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experimental skyline diffusor with pics - comments appreciated Effects Pedals, Units & Accessories
Old 11th June 2012
  #1
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666666's Avatar
experimental skyline diffusor with pics - comments appreciated

Had a bunch of cheap 1"X2" pine furring strips laying around (non-square / rectangular), actual dimensions about 1.5" X 0.75", figured I'd put them to use.

I built some skyline diffusors using the BBC 12X12 calculator. The tallest column is a whopping 22". According to the calculator, this should diffuse down to about 300Hz.

In terms of high frequency diffusion, in the x plane the column widths are 0.75", the calculator says it'll diffuse upwards of 9999Hz. In the y plane the columns are 1.5" wide, the calculator says it'll diffuse up to about 5000Hz.

This work was done prior to discovering the QRDude site, so it is what it is. QRDude does not address aspects of this particular experimental design.

So far I have not found any useful info regarding the use of non-square columns in a skyline diffusor build. Seems that many reject the idea because it hasn't yet been published as something that is recommended, so I submit the idea yet again here to see if anyone might have some educated and/or intelligent comments on why this design may or may not be good. Any degree of educated speculation welcomed.

My take on the design is that the rectangular columns will very simply offer different diffusion performance in each plane. In the x plane the columns are 0.75" wide and in the y plane the columns are 1.5" wide, logic would suggest that the diffusor will diffuse up to a higher frequency in the x plane verses y plane... which, if so, should be fine.

Or is it the type of thing where once you mess with the math, even just a bit, the entire thing completely goes to hell? I do realize that acoustics are a combination of rocket science and black art. Logic often does not apply. This is why I can only refer to this project as "experimental" at best. Seemed like a good way to make use of the extra furring strips I had anyway.

These diffusors are planned for a very small tracking room (about 12' x 20'), the instruments would be no closer than about 6 feet from the diffusors. And yes, the room will also include strategically placed 703 wall and corner traps etc.

So... will this diffusor still diffuse in a somewhat favorable manner, or might it be the type of thing that is worse than no diffusor at all? (I have yet to actually test them by ear in the room and will do so)

One nifty aspect of this diffusor design for the DIY crowd specifically is that each one (12 X 12 grid with longest column being 22") takes only about sixteen 8-foot long furring strips to make. These furring strips can be gotten at any Home Depot or Lowes etc for 95 cents each. Most lumber of nicer quality or more specific dimensions can cost easily four times as much per foot if not a lot more.

Pictured below are TWO 12X12 grids next to each other (288 columns in all, an effective 24X12 grid), total footprint 18" X 18", total cost in column lumber would be about $32 for this.
Attached Thumbnails
experimental skyline diffusor with pics - comments appreciated-diffusor1-72.jpg  
Old 12th June 2012
  #2
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boggy's Avatar
Quote:
Originally Posted by 666666 View Post
...
I built some skyline diffusors using the BBC 12X12 calculator. The tallest column is a whopping 22". According to the calculator, this should diffuse down to about 300Hz.
Looks nice!
Quote:
Originally Posted by 666666 View Post
My take on the design is that the rectangular columns will very simply offer different diffusion performance in each plane. In the x plane the columns are 0.75" wide and in the y plane the columns are 1.5" wide, logic would suggest that the diffusor will diffuse up to a higher frequency in the x plane verses y plane... which, if so, should be fine.
Yes, you are right.
Quote:
Originally Posted by 666666 View Post
Or is it the type of thing where once you mess with the math, even just a bit, the entire thing completely goes to hell?
Diffusers know nothing about our ears, hearing and brain between ears, so if you don't hear any "hell" it is ok . We need diffusers in studio acoustics because our hearing/brain like it... not because math. I never see anything useful in studio acoustics that needs to be that precise (or it generate "hell"), simply because temperature and humidity will change it over time, and nobody like surprising changes in his acoustics . I hope I have explained.
Quote:
Originally Posted by 666666 View Post

So... will this diffusor still diffuse in a somewhat favorable manner, or might it be the type of thing that is worse than no diffusor at all? (I have yet to actually test them by ear in the room and will do so)
This diffuser will diffuse sound in your room not worse than similar built from pine strips with square cross section.
Quote:
Originally Posted by 666666 View Post
Pictured below are TWO 12X12 grids next to each other (288 columns in all, an effective 24X12 grid), total footprint 18" X 18", total cost in column lumber would be about $32 for this.
Great!!!
Old 12th June 2012
  #3
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understand that the BBC design you referenced is a PRD (not QRD) - and is actually an array of many smaller PRDs (hence why the wells are 12x12 --- which does not adhere to the math for a single PRD). so if you wish to build any more units, it would be wise to utilize a PRD or QRD calculator to design the device based on your specific criteria


also,

300hz is ~ 45inches (3.77ft).

