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Advice Wanted: Best Option(s) for Additional Bass-Trapping
Old 3 weeks ago
  #1
Gear Nut
 

Advice Wanted: Best Option(s) for Additional Bass-Trapping

So after years of focusing somewhat more on function than form, I decided that I would begin the process of upgrading some of the aesthetics in my home studio space.

I don't seem to have too many good pictures of what it was like before, but here are the two I could find:

Front:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-0x1-front-before-.jpg

Rear:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-0x2-back-before-.jpg



Anyway, the space was workable, but it was definitely lacking in terms of any "vibe" or visual appeal. The displays were simply on some ikea furniture with a big shelf that I created from home-depot veneer boards to get the monitors out wider. Lots of clutter. Rack Stuff on a short 12U thing on the floor next to the desk. Additionally, my mixing setup had to be positioned Left of center in order for the rooms entrance (a 4-section bi-fold door) to be accessed).


That said, I built my own version of Slate's Core Station and then rotated the contents of the room by 180°. So far, it now looks like this:

New Front:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-01-front.jpg

Advice Wanted: Best Option(s) for Additional Bass-Trapping-02-front-right.jpg

Right Side:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-03-right.jpg

Right Rear:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-04-back-right.jpg

Rear:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-05-back.jpg

Left Rear:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-06-back-left.jpg

Left Side:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-07-left.jpg


So now to the point of the thread:
I still have some additional organization to do, a few guitar hangers to mount on the walls, as well as anything else I can think of to keep on improving things (possibly trimming in the absorbers or additional lighting at the rear?), but things are set up enough that I can start measuring the acoustics and adjusting things as needed.

So far, I only have the graph from Sonarworks to post (I downloaded REW, but I have yet to properly learn it and all I managed to generate last night was a single response graph not too dissimilar to the one Sonarworks created. I still haven't worked out how to do the waterfall graph thing that everyone posts.. I will add that if I figure it out).

So here is the graph from Sonarworks:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-08-sonarworks-graph.png

When comparing this to measurements of the room the way it used to be set up, everything from around 100Hz and higher is quite similar overall (with the primary exception being that things are now centered Left-to-Right and therefore the L/R responses are somewhat more similar than they were before the room was rotated).

The biggest change is in the lowend response: the previous setup showed a ~12dB bump at 50~60Hz and the new setup seems to show that having been reduced to only a ~4.5dB bump at 50-60Hz with a 5dB dip at 82Hz or so... Still not amazing, but it is somewhat less extreme nonetheless.


All of that said.. everything is pretty much as expected, however, I have noticed that while the peaks and valleys of the lowend response appear to be less than they were before.. I now noticed a more pronounced ringing/resonance in the low-end. I might have to get that waterfall thing working to be precise about it, but it seems to resonate near the low F# or C frequencies that would correspond to the rough modal dimensions of the room.

Here is an overhead diagram of the room made to scale:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-studio-layout-october-2019.jpg

The room is:
12' 1/2" (144.5") Front to Back.
11' 11" (143") Left to Right (the closet is a few inches further I suppose).
7' 2 3/4" (86.75") High under the ceiling. (75.75" Under the bulkhead at the rear).

The Left and Rear walls are drywall over studs.
The Front and Right walls are drywall, studs with insulation between, and then the concrete foundation.


The Treatment:
All of the panel absorbers are made from 4.5lbs/cu.ft 2" rigid fiberglass insulation and are framed in such a way that they sit about 1" away from the wall.

The panels behind the speakers are 2' x 4' mounted vertically.
The panel behind/beneath the 43" display is 1' x 4' mounted horizontally.
The 8 panels along the side walls are 1' x 4' mounted vertically.
The cloud is made up of three 2' x 4' panels mounted together for a 6' x 4' total and is suspended more than a foot down from the ceiling.

The 4 corner bass traps are filled with Roxul Safe'n'Sound mineral wool insulation, the insulation is cut into triangles and stacked to fill the entire space back to the corners and all the way floor-to-ceiling. The faces of the bass-traps are all roughly 23" wide and covered to remain porous so they provide additional mid and high absorption.

The rear wall is now fully covered by a Lean-Fuser (DIY). It is constructed from 1/2" good-one-side plywood and painted. The cavities inside it are all currently hollow.

The Speakers:
Primary Monitors are a pair of Adam A77X
KRK 10s2 Sub as part of main system.

Secondary Monitors are a pair of NS-10m (That are placed on top of the Adam monitors on isolation pads when used.)

Yes the room is small and essentially square on its horizontal dimensions (but that never seemed to really be much of a problem before as my mixes, including low-end have translated pretty much how I would expect. One day the bulk of this setup will be transplanted to a better / purpose-built space.. but until then I will work with what I have.)

Yes, the diffusion is only about 6-7' behind me but it appears to be doing its job just fine (perhaps not to its maximum potential) and I can hear no audible distortions and or mid/high ringing unless I basically kiss one of the wells.
(Also, between the carpet and all of the broadband.. the room gets WAY to dry if the back wall is also broadband absorption.)

I know a lot of guys use tiny monitors and just hope when it comes to low frequencies in order to avoid "exciting those frequencies" much, but I have had WAAAAY better results mixing with full range and a sub for the last 10 years, despite the room, than I ever did before or since using small monitors as some do.



The Big Questions:
Since I am now hearing some amount of ringing/resonance.. I want to deal with it. The room worked before, I am going to make it work again.

Sitting in the listening position, the resonance is perceived as happening in front of me / between the speakers (or perhaps at the wall or between the desk and the wall.. depending on how one would characterize it).


My question is this: what would be the most effective way to add additional bass-trapping or treatment to the existing setup?

Off the top of my head, some options could be:

-Building or buying helmholtz resonators (such as the Vicoustic Varibass?) and positioning them somewhere?

-I could, in theory, deconstruct the two front bass-traps and rebuild them with load-bearing internal frames. This would allow me to make some kind of a bulk-head spanning the ceiling to wall corner along the whole front wall. I could then fill the entire thing with Roxul or some other material in order to make the hole thing a big broad-band trap? Would this make a significant enough difference?

-Would it be better to re-build the corner bass traps using a different material or so that there is some kind of limp-mass component to their design? (Would I be losing the broadband absorption benefit?)

-Would there be any benfit to fill the hollow cavities behing the diffusor with Roxul or something? Or would the reflective nature of its surface prevent anything from being absorbed?


Any advice would be much appreciated, and thanks in advance guys!!
Attached Thumbnails
Advice Wanted: Best Option(s) for Additional Bass-Trapping-0x1-front-before-.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-0x2-back-before-.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-01-front.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-02-front-right.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-03-right.jpg  

Advice Wanted: Best Option(s) for Additional Bass-Trapping-04-back-right.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-05-back.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-06-back-left.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-07-left.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-08-sonarworks-graph.png  

Advice Wanted: Best Option(s) for Additional Bass-Trapping-studio-layout-october-2019.jpg  
Old 3 weeks ago
  #2
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bgood's Avatar
I nominate you for the most information-rich help request in GS history

Gorgeous use of a typical small-ish space!

The name of the tech is escaping me, but, I suspect that someone will recommend something tuned to those particular freqs that are problematic... like the sealed tube thing (ugh wtf is that called!)... or a similar system
Old 3 weeks ago
  #3
Lives for gear
 

That's a really nice improvement, aesthetically! Congrats! It looks fantastic.

Quote:
(I downloaded REW, but I have yet to properly learn it
Here's how to do that: How to calibrate and use REW to test and tune your room acoustics

The graphs you are showing are just frequency response, which is only part of the acoustic picture. Time-domain response is arguably more important, so you need to get REW going to see that. Waterfall, spectrogram, RT60, decay, and ETC are what you should be looking at. You should also check the phase response.I would hazard a guess, and say that you need more bass trapping in the rear of the room, to help with the problems you describe. There doesn't seem to be enough bass trapping in there. But REW will show that.

