Help! Help! My mixes suck!

INTRODUCTION Greetings! I live in Bozeman, Montana, USA. I recently built a room to use as a combination recording space/control-mixing space. Construction is finished and the room is in use. I record mostly acoustic instruments and vocals - no drum kit, no overly-loud electric guitars, etc. Sound leaking in and out of the room is not an major issue to me right now: I am currently only concerned with improving the acoustics of the room. I barely finish construction of the room before I had to immerse myself in a recording project with a tight deadline. I hastily threw up a hodge-podge of sound deadening materials and finished the CD, but the results were horrible - I'm hoping I can at least partially blame the room acoustics for the poor sounding CD. ROOM DETAILS/FRAMING DETAILS: The room sits in the corner on the second (top) floor of the building. The floor consists of 11" engineered I-joists, covered with 5/8" OSB (chipboard), glued & screwed. This is covered wall-to-wall with a carpet pad and then Berber carpet on top. There is 6" of craft-faced fiberglass insulation between the floor joists, and the underside of the joists has 5/8" sheetrock attached, which is the ceiling of the room below. The interior walls and ceiling of the room are all sheetrock (gypsum board) except for the doors and windows. Here are overhead and elevation sketches of the room, pretty much to scale: Front and Right walls are exterior walls and are stick framed using 2X6 studs on 16" centers, insulated with 6" craft-faced fiberglass, and the exterior of the building is 5/8" OSB (chipboard) covered with an exterior siding of Hardy cement board panels. On the other side of the rear wall is a seldom used guest room. Construction of this wall uses 2X6 sill plates with alternating 2X4s on 16" centers for each side of the wall, so the sheetrock on the two sides of the wall do not share studs. This wall has 6" fiberglass insulation between the studs. The left wall separates the room from my wife's office. It is actually two separate walls; a 2X6 wall using the same alternating stud construction techniques as the rear wall (described above), with another 2X4 wall inside of that, with a 2" gap between them. The 2X6 wall (with the alternating studs) has 5/8" sheetrock on both sides, while the 2X4 wall only has sheetrock on the interior side (which is the left interior wall of the studio). Both of these walls have fiberglass insulation between the studs. The ceiling of the studio is simply 5/8" sheetrock screwed to the bottom of the roof trusses. There is 11" of craft-faced fiberglass on top of that, between the trusses. Above that is just open attic space up to the roof itself. Throughout the whole room the sheetrock is basically screwed directly to the studs, except that there is a vapor barrier of 6 mil plastic between. All of the sheetrock on the interior of the studio has standard taping/mudding, and is textured with an orange-peel pattern, and painted with semi-flat wall paint. The sheetrock on the two exterior walls is actually Quietrock Quiet Rock I believe the acoustical properties of this product are not substantially different from regular sheetrock, except that it reduces the sound transmission through the walls. In other words, I'm hoping we can consider it regular sheetrock for our purposes here. The only door(s) to the room is on the left wall, as indicated in the overhead sketch. Both doors are good-quality insulated exterior doors which seal fairly air-tight when closed. Both windows are identical: 3' wide and 2' high. Each one is actually two exterior windows mounted back to back with about a 4" gap between them. The room (sadly) is roughly square, 13' 9" wide by 14' 6" long. The ceiling slopes up from 72" at the front wall to peak 9' 5" high located 10" from the back wall (ie the peak runs parallel to the back wall). The ceiling then actually slopes back down a few inches, making the back wall 9' 2" high. Here is a crummy mock up of the room, as viewed from the rear wall looking forward: CURRENT SOUND TREATMENT As mentioned above, there is carpet pad and berber carpet on the entire floor. I have about 150 square feet of 12"X12" acoustic foam squares. 