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.
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.
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?
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.
My inside out ceiling will be filled with light insulation.
But how light? And how thick?
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.
I'll build "soffit wings" to create a good RFZ around the mixing position.
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...
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.
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?
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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), but I am interested in the theory of how these work. (
