Login / Register
 
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)
New Reply
Subscribe
#91
24th October 2012
Old 24th October 2012
  #91
Lives for gear
 
Schaap's Avatar
 
Joined: Sep 2004
Location: Netherlands
Posts: 530

Schaap is offline
Another recording with the Opt. metric diff. esp. for vocals. Diffusion diminishes the 'smearing' and 'glassiness' or how you call it.
Music of AHA.
Attached Files
File Type: wav without - aha exc.wav (2.80 MB, 207 views) File Type: wav modul 5 aha exc.wav (2.83 MB, 174 views)
__________________
"Poetry and music"
http://tinyurl.com/cmtwkp

We say we shall not meet: http://www.youtube.com/watch?v=b4BWwpKTIRI

"People who are absolute sure make the most mistakes,
All theories of today are based on knowledge of yesterday" H. S. '88
Arqen
Thread Starter
#92
24th October 2012
Old 24th October 2012
  #92
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Quote:
Originally Posted by Schaap View Post
Hi Tim et all,

Today I made a recording with a Olympus LS-11 mobile recorder in a room of about 85m3 at the same spot and conditions. I had 5 metric fractal modules laying on the floor next to each other and the music arrived to the diffuser in a indirect way, so not direct from the speakers. Not optimal circumstances to judge(maybe later) but I think it gives the 'essences' op diffusion and the working of the part of the optimized diffuser if you're have decent monitoring.
Music is used for educational purpose from a CD and is not mine. Hope that's not a problem.


The modulation sequence of the modules were 0,4,5,3,5 Total: 1.2 m2
Awesome, Schaap! Thanks a lot for doing those tests.

I'm in a noisy place right now so I can't hear the nuances, but I'll give them another listen later tonight.
#93
26th October 2012
Old 26th October 2012
  #93
Gear nut
 
Storm Mastering's Avatar
 
Joined: Nov 2011
Location: France
Posts: 115

Send a message via Skype™ to Storm Mastering
Storm Mastering is online now
Do you think they will work well "air transparent style" (like in myroom principle) ? mounted in a diffractal way ?
Arqen
Thread Starter
#94
26th October 2012
Old 26th October 2012
  #94
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Quote:
Originally Posted by Cubic Spline View Post
Do you think they will work well "air transparent style" (like in myroom principle) ? mounted in a diffractal way ?
Do you mean, with slots between each step?

It will still produce diffusion mounted that way, but I don't know how it will perform.

Also, I'm not sure how well the diffusers in the MyRoom design studio perform, because without fins between the wells they do not behave like an optimal QRD diffuser. The MyRoom diffusers might work better than a traditional QRD, or they might work not as well. (either way, they do a good job in the context of the MyRoom room design)

When you remove wells from a QRD (or add slots instead of wells), what you get is a diffuser that no longer follows the rules of the QRD design equations. A QRD without fins may indeed perform well, but it's no longer an optimized diffuser.

Likewise, if you add slots to the optimized diffusers I've designed, the performance will change in ways that are difficult to predict. But hey, it's worth a try!
Arqen
Thread Starter
#95
30th October 2012
Old 30th October 2012
  #95
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Quote:
Originally Posted by Schaap View Post
Another recording with the Opt. metric diff. esp. for vocals. Diffusion diminishes the 'smearing' and 'glassiness' or how you call it.
Music of AHA.
I had a hard time hearing the difference (listening through a pair of AKG 271s), but my perception sometimes fools me. I compared the waveforms and time-frequency spectrum of each file and there are subtle differences (most notably in the waveform, which makes sense).

An easier way to hear the difference might be with an impulsive-like sound, or a single-instrument recording.

Judging by the similarities in the time-frequency spectrum of each file, it looks like you had a very consistent experimental setup.

