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PostPosted: Wed Mar 10, 2021 8:13 am 
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Ok, so I'm in the final stages of room build, and did some testing with the speakers. Full mdat for review: https://drive.google.com/file/d/1jnwd6TGM_XGrsXHsAMwygPOwudJOVumv/view?usp=sharing .

If this was your room, which test would look better to you and why? I'm interested in learning what's going on, and how the problem areas could be addressed.

Room dimensions (drywall to drywall):
21'6" (625cm) x 12'3" (375cm) and 7'3" (219cm) high.

The setup is a speaker sitting on a shelf, around 6" from front wall. The shelf is part of framing which is to be wall mount speaker wall. The rest of the room treated with 3.5" SnS in the walls and 24x24 triangular superchunks in the rear corners, plus some 2x4 smaller panels (movable). See the image for this:

Attachment:
construction.jpg


Test 1 (red) - Baffle removed (insulation around speaker still in place)
Test 2 (blue) - Baffle on left side only (2x 3/4" plywood, apps 32"x48", centered on woofer)

Attachment:
test-spl.jpg


Attachment:
baffletest-rt60.jpg


Test 1 (no baffle)
Attachment:
test-waterfall.jpg


Test 2 (baffle)
Attachment:
test2-waterfall.jpg


So my questions:
- The baffle seems to be bumping the ~240-300Hz range. Is this possibly (probably?) baffle resonance because it's not solid/massive/secure enough?
- Is the baffle doing anything for me at all? Seems to tame some peaks below 200Hz, but that's about it ...
- Thoughts on the 64Hz and 155Hz dips?
- There is a big room mode at 27Hz (I think), but not likely I can do anything about it.


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PostPosted: Wed Mar 10, 2021 9:27 am 
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- 27Hz is probably below your speaker range :-)

the baffle should be more effectively leveling the stuff below 200Hz. somehow though it looks like there is also some asymmetrical distribution around those front speakers or perhaps its the camera angles.

did you test this 1 speaker at a time with the omni mic pointed up at the listening position?

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PostPosted: Wed Mar 10, 2021 10:46 am 
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gullfo wrote:
- 27Hz is probably below your speaker range :-)

the baffle should be more effectively leveling the stuff below 200Hz. somehow though it looks like there is also some asymmetrical distribution around those front speakers or perhaps its the camera angles.

did you test this 1 speaker at a time with the omni mic pointed up at the listening position?


Yeah, the speakers go to around 35 Hz. I'm not too worried about the 27 :)

These tests were done with just the left speaker, mic at ear position, 60* from level (as per Stuart's instruction, though vertically, makes very little difference).

The speakers are perfectly aligned on the front wall in terms of angle, but they are shifted around 8" to the right of center ... this is due to bump out beside the left speaker. Could this bumpout, or asymmetry contribute? The right speaker exhibits the same frequency bump around the 260-300 Hz with the baffle in place.

This is the room floor plan:

Attachment:
floor plan.jpg


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PostPosted: Thu Mar 11, 2021 1:56 am 
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Very interesting. On a quick look there seems to be little difference. I would take this as a commendation of the benefits of Soft Flush. Pseudo Soffit....

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PostPosted: Thu Mar 11, 2021 2:16 am 
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DanDan wrote:
Very interesting. On a quick look there seems to be little difference. I would take this as a commendation of the benefits of Soft Flush. Pseudo Soffit....


The measurements do seem to support this ... I'm going to do some more work then report back. Any suggestions or other observations welcome! Overall the room sounds pretty good, but there are definitely strong bass variations when walking around. This is I assume expected in a small room like this, and I don't think there is a reasonable solution short of just picking a good listening position. I'm pretty happy with 30-60Hz flat response, and the >300Hz is fine as well, if a little dead (easily fixed if needed).

My immediate plan right now:
- Finish the SnS superchunks in the front wall (this certainly can't make it any worse, right?)
- Try a decoupled speaker shelf (as per Gulfo's post somewhere ... a stack of concrete blocks or something), so the speakers are not touching the framing or the baffle
- Install the studio door (is there any way the 80"x36" hole in the wall is causing resonance/nulls/weirdness? We'll find out!)


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PostPosted: Thu Mar 11, 2021 3:53 am 
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maybe flip the room so the front of the room is more symmetrical for the listening position and use that inset area for bass trapping. move the doors down toward that area.

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PostPosted: Thu Mar 11, 2021 4:34 am 
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gullfo wrote:
maybe flip the room so the front of the room is more symmetrical for the listening position and use that inset area for bass trapping. move the doors down toward that area.


Lol ... sure ... just move the doors :)

The room is already done, so not much I can do there. The reason the front wall is that wall is because the opposite wall is the exterior wall and it was built inside out already. I could move the speakers, but then I'd lose more space to treatment. Since the primary function is drum/jam room, and mixing secondary, I don't want to do this (plus you know ... hard work and all that, lol).

