Treating a rental rehearsal room 20'x20'x18'?

I'm a wordy SOB - I'll try to get it all in as concisely as I can! We've been renting a rehearsal room for a while, and it is where I do most of our tracking as well (really sucks when the neighboring bands are having band practice when we are trying to track vox :( ). We record all of our practices, and I'd like to tame the room for live recordings, and for tracking. Anyways, the room is 20'x20'x18' (might be 16' ceilings - I'll have to measure). It's mostly concrete and brick (even the ceiling is concrete), and the owners have low-quality 1" foam on most of the walls covered with some thick plastic tarp-like material, and the floor is indoor/outdoor carpet. The back wall contains a large mirror approx 15'x10', but I've covered approx 1/2 of it with a thick moving blanket approx 2" from the wall. Since this is a rental space, anything we do can't be terribly permanent, but I'm not against drilling into the walls or ceiling (as I've already done) to attach some panels. So, the ceiling was the biggest offender since it is concrete w/o any treatment whatsoever. I already built three 6'x4'x4" thick 703 "clouds" - one approx 9' above the drums, one approx 10' above the guitar/bass area, and one pretty close to the ceiling above the singer's monitors - all three are slightly angled back into the room if that makes sense (for aesthetics and keeps the light levels a bit higher). This immediately helped the slapback I was getting, and now I'd like to attack the rest of the room. I was thinking the staggered placement of the clouds with regard to height would tame a broader range of frequencies, and having the drum cloud slightly lower above the drums blocks lots of the room sound from the Overheads' cardioid pattern. I haven't RTA'd the room, but seeing as it is 20'x20' with the ceiling not too far off, I’m sure I have some nasty modes (I know we have a nasty resonance around 35-40HZ, but I think it could be a structural resonance TBH). The room also sounds a hair dark with all of the thin foam (the plastic covering seems to help some), so I'm thinking about using 703FRK foil-faced panels for any corner traps and wall panels. I want to keep it a hair "live", and I prefer a brighter response if possible (kill the 500-2K area, but retain some air in the 5K-8k range)... I have a 10' wide x 5' tall plexiglass shield (gobo) for the drums which I temporarily cover with thick moving blankets, but I'm thinking I'll cover it with 703FRK as well (both sides). Any suggestions on where to start as far as bass trapping and wall panels go? Again, this stuff will need to be removable, and it will be carried up a flight of stairs on top of that. I'm guessing a membrane bass trap might be more appropriate than thick ~6"-8" broadband panels once I figure out the actual response of the room. I'm not up to speed on membrane absorbers in the least - and I'm not sure if they have to be sealed to the existing structure or what not. My initial plans are to do numerous 4" thick 703FRK 2'x4' panels on the walls (maybe 1"-2" off the wall), and then maybe a 6"-8" thick corner absorber that would be 2' wide, and run most of the height of the rear walls (there isn't much space on the front wall corners for bass traps - maybe higher up by the ceiling - otherwise the PA system occupies the front wall's corners from the floor to approx 7' up) Can you guys suggest anything with this (pitiful) info - or do you need the specific room layout and measured response? Please go easy on me - I'm the Drummer and Audio Dude :shot: I'll attempt to make future replies shorter... PS - I attached a crude floor plan if this helps at all (I doubt it :) )

"the room is 20'x20'" The room is square. This is the issue, not the ceiling specifically. You have hard boundaries that are reflecting energy that compounds the problem frequencies due to these dimensions. Whatever the tarp is on the walls only serves to amplify or at least allows to live, the high frequencies. The indoor/outdoor carpet is doing something but it isn't doing what you might think. It's that square room first, and every hard surface you guys have installed second. Alternating absorptive panels on the walls that break up the parallel hard surfaces would help. But it will always be a square room until that is changed.