Big thanks for making these recordings!
#96
30th October 2012
Old 30th October 2012
  #96
Lives for gear
 
Schaap's Avatar
 
Joined: Sep 2004
Location: Netherlands
Posts: 530

Schaap is offline
Quote:
Originally Posted by Arqen View Post
I had a hard time hearing the difference (listening through a pair of AKG 271s), but my perception sometimes fools me. I compared the waveforms and time-frequency spectrum of each file and there are subtle differences (most notably in the waveform, which makes sense).

An easier way to hear the difference might be with an impulsive-like sound, or a single-instrument recording.

Judging by the similarities in the time-frequency spectrum of each file, it looks like you had a very consistent experimental setup.

Big thanks for making these recordings!
It was not an optimal example - indirect sound towards the diffuser -and there was much ambiance of the room. And the recording always 'flattens' the results as you hear it in the room. But e.g. if you listen to the vocal of Aha after second 5 "There's no eeeeend to the.." it gives a subtle enhancement quite similar to using a better mic.


Next time I will do single recordings and other setup. A problem is if the metric is ready the width is 2.80 meter
Arqen
Thread Starter
#97
1st November 2012
Old 1st November 2012
  #97
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Quote:
Originally Posted by Schaap View Post
It was not an optimal example - indirect sound towards the diffuser -and there was much ambiance of the room. And the recording always 'flattens' the results as you hear it in the room. But e.g. if you listen to the vocal of Aha after second 5 "There's no eeeeend to the.." it gives a subtle enhancement quite similar to using a better mic.


Next time I will do single recordings and other setup. A problem is if the metric is ready the width is 2.80 meter
Ahhh, I do hear that enhancement. Thanks for pointing it out!

Can you clarify the last thing you said? Don't quite understand what you mean in the last sentence.

I really appreciate you building them and doing this testing.

Tim
#98
5th November 2012
Old 5th November 2012
  #98
Gear maniac
 
Joined: May 2009
Location: Montreal
Posts: 274

cosmik_debris is offline
I'm a throw this one in the fire...

My partner and I are researching diffusers as we'd like to add some in our live room. At present, our live room is roughly 16 x 23 with 11 foot ceilings. The two short walls are parallel and the two long walls are slightly not. One long wall has the control room window and a sliding glass door to access the dead room which in turn leads to the control room.

We wanted to put up wood paneling on the long wall parallel to that which has the control room window. This at first was purely for aesthetics. Then we got to thinking that maybe it could benefit the room's sound if we could somehow arrange the panels so that some, if not all the wall could act as a diffuser.

My question to you is...does this make any sense? If so, how would we go about doing this? The wall would look something like this...

http://furnitursite.com/wp-content/u...ion-Klee-1.jpg

Those panels run horizontally but we could always make them run vertically if need be.

Can we follow your formula with these panels and arrange them in steps so that some protrude outwards in the sequence you presented, or is this all a waste of time?

We are going to add some absorber/reflective wall panels on the short walls that run parallel. They will be installed at angles offset to each other to eliminate the problem of parallel surfaces.

Thanks!
Derek
Arqen
Thread Starter
#99
7th November 2012
Old 7th November 2012
  #99
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Quote:
Originally Posted by cosmik_debris View Post
I'm a throw this one in the fire...

My partner and I are researching diffusers as we'd like to add some in our live room. At present, our live room is roughly 16 x 23 with 11 foot ceilings. The two short walls are parallel and the two long walls are slightly not. One long wall has the control room window and a sliding glass door to access the dead room which in turn leads to the control room.

We wanted to put up wood paneling on the long wall parallel to that which has the control room window. This at first was purely for aesthetics. Then we got to thinking that maybe it could benefit the room's sound if we could somehow arrange the panels so that some, if not all the wall could act as a diffuser.

My question to you is...does this make any sense? If so, how would we go about doing this? The wall would look something like this...

http://furnitursite.com/wp-content/u...ion-Klee-1.jpg

Those panels run horizontally but we could always make them run vertically if need be.

