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PostPosted: Tue Aug 07, 2018 12:28 am 
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Soundman2020 wrote:
I wouldn't put slats across the bottom of the soffit: you'll be getting reflections down there from the rear of your desk, and everything on it: console, video screens, gear, decorations, etc. The speakers will be "illuminating" those very loudly, since they are very close to the speakers, so there's some pretty serious reflections coming off there and heading forwards again, down to where your slats are. It's better o have absorption down there to deal with that. If you are worried about losing the high end from too much absorption, then cover it with plastic, but that probably won't be an issue.

- Stuart -


Thanks Stuart. I've started working on a new design. After looking at some other threads etc. I'm going to use sorbothane washers and bushings to decouple my speaker box and securely fix it to a riser on my lower shelf, instead of an independant shelf.

I'm still very interested in using the lower section of the baffle as a slat resonator, but I'm looking at moving the slats back and putting 50mm absorption in front of it with a 25mm cavity between it and the slats.

I've also started on my baffle wing design. Here I'm planning to make it a horizontal slat resonator front.

I'll upload some pics when I'm in finished in sketchup


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PostPosted: Tue Aug 07, 2018 1:54 am 
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I'm still very interested in using the lower section of the baffle as a slat resonator, but I'm looking at moving the slats back and putting 50mm absorption in front of it with a 25mm cavity between it and the slats.
I'm not so sure that would be very useful! With the slats hidden behind thick absorption, they won't be doing any of what they do best (reflecting highs and high mids back to the room), and they also won't be tuned as a slot resonator... So I'm not sure what purpose they would serve...
Quote:
I'm going to use sorbothane washers and bushings to decouple my speaker box and securely fix it to a riser on my lower shelf, instead of an independant shelf.
:thu:


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PostPosted: Tue Aug 07, 2018 5:24 am 
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Soundman2020 wrote:
I'm not so sure that would be very useful! With the slats hidden behind thick absorption, they won't be doing any of what they do best (reflecting highs and high mids back to the room), and they also won't be tuned as a slot resonator... So I'm not sure what purpose they would serve...


Can you explain why it won't work as a slot resonator with the absorption? Wouldn't the absorption have little effect below the <200hz mark and therefore still allow the frequencies I'm targeting to reach the slats?


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PostPosted: Tue Aug 07, 2018 4:59 pm 
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Can you explain why it won't work as a slot resonator with the absorption?
The reason why it won't work as a slot resonator is not because of the absorption in front, but rather, because it won't be sealed! A slot resonator MUST have a sealed cavity behind, or it won't resonate! But that cavity CANNOT be sealed, because that's where your ventilation airflow for the speakers comes from! Also, even if that was a sealed cavity, it's not so easy to tune it to typical modal frequencies. Tuning Helmholtz resonators at all is rather difficult, and trying to tune things very low is way harder. Modes are very narrow (high Q) problems. Helmholtz resonators are also very high Q devices. Trying to match the frequency peaks exactly is a tall order...

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PostPosted: Tue Aug 07, 2018 5:48 pm 
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Soundman2020 wrote:
The reason why it won't work as a slot resonator is not because of the absorption in front, but rather, because it won't be sealed! A slot resonator MUST have a sealed cavity behind, or it won't resonate! But that cavity CANNOT be sealed, because that's where your ventilation airflow for the speakers comes from! Also, even if that was a sealed cavity, it's not so easy to tune it to typical modal frequencies. Tuning Helmholtz resonators at all is rather difficult, and trying to tune things very low is way harder. Modes are very narrow (high Q) problems. Helmholtz resonators are also very high Q devices. Trying to match the frequency peaks exactly is a tall order...

- Stuart -


Thanks for the response Stuart. I completely understand the need for it to be a sealed cavity, and it is sealed in the design. Ventilation is provided from the side in my design. The design is based on the newer rear wall design that john uses (I can't seem to find the thread atm). It uses deep slats, in my case 200mm deep x 50mm thick. Also as it spans a corner it has varying cavity depth. Having my in-cavity absorption tight up against my slats, it should widen the frequencies affected, but I'm aware that it will reduce the overall effectiveness. This is a low-mid tuned absorber I'm aiming for, that should have some effect on 40-140hz.


