made from a solid, non-breathable, & non-porous material. For a scatterplate to actually work as intended, it requires a broadband porous absorptive panel behind it.

A tuned membrane trap will only absorb a narrow range of (bass) frequencies, centered on it's resonant frequency. The Scopus T40 is tuned to 40Hz, T70 to 70Hz, & T100 to 100Hz. So a Scopus, with or without an Alpha affixed to the front, is never appropriate at a reflection point. The Scopus tuned membrane bass traps are deployed in zones of high acoustic pressure = at the intersection of two (or three) room boundaries where the particular modal resonant frequency which most closely coincides with T40, T70, or T100 measures strongest. Capiche?

 

[tjcinnamon]

Other than perhaps an aesthetic choice, I see no point to paying the premium to affix a GIK Alpha scatterplate to a Scopus trap. Behind the decorative fabric upholstery, the outward facing resonant "membrane" of the Scopus is made from a solid, non-breathable, & non-porous material. For a scatterplate to actually work as intended, it requires a broadband porous absorptive panel behind it.

A tuned membrane trap will only absorb a narrow range of (bass) frequencies, centered on it's resonant frequency. The Scopus T40 is tuned to 40Hz, T70 to 70Hz, & T100 to 100Hz. So a Scopus, with or without an Alpha affixed to the front, is never appropriate at a reflection point. The Scopus tuned membrane bass traps are deployed in zones of high acoustic pressure = at the intersection of two (or three) room boundaries where the particular modal resonant frequency which most closely coincides with T40, T70, or T100 measures strongest. Capiche?

Totally makes sense! I appreciate your help on this. I would potentially be doing it for looks depending where they would go. Because of the frequencies length.
Regardless of the plate pattern, it will function the same. Therefore, I should just pick what sounds best.

Also, with regards to membrane traps (if I go that direction). Should I measure with REW at the available wall spots and place them where the signal is the strongest on the wall?

 

[VinceHoffman]

...Also, with regards to membrane traps (if I go that direction). Should I measure with REW at the available wall spots and place them where the signal is the strongest on the wall?

Typically you would place a subwoofer in a room tri-corner so that when the sub is driven with a pink noise test signal, it will maximally drive your room's modal resonant frequencies associated with length, width, & height. Then you'd wander about along your room boundaries taking low frequency SPL measurements. Wherever along the room boundary you measure a strong peak SPL for one or more of those modal frequencies, you would place several of the Txx Scopus traps (with the tuning frequency which most closely coincides with the measured modal frequency peaking).

GIK can provide better advice along with a reasonable guesstimate of how many Scopus bass traps you might require if you provide them the same room plan-o-gram you shared in your earlier post. Be aware that it takes a bunch of these things placed cheek-to-cheek along several wall-wall, wall-floor, or wall ceiling boundary intersections to offer useful improvement. With true bass trapping quality is only achieved through quantity.

 

[VinceHoffman]

Typically you would place a subwoofer in a room tri-corner so that when the sub is driven with a pink noise test signal, it will maximally drive your room's modal resonant frequencies associated with length, width, & height. Then you'd wander about along your room boundaries taking low frequency SPL measurements. Wherever along the room boundary you measure a strong peak SPL for one or more of those modal frequencies, you would place several of the Txx Scopus traps (with the tuning frequency which most closely coincides with the measured modal frequency peaking).

The in-house acoustician at GIK can potentially provide better measurement directions along with a reasonable guesstimate of how many Scopus bass traps you might require if you provide him the same room plan-o-gram you shared in your earlier post. Be aware that it takes a bunch of these things placed cheek-to-cheek along several wall-wall, wall-floor, or wall ceiling boundary intersections to offer useful improvement. With true bass trapping quality is only achieved through quantity.

 

[tjcinnamon]

Oh... You are firing across the narrow dimension of the room @tjcinnamon. Hmmm... Well I likely still wouldn't choose QRD's at the primary sidewall reflection points due to their typically quite limited operating bandwidth. Perhaps a couple more GIK Alpha Panels or some polycylindrical diffusers.
BTW, the broadband absorption panel directly behind the coach should be double the thickness you currently are using. Did GIK advise on your room treatment strategy when you purchased from them? 'Cuz they would normally have specced their 8" Monster Traps there...

For my layout, where would you consider putting the QRD panels (5 or 6” depth)?

 

[VinceHoffman]

For my layout, where would you consider putting the QRD panels (5 or 6” depth)?

IMHO, the shallow depth and long width of your current listening room doesn't really make QRD diffusers all that appropriate. They require some space between the MLP and the reflection point this sort of (reflection phase grating) diffuser is placed at in order to work properly.

 

[tjcinnamon]

IMHO, the shallow depth and long width of your current listening room doesn't really make QRD diffusers all that appropriate. They require some space between the MLP and the reflection point this sort of (reflection phase grating) diffuser is placed at in order to work properly.

Even thought I have 8' to 9' from the side walls?

 

[VinceHoffman]

Your side walls are really narrow due to the shallow depth dimension of your room arrangement. Typically QRD (phase grating) style diffusers are used in the rear half of a domestic listening space on the rear wall and possibly the rear sidewalls behind the MLP. But you must have at least 5 or 6 feet of space between the listener's ears and the front face of the diffuser for a 5-6 inch deep diffuser- and more space still for diffusers with a deeper max well depth. Your couch against the rear wall setup precludes this @tjcinnamon .

 

[tjcinnamon]

Your side walls are really narrow due to the shallow depth dimension of your room arrangement. Typically QRD (phase grating) style diffusers are used in the rear half of a domestic listening space on the rear wall and possibly the rear sidewalls behind the MLP. But you must have at least 5 or 6 feet of space between the listener's ears and the front face of the diffuser for a 5-6 inch deep diffuser- and more space still for diffusers with a deeper max well depth. Your couch against the rear wall setup precludes this @tjcinnamon .

That’s helpful! Thanks for all of the advice. Definitely looking forward to my next build