Treatment of a small boxy room - REW file attached

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Greyhound
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Treatment of a small boxy room - REW file attached

#16

Postby Greyhound » Thu, 2021-Dec-30, 15:38

I should add that the treatment designs I’m referring to were done by John in 2014, and he agrees that he would do a number of things differently now based on advances in acoustic design.

I’m learning a ton just from reading through other users’ design and build threads, which are inspiring and really impressive. Next step is to really work through the reading materials and other resources in the downloads section - I’m reading Master Handbook of Acoustics now and it is a really clear ground-up introduction to the science.

Before starting to hang treatment, I think the first thing to do will be to downsize the humongous desk that spans the front wall as per Stuart’s recommendation. This should remove some reflection issues and also leave more room for treatment. I gained access to some adjacent spaces for electronics work I was also doing in this office, so really I can pare things down to a modest desk and my beloved sofa lol.

Thanks again for all the feedback thus far, and to other users who have put so much work into their threads.



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Treatment of a small boxy room - REW file attached

#17

Postby Starlight » Sat, 2022-Jan-01, 15:18

Greyhound wrote:Source of the post... a small-ish basement room ... 12' x 12' and a 7' ceiling ...
That is not so much smaller than Jason Baliban's 144x180x104" room, here, also designed by John Brandt.
Soundman2020 wrote:Source of the postI could say a lot about couches, but I'm running out of time for today!
Stuart, I am curious as I also have a couch.
Greyhound wrote:Source of the post... the initial incarnation of this studio was based on a John Brandt design in 2014. John's design had all walls covered in traps ... I don't think I can copy his plans here ...
John published a studio plan of his in the PDF attached to the first post here.
Soundman2020 wrote:Source of the postThe guy who originally invented them was Tom Hidley, way back in the 70's I think, and he christened them "acoustic hangers" ...
akebrake recalls Tom's original 1975 drawings, here.
Soundman2020 wrote:Source of the postJohn Brandt seems to be one of the very few who use the term "waveguide"
I mentioned Jason Baliban's studio above. In Jason's video, at 8'57" for a few seconds, here, we can see that John's hangers do not hang; they are fixed top and bottom. I wonder if that is why he does not call them hangers.
Greyhound wrote:Source of the postThe diffuser specified by John is a PRD ... this would take considerable effort to build ...
As my studio has been designed by John I will be making a Prime 523 PRD this year.
Soundman2020 wrote:Source of the postNot to mention that it will take nearly a foot of your room length... A useful version of that thing is at least 10" deep, probably 14" or more, plus some more for the support structure, and deep bass trapping behind it... That's a lot of space to lose on your back wall... plus, it weighs a ton! There's a lot of wood in there ... My guess is that John provides that for larger rooms ...
My studio is 6.2m (12'4") long and I will be making the smallest (shallowest) of the Prime 523 diffusors, so it would seem you are right, they are for larger (longer) rooms.

PRD calculator



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Treatment of a small boxy room - REW file attached

#18

Postby gullfo » Sat, 2022-Jan-01, 16:40

actually the "hangers" are a device created by Jeff Cooper back in the early 70's he called a "broadband absorber" :-) using Homesote 440 (a medium dense fibre board) or plywood board with soft 1" insulation attach and hung roughly 100mm (4") apart and angled relative to the opening or straight on if the opening is angled. line the cavity box with 4" insulation. in his studio design book, he has a general calculation for its main operating frequency. and more recently a study by a team in Germany on how these things work (or more correctly behave) based on testing of a Newell designed studio.



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Treatment of a small boxy room - REW file attached

#19

Postby Greyhound » Sun, 2022-Jan-02, 18:59

Thanks Starlight for the replies - I've really enjoyed reading through your thread on the build of your studio. I did all of the isolation build for my much smaller room, as per a John Brandt design, and your thread brought back memories!

That is not so much smaller than Jason Baliban's 144x180x104" room, here, also designed by John Brandt.


