Acoustic Treatment Design based on REW Measurements

[diakonos1984]

So just over a year ago I started a thread about a room I wanted to use as a studio until I can get a purpose built room. Taking the great input I got there, my wife and I decided to scrap the guest room/studio concept and make this room a studio when I am home and her office when I am not. It is working out well logistically, but I need some help making it work acoustically!

Here is the floorplan:


The desk unit we found is less than ideal acoustically, but it is the best compromise for the two of us to be able to use the space. Here are a few pictures of the room and desk unit:


After we painted and floored the room, and installed the base level of furniture/equipment, I got REW and a reference mic and took measurements in 10 locations in the room. The locations are numbered on the floorplan. Below is a graph showing ALL the measurements I took, and another showing only the measurements at the listening position.

Now my task is to design acoustic treatment for this room. How do you recommend I approach this?

Thanks!

 

[mjbphotos]

Are you recording with a mic at any point? If so, a couple of 4" thick x2'x4 rockwool gobos set up 'behind' the mic will help reduce reflections from your vocals or instrument off the front walls bouncing around and getting picked up by the mic. You've got precious little space to put any kind of acoustic treatment symmetrically in the room, and that desk is taking all your front wall's room - not leaving enough space in the corners for traps, and no good place to put your monitor speakers. It looks like the compromise was all your wife's way (but then isn't that always the case?!) Headphones are going to be your best option for monitoring/mixing at this point. SInce you won't be spending much on treatment, spend it on good headphones.

 

[keith.rogers]

Well, it's going to be tough to do an optimal treatment, as [MENTION=39487]mjbphotos[/MENTION] points out, but I can think of a few things I'd do, remembering that you still want to dampen reflections overall and get some kind of bass traps in place, if it's permitted, that is.

You have one corner between the window and closet that you can put a floor to ceiling bass trap in, and I'd do that, built at least 6" thick with rockwool. And, while that 1' space on either side of the wall unit is small, I'd build something for that, floor to ceiling and fit in there, too. Angled panels above the wall unit and the opposite wall (ceiling-wall join) and clouds immediately over the mixing seat, and a couple of large-ish panels on both walls on each side of your chair, as symmetric as possible. Heavy, blocking drapes for the window that can be opened/closed, depending on the room usage will also help.

Then, a rug for the half of the room behind the chair would probably be a help.

The space where you have the monitors is not good, at least from the pictures, so I'd think about removing the doors on the upper part of the wall unit, and moving loose items up there (diffusors ). Get something seriously heavy to put the monitors on to get the height better, and fill the space behind them with a cloth covered rockwool batt, trimmed to size.

Good luck getting the clouds and ceiling-wall angled panels approved...

 

[bouldersoundguy]

Well, first things first. It's hard to tell from the pics, but I think the speakers are too low. Raise them so the tweeters are at or slightly above ear height.

One problem with a small room is that some distance from the speakers is beneficial because it sets things up for normal cross bleed levels. But in a small room the reflections start to become a problem if you get very far at all from the speakers.

In lieu of proper treatment I would open those top cabinet doors to break up that surface. And I'd open every other drawer by different amounts. Leaving the room and closet doors slightly ajar might also help scatter reflections. Get some nice looking heavy drapery for the window.

 

[jimmys69]

I agree with all said previously. The wall unit desk thing is definitely an issue. Can maybe get away with boosting the monitors up as high as they can in the cabinet space with something and also a decoupling material like the Mopads.

But I think you may be able to get away with the 'superchunk' thing there since the wall unit gives structure. In this situation I would fill both sides and top of the beast with Roxul 80 or OC 705 and wrap with cloth to start.

The side reflections really should be addressed as well. Agree that a super heavy curtain (or build a removable panel to fill the window space when mixing) for the window on the right side, and a 2'x4'x2" panel on the left. Cover that with a pretty breathable cloth of wife's choice and call it art.