bear in mind that while depth of the reflection phase grating diffuser does dictate design frequency, that the overall size of the diffuser still needs to be large with respect wavelength (eg, 3.77ft). QRDude software in itself has checkmarks/scorecard to verify that the design meets all of these criteria.

a 15"x15" diffuser that has sufficient depth of the wells to diffuse 300hz is not going to function as a diffuser at 300hz because the 300hz wavelengths will diffract around the diffuser since it is small with respect to wavelength.

please also see the wonderfully written QRDude technical guide (easily digestible for the novice!) - QRD diffusers: Technical Overview

"These diffusors are planned for a very small tracking room (about 12' x 20'), the instruments would be no closer than about 6 feet from the diffusors. And yes, the room will also include strategically placed 703 wall and corner traps etc."

also note the distance limitations for reflection phase grating diffusers: it is best practice to be at least 3x wavelength of the design frequency from the diffuser such that you are in the far-field. eg, a reflection phase grating diffuser (PRD or QRD) that has 300hz design frequency requires ~ 11.28ft distance to be in far-field. one diffuser design constraint is distance, which will determine lowest design frequency of diffuser for your room. a diffuser with design frequency of 550hz (~2ft wavelength) will be a good design if you will be recording approx 6ft from the units.

have fun!
Old 12th June 2012
  #4
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666666's Avatar
Guys, I sincerely appreciate the informative replies.

Yeah, I wish I had seen and digested that QRDude site before I had embarked on my little furring strip project. Well, I only made four 9"X18" footprint units so far, so... not too much lost.

I'd imagine that the experimental diffusors I made would be better than just a bare wall, however, if I'm only going to run four 9"X18" footprint diffusors, I won't be taking advantage of the 22" depth of the diffusors... and thus they are just a waste of valuable space.

At this point, after studying the QRDude site some more, I can see that it's just not worth it for me to make any more of these experimental furring strip diffusors. They are super cheap to make, BUT, and not that this is a surprise, they take a LOT of time to put together, especially when you have to paint each column, etc... not worth it.

SO... ok... I have decided to just do the right thing and purchase a few pre-made, "approved", "proven" diffusors from a reputable company like RPG. I have no more spare time to attempt to design and build any more diffusors. It's obviously something that takes a good deal of time and study to get right. And I actually just got a call to record some drum tracks for an important project and need to focus on that now. After all, I'm a musician, not an acoustician. Shame on me for attempting to build DIY diffusors! Well, live and learn. It's all good.

I'd be more thankful than you could ever know if I could get a few recommendations on the following:

My drum recording room is about 12' wide by 20' long. Drums are pretty much right in the middle of the room, facing the short wall. Behind the kit is my desk, computer, a window, etc, and no room for treatment, aside from 703 corner traps in top and side corners.

The drums are about 9' away from the other short wall, this is the farthest wall from the kit and in theory the best wall to place some diffusion. I'll refer to this as the "diffusion wall". (The long / side walls which are very close to the kit are covered in 4" of 703 to kill close reflections.)

My diffusion wall... due to assorted physical limitations (door, window, vents, etc), the best I can do in terms of a continuous footprint of diffusion is 6 foot wide by 2 foot tall.... and this would be roughly right in the center of the wall. I already have 703 traps in each side corner and at the top and bottom corners.

A 6' X 2' area for diffusion means I can purchase three 2'X2' diffusor panels and put them side by side. I see than RPG does offer a lot of their diffusor products in 2'X2' squares... perfect.

So my question here... I'll just talk about RPG for now since they have a wide variety of things in their catalog... what type of diffusor do you think might be best for my situation?

No, I have not done any scientific measurements of the room, the room actually sounds "ok" but is pretty dead, my goal with diffusion is to try to get a little bit of life back, a little bit of extra upper end zing. I do not ever expect this room to sound "live", that is not the goal... but whatever I can do to ever so slightly "undeaden" it, WITHOUT introducing any damaging "close reflections", would help.

I'm mainly interested in perhaps getting back a bit of 5kHz and up... and the higher the frequency of diffusion beyond that, the better... like if I can diffuse 5k to 10k that would be perfect. Much of the low mud stuff is already being eaten up by the traps which is good, I'm not as concerned about the low end.

The RPG "Diffractal" units look good and come in 2'X2' squares. How about three of these in a row, side by side, in the center of my wall? They're 9" deep, this is ok.

http://www.rpginc.com/ProductDocs/DI...l_Brochure.pdf

Or maybe the QRD 734?