Can we follow your formula with these panels and arrange them in steps so that some protrude outwards in the sequence you presented, or is this all a waste of time?

We are going to add some absorber/reflective wall panels on the short walls that run parallel. They will be installed at angles offset to each other to eliminate the problem of parallel surfaces.

Thanks!
Derek
Hi Derek,

Do you know how wide the panels will be?

It's a very interesting idea, but the way it enhances your sound will depend on the width of the panels. Here's what I suggest you do:

Using any of the 7-step sequences I've given (e.g., the sequence for diffuser A1-LF), try scaling up the size of the geometry so that the width matches the width of your panels, but the proportions are retained (i.e., the whole diffuser will be inflated in size).

Then, download the software AFMG Reflex and try simulating the design (this should not take very long... maybe an hour). My trial version of AFMG Reflex has expired, so I can't simulate your design myself right now... but, if you simulate the design and post the results here I'll be able to tell you whether or not it's worth your time to build your wall like that.

If your panels are as wide as the ones in the photo you've linked to, I expect you will improve the low frequency response of the room because your wall will act as a low frequency diffuser. It will also look neat!

Does what I've mentioned make sense to you?

Keep us posted on how it goes, and if you have questions.
#100
7th November 2012
Old 7th November 2012
  #100
Lives for gear
 
Joined: May 2012
Posts: 2,321

OpusOfTrolls is offline
Low frequency diffusion requires a room of considerable size. It's most practical to aim for diffusion above 400hz. Also, it doesn't work well in the context of mixing, but for listening is a matter of taste.
#101
9th November 2012
Old 9th November 2012
  #101
Lives for gear
 
Schaap's Avatar
 
Joined: Sep 2004
Location: Netherlands
Posts: 530

Schaap is offline
Hi Tim et all,

Made some recordings today with a metric fractal diffuser standing up(vertical) on the floor in the middle of a rather large room with the LS-11 1.5 meter before the diffuser pointed at the speakers to emulate a listening position. I have simply no extra space enough there to mount the diffuser on the wall. So again not the best testing procedure.
The diffuser was set against a 240 x 60 cm plywood of 2.4cm thickness.

First I recorded samples without the diffuser so the plywood acted as a plain “wall”. Then the diffuser with fractals were set against the plywood in a 6 configuration as 0,4,5,3,5,4 cm under the same conditions. There was no room for the last 0 module unfortunately.
Each module was sized 60 x 40 cm.

Samples are from STS testCD; without is no diffuser.
Attached Files
File Type: wav big band without.wav (6.06 MB, 165 views) File Type: wav big band with.wav (6.00 MB, 97 views) File Type: wav harp flute without.wav (2.99 MB, 73 views) File Type: wav harp flute with.wav (2.93 MB, 61 views) File Type: wav piccolo without.wav (2.10 MB, 55 views) File Type: wav piccolo with.wav (2.10 MB, 60 views)
Arqen
Thread Starter
#102
10th November 2012
Old 10th November 2012
  #102
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Quote:
Originally Posted by OpusOfTrolls View Post
Low frequency diffusion requires a room of considerable size. It's most practical to aim for diffusion above 400hz. Also, it doesn't work well in the context of mixing, but for listening is a matter of taste.
Good point. Also, in a small room I expect massive low frequency diffusers could alter the modal response in a favourable way (by spreading modal energy over more frequencies). But, I'm imagining very deep diffusers.

I agree that it's most practical to aim for diffusion over 400 Hz. In Derek's case, this could be used as a guideline when choosing the size of material for each wall panel. I.e., though testing in reflex, he could find out what scaling factor (used to scale an optimized stepped diffuser design) produces a diffuser that starts working around 400 Hz?
#103
11th November 2012
Old 11th November 2012
  #103
Gear interested
 
Joined: Nov 2012
Location: liverpool

kurudrumz is offline
looks very interesting many thanks for the upload!
Arqen
Thread Starter
#104
11th November 2012
Old 11th November 2012
  #104
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Fantastic, Schaap.

