On 12/31/20 4:30 PM, Robert McGregor wrote:
> Hi all,
> 
> I've been building some new acoustic treatments for my recording studio and
> worked out a design for a 2D Quadratic Residue Diffuser (QRD) based on the prime
> number 19, but had no idea what it would actually look like. So, I fired up
> POV-Ray (a year-long hiatus) and after creating a simple 2d array of wood
> lengths I was able to get this pretty decent visualization in no time.
> 
...
> 

Even your quick visualizations look pretty good!

What sort of music - or are you recording for others?

Bill P.

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> Even your quick visualizations look pretty good!

Thanks Bill :)

> What sort of music - or are you recording for others?

I play guitar and sing, and before the pandemic hit I used to to perform live
quite a bit with my classic/hard rock trio. I also recorded and mixed local
singer/songwriters and bands.

Now I'm just focusing on recording a solo album. The genre is a bit ambiguous
but I guess I'd call it melodic progressive rock/metal. Sort of like Rush meets
Opeth meets Dream Theater meets Meshuggah...

Cheers,
Rob

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"Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:
> Hi all,
>
> I've been building some new acoustic treatments for my recording studio and
> worked out a design for a 2D Quadratic Residue Diffuser (QRD) based on the prime
> number 19, but had no idea what it would actually look like....
>
> The physical unit will be 2 x 4 feet and the math says it should diffuse
> soundwaves from ~430Hz to ~5400 Hz, which is just what I need for the rear wall
> of my control room...

Wow, that is some sophisticated thinking! The render looks really cool too.

Would the real-life project be easier (and still perform as intended) if the
blocks were made from some kind of plastic foam, instead of wood?

I also play in a classic-rock band; but for the past nine months, we have
managed to play only about once per month, and only *outside* due to safety
precautions re: Covid-19. (And we all wear masks except when performing/singing
on-stage.) Still not a truly safe environment, I admit. Personally, I would have
preferred to stay safe at home instead. But I was out-voted :-\

Our band's bass-guitar player is currently setting up a home recording studio;
I'll tell him about your experiment.

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"Kenneth" <kdw### [at] gmailcom> wrote:

> Would the real-life project be easier (and still perform as intended) if the
> blocks were made from some kind of plastic foam, instead of wood?

I don't think so, the mass of the wood helps to scatter the sound waves, lighter
materials don't work as well.

> I also play in a classic-rock band; but for the past nine months, we have
> managed to play only about once per month, and only *outside* due to safety
> precautions re: Covid-19. (And we all wear masks except when performing/singing
> on-stage.) Still not a truly safe environment, I admit. Personally, I would have
> preferred to stay safe at home instead. But I was out-voted :-\

Yeah, I opted to stay home

> Our band's bass-guitar player is currently setting up a home recording studio;
> I'll tell him about your experiment.

This is render of a 1D QRD design based on prime number 13, also a 2x4 foot
profile. The diffusion range isn't quite as wide (~520 Hz to ~4500 Hz) but it's
a LOT easier to build, and sounds really good in a small space. I built three of
these a couple of months ago. The the wells are 6" deep and 1.5" wide, with
0.25" wide slats. Blocks for the wells are symmetrical and simple to cut and
glue at depths (in inches, from my POV file):

#declare BlockScale = array[13] {
   1.0,
   0.001,  // 0 IRL
   4.5,
   1.5,
   4.0,
   5.5,
   6.0,
   5.5,
   4.0,
   1.5,
   4.5,
   0.001,  // 0 IRL
   1.0
}


Cheers,
Rob

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Attachments:
Download 'qrd_1d_13_diffuser.png' (3422 KB)

Preview of image 'qrd_1d_13_diffuser.png'

"Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:

>
> This is render of a 1D QRD design based on prime number 13, also a 2x4
> foot profile...I built three of
> these a couple of months ago...

Another cool design! The profile happens to look like a kind of chopped-up
waveform.