If not, then what might be recommended? Again, I have a 6' long by 2' high footprint to work with.

I have not priced the Diffractals but I'd imagine that they're very expensive... but at this point I'd just like to do the best I can here and be done. My attitude now, I'd rather pay the price and be done instantly, and have it done right, as opposed to spending many more days or weeks experimenting, possibly only to arrive at less than optimal results.

I see that RPG may have slightly cheaper options, but at this point, I want the "best" for my application, regardless of cost.

And, no, I don't work for RPG.... I actually just discovered them at the QRDude site and I like the fact that they have so many options and different sizes etc... and they seem to have good designs. If there's anything else out there that is recommended, something that'll cover a 6'X2' footprint, I'm all ears.

Thanks!

-
Old 12th June 2012
  #5
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Quote:
Originally Posted by 666666 View Post
Yeah, I wish I had seen and digested that QRDude site before I had embarked on my little furring strip project. Well, I only made four 9"X18" footprint units so far, so... not too much lost.
nothing is truly lost! group the four (4) units together into a single, large array.
Old 12th June 2012
  #6
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666666's Avatar
Quote:
Originally Posted by localhost127 View Post
nothing is truly lost! group the four (4) units together into a single, large array.
Ok! Well, if I did that... four 9"X18" panels (oriented so that they are 18" top to bottom and 9" side to side) can be put together side by side to cover a footprint of 36" across by 18" high.

Or I could continue to make more and try to fill up my entire available 6' wide by 2' tall available footprint area. But to do that I'd have to make four more.

But, at this point I'm just concerned that these DIY diffusors might not perform as well as a premium, "state-of-the-art", hi-tech diffusor system.

What I am realizing here... pretty much the ONLY space I have for wall diffusors in the entire room is this one 6' X 2' footprint in the center of the one "far" wall... that's it. So, whatever diffusors I place in this "critical" space must be top notch and must perform as best a diffusor could possibly ever perform. I guess if I had a larger room with a lot more space and an ability to hang a lot more diffusors of different types etc it would be a bit less critical.

After reading through the QRDude site and also reading stuff on the RPG site, I'm starting to get very interested in those RPG Diffractal panels and some of the other RPG panels. I still don't know what they cost, maybe the price will be the deal breaker. I'm willing to put a decent amount of bucks down for good diffusion, I know it's not cheap, but there IS a reasonable limit finally. I'm hoping that the RPG panels are real deal tools for pros and not just gimmicky, esoteric eye candy for rich people. Will need to look into it.

In sum, I have a mere 6' X 2' footprint to play with, I want to make the best of it. If I can add a tiny bit of favorable "snap" to this dead room (without harmful close reflections) I'd be happier than you could know.

The real problem is that the room is just too damn small, low ceiling etc, but it's all I have and I need to make it work. I know small rooms like this CAN "work", I've done it before, but I'd really like to optimize this one.

What's on my side too is that I actually PREFER a close, dry, intimate type of drum sound, ala typical 1970's drum production. So the small room can ultimately make me happy if I can just tune it up good.

So, any more thoughts? RPG Diffractals? OR might my DIY panels be ok if I run them in a 6' long configuration?

THANKS
Old 13th June 2012
  #7
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Quote:
Originally Posted by 666666 View Post
Ok! Well, if I did that... four 9"X18" panels (oriented so that they are 18" top to bottom and 9" side to side) can be put together side by side to cover a footprint of 36" across by 18" high.

Or I could continue to make more and try to fill up my entire available 6' wide by 2' tall available footprint area. But to do that I'd have to make four more.

But, at this point I'm just concerned that these DIY diffusors might not perform as well as a premium, "state-of-the-art", hi-tech diffusor system.

What I am realizing here... pretty much the ONLY space I have for wall diffusors in the entire room is this one 6' X 2' footprint in the center of the one "far" wall... that's it. So, whatever diffusors I place in this "critical" space must be top notch and must perform as best a diffusor could possibly ever perform. I guess if I had a larger room with a lot more space and an ability to hang a lot more diffusors of different types etc it would be a bit less critical.

After reading through the QRDude site and also reading stuff on the RPG site, I'm starting to get very interested in those RPG Diffractal panels and some of the other RPG panels. I still don't know what they cost, maybe the price will be the deal breaker. I'm willing to put a decent amount of bucks down for good diffusion, I know it's not cheap, but there IS a reasonable limit finally. I'm hoping that the RPG panels are real deal tools for pros and not just gimmicky, esoteric eye candy for rich people. Will need to look into it.

