Advice on Tuning Room for Mixing

Hi, I recently moved my studio equipment to a warehouse space in Massachusetts, and am currently in the process of tuning my room so that I can mix projects I have recently recorded. The room I have is a bit larger than the rooms I've used in the past. The dimensions are as follow: Length = 19’ 7” Width = 16’ Height = 11’ 6” The room has a hardwood floor, and the ceiling is also wood. The shorter end walls both have drywall. However, the longer side walls are not the same; one wall is all drywall and the other is brick with 2 large warehouse-like windows. A picture of that wall before I moved in is included. I have set up my desk on one of the shorter side walls (not sure if this is the best choice). I have started to treat the room so that I can work on my mixes. However, while the mixes sound decent in the room, they sound a bit muddy and lack high end detail when I play them in my car. So far, here is what I've done: Ceiling: * Hung up 4 long (2'x8') panels with 2" roxul AFB acoustic insulation on the ceiling. These have about 3 inches from the ceiling. * Hung up 2 long (2'x8') panels with 2" roxul AFB where the shorter side walls and ceiling meet - placed diagonally so that the breaks the 90 degree angle above the desk and on the rear wall. Rear Wall: * Hung up two 2'x4' panels with 2" roxul AFB on the rear wall placed vertically, pretty much level with my desk. Corners: * Hung up panels in 4 the side corners (1'x4' with 2" roxul AFB). One of the panels was placed high up in one of the rear corners (practically touching the ceiling) since the entrance door was in the way. Side Walls: This one I am having trouble with. * The 2 large windows on one of the side walls were filled in with 4" of roxul rockboard 60 to lessen exterior noise from coming in to the room. * The other wall has two 2'x4' panels with 2" roxul AFB place horizontally high up on the wall (approx. 8 ft. up) since the door and other things are in the way. This wall is problematic because there is a pole in the middle of this wall about 2 feet from the wall - AND a vent-free gas space heater on the wall (between the wall and pole). Front Wall: * I currently have nothing placed on the wall behind the desk and speakers because I am unsure of what is a best practice for this wall. I've been reading mixed information online where some suggest absorption material and other diffusion. I have not yet added diffusion as I am unsure where that should be place. Is there anything that I am doing incorrectly? Should I add more absorption to the room? Any advice would be greatly appreciated. Best, Wil

Hi there Wil, and welcome! :)

I have set up my desk on one of the shorter side walls (not sure if this is the best choice).

Right! It is generally better to have your speakers pointing the long way down the room, rather than the short way across the room, in order to maximize the path length for sounds bouncing off the rear wall.

* The 2 large windows on one of the side walls were filled in with 4" of roxul rockboard 60 to lessen exterior noise from coming in to the room.

That won't do much at all, actually. It's a common misconception that insulation can stop sound: it cannot and does not. It can be part of an isolation wall, yes, and in that case it performs a vital function (damping internal cavity resonance inside the wall), but by itself it does practically nothing to isolate a room. Think of it this way: If you spill water in your kitchen, then a sponge is a great way of moping up that spilled water. But if you hold that same sponge across the end of the tap, it does nothing at all to prevent the water flowing through. Acoustic insulation is like the sponge: great for "mopping up" sound that splashed in places you didn't want it to go (in other words, great for acoustic treatment), but no use at all for stopping sound getting in or out (in other words, no use at all for acoustic isolation). Isolation and treatment are two very different (and actually diametrically opposite) aspects of acoustics, and they use very different materials. Isolation requires materials that are massive (very heavy), rigid (stiff), hard, and dense. Mineral wool is none of those.... Treatment often requires materials that are light, soft, fibrous, fluffy, and flexible. Mineral wool is all of those.

I have not yet added diffusion as I am unsure where that should be place. Is there anything that I am doing incorrectly? Should I add more absorption to the room? Any advice would be greatly appreciated.

