Upgrade Acoustics in Small Studio

Hello, I am a professional musician from Hillsdale, MI with my own studio that I use for my own recordings mostly. The studio is in my house and is kind of a multi-use space. (Practicing, teaching guitar, recording, guitar repair, small photo/video setup, and sometimes a guest room). I have a project coming up soon in about two months and would like to improve the room as a listening/ mastering environment with a focus on the acoustics. I'm not concerned with Soundproofing. I don't plan to make this perfect as I also am planning to build a new studio in the near future. We will either be building a garage this summer or next summer and I have the opportunity to build a 2nd story on it that will give me a 24' x 24' or a 24' x 36' space. I will be posting my plans soon for that. So with my current studio I don't want to invest in any major construction but am thinking more along the lines of adding more bass traps, changing the layout, etc. Room Description -The room is 12' x 12' x 8' with one indentation (see image below) -All walls are double layer drywall with Green Glue between studs and Drywall and between layers of drywall. -All walls insulated with cheap fiberglass insulation (don't remember what kind). Except exterior wall with windows insulated with closed cell foam. -Ceiling has double layer drywall, Green Glue, and fiberglass insulation -Floor is 2 layers of OSB with Green Glue between and Bamboo flooring on top. 5X7 area rug -windows have accordion style blinds with insulating properties (Sorry no specifics) -doors are both foam filled doors with weatherstripping around edges and door sweep Current Acoustic Treatment -2' x 2' x 4” OC703 with burlap behind each monitor -2' x 4' x 4” OC703 with burlap on ceiling above chair -2' x 2' x4” OC703 with burlap on side walls (one one stand and one hanging on side wall. -See photos for other three 2' x 4' x 4” OC703 with burlap in corners of room -Four 2' x 2' skyline diffusors (pine) on rear wall -monitors placed on Auralex monitor pads. Current Room Measurements Reference of 75dB SPL Right Speaker = Green, Left = Red My Plan Like I said, I will be building a new studio relatively soon so I don't want to invest in new construction on this room. I just thought I could improve it for this upcoming project. My plan is to basically add more of the 4” bass traps. Right now I'm thinking of removing the Diffusors and putting three 2' x 4' traps on the back wall. I also thought I could add 1 – 3 more traps on the ceiling. A final idea for places to put them is on the backs of the doors. My budget is to stay under $500. I'm comfortable with building things myself to save on cost. Questions Is there a possible layout change such us moving the computer to the corner that might improve the symmetry enough to have a positive affect? The reason I'm focusing on adding bass traps is because I know I can easily reuse the OC703 in the new studio I build in the next year or so. Are there other options that I should consider for room treatment or anything I should do to get more out of my bass traps? I realize there are a lot of problems with this room. Any other suggestions for getting the most out of this with what I have to work with would be great. Thanks for your time reading this and for the overwhelming amount of information in this forum. David

Hi David, and welcome to the forum! :) Firstly, about your new studio:

We will either be building a garage this summer or next summer and I have the opportunity to build a 2nd story on it that will give me a 24' x 24' or a 24' x 36' space

Go for the garage, definitely! There's a reason why you seldom see studios on upper floors: It is damn hard to isolate them, and expensive! So unless you have very deep pockets, save your self a lot of trouble (and money) and build on the ground. Also, square rooms are lousy acoustically. Very lousy. I assume you'll be dividing up that 24 x 24 into a couple of smaller rooms, such as CR, LR and maybe a small iso booth, but just in case you were thinking of doing one big room, leaving it as 24 x 24 would be a problem.

I'm not concerned with Soundproofing.

Really? So in Michigan you never get rain, wind, thunder, airplanes flying overhead, trucks, cars, or trains passing by? No police, ambulance or fire sirens? You don't have other people walking around the building, opening and closing doors, flushing toilets, talking, listening to radio / TV? No phones ringing? No vacuum cleaners? No dogs barking in the yard? No neighbors mowing the lawn? ... etc... Unless you manage to schedule all of those (and about a million others) so that they don't interfere with your recording, you might want to re-think the "no soundproofing needed" position....