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PostPosted: Tue Sep 11, 2018 11:54 pm 
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Is there any advantage to lining the inside of the duct baffles with an insulating material such as 701?

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PostPosted: Wed Sep 12, 2018 3:58 am 
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MrWaj wrote:
Is there any advantage to lining the inside of the duct baffles with an insulating material such as 701?


In what way? In a silencer, you need to put duct liner to absorb some of the energy as the sound and air pass through, but I wouldn't swap this for 701 as it has air passing through it and it might swed fibres, I suppose you could seal it in someway but there's not a lot of point when there's a product designed for this purpose already (duct liner).


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PostPosted: Wed Sep 12, 2018 4:55 am 
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but I wouldn't swap this for 701 as it has air passing through it and it might swed fibres,
:thu: Don't substitute here. Only use proper duct liner that is specifically meant for lining the interior of HVAC ducts. Otherwise the airflow will abrade the surface away, and will also pick up dusts, pollen, microbes, and other nasty stuff, then release them later, unexpectedly. Use proper duct liner that has the surface prepared to resist air flow and kill microbes.

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PostPosted: Wed Sep 12, 2018 6:50 am 
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Quote:
Is there any advantage to lining the inside of the duct baffles with an insulating material such as 701?

Yes. Specifically for mid and high frequencies. Unless you increase the material depth to 4" with 3 lb/ft3 density, it won't have much of an effect on low frequencies. Low frequencies are effectively attenuated by the impedance mismatching provided by expansion chambers. This can be achieved by increasing or even decreasing your silencers cross sectional area. The larger the size difference is, the more effective the insertion loss becomes. Introducing several different sizes of paths will attenuate a broader range of frequencies.
Attachment:
Silencer Box Lining Thickness Attenuation.png

Taking expansion chambers into consideration, smaller paths will provide you with more attenuation. However, this will increase both the static pressure and air velocity in your system which is not good. Designing your system is literally a balancing act. Here is a chart showing this:
Attachment:
Duct Size With Duct Liner Attenuation.png

Hope that helps!

Greg


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PostPosted: Mon Nov 05, 2018 9:13 pm 
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Hi all,

So I'm getting back to my design as the build is progressing (albeit really slowly).

I'm weighing up my options once again.
I have spent a lot of time researching the best design for combined recording/mixing rooms.

These are my thoughts:
My priority is an enjoyable room to teach music and play music in. It shouldn't feel oppressive in this room.

My secondary goal is to mix in this room.

That is:
Great to excellent live/recording space.
Good to great mixing space.
In that order.

So my options are:
First option:
Build a great mixing space (RFZ design) with "variable acoustic devices", that is, ones that can be opened/turned etc. to change the sound of the room.
- Although these sound good in principle, it adds a layer of complexity that I would probably rather avoid.

The second option:
Build a room based on a design that lends itself to a multifunction room (My Room Acoustic Design Mark 2).

Now the benefits of RFZ are obvious, you have unaffected sound coming from your speakers to the mix position and it is treated after the fact. Good!

The benefits of My Room Acoustic Design (Mark 2) are reported to add feelings of space by diffusing/scattering mid to high frequencies, whilst absorbing lower frequencies. And with goid results even in very small rooms (typical bedroom size). With musicians saying it feels more live than the measurements show.
This design can acheive good results for mixing too, with rooms being within AES specification for frequency response and RT60.

I am seriously considering this design strategy as it seems to tick my boxes. It may not be quite as effective at tuning the room as RFZ can be, but I believe it to be a good compromise.

What are your thoughts guys?

Dan


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PostPosted: Tue Nov 06, 2018 4:24 am 
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Quote:
Build a great mixing space (RFZ design) with "variable acoustic devices", that is, ones that can be opened/turned etc. to change the sound of the room.
That would get my vote, for sure!

Quote:
- Although these sound good in principle, it adds a layer of complexity
Yes it does. Very true. But it also produces what you NEED to do what you WANT. The other option doesn't.