And yeah, I can see the ceiling clouds being hard to approve... May have to just attempt a thick rug on the floor.

Do you own the home?

 

[diakonos1984]

Thank you all for your great feedback! I can definitely use a lot of it.
I thought I would provide a little more background, and then ask some followup questions.

More Background:
A) I am a total noob at all of this.
B) I am an engineer (electrical, not acoustic or recording), so I am hopeful that I can understand it all eventually, but I definitely don't have all the dots connected in my head. That said, I do like to approach things as scientifically as reasonable.
C) I am also a tightwad, and don't like to just throw money at things without understanding them as well as possible.
D) I am moving very slowly at this (see the progress I have made in a year?! Yeah, me neither).
E) I accidentally made my wife out to look more controlling than she really is. It's more like we have a very small house without a lot of storage, but yet we have two kids and a lot of stuff. Every room in our house has to be multipurpose, and we have spent a lot of time strategizing together on how to best use the space. She won't have any objections to how acoustic treatments look (and I believe I can make them look decent).
F) Yes, I own the house.
G) As I have said before, my current goal is to build an attached garage with a purpose-built studio in it, so this current effort is somewhat temporary and a preliminary experiment so that I can get well up the learning curve before starting a major construction effort.
H) This room is to be tracking and mixing room.
I) I will be using a microphone for some tracks.
J) My current equipment lineup is a PreSonus StudioLive 16.0.2 connected to a custom rack-mount PC running Windows 10 with PreSonus Studio One 3 and Ableton Live 9 Lite. I am using Wharfedale Diamond 8.2 studio monitors, a Soundelux UI95 mic, and I have three sets of headphones: Sennheiser HD280 Pro, Sony MDR7506, and Audiotechnica ATH-D40fs.

Followup Questions (Technical):
Coming from a scientific approach, I understand what I did with REW, but I don't know exactly what to do with the results.
1) Am I correct that taking measurements in 10 locations in the room was unnecessary, and the listening position is the only one of real value?
2) Or do you need to measure in the corners to solve issues in the corners?
3) In the results from my listening position measurements, am I correct in saying I should attempt to address the 40-400Hz range? What about the dip above 4kHz?
4) I didn't do any sort of node calculations for the room. Is that of value at this point? Does that mainly help one determine ideal locations for speaker, listener, and mic? Whereas mine are rather locked in by my furniture? Or is there some other value in calculating room modes?
5) Is it feasible that I can run calculations with a proposed treatment design to predict its effectiveness, or is guess-and-check about all we can do? (See B and C above!)