-The room is 12' x 12' x 8'

:shock: Ooops. There's part of your problem. It is square, but not only that, there's a mathematical relationship between both the length and width as compared to the height. There are serious modal consequences to such rooms. In your case, you have major modes at 47 Hz, 85 Hz, 94 Hz, 105 Hz, 117, 126 ... etc. All of your modes line up, all the way up the spectrum. And looking at your REW waterfalls, you can clearly see some of those, very obviously.

Except exterior wall with windows insulated with closed cell foam.

That is great thermally, but useless acoustically. That wall is probably not isolating very well at all, especially in low frequencies.

doors are both foam filled doors

Once again, not much use for isolation. Solid core is the answer.

-Four 2' x 2' skyline diffusors (pine) on rear wall

They are not doing anything useful for you in such a small room, and in fact could be part of the problem. They are also taking up the exact space where you need lots of deep absorption: the rear wall.

Is there a possible layout change such us moving the computer to the corner that might improve the symmetry enough to have a positive affect?

I would rotate your layout 90° or 180°, so that you are facing a flat wall with no "bumps" near your head. Symmetry is critical in a control room, and you don't have it right now. you can see that on your REW graphs as well: the response in the mids and highs is quite different, with major peaks and dips at different points. In other words, face either the "laundry room" wall at the bottom of your diagram, or the 'two 35" windows' on the left. That will improve your symmetry greatly. I would also suggest getting your speaker off the desk and on to massive, heavy stands just behind the desk. Speakers on desks is never a good idea, for several reasons, mostly related to vibrations and early reflections. Then set up your listening geometry correctly, following the usual guidelines.

-monitors placed on Auralex monitor pads.

Keep those, but put them on top of the new massive speaker stands, to help a bit in decoupling. That shelf right above your speakers is also not doing you an favours....

Reference of 75dB SPL

You should really use 85 dB for testing. That's the "standard" calibration level (if there is such a thing). At 75 dB you might not be triggering all the modes, and in any case it isn't loud enough to allow for good decay detection in REW, on the impulse response.

Right Speaker = Green, Left = Red

... and they are both showing a whopping mode at about 140 Hz! Not surprisingly, that's the frequency where all three dimensions of your room coincide: at 141.3 Hz, you have your 0,0,2 axial mode, and your 0,3,0 axial mode, and your 3,0,0 axial mode, all lined up perfectly. The 47, 85 and 96 Hz modes also seem to be well represented, although it's hard to be sure which is which, and to see what else is going on. Could you post the actual mdat file from REW, so I can download it and take a closer look?

My plan is to basically add more of the 4” bass traps.

Bass traps will help a bit, but the room is fundamentally flawed. Bass traps cannot remove the modes: they can only help to tame them a bit. I would not expect to see a major difference in the very low end modes, but you might get lucky in knocking some dB and ms off that big one at 141 Hz.

Right now I'm thinking of removing the Diffusors and putting three 2' x 4' traps on the back wall.

Yes! Definitely get rid of the skylines. They are part of the problem, not part of the solution. But I would take it much further than you are planning: Do the entire center section of that rear wall with 6" of 703, spaced about 6" away from the wall. In other words, two 4' x 8' panels of 4" 703 side by side, and another pair of 4' x 8' panels of 2" 703 behind them. You could help things even more by leaning those panels forwards, so they are closer to the wall at the bottom and further away up near the ceiling. Then build two "superchunk" bass traps for the two vertical corners. Cover the front faces with 6 mil plastic. You are going to need major bass trapping in there, but you also don't want to kill the highs.

I also thought I could add 1 – 3 more traps on the ceiling

Yes, and angle those two, including the one you already have up there. It is too small, but every bit helps. Angle them lower at the front of the room, and higher at the back. And if you can, then make the new ones hard-backed, to help deal with the vertical modes.

A final idea for places to put them is on the backs of the doors.

That too. And also some of the horizontal corners (wall/ceiling). All room modes terminate in corners, so corners is where you get the most "bang for your buck".

My budget is to stay under $500.

Spend it all on 703, and even forget cloth and framing right now. You can make them pretty later, as finds permit, but you need every last sabin of absorption you can get right now, so go buy a truck load of 703.

Are there other options that I should consider for room treatment or anything I should do to get more out of my bass traps?

