Sounds good gentlemen. I've been trying so hard to make this Acoustic Treatment process, "One Stop Shopping" and its just not that simple. Trying to find one treatment that does it all. Its not the treatments fault, its just that every flat surface, corner, side wall, ceiling, front wall, back wall....... They all require something a little different, with a whole different set of priorities due to positioning inregards to the LP.
Im using OnmiMic's ETC to pin point problems and so far so good.
Nothing has compared to the big fat corner traps floor to ceiling and 2'x2'. The bass has a wonderful decay, footfalls sound like footfalls, no trailing rings, or ringing at all.
Im using OnmiMic's ETC to pin point problems and so far so good.
Nothing has compared to the big fat corner traps floor to ceiling and 2'x2'. The bass has a wonderful decay, footfalls sound like footfalls, no trailing rings, or ringing at all.
There is no real 'rule of thumb' for choice of acoustic treatment for a given problem, at least none that I have been able to benefit from. The rules of thumb seem to apply more to the specific problem in a particular sort of room, rather than to the specific problem in isolation, because the room is sometimes so much a part of the problem that any given component cannot be treated as a separate entity.
Aside from the slap echo, how does the room sound?
If the room is highly reflective and reverberant, you might benefit more from plain absorption to tame the echo because it will also damp the reverberation.
If the reverberation is already controlled and all you really have to deal with is slap echo, diffusion might work better without sucking out so much treble from the ambiance.
Another approach would be using slightly angled reflectors to skew the reflection between the parallel walls. This is also a simple thing that you can test to see if the reverberation is controlled enough once the slap echo is diverted, as well as how large the treatment needs to be for effectiveness in that location.
Note that eliminating, diffusing, or deflecting the reflection from one opposing parallel wall will stop the slap echo between the walls. You might be able to use just one absorber or diffuser or reflector on one wall, but the asymmetry may be noticeable in the imaging. If the room is already asymmetrical anyway, using treatment on only one wall, or dissimilar treatments on opposing walls, may be of benefit.
Note that symmetry applies to the listening position as well as the boundaries of the room.
If the room is symmetrical and very small with carpet plus furniture, it probably makes sense to maintain that symmetry with diffusion on both sides to avoid overly deadening the sound. If the room is larger, or highly asymmetrical, well you have more options, or at least different options, to consider.
Note that a bookcase full of irregularly sized books is usually an OK diffuser, so you could try that as well, if you own books and bookcases (increasingly rare these days). That would also give you an idea of whether diffusion helps without having to invest money and work in the experiment, but also requires some lifting.
The room sounds great! Whats interesting is that i must be used to reflections, sub bass ringing ect. Once i built the bass traps and the bass ringing stopped it sounded better, as i build FRP absorbers i really like the reduction of first reflections. Deadening the room and allowing the speakers to create the spacious sounds has allowed my to hear what the Post Production intended.
I remember building my sealed subs and how long it took to get use to what deep undistorted bass sounds and feels like. I couldnt recognize what i was hearing. Adding treatments takes a little getting use to also. Distortion and reflections and stored bass energy (ringing) muddy up the waters and become unwanted additions to soundtracks.
As of now im doing 7.1 with four 15" sealed subs, next year i'll be upgrading to 7.1.4 Atmos. Treating the room and allowing the soundtrack to shine is what i have discovered and been able to better verbalize the need for a reduction and/or eliminating of reflection points. The rest of the flat (non first reflection piont) reflective surfaces will have diffusers like the ones we are discussing and Skyline everywhere else, to keep the sound energy, but break it up so our brains can sort them out.
Thanx for your reply, acoustic treatments have really improved my already great listening room. Looking forward to building these diffusers soon.
Kg
I remember building my sealed subs and how long it took to get use to what deep undistorted bass sounds and feels like. I couldnt recognize what i was hearing. Adding treatments takes a little getting use to also. Distortion and reflections and stored bass energy (ringing) muddy up the waters and become unwanted additions to soundtracks.