- Stuart -
Old 3 weeks ago
  #4
Gear Nut
 

Quote:
Originally Posted by bgood View Post
I nominate you for the most information-rich help request in GS history
Ha, well I guess I'll take that! I just wanted to give as accurate an impression of the space / size / treatment /etc. so far as I could.. figured that would make it easier to evaluate.


Quote:
Originally Posted by bgood View Post
Gorgeous use of a typical small-ish space!
Quote:
Originally Posted by Soundman2020 View Post
That's a really nice improvement, aesthetically! Congrats! It looks fantastic.
Thanks guys! There's still some more minor things that I would like to do to get things organized and looking as good as they can within my circumstances, but it's nice to hear that the overall objective was successful.


Quote:
Originally Posted by Soundman2020 View Post
Here's how to do that: How to calibrate and use REW to test and tune your room acoustics

The graphs you are showing are just frequency response, which is only part of the acoustic picture. Time-domain response is arguably more important, so you need to get REW going to see that. Waterfall, spectrogram, RT60, decay, and ETC are what you should be looking at. You should also check the phase response.I would hazard a guess, and say that you need more bass trapping in the rear of the room, to help with the problems you describe. There doesn't seem to be enough bass trapping in there. But REW will show that.

- Stuart -
Yeah, I knew I would have a little bit of homework to do to get a real read on the room, but the initial post at least gets the ball rolling. I'll post some waterfalls as soon as I work out how to capture them properly.

-Thanks Again. Back Soon.
Old 3 weeks ago
  #5
Gear Nut
 

Quote:
Originally Posted by Soundman2020 View Post
Here's how to do that: How to calibrate and use REW to test and tune your room acoustics

...Waterfall, spectrogram, RT60, decay, and ETC ...
Okay, so a few things:

1. I played around with REW a little bit more and figured out how to actually generate the Waterfalls / etc. Pretty simple, but I didn't have much time with it yesterday.

2. I calibrated the sound card and then got the levels close(er) to where one might want them, but I will have to find time during the afternoon at some point if the input needs to read -18 instead of the ~ -25 I could get at acceptable volumes for the time of night / evening (on the output). (Quite loud on the output side of things already so I may have to re-do some things again?)

3. I do not yet own a proper/dedicated SPL meter. So I will have to eventually source one.


In the meantime, I ball-parked the SPL using a stupid iOS app (I know) and captured these as a "test case".. assuming that almost everything else is close to correct.

I restricted the image boundaries to 10Hz - 200 or 300Hz to get the zoom a little tighter for this, but are these at all useful as a starting point?


Left + Sub:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-01-l-s-waterfall-oct-22-2019.jpg

Advice Wanted: Best Option(s) for Additional Bass-Trapping-04-l-s-spec-oct-22-2019.jpg

Right + Sub:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-02-r-s-waterfall-oct-22-2019.jpg

Advice Wanted: Best Option(s) for Additional Bass-Trapping-05-r-s-spec-oct-22-2019.jpg

LR + Sub:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-03-lr-s-waterfall-oct-22-2019.jpg

Advice Wanted: Best Option(s) for Additional Bass-Trapping-06-lr-s-spec-oct-22-2019.jpg

Looking at these.. at the very least I can see pronounced peaks at 73.1Hz and 94.3Hz. As well as the giant lobe below 70Hz with its highest point appearing to be ~ 46.5Hz (which is close enough to the dual room mode to make sense).


What I'm really wondering about is the cavernous hole at 80Hz (77Hz?). Which should correspond to the crossover point between the sub and mains. I had flipped it back and forth during setup (it sounded like more low-end to me with it at 0 vs 180 degrees), but I'm wondering if I should re-examine the location of the sub?

Alternatively, there would be a ceiling-to-floor mode at 77.85 (according to a simple calculator) that might also explain the cancelation. Perhaps I should look into a re-designed cloud, something with more bass-trapping capability? (might require some sturdier suspension mounting, but also potentially do-able).
Would it be a stupid idea to consider building a box of some kind that sits against the wall, between the 2 speaker stands.. fill it with Roxul or something low-end absorptive, and then place the Sub on top of it (this would result in the sub being up off of the ground by some amount and would also probably have it firing directly into the back of my desk?)

Also, my main output is fed first to the Sub and from it to the Mains. I can easily do L or R + Sub or I guess Sub by itself, but I don't think I have any easy way of disabling the Sub without it flipping the Mains to Full-range mode (the Sub IS the crossover, etc.)

Do the above graphs indicate anything useful? I can certainly sort out more involved measurements.. I just haven't had large windows of time yet.
Attached Thumbnails
Advice Wanted: Best Option(s) for Additional Bass-Trapping-01-l-s-waterfall-oct-22-2019.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-02-r-s-waterfall-oct-22-2019.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-03-lr-s-waterfall-oct-22-2019.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-04-l-s-spec-oct-22-2019.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-05-r-s-spec-oct-22-2019.jpg  

Advice Wanted: Best Option(s) for Additional Bass-Trapping-06-lr-s-spec-oct-22-2019.jpg  

Last edited by stringsibanez; 3 weeks ago at 02:51 AM..
Old 3 weeks ago
  #6
Lives for gear
 

Quote:
I restricted the image boundaries to 10Hz - 200 or 300Hz to get the zoom a little tighter for this, but are these at all useful as a starting point?
What we need, is the actual MDAT file, not so much images...

- Stuart -
Old 3 weeks ago
  #7
Gear Nut
 

Quote:
Originally Posted by Soundman2020 View Post
What we need, is the actual MDAT file, not so much images...

- Stuart -
Fair enough. I attached the MDAT that I managed to capture tonight to this post.
Let me know if it's properly useable / if or what I need to correct for the next round of testing.


Also, perhaps some additional consideration for this:
1.Some of the panels were moved around slightly when I rotated the room 180 degrees, but all of the panel absorbers and corner super-chunks were built almost 10 years ago

2. I am more than willing to re-build/replace some of the existing trapping if it would show a significant improvement.
-The corner traps are ~16" x 16" x 23" triangles (which makes them only around 8.3" deep from the corner to the face at their deepest).
-I could add a layer(s) of rigid fiberglass to the faces of the two front traps.
-I could completely replace them with a different style/design of trap such as Soffit or limp-mass
-Replacing the front corner traps with Soffit style traps would allow me to easily frame in a Wall-To-Ceiling style soffit trap spanning the whole front wall from left to right. Additionally, I could just build an extension out from this to the center of the room, effectively replacing the 2" 4.5lbs/cu.ft rigid fiberglass cloud with something that is more bass absorptive.

I could theoretically replace the diagram in my original post with something like this (where all of the green is completely filled with Roxul or a combination of Roxul and rigid fiberglass):
Advice Wanted: Best Option(s) for Additional Bass-Trapping-potential-bass-traps.jpg
Attached Thumbnails
Advice Wanted: Best Option(s) for Additional Bass-Trapping-potential-bass-traps.jpg  
Attached Files
File Type: mdat REW-Measurment-Oct 22 2019.mdat (8.27 MB, 9 views)

Last edited by stringsibanez; 3 weeks ago at 07:49 AM..
Old 2 weeks ago
  #8
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akebrake's Avatar
 

Wrong Calibration file

Quote:
Originally Posted by stringsibanez View Post
...Let me know if it's properly useable / if or what I need to correct for the next round of testing.
You seem to have used a room-measurement file as "Soundcard Calibration" in stead of just the Soundcard.
(A pro soundcard plot will show a straight line from ≈2Hz to 20kHz or more).

That means the uploaded mdat is corrupt

Go try again!

PS The main benefit from loop-back measurement (for pro soundcard calibration purposes) is to reveal user errors like this one or feedback due to Direct Monitor not muted.
Attached Thumbnails
Advice Wanted: Best Option(s) for Additional Bass-Trapping-l-s-baseline-soundcard-cal.jpg  
Old 2 weeks ago
  #9
Gear Nut
 

Quote:
Originally Posted by akebrake View Post
You seem to have used a room-measurement file as "Soundcard Calibration" in stead of just the Soundcard.
(A pro soundcard plot will show a straight line from ≈2Hz to 20kHz or more).