Followup Questions (Practical):
[MENTION=196982]keith.rogers[/MENTION] and [MENTION=112380]jimmys69[/MENTION] suggested a lot of things that I had in my head, but was waiting for someone else to say.
+ Fill the 1' space on either side of the wall unit. I have read some discussions of the "superchunk" thing on here before.
6) Would it need to be triangular? Seems like a rectangular column 12" x 16" x 8' would be easiest to build.
+ The ceiling-wall corners. I was thinking of filling ALL of these. It just dawned on me that a rectangular column ABOVE the desk unit (16" x 18" x 8'4") would blend with the rectangular columns on the sides nicely and be easier to build and install than an angled panel.
7) Is there some reason I am missing that I should prefer the angled panel design above the desk?
+ I should be able to do angled panels on all the rest of the ceiling-wall corners.
8) Any guidance on dimensions to actually deal with the frequencies I need to address?
+ I seem to have read somewhere that you don't necessarily want to treat ALL of your corners. With the above I will have treated 6 of the 12 bi-corners, and 6 of the 8 tri-corners.
9) Is that sufficient, or should I still treat the remaining corner between the window and the closet and have a moveable treatment I can put behind the door when it is closed?
+ The ceiling cloud shouldn't be hard to get approved . It just may take some work to build! I want to take down the ceiling fan and build a cloud with integrated diffuse lighting (yes, so we can use the room for other purposes, like photography).
+ A couple years ago I acquired a large lot of used wedge foam acoustic panels (2" x 2' x 4') that some poeple had used to "soundproof" a shed for their son to learn electric guitar in (they covered every interior surface of the shed with the stuff). I am hoping to be able to use it for the side reflections, with a "pretty breathable cloth", as [MENTION=112380]jimmys69[/MENTION] said. I have a TON of the stuff. Can I also use it to:
10) Plug the window? Or do I need to have something more rigid in it? The sill is almost 7" deep, so I can build a pretty thick plug.
11) Line the back of the desk behind the monitors? Or is rockwool really going to be the best bet, as [MENTION=196982]keith.rogers[/MENTION] suggested?
+ The monitors... They are just a couple inches lower than my ear right now. I was hoping to raise them eventually with isolation pads. Sweetwater told me the Mopads were a waste of money and I should either buy something a lot more expensive or not at all...
12) What do you all think about monitor isolation?
+ Interesting ideas about opening doors and drawers, [MENTION=103008]bouldersoundguy[/MENTION]. I will try that out.
+ I am interested in the rug idea that several of you suggested.
13) I thought solid floors were prefered? But it just dawned on me--maybe solid floors are prefered for tracking, but not for mixing?
+ Gobos around the mic. [MENTION=39487]mjbphotos[/MENTION]
13) Is that better than those little foam wedge wrap-around microphone shields? Or do they fulfill different purposes?

I know this was long, but thank you for your time and input! Have a happy New Year!

 

[mjbphotos]

Filling the whole surround of the desk with rectangular rockwool panel would be a good idea.
The foam you got - nope. 2" foam absorbs no mids or lows at all. Try adding it after you have done rockwool panels, you probably won't notice any difference in sound at all.
The all-foam mic shields don't do much of anything. The multi-layer ones that use different materials, including a perforated metal layer,get good reviews from some people. My own opinion is that if you put a box (of anything) around a mic, its going to sound boxy!

 

[keith.rogers]

There were so many questions that my session timed out and my longish answer was lost! I'll try a short one...

Measurement at your mixing spot is probably worthwhile, because it can point out obvious problems. Measurement elsewhere might help you identify where best to tackle the problems, but overall treatment with adequate bass trapping is probably worth doing first. Coverage (sqft) * absorbtion coefficient / room surface will show you how you are doing relative to some of those formal specs for studios, control rooms, etc. You need to be somewhere in that range. After that, ears and listening to your recordings along with input from experienced ears here may offer more guidance than graphs. (Graphs alone are misleading, e.g., what looks good on paper can still have too much reverberant content to be useful for recording some things.)

Rockwool is mentioned most often because it is the most commonly available material that is designed for sound absorption. Unless you get something denser, like Roxul's RockBoard, going to regular insulating material or foam is a waste of money and effort IMO.

Angular installations in corners and joins present more surface area (in a space not usable anyway) and if away from the wall increase that by whatever can get behind the panel and be absorbed there. And, something is always reflected a bit, so angles are better than parallel surfaces. In your case it may not be practical - we all make compromises unless we're building out a garage ($$$$) for this purpose only.

My desktop speaker stands were built from leftover scraps from the panels I built, with the interior void filled with rocks and leftover mortar from another project. My monitors are angled on some closed cell foam I got from packing material. Very practical and better than anything I saw available at too much cost.

Start by covering the window with something heavy (blocking drapes) and see if you need to do more, unless you're certain too much sound will come in, or after using it you decide you're getting too many reflections from it. Moveable bogos can often be used to supplement specific use cases, especially in a room that serves multiple purposes, in addition to the slightly conflicting recording/mixing ones!

 

[diakonos1984]

All right, I think I have a rough plan together, and am going to implement Phase 1 this weekend, Lord willing! Only 4 questions this time...