Quote:
Build a room based on a design that lends itself to a multifunction room (My Room Acoustic Design Mark 2).
Trying to build a room that is great for both tracking and mixing is exactly the same as trying to build an oven that is also great for freezing food.... :)

Quote:
The benefits of My Room Acoustic Design (Mark 2) are reported to add feelings of space by diffusing/scattering mid to high frequencies, whilst absorbing lower frequencies.
The only room I'm aware of that has actually been built, is the one linked to in that same thread on GS: deatils are scant, no useful photos, and the nicest thing that the owner could say after building it is that " I'm very comfortable working in there now, able to make quick decisions and work for a sustained period of time." That's fine, but no actual acoustic details. The paper gives some very vague details, but they don't look much different from a typical RFZ room.

Here's the T-30 graph from that paper:
Attachment:
my-room-mark-2-actualy-builtRT-30.jpg


And the T-30 graph from the corner control room, which is a typical RFZ room, as it is today (still incomplete):
Attachment:
Franks-room-as-built-RT-30.png



And here the highly smoothed ETC graph from that room in the paper:
Attachment:
my-room-mark-2-actualy-built-ETC.jpg


As compared to the similarly smoothed ETC graph from the corner control room:
Attachment:
Franks-room-as-built-ETC.png


Frankly, I don't see the difference!

Quote:
Control Room where measurements are done, have dimensions: W2.6m x H2.9m x L4.9m,
Very similar in size to the corner control room, and I'm getting the same results! That's nice to know... For the record the corner control room measures 3.85m x 3.85m by 2.93 H. 13.5m2 floor area, 38 m3 volume.

However, I would NOT suggest trying to track in that room! Why don't you ask the owner his opinion about that: He has a decent sized live room right next to his control room, so he can give you an honest answer about what instruments he would prefer to track in the LR, and which ones he would track in the CR...

The paper then goes on to talk about the predicted and measured decay times:

Quote:
we can calculate a nominal decay time, which is 0.18s.
When we compare that value with measurement results,
it is obvious that measured decay is higher than nominal
for 30-40ms from 500Hz and above, what is a success,
and method for increasing decay time is approved this
way,

Yup! Which is why I designed the corner control room to have longer decay times too! In fact, we are getting 214 ms right now... nearly 20% higher than the AES prediction for that sized room... and yet is is RFZ, using proven design and treatment methods, and not requiring a ton of timber sticking out all over the place...

It might interest you to know that I was contacted by a potential customer not too long ago, who had a room lined with vertical timber slats all around, that had been designed in this manner... he wanted me to quote for ripping it apart and re-designing it conventionally, since he found it to not be pleasant to work in...

Quote:
It may not be quite as effective at tuning the room as RFZ can be, but I believe it to be a good compromise. What are your thoughts guys?
My thought is that it's never a good idea to compromise when you don't have to! Why settle for less than "the best possible"? If you are going to spend all that money, time and effort, then why go for second best? I've had several customers who have decided to make the change mid-project: starting off with a sort of "Ok, lets do this roughly nice", then as things progress realize their mistake, and decide to go all.out for the best possible room. the corner control is one of those. Rod (from Studio Three) is another. There are many more.

Personally, I would go with the largest room you can possibly build, design it as RFZ, then build the treatment devices such that you can modify that sound to get a brighter, more airy sound with longer decay times and more reflection, so that you can also track some instruments and vocals in there. That's what I would do if that were my room.


- Stuart -



Quote:
With musicians saying it feels more live than the measurements show.
Hmmmm.... which "musicians" would that be? And which "measurements"?

Quote:
with rooms being within AES specification for frequency response and RT60.
So what? :)


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PostPosted: Tue Nov 06, 2018 8:17 am 
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Hi Stuart thanks for your response. I've thought about many of your points and agree with you on many of them.

I think think the appeal of the My Room Design seems to be the fact that it can pretty much be the same design regardless of the room size/dimensions. The simple principle is fit as much absorption as you can behind walls of diffusers with gaps between. Which is a fairly straight-forward design. (It also lends itself to 5.1 surround... which I don't need)

Looking at the results of the corner control room is encouraging though, because it has very similar measurements to the ones in Boggy's paper.
I am very interested in incorporating the PRN "air transparent diffusers" though in my room, as it has quite a lot of merit.

My current plan is this at the moment then:

Finish building the room shell (The dimensions are all set and construction is steadily progressing,with the external wall complete (unfaced), these cannot be changed).