OK, you probably need to take a few steps back, then move forward again. First, lets look at isolation: Do you need any? This is often also called "soundproofing", but that's a word we try to avoid using here, since it means different things to different people. So we use "isolation", which basically means "stopping sound from getting out of your room, or into your room". Do you need to do that? If so, how much? Some people forget that isolation isn't just about not annoying the neighbors, or keeping the cops from shutting you down for violating noise regulations: It is also about keeping sounds OUT of your room, that you don't want. Things like the sounds of wind, rain, thunder, aircraft flying over, street noise, radios, TV, vacuum cleaner, phone ringing, people talking, dogs barking, etc. So think carefully about what you need in terms of isolation. That's the first step. Some people don't need much, others need a huge amount. Each situation is different. Next, after you solve your isolation issues, take all the treatment out of your room, and set up your equipment and chair correctly, in the correct geometric layout. That basically means: your chair is on the room center line, at about 38% of the distance from the front wall to the back wall. Your speakers are spaced evenly to each side of the center line, about 28% of the room width away from the side walls, and either right up against the front wall, or at least 8 feet away from it. Never between 3 and 8 feet. So if your room is not long enough to get your speakers 8 feet from the wall AND ALSO get your chair at 38%, then put the speakers hard up against the wall, with just a couple of inches behind them, for airflow and acoustic treatment (see below...): Your speakers also must be set up on massively heavy stands, never on the desk, console, or other equipment. The stand must be just high enough that the acoustic axis of each speaker is 47-1/4" above the floor. NOTE! That says "acoustic axis", not "top of speaker box" or "bottom of speaker box" or "tweeter". The manufacturer of your speakers probably publishes that information, or will give it to you if you ask. So your stand is high enough to get the speakers in the right position, allowing for a 1" Sorbothane pad underneath the speaker. The speakers must now be "toed-in", or angled towards your chair at about 30°, such that the acoustic axes of the speakers just graze past your ears, and intersect at a point about 18" or so behind your head. Set the bass roll-of controls on the back of your speakers to -6 dB, and the mid and high controls (if there are any) to 0 dB. That gets yous basic geometry right. Now it is time to do a baseline acoustic test of the room, to see what is wrong with it. Download the REW acoustic analysis software (it is free, on the Home Theater Shack website), and run that. Follow the calibration procedure carefully (it's in the manual, which is very well written and easy to follow). Then post the resulting data file here on the forum, so we can take a look at it, and figure out what is wrong with your room, and how to fix it. Do one test with just the left speaker, another with just the right speaker, and a third test with both at once. Then put in the basic treatment that all small rooms need: large bass traps in all the vertical corners, and we recommend the "Superchunk" style of trap. Basically, that's just stacking up triangular pieces of semi-rigid OC-703 insulation in the corners, from floor to ceiling. That's the cheapest and also the most effective form of broadband bass trapping. Then cover the rest of your rear wall (between the traps) with thick insulation, such as more OC-703, about 6" thick. Now do your first reflection points: a panel of 4" 703 at each first reflection point is about right. That means one on each side wall, and also one on the ceiling. Finally, put one more panel of 703 behind each speaker, between it and the front wall, while making sure that there is still enough space for good cooling around the rear of the speaker. Now do a second test with REW, once you have all that in place, to see what has been fixed, and what still needs fixing. That's the normal way of starting out with room treatment. You might find that you need to fiddle and tweak the final locations of the speakers and your chair, to find the best position for all of them, and that includes changing the angles of the speakers if you have to. 38%, 28% and 30° are just guidelines, not laws! Good starting points, but not the final end points.

* I currently have nothing placed on the wall behind the desk and speakers because I am unsure of what is a best practice for this wall. I've been reading mixed information online where some suggest absorption material and other diffusion.

You almost never want diffusion on the front wall, unless you are specifically building a Newell style NER, and following all his techniques, methods and models. But you aren't doing that so far (and I wouldn't recommend that you do anyway! :) ), so just stick with absorption up front, between the speaker and the wall. The very best way of doing the front of the room is with an RFZ design, where the speakers are flush-mounted in "soffits", and everything is carefully angled to force all reflections around and past your head, to the back wall, where they get heavily absorbed. You probably could use some diffusion in your room, since it is borderline big enough to benefit form it, and to be able to actually do it, without suffering the artifacts caused by diffusers in small rooms. But I would leave the decision on hold until you get the basic treatment in, and see if you need them or not. And if you DO need, them, then to figure out what frequencies you need to tune them for, and where you need to place them. So that should get you on the right track! In fact, just doing the correct layout and the basic treatment should make a large difference compared to where you are right now, and you should start to hear the bass tightening up, as well as better clarity and definition in the highs, with good stereo imaging in the sweet spot.