In sum, I have a mere 6' X 2' footprint to play with, I want to make the best of it. If I can add a tiny bit of favorable "snap" to this dead room (without harmful close reflections) I'd be happier than you could know.

The real problem is that the room is just too damn small, low ceiling etc, but it's all I have and I need to make it work. I know small rooms like this CAN "work", I've done it before, but I'd really like to optimize this one.

What's on my side too is that I actually PREFER a close, dry, intimate type of drum sound, ala typical 1970's drum production. So the small room can ultimately make me happy if I can just tune it up good.

So, any more thoughts? RPG Diffractals? OR might my DIY panels be ok if I run them in a 6' long configuration?

THANKS
Hey, nice looking puppies!

I would hang those 4, listen, measure with and without them and decide. But you have already thought this!

Regards
Old 13th June 2012
  #8
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"But, at this point I'm just concerned that these DIY diffusors might not perform as well as a premium, "state-of-the-art", hi-tech diffusor system. "

don't be so discouraged. there are limitations and constraints with any type of "diffuser"...and while yours may not be effective down to 300hz due to physical size of the unit, it doesn't mean it is not very effective at good spatial and temporal dispersion above that. like you said, it's going to be better than a bare wall.

it's not just about perfect diffusion (if such a thing exists), but also construction - as a reflection phase grating diffuser inherently has a relatively high absorption coefficient, and additional losses are easy to accomplish by shoddy construction of the diffuser (unsealed gaps). in a small live room, the additional absorptive component may be beneficial...but that is for your subjective preference to decide.

for a live room in your case i think the issue is more about quantity (coverage) than necessarily quality.
Old 13th June 2012
  #9
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666666's Avatar
localhost127, I greatly appreciate your intelligent and realistic approach / replies. Makes really good sense.

I started getting discouraged about my DIY diffusors for two main reasons:

1. Considering that my diffusors may not diffuse well down to 300Hz (due to how they will be applied and fact that they're not of an "optimum" design and construction), the issue is that it may be a big waste of space for them to be 22" deep (and I can't cut them down at this point of course). I started thinking / realizing that I could have made these perhaps half the depth and still achieved the same "effective" diffusion performance per my situation. Since the room is so small, saving nearly a foot of space is actually a big deal.

2. While these DIY diffusors only cost me say $40 a pop to make (factoring in the value of the furring strips, backing board, paint and glue), they did take a LOT of TIME to make. I flew through the work as fast as I could, had a whole assembly-line thing happening, very organized, but even so, it just simply takes a lot of time to cut, paint and glue 130+ pieces of wood together (per 9"X18" diffusor). I was averaging barely even one diffusor per day (at least in terms of the available time I often have per day)... this is a lot of time for me to spend so I started thinking it might be wiser for me to just buy some pre-made units, even at a high cost.

But, you are indeed giving me a bit more confidence about my DIY diffusors, at least in terms of their effectiveness in my particular situation. And, hard to ignore the cost savings.

Absorption... good point... I was indeed reading at the RPG site about how each of their diffusor models offer different degrees of absorption, inherently. My DIY diffusors likely have a pretty high absorption factor due to the depth and the fact that the work IS "shoddy"... there are indeed plenty of gaps / spaces between the columns, nothing is "sealed". In reality, the work itself is not specifically "shoddy", but the cheap furring strips are of very poor quality, all somewhat warped, twisted, knots, the dimensions are not perfectly consistent piece to piece, etc, so even doing a fairly careful job, there are still a lot of gaps and general inconsistency. I would not have been able to make it much better unless I started planing / milling each and every piece to perfection... or stepping up to a grade of wood at least four times more expensive.

But, this "shoddiness" could work to my advantage potentially, because the more I think about it, if these DIY diffusors tended to absorb below say 700Hz and diffuse above 700Hz, that might actually be a very good thing. Of course I realize how incredibly unscientific I'm being here now, I am aware that normally, one should FIRST measure a room, figure out what needs to be done, then build / obtain treatment to deal with the observed issues.... where as I haven't measured anything and I'm just rolling the dice here in every regard. Shame on me.

But, sometimes, if the application is not overly critical, the "unscientific yet logical DIY approach" and "tuning merely by ear" can potentially be all that's needed. My friend has a small basement room, he put up some foam here and there (yikes) and left a lot of the sheetrock bare, and amazingly the room actually sounds really good for tracking drums... I think he just lucked out due to assorted specific, favorable factors, but... I have to question how much better he could make that room sound for his purpose even if he spent several thousand dollars on the best traps and absorbers known to mankind. Now of course if he was going to use that room as a critical mastering room instead, it would be a different story.