The internal dimensions will be:
5.3m X 3.75m X 2.53m (This is the acoustic height of the inside out ceiling)
Giving a rough volume of 50m3 - Which I'm quite happy with.

Then I'll measure the empty room

Then move on to these:
My inside out ceiling will be filled with light insulation.

My speakers will be flush mounted using a similar method to John, but with sorbathane decoupling the speaker box from the frame (I'm not too worried about decoupling the speaker from the box though). I'll build "soffit wings" to create a good RFZ around the mixing position.

Then I'll measure the again

Then on my rear wall and corners I'll incorporate the PRN "air transparent diffusers". These will diffuse to around 1000Hz and will scatter down to roughly 500Hz. Thick absorption will be above and below the diffusers.

Then I'll measure the again

At this point I will have just ceiling and rear wall treatment. I will then add timber slats to the rear wall absorption and possibly plastic to the ceiling to tune reduce high frequency loss.

Then I'll measure the again

Now at this point I will examine my measurements before proceeding. I'll also play some guitar and sing in there to see how it's sounding.

variable acoustic devices / tuned devices will be constricted to only side walls in this plan.

Here's some images of my current design as it stands:

Attachment:
Nov 2018 Design.png


Attachment:
Nov 2018 Design Rear Wall.png


Attachment:
Nov 2018 Design Front Wall.png


Let me know your thoughts guys.

Thanks,
Dan


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PostPosted: Tue Nov 06, 2018 3:02 pm 
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I think think the appeal of the My Room Design seems to be the fact that it can pretty much be the same design regardless of the room size/dimensions.
I'm not so sure that would actually work in practice, although it does seem to be what they are claiming. I'm always wary of the "one size fits all" type of claim, because in reality it doesn't. All rooms are different, and each needs its own treatment. The problematic frequencies are different for each size of room, and each ratio, layout, and purpose. I can't see how one set of diffusers tuned to one part of the mid and high range is going to work for all room sizes, shapes, and layouts. It would be nice if it did, but acoustics doesn't work like that, unfortunately.

Quote:
Looking at the results of the corner control room is encouraging though, because it has very similar measurements to the ones in Boggy's paper
Exactly! And that was my point there: if conventional treatment works as advertised, with a lot less materials and complexity, then I'm not sure I see any advantage to this proposed new style.

Something that you may not have noticed: the corner control room is square! :) By design. I did that deliberately, since it is a "corner control room" layout, so in order to be symmetrical, it has to be square. Yet the acoustic signature shows no signs of it being square... I'd love to see how the My Room Mk2 concept would work in a square room, since it does not specifically target any frequencies, yet for a square room you most definitely need to target several specific frequencies... I can't see how it would have worked for the corner control room.

Quote:
I am very interested in incorporating the PRN "air transparent diffusers" though in my room, as it has quite a lot of merit.
Color me skeptical on that too! :) You might want to look into the theory of how diffusers work, and why QRD and PRD are so highly valued above all random sequences: QRD and PRD guarantee a flat power response. random sequences do not. :) In other words, with QRD/PRD, you are getting the same power scattered in each and every direction, so the intensity does not change: not matter where you measure, at all equidistant points from a QRD you get the same intensity (assuming that you measure beyond the critical distance, and that N is large enough in the first place, of course! You won't get flat power response for N=3, for example, or if you measure just a few inches away from the surface, but nobody in their right mind would even build an N=3 diffuser anyway, nor place their ears a few inches away!). That does not hold true for random sequences. With a random sequence, the power response is... well.... random! Which implies that there can be large intensity lobing issues, randomly spread around the room. This major issue was, unfortunately, not covered in the paper. They might not even be aware of it...

They would need to fully test their device at an independent test facility. The graphs they show in their paper are simulations, not actual tests. Curiously, they compare their 4m long device to a series of 4 QRD's set up one after another, which is known to cause lobing in diffusion coefficients, and would never be done in practice. I'm surprised they didn't compare theirs against a more typical QRD setup, with alternating panels... I wonder why?

Quote:
5.3m X 3.75m X 2.53m (This is the acoustic height of the inside out ceiling) Giving a rough volume of 50m3 - Which I'm quite happy with.
That's a nice size, actually. Very close to 20m2, and 50 m3 is great. Your room can be pretty good.

