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attic loft control room
Old 4 weeks ago
  #1
Gear Nut
 
n0nspaz's Avatar
attic loft control room

Greetings. I've been working on this mixing-mastering room for a year or two, and have just finished construction. It's on the 3rd floor of a residential 3-story suburban home. This room was done more or less in the style of John Brandt and Boggy. Goal is a dry, neutral space for accurate mixing
& mastering of most pop styles.

Right-side partition wall was made to split the space, and filled with rigid insul. All absorption around studio area is a mix of light and rigid fiber/rockwool, walls are angled, corners have waveguide panels, front & rear walls are 24" deep filled with fluffy. No treatment done to other side of room beyond partition wall.

GoM fabric and wood slats on the walls. Cloud is 100% porous (fluffy). rear wall features a polystyrene (n=32?) stepped diffuser. vaulted style ceiling (with no insulation between roof joists as far as I know).

Extreme low bass region was not otherwise attended to. No VPRs etc.

Would love to hear feedback and recommendations on the results. Not sure how I could improve it at this point.

If anyone wants to see charts of the 'before' or the mdat for REW, please ask.

Thanks, stay safe all.


More studio pix: https://drive.google.com/drive/folde...Ek?usp=sharing
Attached Thumbnails
attic loft control room-img_1032.jpg   attic loft control room-l-r_spl_withslats.jpg   attic loft control room-l-r_topt_withslats.jpg   attic loft control room-l-r_etc_withslats.jpg   attic loft control room-l-r_time_withslats.jpg  

attic loft control room-slatsvsnoslats.jpg  
Old 4 weeks ago
  #2
Can you post the MDAT for analysis?

Are the left and right walls made of different materials? Low end response is showing this. Also the ETC is different on each side(actually in reading your post the right side wall is not supporting the low end on that the bass is going around it).

What are the dimensions? Where is the listening location situated? Woofers from side and front walls? Woofers from ceiling and floor?

What is your overall treatment?
Old 4 weeks ago
  #3
After seeing the front treatment, I was a bit underwhelmed from the SPL graph. Also, decay is quite uneven.

However, you're getting good, flat bass and your holes are relatively narrow.
Old 4 weeks ago
  #4
Gear Nut
 
n0nspaz's Avatar
Floor plan attached. The dark black line was the partition wall I added for left-right symmetry. Yes, there is a 31" gap at the front where low end (and cables) passes through. I am including the studio photos here as well so you can see the wall does not go all the way to front wall or to ceiling. This was an arbitrary decision/learning experience to gain symmetry in midrange & highs.

The approach with this room was to use available porous absorption + lots of coverage around the room (instead of isolated traps) + some intelligent studio construction principles, and DIY on a small budget. As in life, it's an experiment. And it's been a lot of work. I would like to be able to count on it for mastering purposes, until I get a larger space. Side walls are locked down at this point with stapled fabric and nailed slats. I realize it may be hard to retrofit 50Hz traps, which now I wish I had attended to, but I can still get into the front & rear wall spaces, and around the other areas of the loft space, so perhaps there's hope for improvements.


MDAT file contains 5 single-channel measurements:
- one before slats were installed, through Sonarworks room correction (left only)
- 2 after slats were installed, through Sonarworks room correction
- 2 after slats were installed, without Sonarworks room correction

The left wall was part of the ~1980 renovation of this 3rd floor attic space, and has tongue&groove pine boards over non-insulated stud walls (and sheetrock on the bathroom side). Whereas my right-side half-partition wall is filled with 2" rigid rockwool and has pine t&g boards on both sides of it. Treatment 'inner' walls were then built about 8" to the inside of these walls.

Center of woofers is 34.5" from SW fabric, 49.5" from carpet, 17.5" from angled ceiling, and about 33" from T1-11 FW wood panels

MDAT contains info on measurement mic positions as below:
DEFINITIONS:
Dyns= Dynaudio LYD48 3-way monitors
WG=waveguide panels per John H Brandt
FW=front wall, SW=side wall, RW=rear wall