So I will put up my existing four DIY diffusors for now and will need to decide whether to make more and totally "commit" to my DIY project, or if I should go the "proven" route and buy some pre-made, scientifically designed pro-level diffusors. Once I hang the existing four DIY diffusors, I doubt I will detect any difference in the sound of the drums through the mics. I wouldn't be changing enough surface area of the room to really make a difference (would only be like 4 square feet of change). I think I'd need to hang more new diffusors before I'd detect a noticeable difference. If I wind up covering my entire available 6' X 2' wall space, that would be 12 square feet of change, that should make a difference. Point is, I don't think I can arrive at any "conclusions" for now just based on hanging my existing four 9"X18" footprint DIY diffusors.

One question if I may... please...

Another thing I did, based on logic, but may have been a bad idea...

Of the four DIY diffusors I made, I made two of them in a perfectly opposite orientation to the other two. In other words, two are a mirror image of the other two. My thought here was that I wanted to keep the room perfect symmetrical, left to right. Refer to attached image at the bottom of this post to see what I did.

After more reading etc, I am realizing that this may have been unnecessary and just a bad idea in general. But I still have a chance to correct this situation without really losing anything since I could use the two "mirror image" units in another spot and just make more "original orientation" units for the more critical 6'X2' area.

So should I indeed scrap this "mirror image / left to right symmetrical" approach, will this mess with the math and cause greatly reduced diffusion performance where the "left side" units meet the "right side" units? Or does it simply not matter and maybe my mirror image idea is ok???

Thanks!
Attached Thumbnails
experimental skyline diffusor with pics - comments appreciated-diffuser-mirror-image-13.jpg  
Old 13th June 2012
  #10
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Quote:
Absorption... good point... I was indeed reading at the RPG site about how each of their diffusor models offer different degrees of absorption, inherently. My DIY diffusors likely have a pretty high absorption factor due to the depth and the fact that the work IS "shoddy"... there are indeed plenty of gaps / spaces between the columns, nothing is "sealed". In reality, the work itself is not specifically "shoddy", but the cheap furring strips are of very poor quality, all somewhat warped, twisted, knots, the dimensions are not perfectly consistent piece to piece, etc, so even doing a fairly careful job, there are still a lot of gaps and general inconsistency. I would not have been able to make it much better unless I started planing / milling each and every piece to perfection... or stepping up to a grade of wood at least four times more expensive.
It is best to not have gaps, but the downside to having gaps is not as big as with typical "hollow" diffusor designs made out of sheet goods.

With hollow construction the small gaps and the room behind will function as helmholtz resonators, creating much higher absorption coefficient.
Old 13th June 2012
  #11
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boggy's Avatar
Quote:
Originally Posted by 666666 View Post
localhost127....
I started getting discouraged about my DIY diffusors for two main reasons:
1. Considering that my diffusors may not diffuse well down to 300Hz (due to how they will be applied and fact that they're not of an "optimum" design and construction), the issue is that it may be a big waste of space for them to be 22" deep (and I can't cut them down at this point of course). I started thinking / realizing that I could have made these perhaps half the depth and still achieved the same "effective" diffusion performance per my situation. Since the room is so small, saving nearly a foot of space is actually a big deal.
If you concerned about your useful space, so build more shallow (1kHz working frequency) 2D diffusers with same material, and add it to this, which you already have, and it may be mounted somewhere they will not disturb you(r space)
Quote:
Originally Posted by 666666 View Post
2. While these DIY diffusors only cost me say $40 a pop to make (factoring in the value of the furring strips, backing board, paint and glue), they did take a LOT of TIME to make. I flew through the work as fast as I could, had a whole assembly-line thing happening, very organized, but even so, it just simply takes a lot of time to cut, paint and glue 130+ pieces of wood together (per 9"X18" diffusor). I was averaging barely even one diffusor per day (at least in terms of the available time I often have per day)... this is a lot of time for me to spend so I started thinking it might be wiser for me to just buy some pre-made units, even at a high cost.
....
Ok, ok, I know that building diffusers is hard work, but if you build studio for a job, where you can earn more than one RPG diffractal panel per day, so you already have an answer, I suppose.
Old 13th June 2012
  #12
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666666's Avatar
Thanks for the continued replies, guys. Much appreciated!

Yes, I'm starting to think about making more DIY diffusors, but this time making them about HALF as deep. I just went back to the old 12X12 skyline calculator (link below) and discovered that I could make these same diffusors, but only 11" deep (instead of 22" deep), and they'd still diffuse down to about 600Hz (in theory, according to the calculator). I'd think this would be more than fine. There's plenty of 703 on the walls and in corners to help tame what's below that in general. And the room walls are "merely" sheetrock with open space on the other side, thus I'd imagine that a good deal of the lower frequencies just pass right through and out anyway.