Phase 1A: "Superchunk" Surround for Desk Unit.
While most people appear to build their "Superchunk" traps as triangular prisms, I am going to build mine as freestanding rectangular prisms to fill in all the space up to flush with the upper part of the desk unit. I am going to build each of the sides as (3) stacked sections, 12"W x 15.75"D floor to ceiling. Since my readings indicate it is okay to have an airgap behind bass traps, I am going to build it to sit just inside the baseboards, with a resulting gap of 0.75" on the wall side and back. I am going to build the top section as (3) side-by-side sections 15.75"D x 17"H and flush with the side sections on either end. I am going to use 3" thick Roxul Safe'n'Sound because that is what was available locally.
QUESTION 1: I am thinking to make my rectangular prisms actually (2) nested triangular prisms, as shown in the picture below. It will be the same amount of insulation, a little more lumber and definitely more fabric, but it will give me the following significant benefit: my recording rig is portable and triangular prisms would be more useful than rectangular prisms if I take my rig elsewhere for tracking. They will have to be scalene triangles, rather than right isosceles triangles. Can anyone tell me why this would NOT be a good idea?


Phase 1B: Insulation Panels for Wall-Ceiling Corners.
I am going to use locally available 2.5" x 2' x 4' Rockwool Comfortboard 110 in a wood frame, and hang it diagnally across the wall-ceiling corners. I am going to make (6) of these panels and use (2) each in the corners that are NOT on the wall the Desk Unit is on.

Phase 2: Treat the Walls.
I am going to build 4 or 5 traps to hang on the walls with a 2" or less airgap behind, probably using the Comfortboard above. I will probably alternate the direction of the paper backing (facing in or out). I will ensure that at least one on either side is at my point of first reflection. I may make another two for the room door and closet door. I will probably make all of these wall panels easily removable and able to stand freely in order to use as Gobos for tracking, or to take with me if I have to take my rig elsewhere for tracking. I will hang heavy drapes over the window.

Phase 3: Treat the Ceiling.
I am going to build at least 2, possibly 6 panels out of the Comfortboard for the ceiling, starting with the first reflection point above the listening position, and then the back of the room where I anticipate doing the majority of the acoustic tracking. Finally, if I can eliminate the ceiling fan I will put the last two in the middle of the room also.

Phase 4: Treat the Cabinet Space Behind the Monitors.
I will cut to size and line the rear of each of the two side desk compartments with the Comfortboard

Phase 5: Treat the Other Wall-Wall Corner on the Bottom Right of the Diagram
I am hoping NOT to have to do this, as it will eat into usable room space, but I may do a superchunk or a panel in this corner.

I have not yet done the math for the surface area coverage of these treatments, but will update when I do.

QUESTION 2: Does all that sound like a good approach?
QUESTION 3: Are my (used) sculptured wedge acoustic foam panels really of no use in any of this? It would be nice to be able to use things I already own, instead of spending money for new everything...
QUESTION 4: So the Comfortboard seems like it would be easier to build panels with, but has anyone here done it successfully with the less-regid Safe'n'Sound? The Safe'n'Sound is dramatically cheaper than the Comfortboard ($39/15ft3 vs $53/5ft3). It would be nice if I could use the Safe'n'Sound for Phase 1B and 3 also!

Thanks for all your input!

 

[diakonos1984]

My desktop speaker stands were built from leftover scraps from the panels I built, with the interior void filled with rocks and leftover mortar from another project. My monitors are angled on some closed cell foam I got from packing material. Very practical and better than anything I saw available at too much cost.

[MENTION=196982]keith.rogers[/MENTION], I am interested in hearing more/seeing pictures of your speaker/monitor isolators.

 

[keith.rogers]

[MENTION=196982]keith.rogers[/MENTION], I am interested in hearing more/seeing pictures of your speaker/monitor isolators.