100 of these are 2" foam, and 50 are 3", and they are in varying patterns of wedges, pyramids, etc. I placed many of them, including all of the 3" pieces, in the corners. The rest of the 2" foam squares are scattered around the walls of the room, with a large patch of it on the right wall. Each square is held in place with a push pin, so they can be easily moved. There is a large throw-rug on the floor. I have two large, ugly upholstered chairs, one in each rear corner. To help further deaden the rear wall, I've done the following: on the left side of the rear wall I have a large 42" tall 54" wide framed print hanging out about 4" from the wall, with some home-made wedges of heavy 4" foam glued to acoustic ceiling tile mounted behind it. On the right side of the wall a large heavy 4'X7' wall hanging made from blue-jean scraps, with a similar foam wedge structure underneath that (see pic below). There are (mostly empty) book cases on the left and right walls. The desk is cheap-o pressed wood with fake wood veneer. My computer sits in my wife's office next door, with the cables running down through a chase in the floor into the room below and back up into the studio. I use near field monitors, with the centers of the monitors spaced 4' apart, and each speaker about arm's length away from my head. The tweeters are about ear height while seated in the chair. My head is located about 66" from the front wall. MY ASSESSMENT When first constructed, a hand clap produced a horrendous flutter echo, as did whistling, etc. All of the above-mentioned, hasty, ad hoc treatment has greatly reduced the flutter echo but it is still there. The frequency response graphs for 15 - 250 Hz are posted below. I'm also posting graphs of 250-1K, as there's some wacky stuff going on there too (like the 25dB dip at 800 Hz - WTF???) The room sounds quite dead and unnatural. Different bass tones are noticeably louder or softer in different areas of the room. My mixes suck. My mixes will probably still suck after fixing the room, and then I'll need a new excuse! I feel the room sounds too dead. I know it need better bass trapping. I think the square geometry and small size of the room are working against me. I realize I will need to make some compromises between what is best from a recording-space standpoint and from a mixing-space standpoint. MY BUDGET/SKILL LEVEL After getting a quote on ordering some 705 (yikes!), I've already had to adjust my budget upwards. I'm hoping that with the foam I already have that I can treat the majority of the problems with roughly $600 in materials. I could possibly be convinced to adjust that up a little. My skill level with carpentry etc is pretty fair. I am more interested in how the final product sounds rather than how it looks. Here is my so-called "plan", followed by my questions: QUESTIONS Question 1: I'm pretty confident the corner bass traps in my plan drawing are a good idea. Is 4" sufficient, or should I go 6"? How about more? Perhaps another one in the center of the rear wall where it meets the ceiling? Question 2: What about the other first reflection points - on the front wall behind the monitors and on the side walls? Would 2'X2'X2" of 703 be sufficient? Or 4" of 705? Something else? Question 3: I feel the left and right walls are probably the main source of my flutter echoes (right?) Seems to me like parallel walls are the disease, absorption is a band-aid, and deflection/diffusion a possible cure. I've read that deflection/diffusion is less effective in small rooms, but perhaps still worthwhile? How about less foam in these areas and adding some sheets of plywood to the walls to form wings (see drawing)? Or perhaps some plywood bent into a bow? Question 4: Same as above for the rear wall: how about adding some deflection/diffusion on the rear wall, maybe even instead of some of the current absorption? If yes, then any design recommendations for DIY diffusion/deflection? Plywood sheets again? Question 5: I've heard carpet is bad: as it only blocks certain frequencies, makes the room sound too dead, etc. How about a couple sheets of plywood on the floor? Question 6: The ceiling is currently bare. I think its slope helps, but I'm guessing I should put some absorption up there, right? Where, and how much? Given the slope of the ceiling, would putting alternating patches of my foam squares up there be sufficient, or do I need a cloud of 703? Is there a particular spot on the ceiling I should focus on? Of course, these are just preliminary plans (and guesses), and I eagerly await your expert advice. If I've left out anything, please let me know. Thanks in advance! -Chuck

