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attic/loft production/mixing studio
Old 2nd February 2018
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attic/loft production/mixing studio

This is my 4th DIY studio. It's in a ~1980 renovation of a 3rd floor attic of a 1930 construction New England timber-frame home (USA). Purpose is audio post mixing and electro/acoustic pop music production. I might record guitars and vocals and small instruments in the room but not drums. The priority is accurate mixing and a good production vibe.

Specific goals are to improve over my last studio -- including an effective 48" RFZ, ~.4sec RT60 with good decay, ETC showing no reflections above -20, using mostly materials I have, not ripping up the carpet, and doing everything DIY (for learning). I understand my options and am not looking for perfection. I am willing to build membrane absorbers/VPRs if needed (though i'm not sure how/where they would fit into the room design).

I am dismantling all my discrete absorber panels shown in previous studio thread above for a more proper light construction approach. Construction is a few days in, I just got the monitors (Focal Shape 65), I have run all the numbers for room modes etc, but haven't started testing with REW yet.

A partition wall was built to define the space and present some L-R symmetry to the highs and mids. Placement (studio width) determined by anchoring into rafters.

I'm loosely following the excellent designs of John Brandt, and am very thankful to him for his guidance.

Initial observations
- strong sub bass but surprisingly consistent around the room
- overly strong chorus and delay/imaging effects on pop records
- lots of lower honky midrange in both front and rear
- rear section of room has issues on left wall: 2 windows mean only half-height treatments are possible.
- 31" gap from new partition wall - what's the implication here, and should i close it up
- will deep membrane absorbers be needed

This will be constructed over the next 2-3 months and I'll be updating with photos and learning. Please chime in with any serious suggestions. Thanks, all the best to everyone
Attached Thumbnails
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Old 3rd February 2018
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partition wall

partition wall
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Old 3rd February 2018
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front framing

front of room
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Old 3rd February 2018
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rear of room

a/c removed. to be replaced with window. and additional inner window angled according to the plan.
framing in progress
Attached Thumbnails
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Last edited by n0nspaz; 3rd February 2018 at 02:59 AM..
Old 16th February 2018
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waveguides

“waveguide” corner panels in place. Not sure if this will come through as an attachment but the photo with the hand moving the panels demonstrates how floppy the longer (rear) waveguides are.
Attached Thumbnails
attic/loft production/mixing studio-f2a24776-e44a-4c57-a94e-882872860124.jpg   attic/loft production/mixing studio-c6e9e3cc-bcb7-4166-93b1-9e12cc7be81c.jpg   attic/loft production/mixing studio-e8f3d62f-1abe-4650-8782-e6d02bb16c14.jpg  
Old 21st February 2018
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speaker stands

recipe for these MDF & PVC monitor stands is already here somewhere on GS. pipe was covered with fabric, the gluegun seam in the back sand was dried with a fan.

a bit wobbly honestly at this height but then again i did not use any glue/silicone between the flange and the base. i will add 4 more screws in each and see.

height is 38.5”/98cm. most monitor stands I found are 36”.

base is around 14x14” 35cm. double thickness MDF, see glue-up

i would have made a larger top than 9x12” if i had decided earlier what monitors i was getting. but these will suffice.


EDIT: I will add a 3" isolation mount of some sort under the speakers to build them up to 48"/123cm ear level.

The 14" square base is still somewhat rocky (could tip over with a strong hit) on this carpet floor. I would have gone 16". At this point I will try rubber feet or spikes, but they may transmit sound into the house below, whereas the carpet is a natural absorber/decoupler
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Last edited by n0nspaz; 1st March 2018 at 05:38 PM..
Old 1st March 2018
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slats cut

All slats cut to size and numbered on the back by location. Plan is to prime and paint them with satin finish latex, since polyurethane will just show off their nasty look.

Since this project is all about the highest quality I can achieve on a very low budget (under $2500) using as much materials as I already have, these cheap slats are rough lumber called 1”x2” in the US (actually 5/8”x1.5”) with strongly beveled/chamfered edges. Also useful for some of the framing (along with 2x3’s).