Quote:
My inside out ceiling will be filled with light insulation.
:thu: But how light? And how thick? :)

Quote:
My speakers will be flush mounted using a similar method to John, but with sorbathane decoupling the speaker box from the frame
Then you are not using John's method! :) You are using something similar to the Barefoot or Soundman202 method... :) Except that I also usually decouple the speaker from the enclosure box, in addition to decoupling the box from the frame.

Quote:
I'll build "soffit wings" to create a good RFZ around the mixing position.
:thu:

Quote:
Then on my rear wall and corners I'll incorporate the PRN "air transparent diffusers". These will diffuse to around 1000Hz and will scatter down to roughly 500Hz. Thick absorption will be above and below the diffusers.
I would not go that path. There's way too much hard, solid, reflecting surface on that rear wall, and the room isn't long enough for that to arrive back at your ears outside the Haas time. That can lead to psycho-acoustic problems with identifying correct directions, and correct frequency response. If the room was a lot longer, then you might be able to do that, but for a room only 5.3m long, that's a very real problem. That's also going to give you problems with SBIR, since the entire rear treatment setup is going to be one large reflector for low frequencies.

Why did you choose a diffuser that only covers the range you mentioned? You also mentioned "down to 1000 Hz", but didn't mention the upper limit. What is that? Why? All numeric based diffusers have both an upper and a lower limit...

Quote:
I will then add timber slats to the rear wall
... which would increase the specular reflective surface area behind your head, sending even more reflections back to your ears before the Haas time is up...

Take a look at the corner control room. Note that we did add some slats to the rear wall, over the hidden treatment, but not very many. At one point we tried some extra ones, but the reflection issue became too great, so we took those off again. That's when I designed the "poly slat" rear wall for him, since that solves both problems. Note that it is NOT based on a random sequence, but rather on an exponential sequence, to avoid power lobing... It also looks cool like that. There's a lot of reflective surface there, yes, but each slat is carefully angled and dimensioned specifically to avoid sending reflections back to the engineer. Every single slat was ray-traced, for this precise region, and then the angle adjusted to send specular reflections away from the mix position. That's how I could get away with using such large slats on the rear wall in such a small room... I'm giving away a lot of "secrets" here, but mostly to help you avoid making a mistake with your room. You CAN use large slats and large reflexive areas, even in very small rooms, but ONLY if you take the necessary precautions. With large rooms, it isn't so critical, but for small rooms, it is.

Quote:
variable acoustic devices / tuned devices will be constricted to only side walls in this plan.
Ummmm.... then how would you build them such that they could control the overall acoustic response of the room? If you limit them to only one of the three axes, how will you change the acoustics of the other two? :) Why place limits on the performance before you even start?

Quote:
Here's some images of my current design as it stands:
In general it looks fine, except for the rear wall. I would not use an unproven, untested device, based on an untested concept that nobody else has even written about or bothered to try... If you google that device, you'll find that all links either lead back to the original paper itself, or to the brief GS discussion that was posted by one of the authors.... Red flags.... If the device works, then let's see it tested independently, in reputable acoustic labs, with full reports published publicly.... I'm not seeing that, and it's been out there for over two years already... Hmmm...

Unless you really want your room to be a test laboratory, I'd advise against going with treatment plans that nobody else has looked at, or tried, or tested in a lab. If you don't mind being a "Guinea pig", and are prepared to go through multiple iterations of "trial and error" testing with different sizes and thickness of lumber, and different depths of insulation, and different types, and different angles, then great! But if you just want your room to work, first time, guaranteed, then it's probably not a good idea...

- Stuart -

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PostPosted: Sun Nov 11, 2018 8:08 am 
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Thanks for your response Stuart, it's always appreciated.

Soundman2020 wrote:
Quote:
I think think the appeal of the My Room Design seems to be the fact that it can pretty much be the same design regardless of the room size/dimensions.

I'm not so sure that would actually work in practice, although it does seem to be what they are claiming. I'm always wary of the "one size fits all" type of claim, because in reality it doesn't. All rooms are different, and each needs its own treatment. The problematic frequencies are different for each size of room, and each ratio, layout, and purpose. I can't see how one set of diffusers tuned to one part of the mid and high range is going to work for all room sizes, shapes, and layouts. It would be nice if it did, but acoustics doesn't work like that, unfortunately.