Ooops - I accidentally posted my elevation sketch again instead of my mock-up. The mock-up was of questionable value anyway, but I can post it, and/or pics of the studio if requested. Thanks Chuck

Your room is almost square with many parallel walls, there's your horrendous sound. The "My cunning plan" layout is a real good start for an otherwise poorly dimensioned control room.

Hi Chuck, and welcome! A couple of quick comments:

The left wall separates the room from my wife's office. It is actually two separate walls; a 2X6 wall using the same alternating stud construction techniques as the rear wall (described above), with another 2X4 wall inside of that, with a 2" gap between them. The 2X6 wall (with the alternating studs) has 5/8" sheetrock on both sides, while the 2X4 wall only has sheetrock on the interior side (which is the left interior wall of the studio). Both of these walls have fiberglass insulation between the studs.

If I understand that correctly, then that is a three-leaf wall, which is not good. It means that you will get poor isolation in the low frequencies (kick drums, bass, etc.). But you did say that isolation is not a concern, so that's not really important for solving your acoustics issue! However, it is something that you should be aware of if you ever do decide to work on your isolation problems! You'd need to take off one of the layers of sheetrock, preferably the one INSIDE the wall, on the staggered studs. Just taking that off will improve your isolation by about 6 dB (maybe more) even if you do nothing else at all. Your walls must have two leaves, and only two. Not one, three, four or anything else. Anyway, on to the REAL problem:

I believe the acoustical properties of this product are not substantially different from regular sheetrock, except that it reduces the sound transmission through the walls. In other words, I'm hoping we can consider it regular sheetrock for our purposes here.

Yep!

The only door(s) to the room is on the left wall, as indicated in the overhead sketch. Both doors are good-quality insulated exterior doors which seal fairly air-tight when closed.

Solid core?

Both windows are identical: 3' wide and 2' high. Each one is actually two exterior windows mounted back to back with about a 4" gap between them.

How thick is the glass, and what type of glass? Is it angled at all, or are the panes parallel? If it is thin glass, you might have a ringing or resonance issue...

The room (sadly) is roughly square, 13' 9" wide by 14' 6" long.

Like xSpace said, this is your main problem. It's not quite square, and I haven't run the numbers, but that looks close enough to me that you are going to have some pretty bad mode issues. Also, at some point along it, the sloping ceiling is exactly twice the width dimension, and at another point is is exactly twice the length dimension, so you have additional mode issues right there too.

there is carpet pad and berber carpet on the entire floor.

Probably not a good idea. Most people here seem to recommend keeping your floor live, with concrete, wood, laminate, etc. You can always put throw-rugs or similar if you need to deaden a bit, but it's hard to "liven" a carpet floor. Ethan Winer argues that your brain is used to hearing reflections from floors your whole life, so it's better to have a live floor and dead roof. Any chance of replacing that carpet with laminate flooring?

I feel the room sounds too dead. I know it need better bass trapping. I think the square geometry and small size of the room are working against me.

Bingo! That's it, basically. First question: Any chance you can move a wall, or build a new wall, to get rid of that squareness? If so, then look for a room ratio that makes sense, and build for that. Since removing the inner sheetrock from the left wall would be a good idea anyway, how about taking that wall apart, removing the sheetrock, and rebuilding it a few inches inwards, at a point where you get a good ratio? Based on your budget, I guess this is out of the question, but I had to ask! But bass trapping, and lots of it, is probably where you need to start.

Question 1: I'm pretty confident the corner bass traps in my plan drawing are a good idea. Is 4" sufficient, or should I go 6"? How about more? Perhaps another one in the center of the rear wall where it meets the ceiling?

As Ethan always says: it is impossible to have too much bass trapping in a small room. In your case, with a square room, maybe Superchunks in all for vertical corners, floor to ceiling, would be a good place to start. Think BIG!

Question 3: I feel the left and right walls are probably the main source of my flutter echoes (right?) Seems to me like parallel walls are the disease, absorption is a band-aid, and deflection/diffusion a possible cure. I've read that deflection/diffusion is less effective in small rooms, but perhaps still worthwhile? How about less foam in these areas and adding some sheets of plywood to the walls to form wings (see drawing)? Or perhaps some plywood bent into a bow?

Not too sure about that! "Seems to me like parallel walls are the disease, absorption is a band-aid,". Absorption seems to tbe the cure I always see touted for flutter echo. "diffusion a possible cure". Diffusion is a cure, but for a different problem, AFAIK! Andre once explained to me why diffusion is a bad idea in small rooms anyway, and the general consensus here is that small rooms need absorption more than diffusion, (except on the floor). Maybe Andre can offer you advice in that area.

Question 5: I've heard carpet is bad: as it only blocks certain frequencies, makes the room sound too dead, etc.

Yep, carpet is bad. It is selective, and will give your room a dull "cavey" sound.

How about a couple sheets of plywood on the floor?

Sounds like a start. But just one or two sheets, and behind your mix position? I on't think that's enough. I think I'd go for the entire floor! And laminate flooring would be better than plywood. Plus just laying plywood on top of your carpet might not be a good idea, acoustically, as it will leave an air gap in between, and that might do strange things. I think I'd be inclined to remove the carpet entirely. Once again, Andre would be the one to comment on that issue.