Unfortunately, this is a rental room, and the indoor/outdoor carpet, the thin foam and plastic on the walls, and the concrete ceiling were pre-installed by the building owners, and we are not allowed to "modify the room" (believe me - I would NOT have gone that route!). Building false walls or whatever to change dimensions to the golden 3-4-5 is not an option (I wish it were!). All I can really do is attach things to the walls, hang stuff from the ceilings, and use gobos to help break up the room. The slapback off the hard concrete ceiling was driving me nuts (especially near the corners and by the singer's monitors), and the three 6'x4' clouds actually did quite a bit to lessen those nasties. I could already hear a difference on last week's session! With clouds, what is the general rule for how close to the source or ceiling to hang them? The cloud I put above the drums, and the 10' wide 5' tall GoBo around the drums helps to isolate them from the "Cube" of the room, and also helps to break up the front-to-back dimension so it's not a square (the pic shows where the 10' long gobo is) - but I still need a good deal of treatment to bring it into line (at least as straight of a line that a 20x20x18 room can be ;) ). Along those lines, what about trying to keep the high-end somewhat lively/airy by using 703FRK foil-faced panels? If I'll need as much absorbtion as I think I will to tame this quasi-cube I'm in, then the high-end will be very dry and dull. Would you recommend OC703 FRK to achieve a livelier high-end response? What effects can I expect from FRK versus non-FRK once you factor in the burlap covering that is sure to damp some highs as well? As far as bass trapping - I'd assume broadband absorbers will help tame the overall low-end and low-mid repsonse, but I'm pretty sure I have a few strong modes around the 20'/18' dimensions, correct? (I'll have a chance to run a quick RTA this weekend). Would broadband absorbers be able to deal with such modes, or am I looking at membrane bass traps (more robust frequency-specific traps) to help tighten up the low-end? I know I hear a MASSIVE resonance in the 30-45Hz range - and I'm not sure if it might be a structural resonance or just the room modes (they are intense - even closing the door will excite these resonances!). Thanks for your reply, and for putting up with a drummer's machine-gunning questions!!! :cool:

The cloud I put above the drums, and the 10' wide 5' tall GoBo around the drums helps to isolate them from the "Cube" of the room, and also helps to break up the front-to-back dimension so it's not a square

Actually, it still is square. Large flat surfaces inside the room might help to break up flutter echo, but they won't eliminate the modes. Unless you can build them floor to ceiling and wall to wall, and seal them hermetically, then they won't change the modes very much. Of course, doing that is the same as moving the walls, but you say you can't do that, so you are stuck with those modes. Have you considered building a slightly angled wall across one corner or in front of one wall, to break up the symmetry? You say you don't mind drilling the walls if you have to, so how about building a regular stud frame angled slightly away from one wall, and putting a layer of 5/8 drywall on it? It can still be taken out once the rental ends, and would not be too expensive. Maybe start 4" out from one corner and angle it to be a couple of feet out at the other corner, floor to ceiling, sealed. Done deal. Perhaps even fill it with wool, so that you don't create yet another resonator in there. Another idea might be a slot wall in front of another wall.

I know I hear a MASSIVE resonance in the 30-45Hz range

Not surprising! With those dimensions, you have huge modal issues from 28 Hz. to 77 Hz., with big problems at 28.3, 45.2, 56.5, 63.2 and 66.6: All of those are double modes (two modes at the exact same frequency, from two different sets of walls). You also have isolated modes at 35.3, 40 and 53.3. All of the above assumes a 16 foot ceiling. If it really is 18 feet, then things are much worse: your 0-0-2, 1-2-0, 2-1-0, 0-2-1, and 2-0-1 modes all line up practically on top of each other, between 62 and 65 Hz.! It must be hell to play bass in there... The "dark" sound is probably related to all of those, and probably also has something to do with the carpeted floor and useless plastic/foam combination. That is most likely sucking up some highs at random frequencies, and doing nothing at all to the lows. The mirror, of course, isn't helping you either! Maybe one idea would be to install some really heavy broadband bass trapping in there, maybe even tune some of it to the problem frequencies, but that still won't get rid of the modes: it might tame them a little, or perhaps even move them around, but they will still be there. A square room is never going to sound much good until you make it un-square.

I already built three 6'x4'x4" thick 703 "clouds" - one approx 9' above the drums, one approx 10' above the guitar/bass area, and one pretty close to the ceiling above the singer's monitors - all three are slightly angled back into the room if that makes sense...

Do your clouds have solid backs, or are they pure clouds? IF there is no solid back on them, the n you are still not doing anything about flutter echo in the vertical direction. You might want to consider putting hard backs on those clouds, to break that path up a bit. And like xSpace said: At the very least break up your flutter on parallel surfaces with absorption "checker-boarded" on opposite walls. - Stuart -

Soundman2020 wrote:

Have you considered building a slightly angled wall across one corner or in front of one wall, to break up the symmetry? You say you don't mind drilling the walls if you have to, so how about building a regular stud frame angled slightly away from one wall, and putting a layer of 5/8 drywall on it? It can still be taken out once the rental ends, and would not be too expensive. Maybe start 4" out from one corner and angle it to be a couple of feet out at the other corner, floor to ceiling, sealed. Done deal. Perhaps even fill it with wool, so that you don't create yet another resonator in there..