As of now im doing 7.1 with four 15" sealed subs, next year i'll be upgrading to 7.1.4 Atmos. Treating the room and allowing the soundtrack to shine is what i have discovered and been able to better verbalize the need for a reduction and/or eliminating of reflection points. The rest of the flat (non first reflection piont) reflective surfaces will have diffusers like the ones we are discussing and Skyline everywhere else, to keep the sound energy, but break it up so our brains can sort them out.
Thanx for your reply, acoustic treatments have really improved my already great listening room. Looking forward to building these diffusers soon.
Kg
Hot wire cutting expanded polystyrene foam is ok with a cnc but still makes for a larger burnout at the ends, would be limited to 4' likely. Doing it with a manual feed is going to be messy.
Band saw would be the better choice.
What if you made a mold from wood, then made the panels from hydrocal and fiberglass?
Would be a better finish if the mold was made properly, and could be made very sculptural while achieving the desired effect.
https://m.indiamart.com/proddetail.php?i=11740731291&src=Renq
Band saw would be the better choice.
What if you made a mold from wood, then made the panels from hydrocal and fiberglass?
Would be a better finish if the mold was made properly, and could be made very sculptural while achieving the desired effect.
https://m.indiamart.com/proddetail.php?i=11740731291&src=Renq
If you make the diffuser that is in the first post here, you don't need a bandsaw, hot wire cutter, or much of anything. Go to Home Depot or Lowes or Menards, buy the boards, already at the right dimensions (except for some simple plywood cuts they may be able to do for you), get a hammer, listen to it tonight!
I'm gonna eliminate the 34" back board, as mine will be "onwall". I will be sure to space correctly. If i use them as a free stand like you show, i can add plywood later, my location isnt really a super probematic area, just a little slap echo.
Plus, when they are painted, they will look pretty cool. I have a wonderful wife who indulges my obsession, and benefits from a kick*** HT, so WAF=0 , thanx gentleman for giving us on a platter this great design :0)
Plus, when they are painted, they will look pretty cool. I have a wonderful wife who indulges my obsession, and benefits from a kick*** HT, so WAF=0 , thanx gentleman for giving us on a platter this great design :0)
I'm gonna eliminate the 34" back board, as mine will be "onwall". I will be sure to space correctly. If i use them as a free stand like you show, i can add plywood later, my location isnt really a super probematic area, just a little slap echo.
Plus, when they are painted, they will look pretty cool. I have a wonderful wife who indulges my obsession, and benefits from a kick*** HT, so WAF=0 , thanx gentleman for giving us on a platter this great design :0)
Your thoughts please:
The flat surface i have to cover first is 54" wide, and 8' tall, they are parallel walls. Can i eliminate the back 34" wide board and use three 12" wide diffusers and mount it on the wall, provided the spacing is correct, 4.25" i believe, im not sure. I know two would be fine, but im not sure what adding a third one will do, Ty
I am surprised you are getting as much change by placing them on the sides of your diples. Dipoles usually have a null on their sides, so I would not expect for there to be much reflections there to diffuse.
Hi kg,
I don't know how well it would work without the back board. The design was optimized modeling it as on the backboard of that width, I don't know what the computer assumes is beyond the backboard. I suspect the final step off the back board also figures a lot into the performance. Removing the back board makes the diffusor narrower and not as effectively deep.
The design was done by empirical evolution-type optimization (rather than from mathematical formula like with a quadratic, prime number, QRD, or MLS type designs). A mathematical approach guarantees a mathematically analyzable working design, but not necessarily an optimum or most efficient one. The empirical approach (essentially, lots and lots of trial-and-error with computer siimulation analyzing the performance of each attempt) can have better performance than math derived ones and can be subjected to other constraints as well (see my post at http://www.diyaudio.com/forums/multi-way/267682-diy-sound-diffusers-2.html#post4180176 ). The constraints on my design was that they used only off-the-shelf dimensions of boards other than some backing plywood and go low enough in frequency without being more than about 5 inches deep, and the analyzed result looks particularly good.