I am curious as to what effect the beveled edges will have vs the better pine boards you can buy with the more squared-off edges (at 3x the price). Mine will generate less diffraction I assume—but what does that sound like?). As long as they keep life in the room, and if the angles break up the parallel walls, I think they should work fine. They will be 70/30 ratio reflective/absorptive. No slats in the RFZ zone or in small mini-corners of the angled walls.

Photos: note the removable frames to allow access to corners and center front wall. Will be locked down with industrial velcro.
Attached Thumbnails
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Last edited by n0nspaz; 1st March 2018 at 06:35 PM.. Reason: photos
Old 1st March 2018
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absorption choices

Deciding not to rip up the carpet is something I hope I won’t regret. I figured, since the angled ceiling does not make a parallel with the floor, that I will just leave the ceiling mostly untreated.

Once we start measuring, we will see clearly what is going on. Right now the front of the room behind the monitors has heavy sub bass buildup, but the rear of the room does not. Of course, the parallel walls have a very audible midrange boink! problem in front and rear of room.

If anyone wants to chime in as to which type of absorption to put in various places around the room, I do have a plan but I am open to suggestions.

I have 2” & 4” Roxul RHT-80 rockwool, 2” OC703, and 2” OC705 available in my ‘inventory’. I will be buying fluffy stuff for the waveguide panels/corners. Planning to use OC703 for the RFZ, 4” thick rockwool on back wall behind the giant polystyrene diffuser (again, just using what I have already made here), but I am concerned that thick rockwool around the rest of the room will make it too dead (even behind slats).

I hope this thread is not getting too pedantic/boring. Real results will emerge soon. Cheers
Old 1st March 2018
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rear wall diffuser

Thanks to Jens for the inspiration to have this polystyrene stepped diffuser made (a few years ago now) and to Tim at arqen.com for help with the design.

Do I know its actual effect? Did I carefully choose the type of material etc? No, this is a low budget thing that anyone can do. But soon we will start measuring the room with REW...
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Old 19th March 2018
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initial testing, speaker & mic positioning

Lots of progress and now I owe several updates here. Sorry this is not more organized, there is a lot of data to keep track of and I could use some better practices on simplifying.

INITIAL TESTING
- loft preliminary measurements-01.mdat & 2 SBIR files
- maximizing room modes seems to produce peaks at 32, 50, 62, 150, 173, 198, 263-
nulls at 57, 87, 118, 217
- decay time is longest at 32Hz, then 56Hz, then multiples: 75, 107, 210, etc
- also massive null around 310Hz
- moving L spkr from the 37% spot toward fr wall decreases 62Hz (this is true for R side but not as much difference). Both sides: increased 50Hz as spkr moves toward fr wall
- 70Hz peak is higher on R side of room (partition wall)
- extra personnel seem to be having an effect when holding up panels or standing around spkrs
- ceil abs. above spkr is crucial for initial (smearing) reflections. see Filtered IR> 1.2ms

Room modes (don’t change with spkr position): 25Hz, 32Hz, 62Hz, 127Hz, 200Hz

SBIR freq’s (change with spkr position): 60-63Hz? not sure, 70-75Hz, 93Hz, 110-119Hz, 127-130Hz? not sure


1. Extensive experimentation for initial SBIR/speaker positioning (without any treatments in place, not sure if this is how it's usually done). Chose what seemed like the flattest SBIR compromise. This is actually tricky because some peaks/nulls improve and some get worse from plot to plot. Just using my own judgment here.

I ended up choosing a point 2" inward toward room center from the 37% point (from the "outer shell" side walls). Front of cabinets' acoustic centers are 27" into the room, measured from inner shell wall studs. This is pretty far into the room, NOT up against the slanted ceiling. Usually monitors are pushed back to FW as far as possible for best freq response; but response was worse. The slanted ceil must be the difference here.

2. Moved the mic 1.5" forward of the 37.5% point (from outer front wall), as it improved the 183Hz L null a bit. Mic capsule now 102.5" from outer FW (which is an attic eave). Subjectively, more bass in pop music tracks when head is at or forward of the sweetspot (vs in back of it).

images only show limited plots. REW mdat file here

If you want to see micro speaker adjustments too, mdat is here


[Ignore the 32Hz peak in these plots, it is some kind of issue with the speakers switching themselves into "Bass Extension" mode without my setting it]
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Attached Files
File Type: txt TEST NOTES!!.txt (468 Bytes, 58 views)

Last edited by n0nspaz; 19th March 2018 at 05:14 AM..
Old 19th March 2018
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more photos of speaker positioning testing
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Old 19th March 2018
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front corner treatments

Various experiments with front wall treatments.