Question 6: The ceiling is currently bare. I think its slope helps, but I'm guessing I should put some absorption up there, right? Where, and how much? Given the slope of the ceiling, would putting alternating patches of my foam squares up there be sufficient, or do I need a cloud of 703? Is there a particular spot on the ceiling I should focus on?

Search this forum for "cloud", and I think you'll find about 50 different ideas to pursue! Basically, the spot you need to focus on first is right above your mix position, as well as all first-reflection points. You need absorption in both of those places. Search the forum for "first reflection point", to find out how to treat that. It seems that you have your room acoustically "upside down": reflective ceiling, and somewhat absorptive floor! You could try doing your mixes standing on your head! :)

I use near field monitors, with the centers of the monitors spaced 4' apart, and each speaker about arm's length away from my head. The tweeters are about ear height while seated in the chair. My head is located about 66" from the front wall.

That might be another issue: You should aim to have your head roughly 38% of the room length back from the front wall, which is roughly where you are right now, but 38% is not a magic number: just a really good starting point. Try moving your head! You also should try to get your speakers and your head at the corners of an equilateral triangle, so they will be at 60 degree angles. If your speakers are 4 feet apart, and at arm's length from your head, then that probably isn't equilateral (unless your arms are 4 feet long?) And most important of all, you need to position the speakers correctly in relation to that front wall. That might be a large part of your problem. You might have them in a location where the bass interaction with the front wall is doing all kinds of funny things to the low end. I know I have a paper somewhere on positioning, but if I recall correctly, you need to either get them smack bang up against the wall, or at a distance of a couple of meters away, such that the first wavelength where there are comb filtering issues is at a low enough frequency that it doesn't matter. I'll see if I can find that paper. Worst case, you might want to consider soffit-mounting your speakers. But that might be outside your budget, and isn't easy to do right anyway. It sure would tighten up your bass, though!

After getting a quote on ordering some 705 (yikes!),

You might not need 705. I read an excellent explanation by either Ethan or Andre about why 703 can do pretty much the same job. Even plain old fiberglass or mineral wool piled up in the corners will make great bass traps. In your case, you might need to cover at least some of it with plastic, to get back your highs, but I'd leave that until you have the bass traps in place.

but I can post it, and/or pics of the studio if requested.

Photos would be good! As would an accurate SketchUp model. In summary, I'd say that your priorities should be to make your room non-square and a good ratio, followed by huge bass traps, followed by a cloud and treatment at first reflection points, followed by getting rid of the carpet and getting wood on your floor, followed by careful speaker positioning. All of those are first priority! Then you can start looking for specific issues that need individual treatment. That would be my suggestion. If it was my room, that's what I'd do. But that's just me. Maybe one of the real experts here can give you much better advice. I ain't no expert on treatment! - Stuart -

Stuart/xspace: thanks for your responses-sorry I'm a couple days late responding to them. I’m not sure on the window glass specs – they are just standard windows, double layers of glass with dead air between. They are parallel. However, since they are sliders, the surface area of each glass pane is only 15” X 20” - hopefully too small to be too problematic. The door is metal surfaced, wood core on the edges, but I believe it is foam core in the very center, but seems pretty solid.

First question: Any chance you can move a wall, or build a new wall, to get rid of that squareness?

I could probably afford do that. It's the resulting divorce that would be too expensive! :) No, that's not really an option at this time.

It seems that you have your room acoustically "upside down": reflective ceiling, and somewhat absorptive floor! You could try doing your mixes standing on your head! :)

Or else make everyone else listen to the music standing on their heads - would that work?

Yep, carpet is bad. It is selective, and will give your room a dull "cavey" sound. Plus just laying plywood on top of your carpet might not be a good idea, acoustically, as it will leave an air gap in between, and that might do strange things. I think I'd be inclined to remove the carpet entirely. Once again, Andre would be the one to comment on that issue.

Andre? Anyone else? The carpet has to stay for the near term. In the meantime, would 8' X 8' of plywood in the center of the floor help or hurt? It would actually extend from beneath my chair at the listening position out to the recording space, with only a couple feet of carpet on each side.