I am surprised by how few rooms have been built with the design. Their facebook page MyRoom Acoustics LLC, has some more rooms than the one in their paper and some more detailed pics of the construction process.

Soundman2020 wrote:
Exactly! And that was my point there: if conventional treatment works as advertised, with a lot less materials and complexity, then I'm not sure I see any advantage to this proposed new style.

I'm inclined to agree. Providing I can design my room to work for both my live/tracking purposes and mixing (mixing's still secondary :wink:)

Soundman2020 wrote:
Color me skeptical on that too! You might want to look into the theory of how diffusers work, and why QRD and PRD are so highly valued above all random sequences: QRD and PRD guarantee a flat power response. random sequences do not. In other words, with QRD/PRD, you are getting the same power scattered in each and every direction, so the intensity does not change: not matter where you measure, at all equidistant points from a QRD you get the same intensity (assuming that you measure beyond the critical distance, and that N is large enough in the first place, of course! You won't get flat power response for N=3, for example, or if you measure just a few inches away from the surface, but nobody in their right mind would even build an N=3 diffuser anyway, nor place their ears a few inches away!). That does not hold true for random sequences. With a random sequence, the power response is... well.... random! Which implies that there can be large intensity lobing issues, randomly spread around the room. This major issue was, unfortunately, not covered in the paper. They might not even be aware of it...

They would need to fully test their device at an independent test facility. The graphs they show in their paper are simulations, not actual tests. Curiously, they compare their 4m long device to a series of 4 QRD's set up one after another, which is known to cause lobing in diffusion coefficients, and would never be done in practice. I'm surprised they didn't compare theirs against a more typical QRD setup, with alternating panels... I wonder why?


I built the design on a trial of AFMG Reflex and it does seem to have good diffusion and scattering. I used this online calculator to generate the slat depth .
It would be very beneficial if the Author did test it in a lab. I'm not sure of the cost of those though!

The original (aka. Mrk 1 design) of the "air transparent diffusers" was used as an example in "Acoustic Absorbers and Diffusers, Third Edition: Theory, Design and Application" on their hybrid diffusers section. I don't actually own the book (very expensive :lol: ), but I am interested in the theory of how these work. (Pic in the book)

Soundman2020 wrote:
That's a nice size, actually. Very close to 20m2, and 50 m3 is great. Your room can be pretty good.


8)

Soundman2020 wrote:
But how light? And how thick?


Looking at what's available in my area I'm probably going to use this: Superglass Superwall 36. It is a glass wool and has a density of around 20kg/m3, giving approx 9000 Rayls for GFR, but the exact number is not available from the manufacturers. I will use a layer of 100mm, a layer of 50mm and leave a 10-15mm air gap behind it. It's a good price too, as Rockwool has been out of stock for months in the UK now it's coming back at twice the price. £50 for 4 sheets, compared to £27 here. 9000 Rayls with a 150mm depth and 15mm air gap has pretty good absorption

Soundman2020 wrote:
I would not go that path. There's way too much hard, solid, reflecting surface on that rear wall, and the room isn't long enough for that to arrive back at your ears outside the Haas time. That can lead to psycho-acoustic problems with identifying correct directions, and correct frequency response. If the room was a lot longer, then you might be able to do that, but for a room only 5.3m long, that's a very real problem. That's also going to give you problems with SBIR, since the entire rear treatment setup is going to be one large reflector for low frequencies.

Why did you choose a diffuser that only covers the range you mentioned? You also mentioned "down to 1000 Hz", but didn't mention the upper limit. What is that? Why? All numeric based diffusers have both an upper and a lower limit...


Hmm... I hadn't thought about the Haas time here. I was under the impression that a diffuse reflection was sufficiently reduced in intensity to negate this. Are you saying that even if a reflection is reduced by 20db or even 30db below the direct sound it wouldn't be sufficient if within 20ms?

The upper frequency cutoff will be around 7KHz for this design.