Thanks so much for going through the trouble to making these recordings. I do hear differences between in the takes, albeit subtle... so I'll throw them into an audio editor later to make comparison easier.

If you don't mind me asking, where in your room are you planning to mount the diffusers? Or did you just build them for experimentation?

Thanks again,
Tim


Quote:
Originally Posted by Schaap View Post
Hi Tim et all,

Made some recordings today with a metric fractal diffuser standing up(vertical) on the floor in the middle of a rather large room with the LS-11 1.5 meter before the diffuser pointed at the speakers to emulate a listening position. I have simply no extra space enough there to mount the diffuser on the wall. So again not the best testing procedure.
The diffuser was set against a 240 x 60 cm plywood of 2.4cm thickness.

First I recorded samples without the diffuser so the plywood acted as a plain “wall”. Then the diffuser with fractals were set against the plywood in a 6 configuration as 0,4,5,3,5,4 cm under the same conditions. There was no room for the last 0 module unfortunately.
Each module was sized 60 x 40 cm.

Samples are from STS testCD; without is no diffuser.
rez
#105
11th November 2012
Old 11th November 2012
  #105
rez
Gear addict
 
rez's Avatar
 
Joined: Jun 2011
Posts: 387

rez is offline
combine diffusor and absorber?

hello everybody!

we´d like to build some diffusors for the back wall of our control room. as of now i allways was thinking that we need at least 20-30 cm depth with traditional diffusor designs.
now that i found your designs we think of building a b2frac diffusor.
since that design is only about 11 cm in depth we were wondering if it makes sense to incorporate a big absorbing element behind the diffusor? i´m not shure wether it should be just a big porous absorber with open sides or if it would be better to aim for a sealed box that uses the backplate of the diffusor elements as a "swinging plate".

also we´d like to know if we could use the space beneath the diffusor/absorber, behind the couch to place one or more helmholtz resonators to tame some specific troublesome frequencies (mostly probably room modes).

thank you,

rez
__________________
here is some of my own music and some tracks that i have mixed: https://soundcloud.com/blackcapsound
#106
12th November 2012
Old 12th November 2012
  #106
Lives for gear
 
Jens Eklund's Avatar
 
Joined: Oct 2009
Location: Stockholm
Posts: 4,691

Jens Eklund is offline
Quote:
Originally Posted by rez View Post
hello everybody!

we´d like to build some diffusors for the back wall of our control room. as of now i allways was thinking that we need at least 20-30 cm depth with traditional diffusor designs.
now that i found your designs we think of building a b2frac diffusor.
Regardless of diffuser design, and assuming you want good diffusion performance (diffusion coefficient) over a wide bandwidth, then yes; you need to sacrifice at least about 20 cm of depth, but even the best shapes will struggle to provide good performance down to 300-500 Hz (and uniform broadband performance above 4-5 kHz in general) if only 20 cm deep.

High resolution (1/24 oct) full scale simulations from AFMG Reflex of the B2-Frac:
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-argen-b2-frac-stepfractal-diffusion-scattering-coefficients-reflex.gif
rez
#107
12th November 2012
Old 12th November 2012
  #107
rez
Gear addict
 
rez's Avatar
 
Joined: Jun 2011
Posts: 387

rez is offline
@jens: thank you for the response. that is the exact reason for my idea to place an (broadband) absorber behind the b2frac diffusor on the back wall. that way we get absorption and (acceptable) diffusion within the same space that would have been used for diffusion alone.

our control room is on the smaller side with about 25sqm and so i generally look for more absorption in the lowend, but since it is a custom built room it has angeled walls and a slanted ceiling and performs really good for not being a professional design as you can see in my other tread here: which diffusor design? you already contributed to that tread, but it has died since then.



sorry for the big picture, but i found no way to use an attachment from another post here or another way to resize the picture without uploading it again.
so not to jack this tread i´d be glad for any answers here or over in the other tread.