I'm just trying to optimize as best as I can, and experiment a little along the way. If we can understand the problem, even if I choose to ignore it, it might help others with how to analyze the issue. That's really my main goal posting here. There are experts in the filed, or at least much more knowledgeable people than me, so I seek to gain understanding from you folks.


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PostPosted: Fri Mar 12, 2021 2:29 am 
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ok, so maybe leverage that indented section for your front wall absorption and move the speakers out. symmetry will be important and having that corner like that will cause an offset in your perceived response.

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PostPosted: Sun Mar 21, 2021 7:05 am 
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An update, and still the same question ... to baffle or not to baffle!

mdat attached. My interpretation is that the frequency response looks better without the baffle, but the time based response looks better WITH the baffle. I think the frequency response can be helped a bit with eq correction (I have sonarworks, have not used it yet, waiting till physical treatment is done).

So here's where I'm at in terms of the treatment. Basically, pretty much done on the interior of the room:
- finished the front wall insulation. 10" deep between the speakers (1st test)
- added a sheet of 16g steel on the front wall (29"x56"). This is covered by 1" rigid, and the pegboard (2nd test). Based on this idea http://downloads.bbc.co.uk/rd/pubs/reports/1994-12.pdf
- Added 3" rockwool on the back of the front and right walls (before it was just 2 layers of 5/8" drywall) (3rd test)
- Added the 3/4" plywood speaker baffles (4th test)
- finally, added a 2x4 3" rockwool panel diagonally across front wall/ceiling corner (between speakers) (5th test)

I think incrementally, all these changes are for the better ... except maybe the baffles!

Here is the mdat. Specific questions if someone feels like taking a look:
- the Filtered IR shows a huge spike at 7ms. Any guesses as to the source? How can I find what frequency that spike is at
- The 180Hz spike in FR with the baffle bothers me. Also the 290Hz. Any ideas?
- The huge null at 61Hz. Room mode I suspect, so not much to be done there ... just live with it?

https://drive.google.com/file/d/1P1Mmru ... sp=sharing

Attachment:
metalpanel.jpg


Attachment:
pegboard.jpg


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PostPosted: Sun Mar 21, 2021 9:07 am 
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you can try the baffles, and once you're done all round, worst case, you could pull off the hard parts and cover the front with cloth if that makes the overall response of the room more balanced.

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PostPosted: Mon Mar 22, 2021 8:19 am 
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Great work. The metal thing interests me. How deep is the fibre damping? Is it attached or pressing against the steel?
The ETC spike is disconcerting. I presume only one speaker is running? Could you try removing the Loopback and see what happens to that spike.
I don't think this is the reason but perhaps worth saying don't be near the mic during sweeps.

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PostPosted: Mon Mar 22, 2021 12:48 pm 
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I tried a couple new things today ... after a couple beers, I was bored, lol.

Here is the waterfall with the 36"x48" plywood baffle:
Attachment:
plywood-baffle.jpg


I then added a full sheet of 5/8" drywall on top (so baffle is now 48"x86"). Here is the result:
Attachment:
drywall-baffle.jpg


But then I did something I should have done days ago ... I moved the side panels together. Before they were spaced around 3" apart on the wall (aesthetics ... or some shit). Here is the WTF waterfall:
Attachment:
panel-move.jpg


I gotta say, the very low resonance change was a surprise. I did a few passes in case it was a fluke or something.

Anyway, just a point ... don't overlook the very small changes!


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PostPosted: Mon Mar 22, 2021 12:59 pm 
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DanDan wrote:
Great work. The metal thing interests me. How deep is the fibre damping? Is it attached or pressing against the steel?
The ETC spike is disconcerting. I presume only one speaker is running? Could you try removing the Loopback and see what happens to that spike.
I don't think this is the reason but perhaps worth saying don't be near the mic during sweeps.


Thanks Dan. The metal sheet is just sandwiched in there, no glue. So: front wall, 10" rockwool, steel plate, 1" 703 rigid, 1/4" peg board. The 703 (its not really 703, but similar rigid) is probably compressed to ~3/4". The steel panel just rests on the red rubber disks at the bottom, so it's fairy decoupled from the soffit structure.

About the ETC spikes, yeah, that's what I'm hunting now. That, and I'd love to solve that 61Hz null, but maybe not possible. Measurements are always single speaker, and I'm not near the mic ... by the door towards the back. I tried with me outside the room, made little difference. I'll try without loopback tomorrow.


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PostPosted: Wed Mar 24, 2021 5:37 am 
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Tried without loopback, made no difference.

But I did find where the spikes are from! It's the LED light mounting board I have in the cloud. Will need to move the cloud a bit, and maybe angle it down to reflect behind LB. Slowly closing all the holes. Will have more updates soon


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PostPosted: Wed Mar 24, 2021 8:36 am 
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Great news. Steel sheet sandwiched is a variation of the VPR. If you do more, I would go for back wall/corners.

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