Length = 19’ 7” Width = 16’ Height = 11’ 6”

That's a nice sized room, with very nice high ceilings, and a reasonably good ratio. No red flags there. Theoretically, you need about 700 square feet of absorption in that room to get it with spec, so you probably will need more than just what I described above, but at least the outline I've given you should get you a long way down the road. - Stuart -

Thank you so much for the advice and my apologies for the super delayed response. I made a few changes to the equipment in the room so that it has a symmetrical placement within the room. The imaging has already noticeably improved. For the bass traps, I have been reading online that adding a limp mass membrane like cling wrap to the front face of the corner trap would add to the effectiveness. Any thoughts on whether that is accurate? Also, for the rear wall we may dedicate up to 1ft of depth for the bass trap. Would setting up a wood panel membrane absorber type of bass trap (such as the one in the attached picture) on the rear wall work better than a panel bass trap that contains 6" of rigid fiberglass panel covered by cloth. I'll be doing some acoustic testing on the room soon and will post results soon to determine the next steps. Thanks so much. Wil

I made a few changes to the equipment in the room so that it has a symmetrical placement within the room. The imaging has already noticeably improved.

:thu: Glad it worked out for you! :)

I have been reading online that adding a limp mass membrane like cling wrap to the front face of the corner trap would add to the effectiveness. Any thoughts on whether that is accurate?

Cling wrap is nowhere near dense enough. Limp-mass traps need to have surface density measured in many kilograms per square meter, so the only suitable material is MLV (Mass Loaded Vinyl). It is possible to build limp-mass traps with MLV, but they are tricky to tune and need very large depths to tune low enough.

Would setting up a wood panel membrane absorber type of bass trap

Rigid membrane traps are also tuned devices, and once again tuning them is not as easy as it might seem!

Also, for the rear wall we may dedicate up to 1ft of depth for the bass trap.

If you could go a bit deeper than that, say about 18", then I'd suggest doing John Sayers style hangers across the entire rear wall, with one layer of OC-703 behind the hangers (against the wall) and another layer in front. - Stuart -

Attached are a few graphics that demonstrate the test results from the REQ Wizard program (which I hope I ran correctly). I will be installing bass traps within the next 2 weeks in hopes that the peaks and nulls can be tamed. Thanks again, Wil

Attached are a few graphics that demonstrate the test results from the REQ Wizard program (which I hope I ran correctly).

Hard to say if you ran it correctly or not, because you are posting images from the EQ module of REW, which is all about trying to use equalization to "fix" room problems! There's no reason for you to even be using that part of REW right now (and probably never!) You'll need to post the actual MDAT file someplace where we can download it, to take a look at the data. - Stuart -

Thanks. Hopefully I ran the tests correctly. The mdat file can be found here: https://drive.google.com/file/d/0ByYiyF ... sp=sharing Thanks, Wil

Unfortunately, that doesn't seem to be valid data. Firstly, it only goes up to 200 Hz, but you really should run the test across the full spectrum, from 20 Hz to 20,000 Hz. Next, it just doesn't look right at all. Not believable. Did you follow the calibration procedure for your soundcard, and also the calibration procedure for setting the sound level (using a sound level meter)? Please go over all that one more time, measure again, and post the new one. Also, don't forget to label each of the tests as you complete it, so you know which one is which. - Stuart -