And most important of all, you need to position the speakers correctly in relation to that front wall. That might be a large part of your problem. You might have them in a

Actually, I had my listening spot way too close to the wall, and only last week moved it near the "ideal" 38% position. It might not be completely optimal yet, but I can already tell it is WAY better. The bass trapping sounds straight forward. I have located a local source for Thermafiber Safing, a rigid rock wool that is 4.0 psf (which should be 703-ish). I plan to build 2’ wide 4” thick bass traps diagonally floor to ceiling in all 4 corners, and 4 additional 2X4’ panels; one on each side wall at first reflection, another panel in the middle of the rear wall/ceiling junction, and another behind the monitors. This is shown in my original cunning plan sketch above, with the addition of the other trap at the top of the rear wall. Assuming Andre or someone else gives the green light on the plywood over the carpet, that leaves just two "first priority" problems to solve: the reflective ceiling and the bad room geometry. As far as the ceiling, given the dimensions/geometry etc of my room, how about this: 4’X6’ cloud of 4” rockwool, suspended parallel to the ceiling starting at first relection ? Would that be sufficient treatment for the ceiling? Perhaps with some of my 2” and 3” acoustic foam squares moved from the walls to treat spots on the sides of the cloud? I also have some 2’X4’ pieces of Armstrong acoustic tile (can’t seem to find specs for it online). Any benefit to putting some of this up too (say, along the sides), or is it not broad-spectrum enough? Here is a sketch of the above cloud, roughly to scale: Now the walls. I already have some absorption on the rear wall – I may add more later if needed. My feeling is that the side walls are my biggest problem. As you mention, many other posts suggest only absorption to treat these sorts of problems. As this is also a recording space, I would ideally like it not completely dead. What about also incorporating some false walls/panels/gobos/whatevever, on the side walls? Say, sheets of plywood (or even cardboard, ala Ethan W.) that stick out at angles from the walls in places. I have illustrated this a bit in my original "cunning plan" sketch above. Would that not at least partially address both the square geometry and the parallel walls? If this is worth pursuing, I will have further questions about details such as placement, angles, material etc. If this is NOT a good option, what would you folks recommend for a strictly absorption solution? Thanks!!!!!

Hello Chuck.....!, the Advice you have received and the Idea's detailing your plan are indeed correct as Far as I can tell from a Room size I have worked with before though another 2 feet longer and 1 foot wider. Bass-trapping will indeed make a great difference and you really need to use a TON of this stuff, absorbing as many frequencies in the low modes as you can is going to help you to every End. I would suggest 703 and not the denser 705 (See Ethan Winer's site for 703 tests with FRK facing etc) (http://www.realtraps.com) as you want to capture the long, low notes and transfer them into energy via heat, so Corner Super-Chunking / And or a John Sayers Corner trap , (See Acoustics Section) & Stickie's will help here, I would say super chunk, air gap and large Floor to Ceiling 2 foot /120-cm traps 4 inches wide in the location you pointed to will tame things down as will a massive back wall bass trap or absorption. In this type of room situation reflection will not be of use, unless you wheel it in when recording, as for mixing you need to go dead and low, adding your ambience via electronics, as the Room size is actually working against you so you are.... going to have to live within those dimensions unless you so some serious amendments to walls etc as suggested, though I don't see that as a practical solution for you. the Cloud will help, though basically absorption is going to be your friend and not diffusion or reflection. The floor Idea may also help as you will need that upside/down room (Ceiling to Floor) reconfigured, as this will help you translate better, you said you have moved position though in rooms like yours the 38% rule is not a rule to be set in stone and used as such, (See Wes Lachot's 38% Mix room placement) on this site, as their is much debate about it, I would say you need to find a position neither in a major Peak or Null (there will be many around the room though some golden places will be better then others, so find those by moving your chair & speakers around - test for what feels best, and then do the actual tests with an Omni Mic and program if you require hard evidence, though for a room like yours mixing in feel and in knowing what the rooms limitations as far as mixing is concerned - this will help you go a long way to making things better. - by no means is your room size the worst known, though it's a toughie...! You also might want to block those windows - see the forum on that. I do hope to see some pics soon or hear if you have been successful with the plan you devised and advice offered. Cheershttp://www.johnlsayers.com/phpBB2 ... 2&t=11570# ADDA