Tried OC703/5, Roxul RHT80 2" and 4" just placed casually across corners, before I installed the R30 fluffy onto the waveguide panels. Teaser photos below, see links for mdat's.

>>R30 fluffy stapled to either side of all 6 waveguide panels, air gap btwn (no vertical R30 in front of corners yet)

FINDINGS:
L lowered 62 null to 60.5, deepened it by 2db
L deepened 92 by 5dB
L improved 123-300, especially peaks/nulls ~200 & nulls at 283 & 300
R shifted 53 null to 51 and deepened by 3dB
R deepened 93 null by 2db
R flattened 129Hz null completely
R slight improvements 156-161
R improved nulls 400-630Hz avg 4dB. but new massive null at 310
R decreased R channel decay time at 160 & 170Hz in line with other freq’s
reduced 32Hz mode by only 100ms (1000>900ms)
L&R TOPT shaved 100-150ms decay off 100-200Hz (esp. 100!). longest now=250Hz 370ms


front wall .mdat
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Old 19th March 2018
  #13
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rear corner treatments

>>rear waveguides wrapped in 3.5" R30 fluffy compressed to ~2"

FINDINGS:
L 91 null is now 93.5Hz and 2dB deeper, 350 null 3dB better 385 null 5dB better
R 51Hz null better by 1.5dB, 165 & 235 & 268 null better by 3dB, 310 null is back (worst null by far)
FR NOT MUCH DIFF REALLY
L still extremely long decay @ 60hz 440ms. 100Hz is way longer now at 315ms. totally took care of the 250Hz long decay time, now 330ms.
R best 60Hz so far at 350ms (slightly better than roxul/OC) 250Hz decay is back (was gone with roxul/OC) = longest decay 385ms.

I guess I expected SOME <100Hz performance

sorry that some photos come out sideways, sending from iphone

rear wall .mdat
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Old 19th March 2018
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RFZ

>>Experimented with the various panel types in the RFZ position.

LEARNINGS:
- either 2” or 4” roxul outperformed 2” OC705/703 combo on freq response
- only the 4” roxul reduced the long R 250hz decay so i’m going with this
- none of the RFZ options helped 60Hz decay time (of course)

mdat file


>>Chose Roxul RHT-80 4”

FINDINGS:
L 60Hz null worse by 2dB, 93 null better by 8db!, 200-400 (375) nulls better by 5dB
R 51Hz null worse by 1dB, 93 null raised 2dB, 100-200 flattened by 2dB, 310 null gone but HUGE null at 240 now, 360 null worse
L 60hZ decay shortened by 25ms, 125 too short now (190ms), looking good otherwise, 250Hz decay totally normal now (290ms)
R 60hz increased slightly, 100 shows 340ms (longest) now, otherwise all very flat ~250ms
Attached Thumbnails
attic/loft production/mixing studio-loft-rfz-1-topt.jpg   attic/loft production/mixing studio-loft-rfz-1.jpg   attic/loft production/mixing studio-loft-studio-before-after-rfz-corner-waveguides-topt.jpg   attic/loft production/mixing studio-loft-studio-before-after-rfz-corner-waveguides.jpg  
Attached Files
File Type: txt TEST NOTES!!.txt (468 Bytes, 60 views)
Old 19th March 2018
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RFZ photos

also 2 other experiments shown: pseudo-ghetto-VPRs (useless as shown)

...and front wall center OC703 panels:
- actually deepened (worsened) 50, 62, 93, 127Hz nulls by 7-10dB !
-but improved decay times.

Does this have any merit? How do we choose between worse FR and better decay times?
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Old 19th March 2018
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Treatment results so far

I really don't understand the greatly worsened nulls at 51 & 62Hz, and the weirdness around 375Hz. [And again, note that the 32Hz peak is a speaker switch problem not a treatment]

I can understand the difference in the left vs right channel at very low freq's...Again I have tried to create as much symmetry as possible in this space but it's not perfect. Since 50-60Hz isn't really directional, I'm not concerned that the channels have different nulls . I *am* concerned that these nulls are now crazy deep since installation of the corner and RFZ treatments!!