You know - This might actually be an option - but one I'd probably need to pass by the building's owner. The "Sealed" part will be the hard thing to do as I will have to seal it to the current structure (means removing or modifying the pre-installed "Acoustic Treatments", possibly cutting out the carpet, and putting caulking on the brick/mason wall and ceiling). Getting all of the materials up to the room would be a chore, and I've never tried to build a wall taller than 8' (so I'll be hanging sheetrock 18' up! That is a bit scary TBH). If this would negate the need for all of the extreme absorbtion I'm thinking I'll need, then I will give this some serious thought. I know dimensions are key - I just never thought I could do anything about my situation aside from miles and miles of absorbtion... The dimensions you mentioned would not be an issue - I'd likely use the 4" offset by my drums, and have the 2'-4' splayed out where the "2nd Drumset" is now (reference my crappy floor plan above :) ). We wouldn't miss the space - that's for sure! I might even consider covering the mirrorer wall instead (but the door is on that wall as well). Could I start the splayed wall by the door and splay it out to the left as referenced in the floor plan above (covering the mirror)? EDIT/ADD - Would the amount of splaying/offset change if the ceiling is actually 18'? If I do a 2' splay, I'd have close to 18' x 18' where the splayed wall meets the ceiling. Would it be better to waste more space in favor of a more aggressive angle on the false wall? (like 4" at one side, and maybe 4'-6' on the other side?). I guess it will make more sense to discuss this once I'm sure of the ceiling height, huh?

Soundman2020 wrote:

Do your clouds have solid backs, or are they pure clouds? IF there is no solid back on them, the n you are still not doing anything about flutter echo in the vertical direction. You might want to consider putting hard backs on those clouds, to break that path up a bit.

Can you elaborate for slow me? The clouds I built are simple 1"x4" lumber frame, and 4' x 6' with 4" of 703 (three 2'x4' sections - double stacked for 4" - all married together in a common frame). The top and bottom are "open", but covered with tablecloth fabric, and hung from the ceiling with wire and eyelet hooks. How will putting a solid top on them help with flutter echo? Won't that just create other flutter echoes from the top of the cloud's hard reflective surface to the ceiling's hard reflective surface (approx 6'-8' from top of cloud to ceiling), and then bounce back down into the room? I figured that with the top and bottom "open" that the panels are able to absorb reflections from the floor AND from the highly-reflective concrete ceiling - no? Are you saying the flutter echoes pass through the 4" 703, hit the ceiling, and then pass back through the 4" 703 and are still audible? I know the clouds are taming a good deal of flutter (I could hear a marked improvement on the last jam session's recording), but if I can simply add a solid top to them for more control - then I'm all ears!!! Great info, guys! Much thanks for pointing me in the right direction! I'm "absorbing" lots of good info :yahoo:

How will putting a solid top on them help with flutter echo?

You did say they are angled already, so putting a hard top on will be reflecting things at angles, not directly back the way things came. It's one trick that John uses regularly in his clouds, to help deal with flutter. As long as you have a reasonable angle on the cloud it will work fine.

Won't that just create other flutter echoes from the top of the cloud's hard reflective surface to the ceiling's hard reflective surface

You only get flutter between parallel surfaces, so the key here is the angle. If you don't tilt them, then sure, you'll still have flutter, but with slightly different characteristics: But if you do angle them enough, then your flutter is gone.

Are you saying the flutter echoes pass through the 4" 703, hit the ceiling, and then pass back through the 4" 703 and are still audible?

Yup! Each passage through will, of course, remove some energy, but not all of it: things are still bouncing around in there. But if you put a hard top and tilt it, then ALL of the energy is now going in a different direction, after the very first bounce, and won't be back. Search the forum for "cloud" and "angle"...

I guess it will make more sense to discuss this once I'm sure of the ceiling height, huh?