peace, rez
Arqen
Thread Starter
#108
13th November 2012
Old 13th November 2012
  #108
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Optimized Stepped Diffuser

Quote:
Originally Posted by rez View Post
hello everybody!

we´d like to build some diffusors for the back wall of our control room. as of now i allways was thinking that we need at least 20-30 cm depth with traditional diffusor designs.
now that i found your designs we think of building a b2frac diffusor.
since that design is only about 11 cm in depth we were wondering if it makes sense to incorporate a big absorbing element behind the diffusor? i´m not shure wether it should be just a big porous absorber with open sides or if it would be better to aim for a sealed box that uses the backplate of the diffusor elements as a "swinging plate".

also we´d like to know if we could use the space beneath the diffusor/absorber, behind the couch to place one or more helmholtz resonators to tame some specific troublesome frequencies (mostly probably room modes).

thank you,

rez


Quote:
Originally Posted by Jens Eklund View Post
Regardless of diffuser design, and assuming you want good diffusion performance (diffusion coefficient) over a wide bandwidth, then yes; you need to sacrifice at least about 20 cm of depth, but even the best shapes will struggle to provide good performance down to 300-500 Hz (and uniform broadband performance above 4-5 kHz in general) if only 20 cm deep.

High resolution (1/24 oct) full scale simulations from AFMG Reflex of the B2-Frac:
Attachment 316818

If you're building a long diffuser for the back wall, rather than investing the time into building the fractal designs, I suggest you consider building one large stepped diffuser.

A 20 cm deep, N = 36 stepped diffuser will perform better than a large array of B2-Frac diffusers (as Jens simulation shows, the performance is reduced as more modules are added).

You can enhance the performance of the array by mounting modules at different depths; however, I think the simplest solution for you is to build a large optimized stepped diffuser like the one shown below (let me know if you want to know the well depths of this N =36 optimized stepped diffuser, designed by Trevor J. Cox):

#109
13th November 2012
Old 13th November 2012
  #109
Lives for gear
 
Jens Eklund's Avatar
 
Joined: Oct 2009
Location: Stockholm
Posts: 4,691

Jens Eklund is offline
Do you mind passing that Reflex file Tim?

/Jens
#110
13th November 2012
Old 13th November 2012
  #110
Lives for gear
 
Jens Eklund's Avatar
 
Joined: Oct 2009
Location: Stockholm
Posts: 4,691

Jens Eklund is offline
Quote:
Originally Posted by Arqen View Post
(as Jens simulation shows, the performance is reduced as more modules are added).
Yes, as always; longer total panel widths has that effect on the diffusion coefficient. At only 2,1 meter total panel width (five periods of the B2-Frac), the numbers will naturally be higher:
DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-argen-b2-frac-stepfractal-5-periods-diffusion-scattering-coefficients-reflex.gif
rez
#111
13th November 2012
Old 13th November 2012
  #111
rez
Gear addict
 
rez's Avatar
 
Joined: Jun 2011
Posts: 387

rez is offline
thank you very much guys!

this answers were really helpful. sorry argen that your fractal design is not performing good in a bigger flat array. the development from the traditional designs is still looking very good.

would the b2-frac array of five elements, at 2,1m width, perform like the n-36 or better if mounted in the suggested "0 50 60 50 0" order at different depths? if that mounting will lift the performance above the n-36 we don´t mind a little more work since it is still only straight cuts and mills.

today we had the carpenter at our studio to discuss the work and the materials, but since it is my duty to provide the detailed plans for the build and we have some other things to do first, it is no problem to switch to another design! so i probably will propose the build of a n-36 diffusor for the back wall instead.

one more question: how is the performance of the n-36 above 4000hz and is this of any significant relevance in a smallish room like ours? and what if we would put fractals on just some of the wells of the n-36 diffusor? could that be of any benefit to spread the performance to higher frequencies?