Any advice appreciated about the nulls, and thanks for following!
Attached Thumbnails
attic/loft production/mixing studio-loft-studio-before-after-rfz-corner-waveguides-topt.jpg   attic/loft production/mixing studio-loft-studio-before-after-rfz-corner-waveguides.jpg  
Attached Files
File Type: txt TEST NOTES!!.txt (468 Bytes, 64 views)

Last edited by n0nspaz; 20th March 2018 at 06:11 PM..
Old 20th March 2018
  #17
Quote:
Originally Posted by n0nspaz View Post
I really don't understand the greatly worsened nulls at 51 & 62Hz, and the weirdness around 375Hz. [And again, note that the 32Hz peak is a speaker switch problem not a treatment]

I can understand the difference in the left vs right channel at very low freq's...Again I have tried to create as much symmetry as possible in this space but it's not perfect. Since 50-60Hz isn't really directional, I'm not concerned that the channels have different nulls . I *am* concerned that these nulls are now crazy deep since installation of the corner and RFZ treatments!!

Any advice appreciated about the nulls, and thanks for following!
It's perfectly normal, and part of what is best termed "incomplete acoustic treatment"

When we start we have a room of immensely dense "problems" all stacked up.

As we progress we, one by one, start to "kill" those problems.

When we get closer to a well treated room (if done properly) we are left with very pronounced isolated issues that are as obvious as the nose on your face.

Where did they come from?

Well they were always there. "But I didn't measure them before" is the usual cry, and yes that is true, but the sum of all the original interactions is a chaotic dense mess of incalculable complexity, everything is inter-reacting in complex ways and often the very deep issues are in many ways being counteracted by other issues that lessen the noticeable effect. (depending on where you measure from and where you put the source).
As we remove many of the dense problems and don't remove them all we can be left with horrible pronounced issues that are existing unmolested in isolation and with incredible dominance.

One of the most common things we have from customers is them noticing the slap echoes between the floor and the face of the 3 x 10 ceiling beams just before the covering treatment goes on. it is a ping that is massively loud and could be an effect in itself.

Until all our trapping systems are in we often have horrid mid-bass resonances in the confines of the treated outer shell.

It is only at the last minute when our final systems are in that there is a "Eureka" moment and all of a sudden everything sounds fine. All issues are gone.

This is logical, we're not here to waste money, we stop when we fix the problem, and not until we fix it.

There is no such thing as "Acoustic lite" a partial solution that "is good enough"

In my experience what you have is a normal case of being 80% of the way there to sorting it, the further you go the more violent the problems become, but also the more isolated they become.

I can't offer much guidance on what to do, as It's not the approach that I would take from the start (I'm not saying it's wrong - there are many ways to skin a cat) All I'd say is it looks like you are making progress The symptoms are normal for that, it just looks like you need to keep on going to get rid of the last more obvious issues.

Do some wavelength calculations, figure what distances may be affecting things then look at treating surfaces in that zone.

Also..... Use ears and brain, not eyes and screen. Listen carefully and see if you can hear it, often the human cannot hear some High Q dips that analysers love to throw up. Floor reflections are a classic example, almost nobody can hear them, yet they look a mess on an analyser.

Don't dismiss it, not at all, but verify that it is a real acoustic problem by listening, and not an analysis anomaly.

Analysers are for verifying problems and targeting them..... They are NOT for finding problems, that's what our ears (and brain) are for.
Old 21st March 2018
  #18
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Quote:
Originally Posted by Nuisance View Post

In my experience what you have is a normal case of being 80% of the way there to sorting it, the further you go the more violent the problems become, but also the more isolated they become.

Do some wavelength calculations, figure what distances may be affecting things then look at treating surfaces in that zone.

Also..... Use ears and brain, not eyes and screen. Listen carefully and see if you can hear it, often the human cannot hear some High Q dips that analysers love to throw up. Floor reflections are a classic example, almost nobody can hear them, yet they look a mess on an analyser.

Thanks a lot for this advice, and confirmation that my results show progress.