That means the uploaded mdat is corrupt

Go try again!

PS The main benefit from loop-back measurement (for pro soundcard calibration purposes) is to reveal user errors like this one or feedback due to Direct Monitor not muted.
Hmm.. I'll have to look at that next time I'm at my studio location.. I definitely just ran a TRS from ouput to input on my main 1 (of 3 identical) interface.. Pretty sure I'd already shut everything that would effect eq-plot/etc off, but maybe there's something I didn't catch.

In any case, knowing that the calibration plot should apparently look like a straight line is useful.
Old 2 weeks ago
  #10
I don't think this has been mentioned yet but to attack the room mode around 45 Hz, try tuned absorbers (GIK makes some) or buy something like the PSI AVAA if you think you might move one day. The hole around 80 Hz is probably interference with the side walls, could be that your side wall treatment is not effective at those frequencies? You said they're all 2" thick? That won't do much.

PS: Nice pics.
Old 2 weeks ago
  #11
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Jens Eklund's Avatar
Let me first apologize in advance, but I´m taking the opportunity to address the most common rookie mistakes I see people make over and over again. Unfortunately; you managed to cover them all.


1. Low frequency behaviour and how to deal with it:

You have little to no LF treatment. It´s an unfortunate common misconception that all room modes relate to the corners. This is simply not true. The most problematic room modes (lower order axial modes) use the entire walls related to the mode, not only the corners. The first axial mode related to length for example uses the entire front and rear wall, so in your case; the total amount of treated area deeper than 8” seen by this mode is about 11,5%. This is what to expect in terms of performance from a porous absorber only 8” deep compared to a 13” deep absorber:

Advice Wanted: Best Option(s) for Additional Bass-Trapping-8-inches-vs-13-inches.jpg

Threating only 11,5 % of the relevant area with an absorption coefficient of about 0,25 (at the theoretical resonant frequency of your first mode related to length) is doomed to fail.

Same goes for axial modes related to width but with even less percentage area treated (since the room is a bit longer than wide) and when it comes to modes related to height, you have close to no effective treatment.

If relying only on velocity based absorbers (porous only) to tackle the low modal range, they need to be deeper (13-14” or deeper depending on fc of first mode and flow resistivity of the wool used) and you need to cover a lot of the relevant surface area. I consider the entire rear wall to be a minimum. If front wall untreated (in the lowest range); you have then treated 50% of the surface area related to axial modes related to length.

A more effective way of absorbing low frequencies is to use pressure-based absorbers. Not only are they more effective in the low frequency range (for a given depth) but also has the advantage of being reflective above the modal range, so any surface not related to early reflections can be treated with some form of pressure-based absorber. Helmholtz arrays (slotted panel) being the most common type used, easy to predict and most forgiving:

helmholz not very popular?

Also, a note on how to identify your modes:

Need help to tune my control room. (First Measures Included)


2. Early reflection control:

Ceiling acoustic panels

3" Roxul enough for early/first reflections?


3. Diffusers:

Your room is too short (3,67 m) to benefit from diffusers. The purpose of having diffusers on the rear wall is to scatter the energy in the horizontal plane so that this energy can return to the sweet spot via the rear sidewalls. If these surfaces (rear side walls) are treated with broadband absorbers; this energy return will be lost and thus defeat the purpose. The return should ideally arrive at around 20-25 ms after direct sound but down to about 15 ms is ok (at least that’s what I think personally, 12 ms is considered bare minimum). Also, if diffusers are used; they need to offer good performance in the range 300-400 Hz and up (to at least about 3-5 kHz).


Here´s an example of what I would consider minimal treatment in order to reach satisfying results in a small room like yours:

Advice Wanted: Best Option(s) for Additional Bass-Trapping-1.jpg

Dotted vertical and horizontal lines are nodal lines for first and second axial modes related to length and width. We usually try to avoid sitting in the nodal lines related to length, especially the first (centre). Second nodal line might not be critical if room is heavily treated. If possible; also try to avoid placing the speakers in the nodal lines related to width.

If not only porous absorption on rear wall, possibly something like this:

Monitors placement/room acoustic

If one wants to take it one or two steps further, you could add treatment to front wall (to combat the first null due to SBIR related to front wall), doesn’t need to be very deep (8” is ok) assuming the rear wall is properly treated to deal with first and second order axial mode related to length). Possibly using HH arrays close to the floor and ceiling and leaving the middle section (height) broadband to avoid early midrange reflections.

Angled HH arrays on rear sidewalls effectively solves possible flutter echo issues and adds low frequency absorption targeting low order modes related to sidewalls.

Advice Wanted: Best Option(s) for Additional Bass-Trapping-2.jpg

If diffusers are used (represented in green), assuming the room is long enough; rear sidewalls needs to be reflective above the modal range in order to be able to reflect the scattered energy back to the sweet spot.

Advice Wanted: Best Option(s) for Additional Bass-Trapping-3.jpg

As far as the ceiling goes; the same principle as the side wall treatment can be applied.


Again, sorry for being harsh, but the red pill is all I have to offer

/Jens Eklund
Attached Thumbnails
Advice Wanted: Best Option(s) for Additional Bass-Trapping-8-inches-vs-13-inches.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-1.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-2.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-3.jpg  
Old 2 weeks ago
  #12
Lives for gear
Do you use any special ray tracing tool in sketchup Jens?

Great post as usual!
Old 2 weeks ago
  #13
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Jens Eklund's Avatar
Quote:
Originally Posted by JayPee View Post
Do you use any special ray tracing tool in sketchup Jens?
No

Quote:
Originally Posted by JayPee View Post
Great post as usual!
Thanks
Old 2 weeks ago
  #14
Gear Nut
 

Quote:
Originally Posted by Jens Eklund View Post
Let me first apologize in advance, but I´m taking the opportunity to address the most common rookie mistakes I see people make over and over again. Unfortunately; you managed to cover them all.

...

Again, sorry for being harsh, but the red pill is all I have to offer

/Jens Eklund

Okay, so this is a LOT to respond to,
No worries, I'm going to forgive any tone or harshness (which I may have wrongly read into it.. but it certainly read as more of a talking down to someone than a friendly helping hand thing) because it also seemed like maybe you've been sitting on some things that bother you for a while (like my utter hate for certain parroted mixing advice I see over and over and over..so I do get it).


Anyway, I fully acknowledge that the content of your post is accurate and useful information, but I also need advice that can (to whatever degree possible) work within certain immutable limitations.
So, with regard to the "rookie mistakes" comment, your post references a couple of details from my previous posts, but also misses a few key points:


A. The desk and a few aesthetic / interior aspects are new.. and I spun the layout around 180° so that I could finally have left-right symmetry instead of sitting way left, but ALL of the absorption in the room was built 10+ years ago on a pretty tight budget. Given what I had to work with at the time, I think the results were about as good as could be expected/achieved.

B. Unfortunately, the room is the room. I didn't build the structure.. only the contents. As such: I can't change the size. I can't move the doors (which means a big chunk of the back wall is a bi-fold entrance, and so is the left-side wall/closet. They still have to be functional, but I've managed to "work around that" at least as well as I could). I can't remove the carpet or change the flooring, and I can't take up more interior space than the required contents will allow..

..but I can do at least a reasonable amount of whatever-I-want to the interior.

C. This isn't going to be the permanent location of my recording/control room, but it is what I have available to me for at least the next couple of years. With that in mind: a good amount of what I have done / will do is movable and will one day be transplanted to a better location.. or maybe re-done from the ground up (The eventual goal being to float a sizable live room and control room.. possibly an RFZ design.. in a big detached garage or its own out-building.. but one thing at a time).