I had not seen Jason Baliban's room until your link - I read through and it certainly provides a lot of inspiration and food for thought. A couple of things that come to mind:


  • After all Jason's work and expense, the speakers are not flush-mounted despite the advantages that have been noted elsewhere.

    In my discussions with John, and in reading his book (2008 2nd Edition), he did not seem to be a big proponent of flush mounting. Here is an excerpt:

    Do not place your monitors right up against the wall. Due to the boundary effect, your monitors will sound fat or boomy in the corners of the room and likewise to a lesser degree when they are close to the wall in front of you. In order to have the flattest speaker response possible, move them at least one foot from the wall in front of you.


    That being said, "right up against the wall" is not the same as "flush mounted inside the wall". But he doesn't mention flush mount at all in his original book...

    This seems to have been the philosophy applied in my 2014 design, and also in Jason Baliban's (2018). I found Stuart's comments in favour of flush mounting to be quite persuasive, and am just trying to reconcile the different viewpoints (if possible).

  • Again we see a PRD mounted to radiate along a 12' room axis, which is called into question by the Cox and D'Antonio referenced provided by Stuart.

    I've just finished reading up to the end of chapter 14 (Schroeder Diffusers) in the Master Handbook of Acoustics (6th Edition, 2015) by Everest and Pohlmann, which includes the following passage in relation to QRD panels:

    Comparable polar plots, for single frequencies based on a far-field diffraction theory, show a host of tightly packed lobes that have little practical significance. Near-field Kirchoff diffraction theory shows less lobing.


    Question for Stuart: what is the source for the colour image of diffusion lobes you showed in your earlier post? I didn't see it in Cox & D'Antonio, and it provides a lot more information than the polar angle plots used in most of the book. Is it possible that Pohlmann's comment about Fraunhofer vs Kirchhoff models apply to that simulation?

    I was able to find an online copy of Acoustic Absorbers and Diffusers by Cox and D'Antonio, for the 3rd Edition published in 2005, but it may take a while to find the relevant parts (any hints from Stuart are welcome!) There is a discussion of the mathematical prediction of scattering in Chapter 8, which seems pertinent. The 2015 Master Handbook has many D'Antonio references, but none more recent than 1999 (and the 2005 book is not one of them).

    I'm still just trying to get my head around this concept enough to make a semi-informed decision, which includes consideration of the other diffuser types mentioned by gullfo (thanks!)

I could say a lot about couches, but I'm running out of time for today!


I am also interested in hearing more!

John published a studio plan of his in the PDF attached to the first post here.


Thanks for pointing that out - the diffuser and corner traps along the back wall are a reasonable representation of what John recommended for my room. The same goes for the slatted traps along the side walls.

In John's linked example room, the listener would be about 12 feet in front of the back wall diffuser so it's consistent with Stuart's recommendation.

Interestingly, John *did* specify flush-mounted speakers for the room in his speaker placement example. He is also asked for his recommendation for a Focal Twin or Solo 6" (which is what I have). I'm not sure I followed his response, but he seemed to feel that some room dimensions would benefit from flush mounting whereas others would call for "free standing" speakers that should not be too close to the wall.

The width of John's example room (13'5") is not dissimilar to my room (12') or Jason Baliban's room, so from a width standpoint John's flush mount example might work in my room. However, the specific configuration shown would put the listening position around 6' from the front wall. This is dead centre in my room (along both horizontal axes!), which I gather is the worst possible spot in terms of room modes.

I mentioned Jason Baliban's studio above. In Jason's video, at 8'57" for a few seconds, here, we can see that John's hangers do not hang; they are fixed top and bottom. I wonder if that is why he does not call them hangers.


You are right that the vertical vanes in John's corner bass traps are rigidly fixed at both ends, so "hanger" is not the first name that would come to mind (as it does for the other free swinging designs mentioned earlier).