I placed the tuning of this room on temp hold as I had focused my energy on adding a live room down the hallway. However, given that my live room isn't turning out to be as quiet as I had originally hoped, I've been considering creating a DIY stand alone recording booth that would be placed centered by the back wall of the control room with a goal of capturing clean recordings that are not affected by airplane noises entering the room through the ceiling. However, I have some questions before I even consider taking this project on. 1.) The booth would be a stand alone unit that sits on u-boat blocks, has a double wall construction, has a layer of drywall on each side and roxul insulation internally, and has exterior dimensions of 6ft width x 8ft length x 8 or 9ft height. I probably have a budget of about $2,000 for materials for this. Would adding this to the back of my room affect acoustics in a bad way given that now the "back wall" would be the booth's front wall and closer to the mix position? 2.) Would a stand alone DIY recording booth not attached to any existing walls require a building permit, especially since using drywall will make it a difficult unit to move or disassemble? If so, does a Whisper Room require a permit? 3.) Would building a booth that has a trapezoid shape help prevent a "boxy" sound inside the booth? Would the trapezoid shape help with acoustics in the control room (I am assuming that a rectangular shape would negatively affect the room acoustics)? Thanks, WIl

Also, for the rear wall we may dedicate up to 1ft of depth for the bass trap. Would setting up a wood panel membrane absorber type of bass trap (such as the one in the attached picture) on the rear wall work better than a panel bass trap that contains 6" of rigid fiberglass panel covered by cloth

If you have one foot of depth to play with for your rear wall, then I'd suggest doing hangers! A foot is good enough for that, and you can make it deeper in the corners. Angle your hangers so you can make then bigger (and more effective), and build a simple fabric screen in front, to finish it off visually. I already mentioned his in my previous response, but back then I suggested 18". However, you can still get good effect with 12" of hangers. (But 18" would be better!) About your booth:

1.) The booth would be a stand alone unit that sits on u-boat blocks,

That's not a good way of floating a room. You should probably read this, to understand the issues: viewtopic.php?f=2&t=8173

Would adding this to the back of my room affect acoustics in a bad way given that now the "back wall" would be the booth's front wall and closer to the mix position?

Yes it would have an effect. The rear surface of the control room should be as far away as possible, within reason, and at least far enough back that the earliest reflections only reach your ears at least 20ms after the direct sound from the speakers. For most rooms, that means that the rear wall should be at least ten feet behind your head. If you can't make it ten feet, then it still needs to be as far as possible. You should not have any reflective surface in that space, as it will mess up your perception of sound.

2.) Would a stand alone DIY recording booth not attached to any existing walls require a building permit, especially since using drywall will make it a difficult unit to move or disassemble? If so, does a Whisper Room require a permit?

No idea. You'd have to check your local building code to find out. It changes from place to place...

3.) Would building a booth that has a trapezoid shape help prevent a "boxy" sound inside the booth? Would the trapezoid shape help with acoustics in the control room (I am assuming that a rectangular shape would negatively affect the room acoustics)?

The "boxy" sound is more a function of room volume than room shape, and also depends on treatment. You can't do much to fix that, except make the room bigger. The smaller it is, the more treatment it needs to even make it usable, so the ideal is to make it large and treated only minimally. - Stuart -

Hi, Since the last post, I've been working on creating more panels that would add absorption to the room, and on creating a frame along the rear wall that would allow me to add 12" of hanger style trapping. As I work on this I have 2 questions: 1.) I recently bought a portable recording booth. It's a whisperroom approximately 5' width x 7' length x 7' height. I originally planned on setting this up centered the rear wall to maintain some symmetry in the room. However, that felt awkward in the space and decided to place it on the left corner of the rear wall. This new setup now makes the rear wall asymmetrical. Would it make sense for me to set up a 12" hanger style trap along the entire rear wall (wall to wall with about a 9' height), even though this whisperroom booth is now in the room? I guess if the whisperroom would really affect me in making the room useable for mixing, I could consider finding another room to put it in. 2.) I ran an analysis of the room using Fuzz Measure since I was having trouble with REQ. Attached is a screenshot of the analysis results. This analysis was conducted after setting up the whisperroom in the corner of the room. Is there anything that you can advise based on the analysis? Best, Wil Renderos

I just wanted to add a few more images of the room analysis results since I realize that the one I sent may not reveal much. I followed the instructions on the FuzzMeasure site to conduct the test. The mic was in omni at mix position, I believe, and the test tone was sent through both speakers. Please let me know if you have any questions. Thanks, Wil

and decided to place it on the left corner of the rear wall. This new setup now makes the rear wall asymmetrical.