Wondering what kind of absorbant to use for the remaining spaces :

1. remaining side walls. These angled sections taper from 8” to 0” and they face parallel walls. However there will be slats in front which should cure the slapback honk I currently hear. If someone can save me the bother of trying both rigid and fluffy in these areas, I would appreciate. I have lots of 2” rigid, but would have to buy fluffy.

2. rear wall behind diffuser. There is 12” available behind where the diffuser is going, and this large of a gap usually calls for fluffy. It would be easier and cheaper to use rigid but I am willing to buy the fluffy if it would be better. If I do fluffy, would stapling it to the ceiling and letting it hang down in vertical sheets be a good method (this would be a looser method with lots of air in there) or should it be folded over and stacked vertically, with horiz supports every 18” or so, for a denser packing?

3. front wall center. I have 24” depth and 48” across available, and a tapered ceiling. Placing rigid stuff across the front (see previous tests) wasn’t very helpful. Filling it with fluffy seems most logical, but I can’t try this unless I buy it. I may try to make a mini-pseudo-VPR again by hanging a 1mm steel sheet and attach absorbant to it.

But first I need to find where I hear the most buildup of 50/60 Hz.
Old 3rd April 2018
  #19
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OBSERVATIONS from QUICK WALKAROUND TEST:

L ch 60Hz null does not change volume with height. it changes with both front-back and side-to-side movement. loudest along entire FW
R ch 50Hz null changes volume mostly with side-to-side movement. little with fr-back, and not with height. loudest along entire FW, 2nd loudest in crankout windows alcove way at the right of the room (outside of listening area). strangely 50Hz is not loud here.
Old 3rd April 2018
  #20
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front wall center & side walls done

I learned that dense/rigid insulation performs better where wave velocity is highest (at the wall) and lightweight/fluffy performs best at the 1/4 wavelength area (away from wall).

So for the front wall 24" (61cm) depth I had available, I sandwiched (2) 2" OC703 panels together, fixed them parallel to and out from the wall by 4", (so that's 8" depth used) and then added many hanging sheets of 16" wide panels perpendicular to the front wall, leaving it airy in between, not packed densely. No reason for perpendicular except just experimenting.

Also most of the side walls beyond the RFZ were filled with 2" Roxul RHT80 against the wall and 4"+ fluffy in front of that, as space permitted in the angled wall sections.


TREATMENTS:
(2) 2” (total 4”) OC703 spaced 4” off the front wall resting on floor. total length 72” across. in front of that: (11) 16” sheets of 4” fluffy hung vertically in FW center, hung perpendic to front wall. total 24” depth FW center trap

SIDE WALLS: front and most of rear: Added 2” roxul RHT80 against wall and 4” fluffy in front, hung vertically floor to ceiling. no dacron in front yet.
rear wall and ceiling still bare


RESULTS:
L ch FR 58 null and 72 peak both slightly flattened, overall loss of energy ~1-2dB 30-50Hz. ~325 still a mess
R ch FR big improvement in 50Hz null, somewhat in 70Hz. overall loss of energy ~1-2dB 30-50Hz. 335 worse (probly spkr movement)

L decay BIG reduction in 60Hz 340>280ms, also 150 290>155
R decay no reduction in 60Hz but big reduction 100Hz 310>240ms.
all upper freq’s obviously dampened quite a bit ~50ms

so: overall very slightly flatter and much less ringing in the low end *
Attached Thumbnails
attic/loft production/mixing studio-8.0-mic101-l-before-fw-ctr-sw.jpg   attic/loft production/mixing studio-8.0-mic101-l-after-fw-ctr-sw.jpg   attic/loft production/mixing studio-8.0-mic101-r-before-fw-ctr-sw.jpg   attic/loft production/mixing studio-8.0-mic101-r-after-fw-ctr-sw.jpg   attic/loft production/mixing studio-a866b852-8abc-4c22-b257-b9d83b75ccf5.jpg  

attic/loft production/mixing studio-df6fa055-14c7-4030-bcd0-5bdc593834d2.jpg   attic/loft production/mixing studio-9c03598e-358a-47f8-9e54-724916e34d48.jpg   attic/loft production/mixing studio-52990246-5181-4a96-9efe-db91d8317c88.jpg   attic/loft production/mixing studio-517ab840-5450-4172-94f6-3631c353a49a.jpg  

Last edited by n0nspaz; 3rd April 2018 at 03:25 AM..
Old 3rd April 2018
  #21
Gear Nut
 
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most absorption done

I've gone ahead and added 12" R11 fluffy to the back wall (3 layers deep since it is ~4" material). Stapling it to, or draping double-length sections of it over a slat fixed parallel to and out from the wall a few inches, required minimal effort and it looks strong enough to hold up. We'll see if it sags in the future.