D. I mentioned this somewhere above, but a lot of my goal here is to modify, re-construct, or add to the 10 year old treatment. As such, I am already in the process of doing just that.





All of that said,

What probably can't change:

-I can't, unfortunately, do much to the "rear" wall. Most of it is a stupid four-section bi-fold door and while I have managed to cleverly hide it behind a moving section of "diffusion" (which will of course be far more effective once transplanted to a far longer room).. the best I can probably do across the back wall at this point is to "stuff" the hollow cavities of the bigger modules (shown in some diagrams above) with something like Roxul or R20). I'm just not convinced that would accomplish anything at all.

-I understand that diffusion isn't particularly useful, effective, or recommended in a room of this size, but it was built more as something that will eventually be useful.. and also because even as it is, the room is DRY as hell, and even if it doesn't accomplish its maximum potential it at least isn't worsening the dryness, I don't get any slap echoes, there are no audible distortions, and it looks neat (last reason is stupid, but it's nice either way).


What I can change, and what I could gladly have more advice on:

-At a bare-minimum, I am planning to build additional treatment and also completely rebuild/replace the corner traps. I understand that room modes don't only effect corners (of course!), but that was the most sensible place to start when the existing treatment was made a decade back.


My tentative plan is:
1. Build a wall-to-wall bulkhead along the front wall/ceiling.
My thinking is that it will be 18.5" from the ceiling downward and 25.5" from the wall outwards.. It would likely extend to right around the back edge over my desk (which is roughly the limit without it interfering with the closet).

The inside will be:
-> 1" of 4.5lbs/cu.ft rigid fiberglass (closest to the exterior / so sound and air encounter it first)
->15" of Owens Corning Pink R20 (vertically) behind the rigid and closer to the ceiling.
-> There might be a small air gap between the R20 and the ceiling.
-> I might put a layer of standard insulation poly (6mil polyethylene) between the fabric and the rigid in order to mitigate absorption above 1kHz.

-> My plan is to make it four 6" batts thick.. for a total of 24" R20 front to back but only the 15" R20 + 1" rigid top to bottom.
This should still leave enough room in front to suspend a cloud absorber.


2. Re-build the two front-corner traps. My plan there is to replace the triangular traps with square / soffit-style traps.

They will be:
-> 17" x 17" each.
-> 1" of 4.5lbs/cu.ft rigid fiberglass at each exterior face.
-> Possibly an up to .5" of air gap.
-> 15" of Owens Corning Pink R20 within that and closer to the walls/corner.
-> Possibly an up to .5" of air gap between the R20 and wall. (depending on how the construction works.)

These corner traps will extend fully from the floor up to the proposed bulk-head trap.


3. I would also like to rebuild the two rear corner traps using similar construction, but I will likely have to slightly shrink their left-to-right dimensions in order to accommodate the doorway and necessary furniture, etc.


4. I am considering building some kind of a 'BOX' style trap that would be placed underneath my sub-woofer and between the speaker stands. (I am aware of peoples' opinions on subs in small rooms, but my personal experience has still demonstrated a massive improvement in clarity with vs without it.. and I don't tend to have much in the way of mix translation issues.. I just want to get back to or better than the level (or lack) of audible resonance before the room rotation.. and maybe improve the 80Hz null.. which likely has a strong vertical component).

The box would be something like:
->16" up from the floor x 24" outward from the front wall x ~36" wide
->1" rigid on all outward faces.
->R20 filling the interior.

-> the frame would be build to support the sub and its isolation pad on the top (hopefully without the height being a big problem as it would fire the sub into the back of my desk moreso and be closer to the mains).


5. If a more effective cloud could be constructed, I'd love to hear some ideas. My main obstacle is that a heat-register is located above the existing cloud.. so some space is probably necessary.



6. There is some possibility that I could construct an additional, small(er) cloud / ceiling absorber of some kind that I could place between the ceiling lights and the ductwork bulkhead (roughly at the 30% toward rear) but anything that operated in a broad-band sense might need to be accompanied by something that reduces some dryness? maybe a bamboo mat on the floor or something?
-The above dimensions / ideas roughly represent the "~maximum amount of space" that I can probably manage to take up without making the room too small for its purpose.

-If there is a way that I could make better / more effective use of that space (for instance with tuned absorption of some kind rather than broad, helmholtz instead of the box trap on the floor idea, or something else).. or if there is something I am suggesting that sounds like a bad idea I definitely want to hear about it.


Would any of that be an improvement? A measurable or pronounced improvement? If I could just build it from the ground up I would have.. trust me, my whole family is in construction and I'm not afraid of the work.. It just isn't in the cards yet.


Thanks everybody for all of your posts and help so far!

Last edited by stringsibanez; 2 weeks ago at 09:55 AM..
Old 1 week ago
  #15
Lives for gear
 
Jens Eklund's Avatar
Quote:
Originally Posted by stringsibanez View Post
Okay, so this is a LOT to respond to,
No worries, I'm going to forgive any tone or harshness (which I may have wrongly read into it.. but it certainly read as more of a talking down to someone than a friendly helping hand thing) because it also seemed like maybe you've been sitting on some things that bother you for a while (like my utter hate for certain parroted mixing advice I see over and over and over..so I do get it).


Anyway, I fully acknowledge that the content of your post is accurate and useful information, but I also need advice that can (to whatever degree possible) work within certain immutable limitations.
So, with regard to the "rookie mistakes" comment, your post references a couple of details from my previous posts, but also misses a few key points:


A. The desk and a few aesthetic / interior aspects are new.. and I spun the layout around 180° so that I could finally have left-right symmetry instead of sitting way left, but ALL of the absorption in the room was built 10+ years ago on a pretty tight budget. Given what I had to work with at the time, I think the results were about as good as could be expected/achieved.

B. Unfortunately, the room is the room. I didn't build the structure.. only the contents. As such: I can't change the size. I can't move the doors (which means a big chunk of the back wall is a bi-fold entrance, and so is the left-side wall/closet. They still have to be functional, but I've managed to "work around that" at least as well as I could). I can't remove the carpet or change the flooring, and I can't take up more interior space than the required contents will allow..

..but I can do at least a reasonable amount of whatever-I-want to the interior.

C. This isn't going to be the permanent location of my recording/control room, but it is what I have available to me for at least the next couple of years. With that in mind: a good amount of what I have done / will do is movable and will one day be transplanted to a better location.. or maybe re-done from the ground up (The eventual goal being to float a sizable live room and control room.. possibly an RFZ design.. in a big detached garage or its own out-building.. but one thing at a time).

D. I mentioned this somewhere above, but a lot of my goal here is to modify, re-construct, or add to the 10 year old treatment. As such, I am already in the process of doing just that.





All of that said,

What probably can't change:

-I can't, unfortunately, do much to the "rear" wall. Most of it is a stupid four-section bi-fold door and while I have managed to cleverly hide it behind a moving section of "diffusion" (which will of course be far more effective once transplanted to a far longer room).. the best I can probably do across the back wall at this point is to "stuff" the hollow cavities of the bigger modules (shown in some diagrams above) with something like Roxul or R20). I'm just not convinced that would accomplish anything at all.

-I understand that diffusion isn't particularly useful, effective, or recommended in a room of this size, but it was built more as something that will eventually be useful.. and also because even as it is, the room is DRY as hell, and even if it doesn't accomplish its maximum potential it at least isn't worsening the dryness, I don't get any slap echoes, there are no audible distortions, and it looks neat (last reason is stupid, but it's nice either way).


What I can change, and what I could gladly have more advice on:

-At a bare-minimum, I am planning to build additional treatment and also completely rebuild/replace the corner traps. I understand that room modes don't only effect corners (of course!), but that was the most sensible place to start when the existing treatment was made a decade back.


My tentative plan is:
1. Build a wall-to-wall bulkhead along the front wall/ceiling.
My thinking is that it will be 18.5" from the ceiling downward and 25.5" from the wall outwards.. It would likely extend to right around the back edge over my desk (which is roughly the limit without it interfering with the closet).