Making these diffusors only 11" or so deep will save on wood but will not reduce the workload too much... well, just a little. It'll be less total surface area to paint, and I will have less of a headache when dealing with very warped furring strips since the shorter the pieces are for the diffusor, the less of a problem warped stock is. And less wood to carry back from Home Depot. So ultimately, making the diffusors less deep WILL save a little bit of time. Good.

And of course making shorter diffusors (of about 11" deep) will save 11" in terms of space (verses the 22" deep design)! Plus will be lighter, easier to deal with in general, easier to clean / dust, etc.

So I'm strongly thinking of going this route at this point.

But I still really would like to know how critical the orientation of the pattern is and if my left / right "mirror image" idea is ok or not ok. Gut feeling at this point is that I should keep the exact same orientation for all panels and not bother with "mirror image", but I'd love to hear some comments on this. It's easy enough to build the panels either way.

Thanks!
Old 13th June 2012
  #13
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666666's Avatar
Also, another thought... my main array of diffusors would be 18 inches "tall" by 6 feet wide... that's the available footprint I have for diffusors on the "diffusion wall"... at least when using 18" X 18" panels.

Please correct me if I'm wrong... 18 inches is the wavelength of 750Hz, yes? And being that the minimum dimension of my diffusor array would be 18" (18" X 72" rectangle footprint), is it correct to assume that this array, regardless of depth (column height), will not be overly effective at diffusing waves any lower in frequency than 750Hz? If this is so, then I need not build diffusors with a depth that theoretically supports diffusion any lower than 750Hz. Correct?

According to the old 12X12 diffusor calculator, to diffuse 750Hz and above, the max column height need only be about 9". Sound like a plan?

Old 14th June 2012
  #14
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Quote:
Originally Posted by 666666 View Post
my goal with diffusion is to try to get a little bit of life back, a little bit of extra upper end zing. I do not ever expect this room to sound "live", that is not the goal... but whatever I can do to ever so slightly "undeaden" it, WITHOUT introducing any damaging "close reflections", would help.
Just to let you know, this is an impossible goal. As I'm sure you know, diffusion doesn't add any 'life' to a space, at all. It doesn't increase RT60. It may very well sound 'spacious' to your ears, but it will not serve that purpose quoted above. The only way this is possible is if you added your diffuser on to the front of your traps.

Diffusers, as you also know, actually absorb as well too. So by putting diffusers in your room you are actually making it even MORE dead in the room, although at least it will be partially diffuse.

It seems you've done your research, and are going about this in the right way, but you won't un-deaden your room. If the traps have sucked too much life out of the space, you can literally use some wood to bounce some energy back into the room. You can use simple sequences like Newell's sequence for slats.

liven up my live room
This thread has some good ideas too.
Old 14th June 2012
  #15
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Quote:
Originally Posted by kasmira View Post
Just to let you know, this is an impossible goal. As I'm sure you know, diffusion doesn't add any 'life' to a space, at all. It doesn't increase RT60. It may very well sound 'spacious' to your ears, but it will not serve that purpose quoted above. The only way this is possible is if you added your diffuser on to the front of your traps.
Diffusers, as you also know, actually absorb as well too. So by putting diffusers in your room you are actually making it even MORE dead in the room, although at least it will be partially diffuse.

It seems you've done your research, and are going about this in the right way, but you won't un-deaden your room. If the traps have sucked too much life out of the space, you can literally use some wood to bounce some energy back into the room. You can use simple sequences like Newell's sequence for slats.

liven up my live room
This thread has some good ideas too.
I agree. I bolded one sentence though as it is significant. -Do you start with a room with bare walls or a room which has too much of porous absortion?

I had the latter and managed to increase T60 with about 0,1 s above about 4 kHz, lower about 0,15 s at 125 Hz, in between there was a smaller but still improvement = higher T60. (Used 6 m² of DIY BAD-panels + about 7 m² of slats 33 mm wide according to Boggys MLS-sequence. End result got pretty much even from 125 Hz-8 kHz, roughly 0,15-0,2 s.)
Old 14th June 2012
  #16
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Guys, once again, thanks so much for taking the time to add helpful replies here.

Yes, I am actually aware of the concept of adding slats to the front of absorbers, in the Newell sequence, etc... and I indeed plan on doing this.