Corners. Put as much as you can in corners. Make them big, floor to ceiling, and as wide as you can afford.

Any other suggestions for getting the most out of this with what I have to work with would be great.

Without moving the walls, and on such a tight budget, there isn't much more you can do. Just throw all the absorption you can at it, and cover the corner bass traps with plastic to keep the room a bit live. The other thing you could do is to optimize the speaker/head geometry, once you get your desk turned around. That might help some. But please do post the actual REW data file, for further analysis. - Stuart -

Stuart, Thanks so much for the detailed response. It looks like the garage project is getting pushed back another year so I'm willing to invest a little more in the space I have right now. As far as the soundproofing. I am concerned with it. I just meant I don't think it's worth it to invest in this area right now. The acoustic balance seems much more important. Here's the updated plan. https://dl.dropbox.com/u/63126223/Updated%20Studio%20plans%201.30.13.skp Layout changes -I have moved the desk (and will have to use a smaller desk to make this work) to the opposite wall. -Bookshelf is moved to opposite wall Absorption (all OC 703 wrapped in 6mil plastic) -I have a 4' x 8' x4” bass trap behind the studio desk. I have tilted the upper half of this out from the wall for up to 8” off space behind the top of the trap. It's unclear to me if the sides of the trap should be enclosed. If so, with what? -On the same wall as the desk I have a corner super chunk 24” wide and 8' tall. The other corner on this wall will have a moveable 2' x 8' x 4” trap -The backwall has a 6' x 6' x 6” trap with 6 – 8” of space behind it. Note the upper 2 feet will angle back towards wall due to lighting hanging from ceiling. (Question: Is the air space better or would it be better to fill completely with OC703?) -This wall also has a moveable corner trap by the closet door 2' x 8' x 4”. -The ceiling has three 2' x 4' x 4” traps tilted with increasing angles as they get further away from the desk. Also unsure if the sides and backs of these need to be enclosed or if they can just be suspended with wire. Other changes -I plan to swap the doors out for solid wood doors. -Monitors will be on stands. I'm thinking of doing PVC filled with sand with Wood plates on each end. -I'm considering moving the CPU into the closet. Also here's the dat files from previous measurements. https://dl.dropbox.com/u/63126223/Left%20mod.mdat https://dl.dropbox.com/u/63126223/Right%20room%20mod.mdat When I did the measurement I tried getting the SPL reference higher than 75dB but the peaks of some of the frequencies were apparently clipping in REW around 94db or so. 75dB was the highest I could go without clipping. Thanks again for all the information.

I just meant I don't think it's worth it to invest in this area right now.

OK, as long as you are aware that improving isolation is usually very hard to do after the treatment is in place, and that it can even change the treatment needs.

Layout changes -I have moved the desk (and will have to use a smaller desk to make this work) to the opposite wall. -Bookshelf is moved to opposite wall

That looks much better! :)

-I have a 4' x 8' x4” bass trap behind the studio desk. I have tilted the upper half of this out from the wall for up to 8” off space behind the top of the trap. It's unclear to me if the sides of the trap should be enclosed.

Excellent. No need to enclose the sides. In fact, that extra exposed area of insulation actually helps, by increasing the surface area that is exposed to the room. You can cover it in cloth, of course, since it isn't very pretty!

-The backwall has a 6' x 6' x 6” trap with 6 – 8” of space behind it. Note the upper 2 feet will angle back towards wall due to lighting hanging from ceiling. (Question: Is the air space better or would it be better to fill completely with OC703?)

That's fine. The air space is also OK, but you can put more 703 in there if you want! It won't do any harm, that's for sure.

-The ceiling has three 2' x 4' x 4” traps tilted with increasing angles as they get further away from the desk.

Great, but they are tilted the wrong way! The should be tilted lower at the front, higher at the back. You could probably also put the front one lower down, the middle one a bit lower and leave the rear one at the same height it is at present.

Also here's the dat files from previous measurements.

Those are from BEFORE you made these changes, right?

When I did the measurement I tried getting the SPL reference higher than 75dB but the peaks of some of the frequencies were apparently clipping in REW around 94db or so. 75dB was the highest I could go without clipping.