Ha. Don't want to oversell my ability here - just using up what was laying around. Plus my monitors are only 5" so don't require a really large mass to isolate sufficiently on my pretty solid desk.

This is one pic of my small room and monitors on the stands. All panels were done with Safe'n'Sound. I've got a few more to do that will be freestanding, but have some daunting decluttering and discarding to do in another room so I can rearrange some bookcases before I get to that so I have a place to keep them out of the way when not in use.

 

[keith.rogers]

...
QUESTION 1: I am thinking to make my rectangular prisms actually (2) nested triangular prisms, as shown in the picture below. It will be the same amount of insulation, a little more lumber and definitely more fabric, but it will give me the following significant benefit: my recording rig is portable and triangular prisms would be more useful than rectangular prisms if I take my rig elsewhere for tracking. They will have to be scalene triangles, rather than right isosceles triangles. Can anyone tell me why this would NOT be a good idea?
...

Once you have a trap that's 8' in height, you may wonder if moving it around is actually a good idea!

I actually built my corner traps with double layers of Safe'n'Sound and found out when I tried to stack 2 4' panels - didn't build them to 8' - that it was not possible to actually fit them into an 8' ceiling without a lot of scraping. So, I used the 4' pieces on the bottom, and made the top half about 1" shorter so I could assemble them in the room. I wrapped some egg-crate packing foam in cloth and wedged that in to the top, after fastening the top and bottoms together, to keep everything tight. It's not something you want toppling over!

The fabric and lumber make up a good part of the cost, so I wouldn't build them the way you plan unless you're sure you'll be using those in the way you describe. For not much more money you could just build the corner traps as single units and build some more moveable ones that would be easier to move around, and perhaps be usable in that space, as well. Depends on how much mobile work you'd plan to do, I suppose, or if you just want to plan ahead to when you'll be in a different space, and make something less custom fit for the room you're in now.

 

[diakonos1984]

So I am making good progress on my Phase 1A and 1B, but I have run into a little problem...
As I mentioned in this thread, I want my traps in the ceiling corners to be white, so as to blend into the ceiling, but I am having trouble finding white fabric that sufficiently opaque (my first sample fabric you could see the frame and the insulation through 2 layers...). Anybody come up with anything particularly well-suited?

 

[keith.rogers]

... I want my traps in the ceiling corners to be white, so as to blend into the ceiling, but I am having trouble finding white fabric that sufficiently opaque (my first sample fabric you could see the frame and the insulation through 2 layers...). Anybody come up with anything particularly well-suited?

My white covered ones are unbleached muslin, so off-white, but there's a bleached version around that probably will work. I discovered the same thing when I built the first pair, i.e., you can see the darker Safe'n'Sound (or whatever) through the muslin.

So, when I built the bass trap top boxes (in the pic), I put a single layer of muslin on the front before covering the front and sides. I used spray adhesive around the top edge, just using newspaper laying on the Roxul and a piece of cardboard to minimize overspray on the sides. Then put the fabric piece on, cut approximately to size, pulled it tight while the adhesive held it and then trimmed it off with a decent pair of scissors. Then I wrapped the box front and sides with a single layer. In direct light there's a tiny bit of difference between the frame and center, but I think it looks fine. And two layers of muslin is not going to stop anything.

 

[diakonos1984]

Thanks, Keith! I'll go look for muslin. I was looking at some upholstery fabric on Amazon too, but wondering if it was going to be overkill...

...I put a single layer of muslin on the front before covering the front and sides. ...Then I wrapped the box front and sides with a single layer.

I understand your two layers. Am I also correct in understanding that you didn't wrap the back at all?

 

[keith.rogers]

Thanks, Keith! I'll go look for muslin. I was looking at some upholstery fabric on Amazon too, but wondering if it was going to be overkill...

I understand your two layers. Am I also correct in understanding that you didn't wrap the back at all?