It also takes up the space where you need to put a large bass trap. So that's not a good place to have it.

I guess if the whisperroom would really affect me in making the room useable for mixing, I could consider finding another room to put it in.

That's what I would suggest, yes. A little asymmetry at the rear isn't normally an issue, but a monstrous thing like that is.

I ran an analysis of the room using Fuzz Measure since I was having trouble with REQ. Attached is a screenshot of the analysis results.

Most people on the forum use REW. I'd suggest giving it another shot. Also, regardless of which program you use, a single screenshot is not much use. We'd need the actual data, so we can analyze it in detail. If you export the raw impulse response file, then that would be useful: that can be imported into REW for deeper analysis.

This analysis was conducted after setting up the whisperroom in the corner of the room. Is there anything that you can advise based on the analysis?

Nope, not much. There's just one single measurement there, but we'd need six to be able to say anything intelligent: we'd need one measurement taken using only the left speaker before the whisper room was installed, one using only the right speaker before the whisper room, and one using both speakers before the whisper room. Then another set of three after the whisper room was installed: one left speaker only, one right speaker only, and one with both speakers. In all six cases the mic must be in the exact same position within the room, accurate to within about 1/4", and everything else must be identical too, except for the whisper room. That must be the only thing that changes between the two sets of readings.

a few more images of the room analysis results since I realize that the one I sent may not reveal much.

That helps a bit, but very little. You have some modal stuff going on, or it might be SBIR. Hard to say. Or it might be something in the room resonating. Lots of possibilities, but not enough data to figure it out...

The mic was in omni at mix position, I believe, and the test tone was sent through both speakers. Please let me know if you have any questions.

"Believing" that the mic was set up correctly isn't very useful! And neither is a single measurement done with both speakers at once. I'd suggest that you re-do the tests, using REW, and do the two full sets, as I described above. One set of three without the whisper room in place, the other set of three with it installed, and making certain that the mic is in the exact same location and set up the same way ("omni"), with no other changes to anything. If you post teh MDAT file produce by REW, then I'll be happy to take a look at it, and see what it shows. You can save all six measurements in one file, but do be sure to name them! - Stuart -

Thanks so much for the advice. I tried using REW but it kept crashing with my mac, so I redid the tests using FuzzMeasure. Attached are the freq response export files for all 3 tests (each speaker individually and both combined). I did 3 shootouts for each test. Hopefully, you are able to open these to look at the data. If not, please let me know and I will find another way to get the data to you. These tests were done with the whisperroom in the left corner of the rear wall. I am unsure at this moment if I can move the booth out into another room, and would like to see if I can still make the room usable for mixing with it in the room. I can move the booth forward about 16" or more from the rear wall so that I can still create a hanger style bass trap that spans about 10' of the rear wall if that will make a difference. Thanks, Wil

I tried using REW but it kept crashing with my mac,

Did you download the latest version of REW? There were a bunch of fixes for Mac issues a while back.

Attached are the freq response export files

Right, but those are ONLY frequency response data sets, as the name says. What we need is the IMPULSE response data set, which gives the complete picture. Frequency response is just a very small part of room acoustics. Not even the most important: It only tells you about the SPL level of each frequency in the room, which is only mildly useful. The really useful data comes from the impulse response. - Stuart -

Thanks. I downloaded REW and ran some tests using the software. The mdat file is too large to attach so here is the link to download the file via WeTransfer (https://www.wetransfer.com/downloads/0e ... 942/0c7452) I followed the instructions on a YouTube video, but please let me know if the tests seem inaccurate. Thanks, Wil

Thanks. I downloaded REW and ran some tests using the software. The mdat file is too large to attach so here is the link to download the file via WeTransfer (https://www.wetransfer.com/downloads/15 ... 143/e03468) I followed the instructions on a YouTube video, but please let me know if the tests seem inaccurate. Thanks, Wil