I'm curious: For these, would there be an improvement (i.e. 'better' sound
absortion) if one or two of the three panels were mounted horizontally rather
than vertically? To 'catch' sound waves that the vertical panel(s) may have
missed? My own uninformed theory about these things is, the more 'random' the
orientation, the better. But that's based on.. nothing in particular, just a
hunch ;-)

There is a local restaurant/bar here that our band plays at on a regular basis.
The small 'stage' is located in a corner of the room-- with hard walls
everywhere, and a low hard ceiling. This set-up results in some weird and
expected over-amplification of the bands' instruments, with the sound bouncing
around; on-stage, we never truly hear what the audience hears. For *years*, I've
been trying to convince the venue's owners to put *some* kind of sound-absorbing
panels (or whatever) on the L-shaped walls that surround us. But they don't seem
to think it's important. *sigh* :-(  I haven't given up, though!

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"Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>
> > Would the real-life project be easier (and still perform as intended) if the
> > blocks were made from some kind of plastic foam, instead of wood?
>
> I don't think so, the mass of the wood helps to scatter the sound waves, lighter
> materials don't work as well.
>
> > I also play in a classic-rock band; but for the past nine months, we have
> > managed to play only about once per month, and only *outside* due to safety
> > precautions re: Covid-19. (And we all wear masks except when performing/singing
> > on-stage.) Still not a truly safe environment, I admit. Personally, I would have
> > preferred to stay safe at home instead. But I was out-voted :-\
>
> Yeah, I opted to stay home
>
> > Our band's bass-guitar player is currently setting up a home recording studio;
> > I'll tell him about your experiment.
>
> This is render of a 1D QRD design based on prime number 13, also a 2x4 foot
> profile. The diffusion range isn't quite as wide (~520 Hz to ~4500 Hz) but it's
> a LOT easier to build, and sounds really good in a small space. I built three of
> these a couple of months ago. The the wells are 6" deep and 1.5" wide, with
> 0.25" wide slats. Blocks for the wells are symmetrical and simple to cut and
> glue at depths (in inches, from my POV file):
>
> #declare BlockScale = array[13] {
>    1.0,
>    0.001,  // 0 IRL
>    4.5,
>    1.5,
>    4.0,
>    5.5,
>    6.0,
>    5.5,
>    4.0,
>    1.5,
>    4.5,
>    0.001,  // 0 IRL
>    1.0
> }
>
>
> Cheers,
> Rob

Both look great ! Would you mind it if I Shared the pictures on Facebook with
proper credit and your small explanation of what they are?
If so I would ask you: Did you use front end 3D editor(s) or not at all?
depending on it I would share on one group or the other.
I like to advertise elsewhere as I noticed many people
don't come here and still enjoy  getting to see what is actually achieved with
POV.

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> "Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:
> 
>>
>> This is render of a 1D QRD design based on prime number 13, also a 2x4
>> foot profile...I built three of
>> these a couple of months ago...
> 
> Another cool design! The profile happens to look like a kind of chopped-up
> waveform.
> 
> I'm curious: For these, would there be an improvement (i.e. 'better' sound
> absortion) if one or two of the three panels were mounted horizontally rather
> than vertically? To 'catch' sound waves that the vertical panel(s) may have
> missed? My own uninformed theory about these things is, the more 'random' the
> orientation, the better. But that's based on.. nothing in particular, just a
> hunch ;-)
> 
I don't think that the orientation really mater. Sound waves are 
compression waves and not polarized.

Reverberation reducing tips :
1) If possible at all, avoid parallel surfaces.
2) Use sound diffusing geometry like those shown in this thread.
3) Use absorbing acoustic foam. On at least one wall. It don't need to 
cover it all.
4) Fully or partially cover a wall with some curtains.
5) Have a carpet.
6) Do not leave the room bare.

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"Kenneth" <kdw### [at] gmailcom> wrote:

> Another cool design! The profile happens to look like a kind of chopped-up
> waveform.