The inside will be:
-> 1" of 4.5lbs/cu.ft rigid fiberglass (closest to the exterior / so sound and air encounter it first)
->15" of Owens Corning Pink R20 (vertically) behind the rigid and closer to the ceiling.
-> There might be a small air gap between the R20 and the ceiling.
-> I might put a layer of standard insulation poly (6mil polyethylene) between the fabric and the rigid in order to mitigate absorption above 1kHz.

-> My plan is to make it four 6" batts thick.. for a total of 24" R20 front to back but only the 15" R20 + 1" rigid top to bottom.
This should still leave enough room in front to suspend a cloud absorber.


2. Re-build the two front-corner traps. My plan there is to replace the triangular traps with square / soffit-style traps.

They will be:
-> 17" x 17" each.
-> 1" of 4.5lbs/cu.ft rigid fiberglass at each exterior face.
-> Possibly an up to .5" of air gap.
-> 15" of Owens Corning Pink R20 within that and closer to the walls/corner.
-> Possibly an up to .5" of air gap between the R20 and wall. (depending on how the construction works.)

These corner traps will extend fully from the floor up to the proposed bulk-head trap.


3. I would also like to rebuild the two rear corner traps using similar construction, but I will likely have to slightly shrink their left-to-right dimensions in order to accommodate the doorway and necessary furniture, etc.


4. I am considering building some kind of a 'BOX' style trap that would be placed underneath my sub-woofer and between the speaker stands. (I am aware of peoples' opinions on subs in small rooms, but my personal experience has still demonstrated a massive improvement in clarity with vs without it.. and I don't tend to have much in the way of mix translation issues.. I just want to get back to or better than the level (or lack) of audible resonance before the room rotation.. and maybe improve the 80Hz null.. which likely has a strong vertical component).

The box would be something like:
->16" up from the floor x 24" outward from the front wall x ~36" wide
->1" rigid on all outward faces.
->R20 filling the interior.

-> the frame would be build to support the sub and its isolation pad on the top (hopefully without the height being a big problem as it would fire the sub into the back of my desk moreso and be closer to the mains).


5. If a more effective cloud could be constructed, I'd love to hear some ideas. My main obstacle is that a heat-register is located above the existing cloud.. so some space is probably necessary.



6. There is some possibility that I could construct an additional, small(er) cloud / ceiling absorber of some kind that I could place between the ceiling lights and the ductwork bulkhead (roughly at the 30% toward rear) but anything that operated in a broad-band sense might need to be accompanied by something that reduces some dryness? maybe a bamboo mat on the floor or something?
-The above dimensions / ideas roughly represent the "~maximum amount of space" that I can probably manage to take up without making the room too small for its purpose.

-If there is a way that I could make better / more effective use of that space (for instance with tuned absorption of some kind rather than broad, helmholtz instead of the box trap on the floor idea, or something else).. or if there is something I am suggesting that sounds like a bad idea I definitely want to hear about it.


Would any of that be an improvement? A measurable or pronounced improvement? If I could just build it from the ground up I would have.. trust me, my whole family is in construction and I'm not afraid of the work.. It just isn't in the cards yet.


Thanks everybody for all of your posts and help so far!
Again, sorry for using your room as an example of what not to do, and as much as would like to offer personalized detailed help to everyone posting on the forum, I won´t for the following reasons:

1. No one would learn anything.

2. The risk of giving bad advice due to incomplete information on how the room behaves (especially in the modal range).

3. Even if the points above where moot; I would do nothing else than designing rooms for free all day …

I can only show you the path. You need to walk it.


The most common mistakes made when trying to deal with the lower range is to use ineffective treatment options placed on the wrong surface areas and/or way too little area covered.

Understanding how room mode behave and analyse the room based on measurements, and then apply treatment (that actually does something in the lower range …) on the relevant surfaces and possibly reposition speakers/sweet spot (to avoid modal nulls as much as possible, at least in length dimension) is the only way to it.

The upper range is less complicated but still, people are often using way too thin treatment options, and also too little area covered and/or many smaller panels spread out (instead of going large at the relevant areas).
If you need more info on how to design different types of panels, there are many threads covering most of what need to be known. Yes I know, they can sometimes be hard to find, but if you spend some time looking around on GS, you´ll find them sooner or later. If not; let me know and I´ll help you find them.

If you don´t know already; the term GFR (Gas Flow Resistivity) is something you need to be aware of (I didn’t see it mentioned in your previous posts).


/Jens
Old 1 week ago
  #16
Lives for gear
 
Jason Foi's Avatar
 

Quote:
Originally Posted by Jens Eklund View Post
Let me first apologize in advance, but I´m taking the opportunity to address the most common rookie mistakes I see people make over and over again. Unfortunately; you managed to cover them all.


1. Low frequency behaviour and how to deal with it:

You have little to no LF treatment. It´s an unfortunate common misconception that all room modes relate to the corners. This is simply not true. The most problematic room modes (lower order axial modes) use the entire walls related to the mode, not only the corners. The first axial mode related to length for example uses the entire front and rear wall, so in your case; the total amount of treated area deeper than 8” seen by this mode is about 11,5%. This is what to expect in terms of performance from a porous absorber only 8” deep compared to a 13” deep absorber:



Threating only 11,5 % of the relevant area with an absorption coefficient of about 0,25 (at the theoretical resonant frequency of your first mode related to length) is doomed to fail.

Same goes for axial modes related to width but with even less percentage area treated (since the room is a bit longer than wide) and when it comes to modes related to height, you have close to no effective treatment.

If relying only on velocity based absorbers (porous only) to tackle the low modal range, they need to be deeper (13-14” or deeper depending on fc of first mode and flow resistivity of the wool used) and you need to cover a lot of the relevant surface area. I consider the entire rear wall to be a minimum. If front wall untreated (in the lowest range); you have then treated 50% of the surface area related to axial modes related to length.

A more effective way of absorbing low frequencies is to use pressure-based absorbers. Not only are they more effective in the low frequency range (for a given depth) but also has the advantage of being reflective above the modal range, so any surface not related to early reflections can be treated with some form of pressure-based absorber. Helmholtz arrays (slotted panel) being the most common type used, easy to predict and most forgiving:

helmholz not very popular?

Also, a note on how to identify your modes:

Need help to tune my control room. (First Measures Included)


2. Early reflection control:

Ceiling acoustic panels

3" Roxul enough for early/first reflections?


3. Diffusers:

Your room is too short (3,67 m) to benefit from diffusers. The purpose of having diffusers on the rear wall is to scatter the energy in the horizontal plane so that this energy can return to the sweet spot via the rear sidewalls. If these surfaces (rear side walls) are treated with broadband absorbers; this energy return will be lost and thus defeat the purpose. The return should ideally arrive at around 20-25 ms after direct sound but down to about 15 ms is ok (at least that’s what I think personally, 12 ms is considered bare minimum). Also, if diffusers are used; they need to offer good performance in the range 300-400 Hz and up (to at least about 3-5 kHz).


Here´s an example of what I would consider minimal treatment in order to reach satisfying results in a small room like yours:



Dotted vertical and horizontal lines are nodal lines for first and second axial modes related to length and width. We usually try to avoid sitting in the nodal lines related to length, especially the first (centre). Second nodal line might not be critical if room is heavily treated. If possible; also try to avoid placing the speakers in the nodal lines related to width.

If not only porous absorption on rear wall, possibly something like this:

Monitors placement/room acoustic

If one wants to take it one or two steps further, you could add treatment to front wall (to combat the first null due to SBIR related to front wall), doesn’t need to be very deep (8” is ok) assuming the rear wall is properly treated to deal with first and second order axial mode related to length). Possibly using HH arrays close to the floor and ceiling and leaving the middle section (height) broadband to avoid early midrange reflections.

Angled HH arrays on rear sidewalls effectively solves possible flutter echo issues and adds low frequency absorption targeting low order modes related to sidewalls.