>mic 75" from inner FW studs
>mic 59" to each SW inner stud
>mic at 48.5"H, pointed btwn spkrs
>FW rigid 703 + R30 3.5" fluffy + air gaps
>RW 24" deep R11 fluffy sheets w/air gaps
>RFZ: 4" roxul RHT80 48"W flr to ceil + 4"air gap at wall side
>FW covering: T1-11 Plywood Siding Actual: 0.563 in. thick. not screwed down yet.
>RW: n=36 stepped diffuser installed in front of 24"D R11 3.5" fluffy sheets hanging from ceiling. with air gaps. arqen.com
>4 CORNERS: flr-ceil. 24"W across rear, 48"W across front
R11 3.5" fluffy stapled & tied around 3 vertical waveguide OSB panels for 2" compression. R11 3.5" fluffy added in front of WG panels to semi-fill corners. air gaps between.
>carpet floor
>vaulted ceiling 100"H at peak
>ALL FABRIC INSTALLED. GoM Anchorage
>Dacron installed between most insulation and fabric. inc. cloud
>ALL SLATS INSTALLED. none in RFZ (yet)
>Partition wall finished with pine T&G board on both sides, filled with 2" dense RHT80 rockwool
>2" concrete slabs under monitors on sand-filled PVC pipe & masonite stands
>Dyns: Sens 0, Bass -10dB, (increased low end extension), BRIGHT, FREE
[email protected] is due to the (preferred) -10 Bass setting, doesn't affect higher freqs
>0-degree UMik USB MIC CAL file
>me sitting behind mic during testing


MORE CONSTRUCTION DETAILS IN THIS THREAD:
gearslutz.com/board/photo-diaries-of-recording-studio-construction-projects/1200392-attic-loft-production-mixing-studio.html#post13207777

older MDATs are available for each stage of construction.
Thanks, enjoy
Mark
Attached Thumbnails
attic loft control room-loft-floor-plan-inches-studio-plan.jpg   attic loft control room-img_1038.jpg   attic loft control room-img_1032.jpg   attic loft control room-img_1033.jpg   attic loft control room-img_1034.jpg  

attic loft control room-img_1035.jpg   attic loft control room-img_1036.jpg   attic loft control room-img_1037.jpg  
Attached Files
Old 4 weeks ago
  #5
Gotta ask: Are you working with John Brandt on this on not?
Old 4 weeks ago
  #6
Gear Nut
 
n0nspaz's Avatar
No, I did hire John a while back, learned a lot, then time passed, family & life got in the way, and I pretty much went for it alone.
Old 4 weeks ago
  #7
Quote:
Originally Posted by n0nspaz View Post
Floor plan attached. The dark black line was the partition wall I added for left-right symmetry. Yes, there is a 31" gap at the front where low end (and cables) passes through. I am including the studio photos here as well so you can see the wall does not go all the way to front wall or to ceiling. This was an arbitrary decision/learning experience to gain symmetry in midrange & highs.

The approach with this room was to use available porous absorption + lots of coverage around the room (instead of isolated traps) + some intelligent studio construction principles, and DIY on a small budget. As in life, it's an experiment. And it's been a lot of work. I would like to be able to count on it for mastering purposes, until I get a larger space. Side walls are locked down at this point with stapled fabric and nailed slats. I realize it may be hard to retrofit 50Hz traps, which now I wish I had attended to, but I can still get into the front & rear wall spaces, and around the other areas of the loft space, so perhaps there's hope for improvements.


MDAT file contains 5 single-channel measurements:
- one before slats were installed, through Sonarworks room correction (left only)
- 2 after slats were installed, through Sonarworks room correction
- 2 after slats were installed, without Sonarworks room correction

The left wall was part of the ~1980 renovation of this 3rd floor attic space, and has tongue&groove pine boards over non-insulated stud walls (and sheetrock on the bathroom side). Whereas my right-side half-partition wall is filled with 2" rigid rockwool and has pine t&g boards on both sides of it. Treatment 'inner' walls were then built about 8" to the inside of these walls.

Center of woofers is 34.5" from SW fabric, 49.5" from carpet, 17.5" from angled ceiling, and about 33" from T1-11 FW wood panels

MDAT contains info on measurement mic positions as below:
DEFINITIONS:
Dyns= Dynaudio LYD48 3-way monitors
WG=waveguide panels per John H Brandt
FW=front wall, SW=side wall, RW=rear wall