I don't think Jason used any of the "waveguide" traps that John specified for my room and which he also shows in the rear corners in the GS thread on speaker placement. Jason's seem rather to be membrane traps (there is no membrane in the waveguide trap and the front face presents a PRD profile). I have seen the term "waveguide" used to describe ports designed to allow passage of fibre optic cables or non-conductive tubing through a Faraday cage while blocking EM waves in a certain frequency range (eg https://hollandshielding.com/Waveguide); the name applies since these are short waveguide tubes tuned to act as an absorber. I still can't quite see the connection with John's corner trap though - would be nice if there was a reference somewhere.

As my studio has been designed by John I will be making a Prime 523 PRD this year.


You probably have the same plan I was provided - I'll be interested in seeing how you make it!

My studio is 6.2m (12'4") long and I will be making the smallest (shallowest) of the Prime 523 diffusors, so it would seem you are right, they are for larger (longer) rooms.


I will certainly hold off until I understand the physics better... I'm not too concerned about the physical incursion into the room, but would want to be sure there is an acoustic benefit before building something with so many precise cuts.

btw are you close to the Tatras? My wife is from Poland and until the pandemic we used to vacation in Zakopane every few years. It is a really beautiful region!



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Treatment of a small boxy room - REW file attached

#20

Postby Greyhound » Sun, 2022-Jan-02, 19:00

gullfo wrote:Source of the post actually the "hangers" are a device created by Jeff Cooper back in the early 70's he called a "broadband absorber" :-) using Homesote 440 (a medium dense fibre board) or plywood board with soft 1" insulation attach and hung roughly 100mm (4") apart and angled relative to the opening or straight on if the opening is angled. line the cavity box with 4" insulation. in his studio design book, he has a general calculation for its main operating frequency. and more recently a study by a team in Germany on how these things work (or more correctly behave) based on testing of a Newell designed studio.


Thanks for the additional background - I am really trying to understand the physics of this, and these posts are very helpful. The history is also fascinating!



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Treatment of a small boxy room - REW file attached

#21

Postby Starlight » Tue, 2022-Jan-04, 11:22

Greyhound wrote:Source of the postAfter all Jason's work and expense, the speakers are not flush-mounted despite the advantages that have been noted elsewhere.
I am of the impression that John's standard design starts from the basis that speakers will not be flush-mounted, although I can see from the stuff John gives his clients access to that he has drawings for flush-mounting so it is clearly something he can include, just as you spotted. There is a fair bit on gearspace from John and Rod Gervais from around the 2010-2014 period where both of them do not recommend flush-mounting, which seems to be aimed at non-clients.
Greyhound wrote:Source of the postI found Stuart's comments in favour of flush mounting to be quite persuasive, and am just trying to reconcile the different viewpoints (if possible).
Stuart has persuaded me too, along with discussions about the positives of flush-mounting and sub-woofers on gearspace.
Greyhound wrote:Source of the postbtw are you close to the Tatras? My wife is from Poland and until the pandemic we used to vacation in Zakopane every few years. It is a really beautiful region!
We are in Poprad, just the other side of the High Tatras from Zakopane. Here is a photo from our Boxing Day walk.
4725LaM.jpg



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Treatment of a small boxy room - REW file attached

#22

Postby Greyhound » Tue, 2022-Jan-04, 15:02

Starlight wrote:Source of the post We are in Poprad, just the other side of the High Tatras from Zakopane. Here is a photo from our Boxing Day


What a beautiful photo (the scenery + you guys looking so happy)! I have never been in the winter, but just love this region. You are very fortunate to be so close.

Below is one of my favourite photos, showing a rather younger (and skinnier) version of me resting on a hike across the ridge from you guys.

TatryiRickLezacy.jpeg


I hiked several hundred km on that trip, wearing an ill-fitting pair of dress shoes I'd bought for my sister-in-law's wedding in Wrocław. Don't think I've ever had a better time!



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Treatment of a small boxy room - REW file attached

#23

Postby Greyhound » Fri, 2022-Jan-21, 16:20

Hi all,

I've been busy reading and getting up to speed with some CAD planning. I have access to Fusion 360 from work and have been learning to use that. It might not be ideal for architectural drawing, but the parametric foundation is great and it's a lot less idiosyncratic (to me) than Autocad. I know that Sketchup is the de facto standard, but I actually found Fusion easier to use (plus I do some machinist work and this will be useful there as well).