As for my desire for diffusors... well, I do have this 6' X 2' footprint of bare space on the farthest wall. I do already have 703 corner traps in all corners of this wall (sides, top and bottom). I was going to add another 703 trap in the 6' X 2' space but this didn't seem to make sense since I am already battling with an overly dead room.

Another option for this 6'X2' bit of wall space would be to simply leave it bare, but the way things are situated in the room, I would not feel too comfortable about doing this in fear of having close-reflection related issues. So, I decided to go with DIY skyline diffusors for this space, seemed like the "best" option, at least in terms of a fairly unscientific, DIY approach. From what I have learned here so far, the diffusors, while they very well may absorb to a decent extent in the lower range, should hopefully scatter and send upper frequency energy back into the room, but at least not in the form of direct close reflections. This is my train of logic anyway. The diffusors will "reflect" back more than a trap would in any case, and scatter to boot.

Even if the diffusion does merely serve to "sound 'spacious' to the ears", what that means to me is that it should, in theory, make the room sound a tad bit larger than it is... good. That's what I need. If it "sounds spacious", then this means it does have a sound... where as a trap would technically have no sound (well, very slight)... and a bare wall might have a very nasty sound (likely serious close reflections and even standing waves considering that the instrument and mics are not far away and straight on, as well the room is rectangular). So again, just another bit of logic to support my desire for diffusors on this one wall.

Side note: I am not at all claiming that my logic is correct, but merely explaining why I have arrived at the plan I am describing.

So, at this stage, I DO plan on adding "Newell slats" to a number of my traps around the room. As well I still think I will cover the 6'X2' space on the far wall with DIY skyline diffusors... UNLESS you guys have a better idea for that space.

I must add that in the area of the room in front of the drums, between the drums and the "far wall", I have a bare hard floor and the ceiling there is also bare sheetrock. I left the floor and ceiling bare here to help retain a bit of snap in the room. However, the ceiling directly over the drums and the walls directly to the sides of the drums are almost fully covered in 4" of 703 with the goal of killing as much close reflection related issues as possible.

And did I mention that the ceiling height is less than 7 feet? You can see why I'm struggling here. Again, this room is all I have, I need to make it work, as far from ideal as it is. The one really good thing about it though, it's isolated REALLY well, I can play all day long without disturbing anyone inside or outside the building, that is a big advantage that cannot be ignored, hard to find / achieve this around here... all the more reason I strive to make this tiny room work.

One reason why I'm scared to death of "close reflections"... I once had a drumkit in a small room much like the one I'm dealing with now. It was treated with some degree of absorption, but not too much. I remember having a heck of a time tuning those drums. Had all kinds of weird head resonances and ringing, crazy snare buzz, etc, almost impossible to tune. I could never get the kit itself to sound good, let alone get the room to sound good. At the time I thought it was just me not being experienced enough at tuning. Then one day I pulled that very kit out of that room and into a much larger room with a high, angled ceiling.... the kit instantly sounded incredible! All the wacky head resonance issues, snare buzz, ringing, etc, instantly gone! The kit itself now sounded quick, tight, great tone, etc. Night and day difference. It was obvious to me that the SMALL ROOM (which was not treated well enough for close reflections) was causing all the trouble and making it nearly impossible to tune the kit. That's why when I got into this new small room, the first thing I did was cover all the close surfaces with as much 703 as possible. This seemed to be the best idea since there is literately not enough physical space for any type of other more esoteric treatment... I can barely sacrifice the 4" on the walls and ceiling as it is for the 703 (actually 5.5", I have a 0.75" air gap behind the 703 and 0.75" of cotton batting in front of the 703).

Anyway, ok, sorry for the long winded posts, just trying to adequately respond to the excellent replies I'm getting here. I greatly appreciate all the help. Ultimately I will incorporate all the suggestions here into the room and then just tune by ear from there. I'd like to think that adding the Newell slats to some of the traps plus add the diffusors on the "far wall" will get me closer to where I'd like to be.

I do promise to post some recordings from inside this room once I get it to a spot where I'm happy. Again, my goal is not to necessarily have the room sound "big and live", I know that would be impossible. But as I had mentioned, I actually prefer a tighter, fairly dry, intimate drum sound, ala typical 1970's drum production, in which a small room can work. I'm just seeking a good overall frequency balance (including keeping it from being too dry and too "dead") while trying to make sure to keep any typical "small room issues" at bay.

Thanks again!
Old 14th June 2012
  #17
Lives for gear
 

+1 to above. diffusers will only "add life" if they are replacing a more lossy treatment.