>mic 75" from inner FW studs
>mic 59" to each SW inner stud
>mic at 48.5"H, pointed btwn spkrs
>FW rigid 703 + R30 3.5" fluffy + air gaps
>RW 24" deep R11 fluffy sheets w/air gaps
>RFZ: 4" roxul RHT80 48"W flr to ceil + 4"air gap at wall side
>FW covering: T1-11 Plywood Siding Actual: 0.563 in. thick. not screwed down yet.
>RW: n=36 stepped diffuser installed in front of 24"D R11 3.5" fluffy sheets hanging from ceiling. with air gaps. arqen.com
>4 CORNERS: flr-ceil. 24"W across rear, 48"W across front
R11 3.5" fluffy stapled & tied around 3 vertical waveguide OSB panels for 2" compression. R11 3.5" fluffy added in front of WG panels to semi-fill corners. air gaps between.
>carpet floor
>vaulted ceiling 100"H at peak
>ALL FABRIC INSTALLED. GoM Anchorage
>Dacron installed between most insulation and fabric. inc. cloud
>ALL SLATS INSTALLED. none in RFZ (yet)
>Partition wall finished with pine T&G board on both sides, filled with 2" dense RHT80 rockwool
>2" concrete slabs under monitors on sand-filled PVC pipe & masonite stands
>Dyns: Sens 0, Bass -10dB, (increased low end extension), BRIGHT, FREE
[email protected] is due to the (preferred) -10 Bass setting, doesn't affect higher freqs
>0-degree UMik USB MIC CAL file
>me sitting behind mic during testing


MORE CONSTRUCTION DETAILS IN THIS THREAD:
gearslutz.com/board/photo-diaries-of-recording-studio-construction-projects/1200392-attic-loft-production-mixing-studio.html#post13207777

older MDATs are available for each stage of construction.
Thanks, enjoy
Mark
On your filtered ETC at 315hz where the nulls is in frequency response there is a huge reflection of energy around 17.1m-18.9m on the All Slats L and R measurement. Have you tried to figure out where its building up from?

Also it looks like the null at 88hz on the left speaker is from a modal reflection and on the right side its SBIR.
Old 4 weeks ago
  #8
Gear Nut
 
n0nspaz's Avatar
Quote:
Originally Posted by thethrillfactor View Post
On your filtered ETC at 315hz where the nulls is in frequency response there is a huge reflection of energy around 17.1m-18.9m on the All Slats L and R measurement. Have you tried to figure out where its building up from?
I was always curious why treatments did not take care of the 315Hz issue...

I am not sure how to convert time to distance based on the ETC
spikes, or how it coordinates with frequency nulls. I would love to learn, thanks.

Aren't the spikes at ~5ms a big issue too?

Quote:
Also it looks like the null at 88hz on the left speaker is from a modal reflection and on the right side its SBIR.
Did you calculate freq null based on room size, or is there something you see just by comparing left and right channels?

I haven't measured for speaker position/SBIR since early construction, before absorption installation. So it's time to revisit this. I will test various positions in 1" increments and report back. thanks.
Old 4 weeks ago
  #9
Quote:
Originally Posted by n0nspaz View Post
I was always curious why treatments did not take care of the 315Hz issue...

I am not sure how to convert time to distance based on the ETC
spikes, or how it coordinates with frequency nulls. I would love to learn, thanks.

Aren't the spikes at ~5ms a big issue too?
Yes the 5ms(or 4.43ms) is a problem, but it looks like its been there even without the slats?

When you filter it out its what's causing the nulls between 8k-10khz.

If you hold down the control key(Mac) and right click drag to 0m from the peak it will give you the round trip amount from speaker to reflection to microphone.

It shows 4ft 9.04inches.

The spike at 2m says 2ft 3.13inc.


Quote:
Originally Posted by n0nspaz View Post
Did you calculate freq null based on room size, or is there something you see just by comparing left and right channels?

I haven't measured for speaker position/SBIR since early construction, before absorption installation. So it's time to revisit this. I will test various positions in 1" increments and report back. thanks.
I analysized by dimensions/mode analysis plus the phase selection in SPL and Phase measurement. A 180 degree phase line usually lines up to a reflection at a null. This normally corresponds to either a hard boundary at the first or second mode and sometimes its strong if not treated properly.

When it doesn't and the lines decay over the null, it usually shows up as SBIR. This is just something i've noticed over time, but is not intended for that use.

SBIR is too difficult to measure based on distance alone as we are talking about multiple reflections being summed at the listening location.
Old 4 weeks ago
  #10
Lives for gear
 
akebrake's Avatar
 

PLD, Path Length Difference

Quote:
Originally Posted by n0nspaz View Post
...I am not sure how to convert time to distance based on the ETC spikes, or how it coordinates with frequency nulls. I would love to learn, thanks.
Nice room you got there! I'm impressed!