Can you explain a bit more about how it would affect SBIR? If this diffuser allows low bass frequencies to pass through it into the 200mm of insulation behind it, and also has a variable helmholtz effect. This surely would be as effective, if not more effective, against low frequencies than just 200mm of insulation alone?

Soundman2020 wrote:
Quote:
variable acoustic devices / tuned devices will be constricted to only side walls in this plan.

Ummmm.... then how would you build them such that they could control the overall acoustic response of the room? If you limit them to only one of the three axes, how will you change the acoustics of the other two? Why place limits on the performance before you even start?


I didn't mean I was placing limits, I meant because the entire rear wall was treated with the PRN air transparent diffusers then there wasn't any room left for variable-acoustic devices, and the front wall has the flush mount baffles, so only the side walls were left for these devices. I was just highlighting it. :)

Soundman2020 wrote:
In general it looks fine, except for the rear wall. I would not use an unproven, untested device, based on an untested concept that nobody else has even written about or bothered to try... If you google that device, you'll find that all links either lead back to the original paper itself, or to the brief GS discussion that was posted by one of the authors.... Red flags.... If the device works, then let's see it tested independently, in reputable acoustic labs, with full reports published publicly.... I'm not seeing that, and it's been out there for over two years already... Hmmm...

Unless you really want your room to be a test laboratory, I'd advise against going with treatment plans that nobody else has looked at, or tried, or tested in a lab. If you don't mind being a "Guinea pig", and are prepared to go through multiple iterations of "trial and error" testing with different sizes and thickness of lumber, and different depths of insulation, and different types, and different angles, then great! But if you just want your room to work, first time, guaranteed, then it's probably not a good idea...


I am inclined to agree at this point. The original concept from 11 years ago got quite a bit more of a look at by the community. It seems over at Gearslutz they have a lot of people who want to use LEDE and Newell designs, no one really does much else these days. Also most of the guys who know their stuff over there are professional designers/sell products so they tend to have their own ideas and not want to use someone else's, or they keep their designs close to their chest.

I am interested in testing the effect of the diffuser design in my room. I'm thinking of building 1 or 2 smaller modules using his method taking measurements. It's obviously not laboratory accurate but it would be interesting to test the concept, When I get to my measurements stage I'd love to have your input Stuart, and maybe guide me in the best way to test this device (assuming you're interested in the results yourself and have some free time).

I've been looking over some of John's posts from the past and rethinking my rear wall, and this is a new design I'm considering:

Lower rear corners, deep slat helmholtz tuned to 40-100hz. It will use 3 depths of wood 70mm, 140mm, and 195mm x 45mm and arrange these to give a bit of diffusion (non-numeric).
Then measure the effect, if it's good, place the same device in the top rear corners too.

Middle (vertically) rear corners superchunk at listening height, for reflections.

Middle of rear wall, 200mm thick absorption panel.
In front of the absorption a full height polycylindrical absorber that is cut down the middle and swings on hinges.

When open, the rear absorption panel is exposed and the "inside" of the poly "doors" exposes more absorption.
Closing the poly covers the absorption to add more liveliness to the room.

Attachment:
Rear wall new design 1050px.png


Attachment:
Rear wall new design closed 1200px.png


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PostPosted: Sun Nov 11, 2018 9:10 am 
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Joined: Sat May 20, 2017 7:47 am
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Location: Surfleet, UK
And here's a detail shot of the a poly "door", with the top bracing and fabric backing hidden:

Attachment:
Rear poly detail.png


I've thought about how I will physically contruct this. Here's my idea:

  • Bend the poly face into shape between the edge peices of wood "sandwich", and attach some temporary support bracing across the back. (True catenary method that is shown on one Stuart's posts on page 3 of this thread)
  • Then stand the poly onto some 18mm MDF and trace the inner edge of the curve.
  • Cut five of these out with a jigsaw.
  • Cut the pieces in half and cut a wedge out of the center section to stop them getting jammed when opening.
  • Place the 10 curved MDF braces against the inside face of the poly and screw through the poly face into them, and screw them to the edge wood framing.
  • Screw a side piece of MDF on to each respective door's center
  • Now I remove the temporary support bracing and then
  • Cut the poly down the center vertically
8)

How that works in real life remains to be seen! :lol:
Dan


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