Also completed adding dacron poly batting over everything (except RFZ panels for no real reason, and on the rear wall where diffuser is going).

Still no ceiling cloud, rear diffuser, or wood slats in front of side & corner panels.



REAR WALL 12” FLUFFY, ALL POLY BATTING DONE (no cloud, no diffuser, no slats)
  • L ch FR: 2-3dB flatter from 50-300.
  • R ch FR: no significant changes
  • L decay worse: 200Hz shot way up by 100+ms to over 350ms! what is the problem? 100Hz even lower at 120ms (too low)
  • R decay similar results but less extreme

SPECTROGRAM:
  • L&R 200-350 is much more consistent. and much more energized (more even red color)
  • L dips at 90, 125, 145 are slightly improved
  • R dips at 95, 105, 125 are slightly improved
  • mild improvement with the back wall flufffy.

LEARNINGS
  • position 8 FR is flatter than pushing spkrs up against front wall/ceil (pos 17)
  • position 8 fills in the 100Hz gap on the waterfall (vs 17)
  • pushing spkrs back from position 8 to 17 energizes 200-350Hz which creates more disparity in decay times
  • YET pos 8 creates a huge hole at 325Hz on spectrogram. pos 17 pushes that up into the 425+ region and it is less pronounced.
  • more COVERAGE leads to smoother room response, but expect only 2-3dB per wall/room region.
  • WALL spkr switch only slightly lessens the decay times of 25 & 30Hz ringing (waterfall)
  • why has the rear wall fluffy added to the 200Hz decay time, and lessened 100?

note on photos: duplicate of previous post’s waterfalls included for easy comparison.
Attached Thumbnails
attic/loft production/mixing studio-8.0-mic101-l-after-fw-ctr-sw.jpg   attic/loft production/mixing studio-8.0-mic101-l-after-fw-ctr-sw-rear-wall.jpg   attic/loft production/mixing studio-8.0-mic101-r-after-fw-ctr-sw.jpg   attic/loft production/mixing studio-8.0-mic101-r-after-fw-ctr-sw-rear-wall.jpg   attic/loft production/mixing studio-60f5980b-a942-4124-bc91-5392df7eab4a.jpg  

attic/loft production/mixing studio-3e4dd659-4e20-4806-bc7b-934f0ed03d31.jpg   attic/loft production/mixing studio-f9391747-9695-4bf3-b9af-37e64c4e9d73.jpg   attic/loft production/mixing studio-d57aed85-cbdc-4754-bc80-505164317659.jpg   attic/loft production/mixing studio-26648783-f1ea-49bd-ad5a-e3491c4f199e.jpg  
Old 25th February 2019
  #22
Gear Nut
 
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CLOUD

CEILING CLOUD constructed and installed. This was done last year so I don't have an accurate progress report, except that the waterfalls and REW file are attached. Adding the cloud definitely focused and clarified the sound, at the expense of making things even deader (expected).

After working in the room like this (all absortption, no wood slats or diffusion installed yet), my mixes are coming out rather smiley-faced on these very flattish monitors. It's a work in progress...I'll be back.
Attached Thumbnails
attic/loft production/mixing studio-loft-0918-all-absopt-no-diffus-first-cloud-mm-pos8-l1.jpg   attic/loft production/mixing studio-loft-0918-all-absopt-no-diffus-first-cloud-mm-pos8-r1.jpg   attic/loft production/mixing studio-img_5380.jpg   attic/loft production/mixing studio-img_5360.jpg   attic/loft production/mixing studio-img_5280.jpg  

attic/loft production/mixing studio-img_5391.jpg   attic/loft production/mixing studio-img_5390.jpg   attic/loft production/mixing studio-img_5389.jpg  
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