Regarding ETC and math...

I did a sketch (some time ago) to illustrate the relationship between ETC peaks and FR nulls & peaks due to Path Length Difference. (LINK)

What usually shows in the ETC is not the whole ”roundtrip” but the Path Length Difference (PLD) expressed as time (or distance)
(E.g the travel time between spkr and microphone is not visible on the ETC)

BTW What is the physical distance between the Spkr & Microphone?

Best
Old 4 weeks ago
  #11
Gear Nut
 
n0nspaz's Avatar
Quote:
Originally Posted by thethrillfactor View Post
Yes the 5ms(or 4.43ms) is a problem, but it looks like its been there even without the slats?
Actually this spike looks to have become more pronounced since the slats were installed. Now -18dB vs -22dB, and was at -28dB a while ago, when only the room perimeter was finished with absorptive treatment, before hard front inner walls were in place and before any fabric or the cloud were installed.

(Also a large table was removed from the right side, and a smaller 10sp rack was placed there instead. But I am only looking at the left side graphs here, so irrelevant.)


Quote:
When you filter it out its what's causing the nulls between 8k-10khz.
Sorry can you show me how to "filter it out" ? And how you get the correlation between these spikes and changes in frequency resp is likewise still magic to me. Very motivated to learn but I realize that I know just enough to be dangerous


Quote:
If you hold down the control key(Mac) and right click drag to 0m from the peak it will give you the round trip amount from speaker to reflection to microphone.
OK then, 5.03ft shown in REW is twice the distance to the reflection point. I started a 2.5ft string from front of the (midrange? which?) driver, and moved in a radius to find possible bounce points. It's gotta be the back of my 40" touchscreen. And in turn, that is probably reflecting to hard front wall as well. This will be a challenge to treat with absorption and still get adequate ventilation, and aesthetics



Quote:
The spike at 2m says 2ft 3.13inc.
I see a double-spike at 2.06ft and 2.25ft. The only thing around 1ft from the driver is the cloud. I am starting to suspect that my Guilford of Maine Anchorage fabric with the "NRC .85" rating is causing a bounce
Old 4 weeks ago
  #12
Gear Nut
 
n0nspaz's Avatar
Quote:
Originally Posted by thethrillfactor View Post
I analysized by dimensions/mode analysis plus the phase selection in SPL and Phase measurement. A 180 degree phase line usually lines up to a reflection at a null. This normally corresponds to either a hard boundary at the first or second mode and sometimes its strong if not treated properly.
So the blue lines in the attached show points where there is a shift in both freq and phase, thus a wave is hitting a boundary and starting to cancel itself, causing a null. So the phase plot helps you see where boundaries are causing issues in the freq response. cool This is only part of the picture i suppose, and impulse tells us another big part (time & distance).


Quote:
When it doesn't and the lines decay over the null, it usually shows up as SBIR. This is just something i've noticed over time, but is not intended for that use.
I see, so where there is a null WITHOUT the massive phase shift, it's probably NOT a boundary issue, rather it's usually SBIR (which is another kind of boundary issue I guess). We might be seeing that a bit at 200Hz on the attached chart yes?

If the goal is to find these boundaries and treat them, I'm at a loss until learn how to think in terms of 'converting' from frequency response chart to distances. Any resources that would help me learn how to apply all this data would be appreciated, thanks!


Also, what is going on from 5k to 10k, where the whole phase response is constrained to the high region, and not sweeping up or down much? Does this point to needing diffusion? (getting ahead of myself here)
Attached Thumbnails
attic loft control room-loft-all-walls-finished-phase.jpg  
Old 4 weeks ago
  #13
Gear Nut
 
n0nspaz's Avatar
Quote:
Originally Posted by akebrake View Post
Nice room you got there! I'm impressed!

Regarding ETC and math...

I did a sketch (some time ago) to illustrate the relationship between ETC peaks and FR nulls & peaks due to Path Length Difference. (LINK)

What usually shows in the ETC is not the whole ”roundtrip” but the Path Length Difference (PLD) expressed as time (or distance)
(E.g the travel time between spkr and microphone is not visible on the ETC)

BTW What is the physical distance between the Spkr & Microphone?

Best

Thanks, that helps! Once I realized that the distance shown in REW is twice the distance to the boundary, then I can search for the reflection points.
Old 4 weeks ago
  #14
Quote:
Originally Posted by n0nspaz View Post
So the blue lines in the attached show points where there is a shift in both freq and phase, thus a wave is hitting a boundary and starting to cancel itself, causing a null. So the phase plot helps you see where boundaries are causing issues in the freq response. cool This is only part of the picture i suppose, and impulse tells us another big part (time & distance).