Upholstery, or drapery, fabric works too, and that's what some of the more colorful baffles are in my room, but it's a lot more expensive. I'd check Walmart if you're in the states for the best prices. It adds up fast. (I just picked up ends for the best price so have a pretty good mess from a design POV - luckily my wife stays out )

I covered the back with a black fabric that is the kind you'd find on the bottom of an upholstered chair. It's pretty cheap, too, but only comes in dark colors, and is actually pretty sheer, i.e., you can see through it. I had bought a bunch of it when I started the project but muslin would be fine for that too.

Edit: link to a thread in another forum showing some pix.

 

[diakonos1984]

Studio build update!

So I have completed several phases of my acoustic treatment project and have pictures and results to share, for comment and advice going forward.
I have completed:
Phase 1A: "Superchunk" Surround for Desk Unit.
Phase 1B: Insulation Panels for Wall-Ceiling Corners.
Phase 3: Treat the Ceiling.

I still lack:
Phase 2: Treat the Walls.
Phase 4: Treat the Cabinet Space Behind the Monitors.
Phase 6: Isolate the monitors

Here's a picture.


Here's before and after frequency response from REW (Red is before, blue is after, green is my monitor's characteristics).

Most notable improvements were in the 20-30Hz and 50-80H regions.
I still have issues in the range of 40Hz, and 200-300Hz is worse after than before, so I'm thinking those should be my focus now.

I spent some time with the really cool amroc room mode calculator, and it looks like the 40Hz mode corresponds to the depth of my room with the closet. And as I understand it, the 200-300Hz is getting into the broadband region.


I've read that RT60 isn't really relevant for small rooms like this, but boy there is a big difference in the before and after!

The room definitely sounds dramatically different. Quieter. It takes more effort to be loud.

Here's a waterfall graph. I don't know what to do with it, but it's pretty.


Any comments are welcome! I will post my specific questions for going forward in a seperate post.

 

[diakonos1984]

Here are more pictures of the room.



The math says I have the following treatment coverages on each surface:
Ceiling: 65%
Front Wall: 34%
Left Wall: 22%
Right Wall: 27%
Back Wall: 8%
Floor: 0%

 

[diakonos1984]

So my big question is primarily about Phase 2: Treat the Walls.

Question 1: Location
Clearly I need to treat the first reflections on the left and right side. The, just based solely on wall space, I was thinking (2) 2' x 4' panels on the left wall, (2) on the right wall (one on either side of the window), and (1) on the back wall. I will also get a heavy curtain for the window. I feel like the back wall needs more treatment, especially with the 40Hz node that seems to be related to the closed, but I'm not sure how to treat the closet space or closet door.
Thoughts?

Question 2: Material
If you hadn't already noticed, my OP about this room was in December. My original analysis of the untreated room was exactly a year ago. I am moving very slowly, and it hurts. Also, I changed jobs, and now work from home so this room's dual purpose is now my home office. This both slows me down, AND makes me more motivated to finish, since I live in this room 8+ hours a day.
I am thinking I need at least (5) 2' x 4' wall panels. I could make them myself, but I move so slowly at that, and I am ready to have this done. I HAD to do the desk surround myself, since it was so custom, but I am thinking commercial products for the wall treatment now. A rough calculation says it costs me in materials alone about 50% of what this ACOUSTIMAC DMD-BT4000 BASS TRAPS 48"X24"X4" costs. My time has become very precious to me, so I am about to just bite the bullet and order these.
What do you think? Is there a better value product out there?

Thanks for all your great input over the last year!

 

[keith.rogers]

Those prices are pretty good. Yes, you'd be at least 50% doing it yourself, and I'd say probably more like 30% of those current (sale?) prices, depending on the fabric, largely. But, not a bad option.

I'd get the 6" deep ones and stack a pair floor to ceiling in all the corners you can for good bass trapping. Then, minimally, a couple of maybe just 2" ones at early reflection points beside and above your mixing position, and then some more on the end of the room.