If diffusers are used (represented in green), assuming the room is long enough; rear sidewalls needs to be reflective above the modal range in order to be able to reflect the scattered energy back to the sweet spot.



As far as the ceiling goes; the same principle as the side wall treatment can be applied.


Again, sorry for being harsh, but the red pill is all I have to offer

/Jens Eklund
OMG, you're becoming Stuart!

Great to see you around again. Hope all has been well.
Old 1 week ago
  #17
Lives for gear
 
Jens Eklund's Avatar
Quote:
Originally Posted by Jason Foi View Post
OMG, you're becoming Stuart!

Great to see you around again. Hope all has been well.
Haha

Not sure if I should say thanks, or thanks for the warning …
Old 1 week ago
  #18
Lives for gear
 
Brian M. Boykin's Avatar
Quote:
Originally Posted by Jason Foi View Post
OMG, you're becoming Stuart!

Great to see you around again. Hope all has been well.
I learn the most from posts that Stuart posts and the one Jens posted in this thread. No parsing if words. Straight to the point. He gave the “why.” I’m pretty deep into my room and chose an RFZ design based on room dimensions and room volume and after reading the Davis & Davis approach in Floyd Toole. The only mistake I see I may have made thus far is placing the speakers in room modes. That’s actually an easy fix if I did. Other than that I’ve treated with 8“ minimum broadband in side wall first reflections. (The thickest space would allow) Front wall is 20”. Rear wall is 9” and just under 10ft from the listening position. The frequency response is flattening out. I have some lowend issues as expected from the smallish room (Why I read this thread) and some high frequency roll off I’m hoping is ceiling bounce that will get better once the cloud is up.

The kind of post Jans made are buried inside threads and have to be sought out. It’s why you need to be reading every thread.

Btw, the RSL 3 way monitors were no worse or better than the Event 20/20’s according to REW so I kept them for front line duties. If anything they were more flat through the mods as expected with a 3 way. I can now seal off the front wall and never have to worry about adjusting active amps or heat issues.
Old 1 week ago
  #19
Gear Nut
 

Quote:
Originally Posted by Jens Eklund View Post
Again, sorry for using your room as an example of what not to do, and as much as would like to offer personalized detailed help to everyone posting on the forum, I won´t for the following reasons:

1. No one would learn anything.

2. The risk of giving bad advice due to incomplete information on how the room behaves (especially in the modal range).

3. Even if the points above where moot; I would do nothing else than designing rooms for free all day …

I can only show you the path. You need to walk it.


The most common mistakes made when trying to deal with the lower range is to use ineffective treatment options placed on the wrong surface areas and/or way too little area covered.

Understanding how room mode behave and analyse the room based on measurements, and then apply treatment (that actually does something in the lower range …) on the relevant surfaces and possibly reposition speakers/sweet spot (to avoid modal nulls as much as possible, at least in length dimension) is the only way to it.

The upper range is less complicated but still, people are often using way too thin treatment options, and also too little area covered and/or many smaller panels spread out (instead of going large at the relevant areas).
If you need more info on how to design different types of panels, there are many threads covering most of what need to be known. Yes I know, they can sometimes be hard to find, but if you spend some time looking around on GS, you´ll find them sooner or later. If not; let me know and I´ll help you find them.

If you don´t know already; the term GFR (Gas Flow Resistivity) is something you need to be aware of (I didn’t see it mentioned in your previous posts).


/Jens
All of this is accurate and useful in a broad sense. It's just that without the option of changing the physical structure of the room or building a new one from scratch (which are not options at this time) I can't apply any kind of 1:1 implementation of what you have illustrated in your posts.

I was hoping that I could get at least some broadly useful input on the composition/construction of the new treatment I had outlined above (and that is possible to implement given the room's parameters and door(s) positions /etc).. or possibly be steered in a better direction if there was one (such as something specific to build or buy rather than the porous absorption designs I am currently aiming toward or whatever) but okay.



My best (abridged) summary of the thread so far I guess is:
1. My initial post outlined some changes I had recently made to the look and layout of my room, provided a lot of specifics about it's current composition, and described the issue I was now experiencing.

2. I received some nice complements about the new look, and some helpful advice on how I might make some useful measurements going forward.

3. I made a first attempt at some REW measurements (as I am currently learning the software and still need a proper SPL meter).

I also pointed out that the room's existing treatment was 10+ years old and outlined a first draft of potential updates I thought I could construct.

4. It was pointed out that I have some more to learn about REW to get accurate readings (and as soon as I have a proper SPL meter I'll be back at that). I also got one suggestion about an active treatment product.

5. Your first post seemed to ignore or miss the part about the existing treatment being old as well as my intent to re-do the relevant parts of it (the point of the thread) and the limitations of the room's construction and doors etc. It also did all of this while seeming to assume that the old treatment was the result of my having zero knowledge/understanding of basic acoustic principles as opposed to being the result of the budget and practical constraints at the time of it's creation (as I'm sure most DIY builds are?). It provides useful information for a ground-up build, but not so much if my room wouldn't facilitate that arrangement.

6. I tried to re-state the relevant constraints within which I am working and perhaps direct your focus more toward what I'm looking for advice on (alternative treatment design for the room I'm stuck with) as well as outlining my updated construction ideas for new bass-trapping (arrived at using a combination of AFMG Soundflow and the http://www.acousticmodelling.com/multi.php calculator, different porous models, scouring the internet for addition information, etc.).

7. You seemed to skim over or ignore a lot of the details / explanations in my response and double-down on being as broad as possible. That's fine, I suppose you're more intent on giving advice to all than advice to my exact situation.. or maybe you avoid specifics as this topic is related to your vocation and you only get specific when hired? I'm not sure... either way:


-I can't move the walls or doors & a different room isn't an option at this point in time.

-I understand the problems with the existing treatment and was hoping for more input on composition/construction options.

-I am well aware that thin treatment won't reach low and that the old roxul triangles weren't up to the task.

-The sidewall treatment is made in narrower strips in order to allow the 4-section bi-fold door to still open and close properly (and maintain symmetry). It is still hitting first reflection points, but isn't absolutely ideal. I have considered trying to get it spaced an additional inch off the walls to extend it down a little further (maybe 100Hz more than it would currently reach), but that's separate from the larger/lower issue.

-As far as I can figure, my speakers don't fall directly on any modal lines and I am sitting somewhat forward of the lengthwise center point (maybe 38-45% back from the front wall?).

-I did a lot of research and simulation calculating to arrive at the designs I've gotten to, but some perspective would still be useful (I could always have missed something or might not be considering some alternative).


So far I have constructed this as a bare minimum addition:

Advice Wanted: Best Option(s) for Additional Bass-Trapping-09-bulkhead-front.jpg

Advice Wanted: Best Option(s) for Additional Bass-Trapping-10-bulkhead-bottom.jpg

The bottom facing the ground is 1" of 4.5lbs/cu.ft rigid fiberglass and the pink/fluffy insulation above it is 15" high x 24" deep R20. (There is a small amount of air between the R20 and the ceiling, maybe 0.5 ~ 0.75")
Based on aggregated information:
->The rigid should have a GFR of ~23000Pa.s/m2 (or somewhere between that and maybe 28000)
->The R20 should have a GFR of ~4000Pa.s/m2 or maybe up to 6000 depending on your source.
My intent at this point is to build 17" x 17" square traps from the floor up to the bottom of this bulkhead trap using a similar construction of 1" rigid on the exterior with 15" squares of R20 filling the insides. (unless someone has a better alternative I should consider?)