Quote:
Originally Posted by kasmira View Post
liven up my live room
This thread has some good ideas too.
lol thanks for that - fun read.
especially the contention regarding scattering vs diffusion in the early part of the thread. no wonder SAC stopped posting here
Old 14th June 2012
  #18
Lives for gear
 
Jens Eklund's Avatar
Quote:
Originally Posted by 666666 View Post
Even if the diffusion does merely serve to "sound 'spacious' to the ears", what that means to me is that it should, in theory, make the room sound a tad bit larger than it is... good. That's what I need.
How "large" a room feels (sounds) depends mostly on the ITD-gap (Initial Time Delay), and the termination of it (when and at what level). To make a room sound larger that in actually is, you need to extend the ITD-gap for as long as practically possible (within limits). Use absorption or geometry to absorb/redirect, early reflections that otherwise shortens this gap. Use diffusers to tame sparse, strong reflections after the termination of the gap (or if you have enough space; use diffusers to terminate the ITD-gap). As stated previously; it´s not the diffusers per se that makes a room sound "larger" or "more spacious", it´s the use of appropriate acoustic treatment, applied correctly that achieves this. Diffusers in general are used manly to prevent single strong reflections after the termination (but the termination itself can also consist of the energy return from diffusers) without absorbing too much energy (compared to broadband absorbers). You might want to consider 1D diffusers if the space is limited since this usually offers more possibilities to steer the energy to where you want it, avoiding partial scattering back to the sweet spot/mic position, possibly within the ITD-gap.
Old 14th June 2012
  #19
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666666's Avatar
Quote:
Originally Posted by Jens Eklund View Post

...You might want to consider 1D diffusers if the space is limited since this usually offers more possibilities to steer the energy to where you want it, avoiding partial scattering back to the sweet spot/mic position, possibly within the ITD-gap.
Thanks Jens.

Considering my situation, the room is 20' (6m) long and the instrument / mics are about 8' (2.5m) from the wall in question, is there a specific 1D diffuser product that can be purchased that you'd recommend? I need to cover a 6'X2' space so I'd need three 2'X2' panels. I don't think I'd want to tackle trying to calculate and build a good 1D unit myself, I'd rather purchase. It does make sense to me, based on your description, that a 1D may indeed be a better option in my case than a 2D, considering my goals and small available footprint.

Earlier in this thread I started looking at the RPG Diffractals and other RPG 1D 2'X2' panels... comments? Anything else?

EDIT: I actually just spent some more time with the QRDude software and starting to consider trying to build some 1D diffusers. That software is indeed very cool. The 1D diffusers always looked a bit confusing to me, but after more research, and considering I'd only need to cover a 6'X2' space, I think I can handle it. The trick for me now is to try to determine what freq range I'd want to focus on etc. I do have easily 12" depth if needed, though it seems that more than 9" depth may not be necessary for dealing with mainly upper freqs. In general, I know that the frequencies of drum attack tend to be in the 4k - 8k area... this is a predominant mid/upper freq range... so I'd want to be focusing in this range, etc.... I also must consider that the mics etc will be about 8' from the diffusors... the QRDude software seems to address all these things, very cool. And even better, it would appear that 1D diffusors would be way less time consuming to construct than 2D (yes, I have good woodworking tools, table saw, chop saw, etc, etc)... I'm getting excited again. I can see now also that any pre-made product will likely not be specifically tuned per my situation / purpose... and will cost a small fortune... would seem way wiser to try to build these DIY. I will mess with the QRDude software some more and will attempt to arrive at a final design / dimensions for a proposed 1D for my room... and if I may, I'd like to share that info for approval here just to make sure I'm not making any dopey errors. Thanks!
Old 9th May 2013
  #20
Gear interested
 

Could an acceptable skyline diffuser be made from Legos?
Old 9th May 2013
  #21
dry
Gear Maniac
 
dry's Avatar
 

If only

Legos.... Ha. I wish. That way I could threaten the kids to pick up their toys or daddy,s going to add it to his diffuser grid.
Old 9th May 2013
  #22
Lives for gear
 

lol.
Old 10th May 2013
  #23
Gear interested
 

Quote:
Originally Posted by dry View Post
Legos.... Ha. I wish. That way I could threaten the kids to pick up their toys or daddy,s going to add it to his diffuser grid.


You're looking at this the wrong way; your kids can BUILD them for you and think it's a playtime project!

The relatively square blocks are 8mm square and 9.6mm tall. A 3x3 grid is 24x24mm (.94 in.). A peak of 5.29 inches would require 14 stacked bricks (for a 7-prime diffusor).

Would the round buttons on top be a problem, or would they help hi-f diffusion? And would the little hollow spaces between pieces cause too much absorption?

Otherwise, the only downize I can think of is that your kids might decide to disasembe them.
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