Yup! :) - Stuart -

A killer reply! Makes complete sense. I was overlooking the angle on the clouds and the beneficial effects of "angle of incidence = angle of reflection" as you mentioned. Sounds like it will also help to keep some of the "air" and RT60 of the high ceilings to boot since 1/2 of the absorption is now replaced with re-directed reflections! I'd like to keep the room as live as possible while nixing the negative attributes of the poor relative dimensions (to whatever degree is possible)... I will get some hard dimensions this weekend, and also make a few quick RTA measurements of the room. I've only done RTA readings for speaker+room correction - but since my "sources" (the instruments) are scattered throughout the room, should I consider moving the reference speaker (Dynaudio AIR15) to the location of the instruments and get some RTA readings in that fashion? Or does this even matter at this point? I'd guess I will get the raw dimensions, determine the placement of the false wall, and then RTA the room after this wall is up - and FINALLY decide how much bass trapping I feel I'll need to get me where I want to be? I guess common sense can help in some cases - but clearly not without some good input from smart feller's like you :) Thanks again for your most excellent input! 8)

Randy, If you placed the hard surface in-between the insulation on your clouds, you would get the effect of the hard surface plus the insulation would help to break down the flutter between the top ceiling and the top of the cloud. My real apprehension about this whole affair is that most of the materials you guys have installed or may install (burlap) are flammable. That worries me, I find the older I get the more energy I spend on caution and, well, basically, fear :) >If< you guys could construct a splayed wall like Stuart mentioned, you may could build it as tall as possible and still get the benefit. It would take some attention to detail, like build the splayed wall to 12 feet tall and re-establish the clouds to that height. Or 9 foot tall, whatever you can do safely and that can be secured to the existing structure that does not have any opportunity to move either in or away from the existing wall. If you have a few sheets of plywood you could lay those directly on the carpet at the position the singer is in, to gain back some of whatever is being taken away with that indoor/outdoor carpet. If you do not like the sound, you can always move it. You could try this on amps that are miced or anything that has a mic and your ears tell you something is gone in the high frequency range. As to adding more insulation with a foil face, yea, that would bring back some of the highs but I would look in other areas first in an attempt to get rid of the offending frequencies.

The clouds I built are actually using Tablecloth Fabric – I’m thinking that should be somewhat fire retardant since it is likely that candles and stuff would be placed on a table cloth. I can do a quick burn test on some scrap fabric I have to be safe. I bough some burlap with the intent of using it on the wall panels and to treat the Plexiglas drum shield – but your fire-retardant concerns have caught my attention. I won’t use the Burlap, and I will instead buy more tablecloth type material that suits the aesthetics of the room (probably look more interesting than burlap anyways ;) ). You can just barely see through this tablecloth fabric – so I’m assuming it will be a descent choice and won’t hamper the absorption too much… I've been pondering using some plywood on the floor. I already have a small piece under my snare to get the snare wire sound back into the room. I never really considered using it for the vox or guitar/bass – but I can see that it might help - Great suggestion! Back to the splayed false wall – Do you really think I need to go that drastic with the angle, and end up with only 12’ of the 20’ dimension in one corner? Could you loosely define the differences I’d hear if I spayed the wall, say 3’-4’, versus 6’-8’ as you suggest? I’m assuming you are trying to get me away from having the wall end up at 18’ or 16’ when the ceiling will be that same dimension – correct? So you are trying to get the splayed wall to end up “shorter” than the ceiling height – correct? EDIT - I see you were speaking on wall HEIGHT and not the angle of the splayed wall - I read too quickly :) I guess I still need a hard ceiling dimension before I can get a suggestion on the placement of the wall (I'll be able to measure tomorrow). I think if I do go through with the false wall, I’d suck it up and take it to the ceiling. I might get someone more experienced to help me – or maybe even frame the wall myself and do the bottom course, but hire someone to do the top course to the ceiling, and tape/mud it so it looks clean (my taping skills really aren’t all that bad TBH). If I *did* decide to go with a 12' high false wall - would it still need to be sealed at the top back into the wall (fold back into the original wall)? Or could I leave the top of the false wall open and stuff it with insulation? Just curious... Since this is a rather tricky proposal in my scenario – what can I realistically expect (sound wise) from going through with this and treating the room properly versus what I have now plus a dozen or so broadband absorbers checkered around the room? If the difference will really be dramatic and blatantly obvious in my tracks, then I will push and nag the owner until he caves. Otherwise – if the benefits would be negligible or slightly audible, then I might lean towards simple broadband absorption instead, and leave the building's owner out of this altogether (don't want to rock the boat unless it's really worth it). EDIT #2 - On the clouds - putting wood in between the layers would be a good deal of work (have to remove the fabric, probably re-build the frames too, etc). Would you recommend leaving them "open", or putting the solid wood on the top? The angles are approx 15*-20* or so, but I could take it steeper if needed to eliminate the parallel slap-back issue. I'd assume having the hard top would leave a bit more "air" in the room, and retain some of the natural decay as long as the angles are kosher Thanks again for your expert outlook (I can’t say this enough) 8)

randy, I don't know how dense your table cloth really is but keep in mind that you should (at least) be able to breathe through it. if it's too dense it'll reflect. you can use burlap but: "...you must purchase fire-retardant materials to properly treat the fabric." (rod gervais, home recording studio, build it like the pros, page 175). cheers, carsten

... -> EDIT #2: 12° is commonly said to be enough to avoid flutter, afaik solid back on the top might work also: look here: click click c.