peace, rez
#112
13th November 2012
Old 13th November 2012
  #112
Lives for gear
 
Joined: May 2012
Posts: 2,321

OpusOfTrolls is offline
Question about Reflex, can it model a diffuser with absorptive elements? Could a well of this design be replaced with an absorber?
#113
13th November 2012
Old 13th November 2012
  #113
Lives for gear
 
Jens Eklund's Avatar
 
Joined: Oct 2009
Location: Stockholm
Posts: 4,691

Jens Eklund is offline
Quote:
Originally Posted by OpusOfTrolls View Post
Question about Reflex, can it model a diffuser with absorptive elements? Could a well of this design be replaced with an absorber?
Not in the current version. The request for that feature has been communicated to AFMG.
Arqen
Thread Starter
#114
13th November 2012
Old 13th November 2012
  #114
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Quote:
Originally Posted by Jens Eklund View Post
Do you mind passing that Reflex file Tim?

/Jens
I've attached performance reports (pdf files) for the n = 36 optimized stepped diffuser.
The well width is 59 mm, and the sequence of well depths are given in the performance reports.

Unfortunately, I don't have the Reflex file because I was using a demo version of Reflex (it does not allow saving).

But I hope this helps!

Tim
Attached Images
Attached Files
File Type: pdf cox-opt-n36-0deg-vs-diffuse.pdf (404.8 KB, 119 views) File Type: pdf cox-opt-n36-25deg-vs-diffuse.pdf (417.7 KB, 130 views) File Type: pdf cox-opt-n36-45deg-vs-diffuse.pdf (419.5 KB, 79 views)
#115
13th November 2012
Old 13th November 2012
  #115
Lives for gear
 
Jens Eklund's Avatar
 
Joined: Oct 2009
Location: Stockholm
Posts: 4,691

Jens Eklund is offline
Thanks Tim!


Quote:
Originally Posted by Arqen View Post
Hi Jens,

I appreciate you taking the time to check my results.

First off, I'll need to clear up something in my explanation: 5-10 modules should be 5 OR 10 modules, depending on the length of the module. If the modules are full-height (4' long), then only 5 modules would be used. If the modules are half-height (2'), then 10 would be used.

I optimized the 2D shape in an array of 5 modules, so optimal results are only expected when there are 5 repetitions
Once I´ve made a Reflex model, I usually play around a bit with it and I noticed regarding the B2-Frac, that you don´t need to exclude periods between 5 and 10 since if you take the average diffusion coefficient between 400 Hz and 10 kHz for each curve (see below) and compare with the total panel width; you´ll find a close to exact linear relation. So don’t be afraid to use the B2-Frac in 6, 7, 8 or 9 periods i o w. It won´t perform any worse than if used in 5 or 10 periods. Naturally, any diffuser will show a decrease (some more than others but still) of the diffusion coefficient for larger total panel widths, so in order to achieve good performance for larger panels, deeper depth is unavoidable.

DIY Sound Diffusers—Free Blueprints—Slim, Optimized DIY Diffuser Designs (+Fractals)-b2-frac-diffusion-coefficients.gif
B2-Frac diffusion coefficients for 5, 6, 7, 8, 9 and 10 periods.
#116
13th November 2012
Old 13th November 2012
  #116
Lives for gear
 
Joined: May 2012
Posts: 2,321

OpusOfTrolls is offline
What would happen if I mounted an array of these diffusers in front of a porous absorber, and between the diffusers in the array added a gap? Can that be modeled with software?
#117
13th November 2012
Old 13th November 2012
  #117
Lives for gear
 
Jens Eklund's Avatar
 
Joined: Oct 2009
Location: Stockholm
Posts: 4,691

Jens Eklund is offline
The complete system; no, not to my knowledge and that would not be necessary. The array of Helmholtz absorbers formed by this arrangement (or wide slats i o w) can be modeled in software, SoundFlow (AFMG) being one example.
Arqen
Thread Starter
#118
14th November 2012
Old 14th November 2012
  #118
Gear addict
 
Arqen's Avatar
 
Joined: Jan 2012
Location: Victoria, BC
Posts: 306

Thread Starter
Arqen is offline
Quote:
Originally Posted by Jens Eklund View Post
Thanks Tim!