So far no one has commented on my idea regarding a similarly composed box that could sit in the floor-wall corner under my sub-woofer? Maybe that idea is stupid? I don't know.
Attached Thumbnails
Advice Wanted: Best Option(s) for Additional Bass-Trapping-09-bulkhead-front.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-10-bulkhead-bottom.jpg  
Old 1 week ago
  #20
Gear Nut
 

I'm probably doing this wrong since I'm not sure how (or if it's possible) to tag someone in a thread, but:

Quote:
Originally Posted by Glenn Kuras View Post
... Honestly all rooms are different, so what might be right for one might not be right for another....
Quote:
Originally Posted by Ethan Winer View Post
No bass trap can target very low frequencies "efficiently," because no matter what approach you use it will be very large and take up a lot of space. But large porous traps can have a profound effect as low as 30 or 40 Hz if you have enough of them. In my Hearing is Believing video you can see a big improvement at 40 Hz in a well-treated bedroom size space. And that's with our 6-inch thick 2x4 MondoTraps. I promise you that replacing all the MondoTraps in the corners with MegaTraps would make an even larger improvement. Much larger. Doing a follow-up test with MegaTraps is on my to-do list.

--Ethan
Quote:
Originally Posted by avare View Post
...The short is the thicker the absorber, the LIGHTER the material. Up to ~4" thick 3 lb/ft3. At thicker than 12", regular insulation. Yes the cheap stuff!

Andre

Based on my ideas for improving my room (details above), are my bass-trap plans decently well founded? Ridiculous? Would any of you suggest I adjust course in an obvious way?

Thanks.
Old 1 week ago
  #21
Lives for gear
 
Brian M. Boykin's Avatar
Try this room mode calculator:

https://amcoustics.com/tools/amroc?l...2&h=12&r60=0.6

Use it on a real computer, not your phone. Put in your room dimensions. Change the room to the DIN15996-Studio. You’ll see a keyboard with vertical lines on it. Run the mouse arrow over the line. It will state the frequency. A 3D room will show where those modes will be present in your room. It will give you your rooms Schroeder Frequency. It also gives the approximate square footage you will need to cover in your room AND the average absorption coefficient you need to have. You can now use the porous absorber calculator to engineer traps.

http://www.acousticmodelling.com/porous.php

First reflections should be broadband. The thicker the better. I turned as much of my front wall as possible into a 20” trap. My rear wall will be a 9” trap when done. My cloud will be a 22” trap when done. The side wall first reflections are 7” traps. I’m going for 330 square feet of total coverage. Then I’ll treat specific frequencies. I expect the room to be too dry when I’m done. I can then add slats over non first reflections to get some life back. I’m testing all along the way with REW to watch trends. It’s very motivating to see the waterfall graphs even out, the frequency response flatten out, and decay times get under control. And you can hear the details and clarity increase with each step. Here are some pics of my room in progress.
Attached Thumbnails
Advice Wanted: Best Option(s) for Additional Bass-Trapping-9d9cf02a-3e20-4e72-b397-9f16dc2da9c6.jpeg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-434ce0d2-f366-498d-8f40-4f73f5f55f14.jpeg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-73db580c-bb2d-42d8-a7d9-fe2498865d0c.jpeg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-066334c8-e200-4559-bbf7-7836017e7e20.jpeg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-d6fbe09d-ff24-4883-a22b-061a399bef97.jpeg  

Advice Wanted: Best Option(s) for Additional Bass-Trapping-388e8abe-7af9-4de6-9933-46b9a60837b6.jpg  
Old 1 week ago
  #22
Lives for gear
 
Brian M. Boykin's Avatar
It’s very difficult to give specific answers for rooms. General guidelines are much better. You, the room owner have to be willing to do the work and be prepared to rip stuff down and do it over if you don’t like the results. This is an expensive endeavor but way worth the effort.

My advice is with your room size to build an RFZ zone. Ditch the deflection on the rear wall. Build the thickest possible absorption traps floor to ceiling. Cover as much of the front and rear wall as possible. Build the thickest cloud possible and as big as possible. Your ceiling can be one big huge absorber. You have a very nice set up and it’s obvious you’ve spent money and take your recording seriously, don’t skimp here. There’s nothing more frustrating than mixes that do not translate. It doesn’t matter how awesome your gear is if the final mix doesn’t translate.

Just my 2¢ and it’s up for correction by those more educated than me. I’m still learning.
Old 1 week ago
  #23
Gear Nut
 

Quote:
Originally Posted by Brian M. Boykin View Post
It’s very difficult to give specific answers for rooms. General guidelines are much better. You, the room owner have to be willing to do the work and be prepared to rip stuff down and do it over if you don’t like the results. This is an expensive endeavor but way worth the effort.

My advice is with your room size to build an RFZ zone. Ditch the deflection on the rear wall. Build the thickest possible absorption traps floor to ceiling. Cover as much of the front and rear wall as possible. Build the thickest cloud possible and as big as possible. Your ceiling can be one big huge absorber...

Thanks for your responses. You have me putting some additional thought into a few potential modifications.

Yeah, those are definitely the same Room Mode and Porous Absorber calculators/sites that I've been going back to quite often. (As well as some occasional AFMG Soundflow to simulate more complex structures.) The basic design/composition I arrived at for the traps described above was the "best I could find" using combinations of available materials and given the sizes I am able to fit in the room. I modeled various potential compositions using Miki, Allard and Champoux, and Komatsu; the design I chose had the best projected performance using all 3 models.


So far, I have added this wall-to-wall bulkhead/soffit style trap (described in my previous post) in the front wall-ceiling corner:

Advice Wanted: Best Option(s) for Additional Bass-Trapping-11-covered-bulkhead.jpg

It just barely overhangs the back edge of my desk.
I couldn't, unfortunately, extend it any further into the room as it would interfere with the closet which is only a few inches away from the left edge:

Advice Wanted: Best Option(s) for Additional Bass-Trapping-z1-closet-bulkhead.jpg


My next missions are:
A. Front Corners/Wall
B. Cloud
C. Side Walls (maybe).


With respect to the front wall, the practical options I could construct would be:

A1. 17 x 17" Soffit-Style Traps (described above):
Advice Wanted: Best Option(s) for Additional Bass-Trapping-z2-front-option-01.jpg

A2. If I sacrifice even more space (which starts to get tight for accessing the rear of the desk/etc, but could be workable?) I could construct something like this under the bulkhead trap in the two front corners:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-z2-front-option-02.jpg

If I did something triangular/angled like this, I might have to consider different fill material.
-Broadly speaking, all of my porous modeling appears to indicate that 1" or 2" of Rigid in front of R20 insulation is pretty much always better than just Rigid or Rigid + Air Gap. This of course assumes that the sound is encountering the face of the trap straight-on rather than at an angle (which would thicken its travel through the rigid).

-I'm sure real-world doesn't exactly line up to modeled, but imagining the axial modes as travelling back and forth between the walls.. more of the wave would encounter the square traps at 90 degrees for optimal results vs at an angle which would cloud the predictions.
It's possible (likely?) that given the sheer volume of the triangular design, I might get better results with just solid Pink R20 and no Rigid facing.
That said, I could also add to that by building the Riser Box/Trap for the Sub to sit on and then placing an up to maybe 8" deep trap on the wall above it (between the speakers). The wall trap can't run all the way down the wall or the sub-woofer and it's connections/cabling wont be able to fit.

Here is what that would look like:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-z2-front-option-02b.jpg


B. Regarding a new Cloud:
-The ceiling being so low (86.75") means that I do have to consider headroom when designing a new absorber.
-I am still working on the specifics, but no matter what I come up with, I will still have to work around the lighting, and this:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-z3-heat-register.jpg

Anything I do will have to avoid or work around this furnace/AC vent so as not to cause any issues.


C. Unfortunately, there is nothing I can do about the closet being where it is. At best, I may be able to construct somewhat deeper traps for the first reflection points, but they can't be more than maybe 3' wide x 8" deep at maximum, and can't go from floor to ceiling. (Even this idea would require my converting half of the closet door so that it swings open rather than bi-folding).