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The Diffuser Fabrication document stated that when repeating the pattern, the mounting depth needs to be varied to avoid "periodicity" (which I would assume to be similar to a comb filter effect). The center one could be slightly raised more than the flanking 2.
Diffuser-A1LF-Fab-Drawings-Arqen.pdf
This one uses 5 and multiple depths.
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I understand that there would be 2nd, 3rd, nth order reflections, but I thought the primary objective was to target/diffuse strongest first order reflections.
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Hi, I am still using the diffusers and they do a great job taming my room. I would agree that it seems unusual that they would help dipole speakers in general. My ESLs like all Matin Logans are curved. This causes part of the rear of the speaker to in a chris-cross fashion to aim to the sides. In my case the ESLs themselves are angled inward about 30 degrees. This results in a goodly portion of the back wave going toward the side walls. The diffusers soften its effects. They may do other things, but it would be hard to quantify what they might be. They just work and quite well at that. The change was not subtle.
Hi Bill, the arrivals from these diffusers are by no means the first reflection in the room correction?Well, here is a graph of log-magnitude of room impulse response (very similar to the usual Time-Energy-Curve) measured using the original (non-curved) DepotDiffusor. The late arrival is at about 13msec on the plot:
Here is the same with the curved "CoFusor"
Notice how all the stuff just past 13msec is taller? There's no vertical scale on the graph, so you'll have to take my word on it that the stuff just after 13msec is about 9dB higher than in the first plot.
(There's a dB scaled plot of Time-Energy-Curve in the article in Linear Audio, but I don't want to be posting a lot of stuff here that is directly from the article. Jan probably wouldn't like that!).
Would the first reflection arrival be the ~1.5ms spike? I'm doing some treatment in room, and my speaker is very close to sidewall due to small room and large screen, don't ask haha..
Anyway, I'm getting significant image and soundstage smearing using diffusers at sidewall first reflection. Sounds a lot cleaner using absorption at the sidewall.
Here's the Etc measured at listening spot, I have a - 10db spike at 1.5ms.
This is what the sidewall looks like with diffusers.
This is me trying absorption at sidewall reflection, will try to get measurements soon.
Thanks for the comments and feedback!
Sent from my X9009 using Tapatalk
They are exactly the multiples of the given wood dimensions. The model was optimized restricting to such dimensions. I think the AFMG screen of this one is the attached (not sure, but it's at least a close one)
It is not a mathematically derived type diffusor like an MLS or RPG type, it is an empirically optimized/analyzed type (which can be just as effective, by the way).
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That's true. These aren't used in my room for breaking up first reflections, but for adding spaciousness via diffuse delayed energy from the sides and rear. Different goals I think.
Well, 1.5msec is about 1.5 feet of extra travel distance, which would be something to the side of about maybe 12" to 15" away. Probably cabinet edges nearby. The waveguides' cabinets are 25" wide.
Sorry to hear that. Your diffusors might be too close to the speaker or to you. They need to be about 4 or 5 feet from either to be fully effective (a wave arriving at the whole panel or traveling to you from about the same distance from most areas on the panel), while absorbtion doesn't have closeness restrictions.
rhapsodee --
You might try orienting your waveguide vertically instead of horizontally if that close to the wall. At least the higher frequencies would be directed away from it that way. Though a dee[ absorber might be just the ticket instead. I think those diffusors there just put more diffracting and reflecting stuff up close to the speaker, probably not what you want with speakers that close to a side wall.
You might try orienting your waveguide vertically instead of horizontally if that close to the wall. At least the higher frequencies would be directed away from it that way. Though a dee[ absorber might be just the ticket instead. I think those diffusors there just put more diffracting and reflecting stuff up close to the speaker, probably not what you want with speakers that close to a side wall.