Once I´ve made a Reflex model, I usually play around a bit with it and I noticed regarding the B2-Frac, that you don´t need to exclude periods between 5 and 10 since if you take the average diffusion coefficient between 400 Hz and 10 kHz for each curve (see below) and compare with the total panel width; you´ll find a close to exact linear relation. So don’t be afraid to use the B2-Frac in 6, 7, 8 or 9 periods i o w. It won´t perform any worse than if used in 5 or 10 periods. Naturally, any diffuser will show a decrease (some more than others but still) of the diffusion coefficient for larger total panel widths, so in order to achieve good performance for larger panels, deeper depth is unavoidable.

Attachment 317038
B2-Frac diffusion coefficients for 5, 6, 7, 8, 9 and 10 periods.

Thanks for doing those tests, Jens!

The results are very interesting. I'm curious: was aperiodic modulation applied to the sequences?
#119
14th November 2012
Old 14th November 2012
  #119
Lives for gear
 
Jens Eklund's Avatar
 
Joined: Oct 2009
Location: Stockholm
Posts: 4,691

Jens Eklund is offline
Quote:
Originally Posted by Arqen View Post
Thanks for doing those tests, Jens!

The results are very interesting. I'm curious: was aperiodic modulation applied to the sequences?
Yes.
#120
14th November 2012
Old 14th November 2012
  #120
Lives for gear
 
Joined: May 2012
Posts: 2,321

OpusOfTrolls is offline
Quote:
Originally Posted by Arqen View Post
Good point. Also, in a small room I expect massive low frequency diffusers could alter the modal response in a favourable way (by spreading modal energy over more frequencies). But, I'm imagining very deep diffusers.

I agree that it's most practical to aim for diffusion over 400 Hz. In Derek's case, this could be used as a guideline when choosing the size of material for each wall panel. I.e., though testing in reflex, he could find out what scaling factor (used to scale an optimized stepped diffuser design) produces a diffuser that starts working around 400 Hz?
Massive diffusers would break up LF resonance, but that is not an argument for their adoption.

I have read the Master Handbook of Acoustics by Alton Everest and on one particular section, noticed a drawing of an RFZ control room that had a LF diffusive rear wall. I said to myself how could this be any better than a dead wall? The diffuser doesn't absorb (AFAIK), but it does minimize the interference of the first reflection. Knowing physics there will be another reflection soon after, and I doubt it would be very predictable. But could it be beneficial?

Think about the wavelength of a LF soundwave, and how long it takes to actually realize the dynamic. Could adding temporal diffusion to a slow to begin with frequency band make the sound any better? It might, but I will say the effect is narrow in respect to the source audio. It will modify the dynamics and create masking in the frequency band. This is obviously not beneficial to critical listening, but I have heard many records with LF reverberation that without wouldn't have had the same conveyance.

So I do believe it is a matter of taste. In my own personal testing with headphones and my DAW I really felt that diffusion under 400hz is unnecessary and creates too much mud which masks the critical dynamics of that frequency range.
New Reply Submit Thread to Facebook Facebook  Submit Thread to Twitter Twitter  Submit Thread to LinkedIn LinkedIn  Submit Thread to Google+ Google+ 
 
Topic:
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
Ethan Winer / Bass traps, acoustic panels, foam etc
86
Riddler / Bass traps, acoustic panels, foam etc
18
Soundproof / Post Production forum!
6
DaleNixon / Low End Theory
14
nuendoness / Low End Theory
15

Forum Jump

SEO by vBSEO ©2011, Crawlability, Inc.