Thanks, I like the symmetry and they work well in a array of three side-by-side.

> I'm curious: For these, would there be an improvement (i.e. 'better' sound
> absorption) if one or two of the three panels were mounted horizontally rather
> than vertically? To 'catch' sound waves that the vertical panel(s) may have
> missed? My own uninformed theory about these things is, the more 'random' the
> orientation, the better. But that's based on.. nothing in particular, just a
> hunch ;-)

Both ways work, it just depends on the situation. A diffuser like the first
image that I posted scatters both horizontally *and* vertically (2D), while the
second scatters horizontally (1D). For a listening environment like a studio
control room I personally like a little of both. They make a small room sound
bigger, mitigating flutter echo and breaking up standing waves. Some people
think that scattering sound waves to the floor and ceiling is a bad idea.

An array of horizontal diffusers, side-by-side, seems to be the most common
approach in professional studios, usually on the rear wall and rear side walls.
Of course diffusers don't actually absorb sound (much), they scatter.




difference in the absorption rating. I use the 8 lb per cubic foot density,
because more density = more absorption.

To tame bass frequencies you can cut these same size mineral wool panels in half
(2x2 feet) and then cut those diagonally into triangles. Stacked floor to
ceiling in the corners of a room these make great bass traps.

> There is a local restaurant/bar here that our band plays at on a regular basis.
> The small 'stage' is located in a corner of the room-- with hard walls
> everywhere, and a low hard ceiling. This set-up results in some weird and
> expected over-amplification of the bands' instruments, with the sound bouncing
> around; on-stage, we never truly hear what the audience hears. For *years*, I've
> been trying to convince the venue's owners to put *some* kind of sound-absorbing
> panels (or whatever) on the L-shaped walls that surround us. But they don't seem
> to think it's important. *sigh* :-(  I haven't given up, though!

I hear you, I've been through the exact same thing. A couple of years ago I
finally convinced the owner at my local "super-reverberant" regular gig venue to
let me make hang some of my absorber panels on the walls. It made such a big
difference that he paid me to make and install  25 of them :)

Cheers,
Rob

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"Mr" <nomail@nomail> wrote:
> Both look great ! Would you mind it if I Shared the pictures on Facebook with
> proper credit and your small explanation of what they are?

Thanks "Mr" - sure, go ahead and share.

> If so I would ask you: Did you use front end 3D editor(s) or not at all?
> depending on it I would share on one group or the other.

I did not use any 3D modelers for these images, I think that's what you're
asking? I used only POV-Ray SDL via Chris Cason's awesome POV-Ray for Windows
integrated text editor/renderer.

> I like to advertise elsewhere as I noticed many people
> don't come here and still enjoy  getting to see what is actually achieved with
> POV.

Please feel free to share my website that is filled with my POV-Ray imagery as
well: www.mcgregorfineart.com

Cheers,
Rob

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"Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
> > For *years*, I've been trying to convince the venue's owners to put *some*
> > kind of sound-absorbing panels (or whatever) on the L-shaped walls that
> > surround us. But they don't seem to think it's important. *sigh* :-(
> > I haven't given up, though!
>
> I hear you, I've been through the exact same thing. A couple of years ago I
> finally convinced the owner at my local "super-reverberant" regular gig venue to
> let me make hang some of my absorber panels on the walls. It made such a big
> difference that he paid me to make and install  25 of them :)
>

Ha! Congratulations. The owner of that venue is obviously more pro-active, and
listens to reason.

Sound absorbing vs. sound scattering: I have to admit that I never thought about
the differences(!) Thanks for the brain-boost ;-)  My previous ideas about
modifying my local venue's L-shaped corner involved using lots of
randomly-oriented carpeted/padded panels, sticking out from the walls. (Based on
low cost.) But perhaps the panels should have hard surfaces(?) I obviously need
to do more research, ha. (Not that I have much chance of implementing the idea,
sad to say.)

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