After getting the broad strokes of the room envelope sorted, I've taken a stab at an initial sketch of how soffit mounting might work. This is a naive attempt, and I am trying to figure out how to handle the frontmost window (I could close one of these off, as they look out under a wooden deck and get very little light - I'd need to leave at least one for fire code though).

Attached are some screen grabs of this effort - I would be grateful for any advice on how to adapt the flush mount concept to this non-ideal room configuration. All dimensions are in metres, and the distance from front wall to speaker axis intersection is based on an “optimal” value from John’s original (non soffit) design.

D2CA8E9E-9802-4357-A2F3-D94D41D63512.png


228A4584-5321-480E-A39E-30BBE4799229.png


Here is a view showing more of the general space envelope, including those interior walls bounded by concrete foundation walls:

B1419D28-1DE6-4CE5-9E62-059E18A8F287.png



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Treatment of a small boxy room - REW file attached

#24

Postby gullfo » Fri, 2022-Jan-21, 19:24

if you have access to SU (such as the free downloadable Make 2017 version - the web version doesn't support dynamic components) attached is a dynamic component for sizing up a simple soffit wall.
Attachments
soffit_wall_simple (SU2017).skp
(152.11 KiB) Downloaded 416 times
soffit_wall_simple (SU2017).skp
(152.11 KiB) Downloaded 416 times



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Treatment of a small boxy room - REW file attached

#25

Postby Greyhound » Fri, 2022-Jan-21, 20:04

Thanks Glen - will check it out!



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Treatment of a small boxy room - REW file attached

#26

Postby Starlight » Fri, 2022-Jan-21, 20:16

gullfo wrote:Source of the post if you have access to SU (such as the free downloadable Make 2017 version ...
Look for the big green link at the bottom of the OP in Stuart's topic Where to find the REAL SketchUp.



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Treatment of a small boxy room - REW file attached

#27

Postby Greyhound » Fri, 2022-Jan-21, 21:21

For some reason, I get the following message when I try to open the soffit extension file with SketchUp 17:

23017083-CB88-4171-AFC2-D489E54C29D1.png


I am using the MacOS version of SketchUp - no sure if that is an issue. I downloaded the trial version of SU 2021, and the file opens with no problem. I think I can parameterize this in Fusion so it's still quite helpful.

Thanks all!



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Treatment of a small boxy room - REW file attached

#28

Postby Greyhound » Fri, 2022-Jan-21, 23:04

Using the construct in the file Glen sent, I can get to something like this (dimensions are in metres).

2936A818-CFCB-41ED-A1DA-7F045B1C7578.png


The general constraints are:


  • Listening position is 40% of room depth from front wall
  • Speaker axes are aligned at 24-40deg from room midline
  • Intersection of speaker angles is 5" behind the listening position
  • Baffle width is > 3-5x woofer dimension (6" on Focal Solo6)
  • Speaker axis is placed slightly off-centre with respect to baffle, to avoid "resonances" (resonances of the baffle?)

Adding the outer sections parallel to front wall allows for a more flexible design - this layout would require blocking out one window (which is ok).

Much of the info came from Snailboyawayyy's thread, which is really informative thanks to all the effort he and others put in.

Thanks again for any feedback!



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Treatment of a small boxy room - REW file attached

#29

Postby gullfo » Sat, 2022-Jan-22, 12:10

apologies. i saved it as SU 2017. then (by instinct) hit Ctrl+S which unfortunately then automatically re-saved it as 2021... this is the 2017 file. updated file in original post.



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Treatment of a small boxy room - REW file attached

#30

Postby Greyhound » Sat, 2022-Jan-22, 15:23

gullfo wrote:Source of the post apologies. i saved it as SU 2017. then (by instinct) hit Ctrl+S which unfortunately then automatically re-saved it as 2021... this is the 2017 file.


Thanks for following up Glen - that version loads fine in 2017!




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