I see, so where there is a null WITHOUT the massive phase shift, it's probably NOT a boundary issue, rather it's usually SBIR (which is another kind of boundary issue I guess). We might be seeing that a bit at 200Hz on the attached chart yes?

If the goal is to find these boundaries and treat them, I'm at a loss until learn how to think in terms of 'converting' from frequency response chart to distances. Any resources that would help me learn how to apply all this data would be appreciated, thanks!


Also, what is going on from 5k to 10k, where the whole phase response is constrained to the high region, and not sweeping up or down much? Does this point to needing diffusion? (getting ahead of myself here)

Its a little more involved. I normally wrap the phase, generate minimum phase and show the excess phase as well. Also in the Group delay(excess delay) page i look at how much is a specific frequency delayed and that gives me an idea what the room or boundaries are doing and if a specific treatment on a specific frequency can be targeted.

In REW it shows minimum phase in the lower frequencies even though we know some nulls are not(which you can see in the slope of the phase).

By the way the excess group delay page is showing non minimum phase issues at 87.9hz, 321.8, 1khz.
These show "greater variation with position and to be more affected by changes within the room" according to REW, so these are more a result of SBIR or listening position than anything.
Attached Thumbnails
attic loft control room-screen-shot-2020-06-04-11.04.11-pm.jpg   attic loft control room-screen-shot-2020-06-04-11.04.36-pm.jpg  
Old 4 weeks ago
  #15
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jhbrandt's Avatar
Hey buddy, you did the slats wrong... Take em down and put them on the FRONT wall only. You can't have reflecting points on the sidewalls unless they are angled toward the rear of the room.

Cheers,
John
Old 4 weeks ago
  #16
Lives for gear
 
jhbrandt's Avatar
Quote:
Originally Posted by akebrake View Post
Nice room you got there! I'm impressed!

Regarding ETC and math...

I did a sketch (some time ago) to illustrate the relationship between ETC peaks and FR nulls & peaks due to Path Length Difference. (LINK)

What usually shows in the ETC is not the whole ”roundtrip” but the Path Length Difference (PLD) expressed as time (or distance)
(E.g the travel time between spkr and microphone is not visible on the ETC)

BTW What is the physical distance between the Spkr & Microphone?

Best
As ake said... it's not the nulls that you need to treat. Treat the source of the problem. The above should get you sorted.

If you still have issues after the reflections are corrected, you don't have enough bass trapping. What's the RT60?
Old 3 weeks ago
  #17
Gear Nut
 
n0nspaz's Avatar
Quote:
Originally Posted by jhbrandt View Post
Hey buddy, you did the slats wrong... Take em down and put them on the FRONT wall only. You can't have reflecting points on the sidewalls unless they are angled toward the rear of the room.

Cheers,
John

Hi John! I only have slats on side walls where the angle is at least 11? 15? degrees (I forget, will have to look it up) pointing toward the rear of the room. I didn’t put slats reflecting directly toward the mix position. ??

For front walls, I used T1-11 sheets. If the 100% solid panel is a problem there, I will create perforations. What is the ideal passthrough/reflection % ?

Thanks!
Old 3 weeks ago
  #18
Gear Nut
 
n0nspaz's Avatar
Quote:
Originally Posted by jhbrandt View Post
As ake said... it's not the nulls that you need to treat. Treat the source of the problem. The above should get you sorted.

If you still have issues after the reflections are corrected, you don't have enough bass trapping. What's the RT60?
1. Do the TOPT charts in post #1 show you this, or is RT60 different?

I think I need 50Hz trapping since the TOPT decay is really long. I did not specifically address this at any point in construction. Will a couple limp mass absorbers placed in 50Hz hotspots in the adjacent area (with the spiral staircase) help, or do they need to be closer to have an effect, like in the front/rear walls in the studio area? The air space is quite open, as I am using half the larger room for the studio.

2. I am finding that my cloud design, and the fact that the speakers are close to the sloped ceiling (what can I do?) are causing reflections. Phase improves noticeably when absorbers are temporarily placed around the monitors and the rear of the desk is damped.

3. I still cannot find the source of the 8k dip. Nothing I did this week to dampen areas around the monitors seems to affect it.
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