Advice Wanted: Best Option(s) for Additional Bass-Trapping-z4-closet.jpg


Lastly, I took this additional picture to illustrate why my rear wall is complicated:
Advice Wanted: Best Option(s) for Additional Bass-Trapping-z5-entrance.jpg

This entire red square is the door in and out of the room. The white panels and part of the rear table move out of the way, but ~40% of the rear wall is door (rather than solid wall). That being the case, any rear wall treatment has to account for getting in and out. I'm sure this probably messes with room predictions somewhat as well.

Quote:
Originally Posted by Brian M. Boykin View Post
... You have a very nice set up and it’s obvious you’ve spent money and take your recording seriously, don’t skimp here. There’s nothing more frustrating than mixes that do not translate. It doesn’t matter how awesome your gear is if the final mix doesn’t translate...
Thanks, I actually built the desk myself, but the equipment in it did involve some spending. As for translation, I haven't traditionally had much of an issue with that, however re-arranging the room has brought with it the low-end resonance described in the first post. It just wasn't there before (despite my being most of the way toward my left-hand wall and under the duct-work bulkhead which is now visible above my new "rear wall". Lots of reasons that could be including: height above the speakers/sub (definitely playing a role in a new 75~80Hz null which I hope the new ceiling trap helps), I am now facing a concrete wall rather than just an empty stud wall, I am now sitting centered, and lastly.. the sub is centered left-to-right and unimpeded width-wise by any obstructions (the old desk had solid sides running to the floor and the sub sat under it/between them).
Attached Thumbnails
Advice Wanted: Best Option(s) for Additional Bass-Trapping-z5-entrance.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-11-covered-bulkhead.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-z2-front-option-01.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-z2-front-option-02.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-z2-front-option-02b.jpg  

Advice Wanted: Best Option(s) for Additional Bass-Trapping-z3-heat-register.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-z4-closet.jpg   Advice Wanted: Best Option(s) for Additional Bass-Trapping-z1-closet-bulkhead.jpg  

Last edited by stringsibanez; 1 week ago at 11:41 AM..
Old 1 week ago
  #24
Lives for gear
 
Brian M. Boykin's Avatar
Ok, here are my thoughts without saying “do this.” More surface area covered is better and thicker is better. Ask yourself how much you access the rear of your desk. I put mine on casters so I can roll it around. I’m leaning towards the angled corner traps and the center trap for this reason. Symmetrical is best for a control/mix room. However you treat the closets just be sure to repeat on the other side. Have you considered a Gobo style trap for the bifold closet that you could put on casters and roll in and out of place? For the cloud, do you know what the ceiling joists are made of. 2x6’s or greater would allow for some decent depth. This would require removing sheet rock. That’s no small task but worth the effort if your really trying for real world results. I do think you need to ditch the diffusers for absorption. We have small rooms with a small total cubic volume. Diffusion is never recommended from what I’ve read from numerous sources and posts by professionals. Ethan claims only of the back wall is greater that 10 ft from the listening position, however, we have small rooms and absorption absorption absorption is your friend. It looks fantastic but I think you’ll benefit from stuffing the thickest amount of broadband in there as you can.

I’m only giving food for thought here. I’m not a professional. I don’t think I’ve suggested anything I have not read about small rooms. It sounds like you’ve read the same. If you look at my front wall I mounted my monitors in the absorbers. Consider that as a way to get more front wall absorption. It makes adjusting active monitors a hassle but anywhere a small room can gain absorption it’s a plus.
Old 1 week ago
  #25
Gear Nut
 

Quote:
Originally Posted by Brian M. Boykin View Post
Ok, here are my thoughts without saying “do this.” More surface area covered is better and thicker is better. Ask yourself how much you access the rear of your desk. I put mine on casters so I can roll it around. I’m leaning towards the angled corner traps and the center trap for this reason.
Your first posts actually got me thinking harder about the "more and thicker" aspect of all this, which is where I decided to add the angled corner idea into the mix in the first place.

The more I think about it, the square traps were mainly considered because they provide ~double the depth of my old triangular corner traps, but the new one's I'm proposing would pretty much contain all of that additional depth (+ extra) within them.. and also add more surface area (of decent depth for most of it) from each direction sound could arrive.


Definitely a few things, including desk mobility, that would be simplified by not having a carpeted floor. Unfortunately removing the carpet isn't currently an option. (I'll basically have to restore this room to it exact pre-treated condition whenever I can finally move on to a better room).


The sizes and shapes in the diagram are mostly so I can still accommodate the speakers and stands. I'd actually love to more thoroughly eliminate SBIR with a full-wall thick trap or soffit-mounting, but it would mean pushing my listening position back to (or past) the half-way point lengthwise (which wouldn't be good). Probably couldn't quite get the angle perfect either given the stupid closet. I also occasionally add a second set of monitors on top of the Adams which would get tricky if they were built-in.



Quote:
Originally Posted by Brian M. Boykin View Post
Symmetrical is best for a control/mix room. However you treat the closets just be sure to repeat on the other side. Have you considered a Gobo style trap for the bifold closet that you could put on casters and roll in and out of place?
Somehow, despite the fact that I've created move-able objects for the rear wall, I've never really considered side-wall treatment that doesn't hang on the door or walls. I'm not sure that wheels would work particularly well as the carpet tends to grab little casters, but if the overall construction of whatever were to be light enough.. I could probably just have it sit directly on the ground and slide it about the room as needed. It still probably wouldn't work to have it reach the ceiling (so I'm still left without side wall-ceiling traps due to the closet and window), but it would at least provide better side absorption. My initial thought it to try and cover the front half of the closet with a thick trap.. which should be a manageable size for moving.

I should really put more thought into what would be the most workable design for this, and how it might all fit together (so it looks relatively seamless when in place).


Quote:
Originally Posted by Brian M. Boykin View Post
For the cloud, do you know what the ceiling joists are made of. 2x6’s or greater would allow for some decent depth. This would require removing sheet rock. That’s no small task but worth the effort if your really trying for real world results.
I don't think I have the freedom to put the cloud within the ceiling, but that is an interesting option I'd not considered. My main obstacle to a good cloud is definitely going to be working around the Heat/AC vent. Either way I need to look at what my minimum headroom needs to be and run some numbers through the calculator.


Quote:
Originally Posted by Brian M. Boykin View Post
I do think you need to ditch the diffusers for absorption. We have small rooms with a small total cubic volume. Diffusion is never recommended from what I’ve read from numerous sources and posts by professionals. Ethan claims only of the back wall is greater that 10 ft from the listening position, however, we have small rooms and absorption absorption absorption is your friend. It looks fantastic but I think you’ll benefit from stuffing the thickest amount of broadband in there as you can.
I'm not going to dismiss this idea out of hand.. as it is completely valid.
Due to some space constraints, I will probably finish the front half of the room (including the cloud) and get it completely set up with the speakers and such brought back in before I start work on the back. So I will be able to take a few measurements and listen to the change at that midway point.


Also, I am definitely now working with the mentality of trying to get the thickest (for low-end response) trapping into the room that I can manage. That said, if so much of it will be broad-band (and thus also absorb the mids and highs), what would be my recourse for the room getting overly dry/dead? As it stands, I thought it was pretty close to too-dry with the original treatment.



Thanks for your thoughts. It's definitely helpful to have some back-and-forth about the limitations and potential solutions.
Old 1 week ago
  #26
Lives for gear
 
Brian M. Boykin's Avatar
Making existing treatments thicker should not make the room dryer, only extend the frequency range lower. Only 2 to 4 inches is needed for mid and high frequency absorption that sucks the life out. When you have the low end as good as you can get it, you can then introduce small slats of different sizes over absorbers that are not in first reflections. My front wall corner absorbers have FRK Facing the room. Any non first reflection absorbers can have this to keep the room lively. It’s a balance. It requires testing with REW every step of the way and calling audibles when need be. My understanding is to get the low end under control it takes deep absorbers, tuned absorbers and lots of coverage. All 3 may not be possible in the small rooms we have.

Again, my 2¢, I'm not a pro. I’ve read the same things you have.
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