Did you calibrate REW before you did that? Clipping is a function of your mic, interface and sound card, not REW itself. If REW is showing clipping at only 75 dB, then it is likely that either you did not calibrate REW correctly, or there is an issue somewhere in your signal chain. 75 dB is only the level of loud speech, and that should not be causing clipping. Also, for some reason the analysis only ran up to 10 kHz, so I can't tell you anything about what is happening in the high end, but there clearly are issues in the low end, as well as several problems with early reflections. There seem to be room mode issues at around 49 Hz, 89 Hz, 129 Hz, and 160 Hz., and there are reflection issues which I suspect are coming off the desk. It will be interesting to see how that changes after you have done all the modifications you mentioned, and measured the room again. Only this time, please make sure that REW measures all the way up to 20 kHz! - Stuart -

Thanks for all the great info, Stuart! So I spent the weekend upgrading the room to the previous plan. I was a little nervous about doing this but I used Roxul Safe N' Sound instead of OC 703. I looked at the coefficient chart and it appeared I'd get better results at my 125Hz problem and the rest seemed not too far off from OC 703. I also read the OC703 is the most cost effect at about 4” thick while the Roxul Safe N' Sound is more cost effective for thicker panels. I don't know if this is true but I felt confident enough from the charts to go with it and save some money. Feel free to attack me if this was a bad idea. For the large rear trap I ended up with 9” thick Roxul with 3” space behind it instead of 6” thick with 6” space . The front wall is 6” thick instead of 4”. I also made this one another 16" wider. One thing I have not done yet is gotten the speakers off the desk. I've made some monitor stands but the paint needs to dry. I have also had to get a new desk that I need to modify so that should all come into place in the next week. I'm not at all used to looking at the measurements to know what is good but I definitely see an improvement with more consistency across the frequency range. One thing to note about the new measurements is that I used 80db SPL as my reference instead of 75db SPL in the first measurements. And now I'm just reading one of your previous posts that 85db is the standard. Auggghhh! There still seems to be a big problem around 125Hz. Any thoughts on how I could best control this? Would it mostly be the corners causing this? Current Measurements with 80dbSPL reference: https://dl.dropbox.com/u/63126223/Left% ... 0full.mdat https://dl.dropbox.com/u/63126223/Right ... 0full.mdat I'll post the updated measurements and photos when I get the desk and monitor situation complete. Thanks again! David

I looked at the coefficient chart and it appeared I'd get better results at my 125Hz problem

Looking at the REW data, I don't really see a 125 Hz problem. What I do see is this electrical hum problem at 120 Hz... That's not a mode: it is just your mic or cables picking up mains hum.

Current Measurements with 80dbSPL reference:

Looking pretty good, actually. I wanted to compare that against your original readings, but since you didn't follow the forum rules, and just linked to the photos instead of actually posting theme here, I can't do that: they are gone. So this thread isn't much use anymore, to people who want to learn from what you did.

One thing I have not done yet is gotten the speakers off the desk

There are some reflections visible in your IR data which are likely from your desk. It will be interesting to see how those change once you get the speakers onto those stands.

I'm not at all used to looking at the measurements to know what is good but I definitely see an improvement with more consistency across the frequency range.

Yup! You still need some more treatment in that room, but is is looking fairly decent. The highs especially need more treatment: strangely enough, you don't seem to have enough absorption in the high end. Or maybe there's a problem with your speaker settings? How are the controls on the back of your speakers set?

One thing to note about the new measurements is that I used 80db SPL as my reference instead of 75db SPL in the first measurements. And now I'm just reading one of your previous posts that 85db is the standard.

That's fine. 85 dB is for both speakers. One method is to set each individual speaker at 80, so both together will be at 83. Your room seems fairly quiet, and your IR is clean, so you are fine.

There still seems to be a big problem around 125Hz. Any thoughts on how I could best control this? Would it mostly be the corners causing this?

The thin "tail" you see on that graph above is not a room issue, and is mains hum. That is probably messing the readings a bit. The general "hump" in the lows looks like it might be a sub set up incorrectly, or just the normal consequences of speakers in rooms, close to walls, or perhaps the speaker setup. What speakers do you have, where are they located in the room, and what are the setting on the rear panel? Is there a sub, and if so, how is the crossover set? - Stuart -