It's very easy to breathe through (I tested that before I purchased it ;) ), and you can vaguely see through it if you hold it in free-air. Of course once it is on the panel, you can no longer see through it. It's your basic thin/lightweight tabecloth material. The three current clouds seem to have helped noticably - so I'm hoping taking this to the next level with the wall will make a dramatic difference... Thanks for the clarification on the cloud angle as well. I'll read the link a little later (The College Basketball Tournaments at work are driving me nuts!!!) 8)

tennessee vs mississippi? you're nuts hehehe we're all addicts..aren't we?! 8)

carsten_d wrote:

tennessee vs mississippi? you're nuts hehehe we're all addicts..aren't we?! 8)

We actually have about 21 different games on our plate tonight! :shock:

and also make a few quick RTA measurements of the room. ... should I consider moving the reference speaker (Dynaudio AIR15) to the location of the instruments and get some RTA readings in that fashion?

Put your speaker right on the floor in one corner, as tight into the corner as you can get. That way it will probably excite all the modes associated with all three of those surfaces (wall, wall, floor). Since you also suspect your ceiling is a problem, try to figure out a way to repeat your reading with the speaker stuck up in the wall-wall-ceiling corner. You do this because modes terminate on walls, and at least three walls meet in corners, so you should be able to excite the modes for all three at once. If you were to put your measurement mic in the diametrically opposite corner, you'll have the best chance of picking up all those modes. Put a better idea is to put the mic where you normally listen, since that's the spot where ... well ... where you listen! That's what you want to analyze. - Stuart -

Makes sense - I'll favor my drum throne position since I'm the one paying rent :P (friggin' guitar players!!!) Any comments on the actual sonic benefits I'd experience by going through all of the trouble of 1) Convincing the owner to let me do this and 2) The associated labor and cost involved for the false wall? I'm basically looking for "Heck yes - you'll hear a huge difference and your raw tracks will sound 'x' better" or a "The sound will improve slightly" type thing. I know acoustics in general is a game of inches - and I'm not wanting to go far out of my way to gain an inch or two... So - Build the wall and all that's involved vs. sticking with what I have + throwing up 12-16 broadband absorbers sprawled about the room? How drastic will the end results differ between the 2 scenarios (ballpark)? I would love to have a good sounding room - but this room is not a great starting point to begin with - ya know? Much obliged! Back to work! :cen: PS - Your continued valuable input has encouraged me to donate to the forums. I hope it helps keep this place online! :thu:

Anything that you can do to change the physical hard boundaries of the room, change the geometry, will be an improvement. It will reduce flutter which is a by product of parallel walls which you have at least two pair that we are aware of. Also by changing the room, e.g altering same length wall measurements, you take the rooms ability to enforce or re-enforce frequencies specific to those square dimensions. If I can add this. The hard boundary on top of the cloud works against you. In a typical situation it might be three four inches +/- from a hard boundary. In yours, the sound has (depending on what the actual height of your square room winds up being) no less than four or five >feet< to hit another hard boundary and find another way out of this area right back into your room, creating more problems. The improvement will be a more even response. This does not suggest that broad band absorption will not be part of the continuing process. It very well may be. But this square hard reflective room has to be tamed first.

Would raising the clouds and adding a hard top help my cause? My initial rationale was: The lower the cloud is, the more of the mic's pattern is covered by the cloud. If I'm directly below the cloud (like my drums and all of the drum mics are) and the cloud is low, I can't "see" as much of the concrete ceiling because the cloud is obstructing my view. If the cloud is high, then I can "see" much more of the hard concrete ceiling and likely hear more of the concrete reflections. That was why I placed the drum cloud a bit lower (around 8'-9' from the floor with 6'-8' above the cloud). The reason I started with the clouds (and not with wall/corner absorbers) was that the walls have the pre-installed crappy foam and plastic on the them, but the ceiling was completely untreated. This also gets the PA system's horns from having a direct line of sight to the reflective ceiling. I'm sure you've seen all kinds of "I thought..." situations - and I'm obviously no different! :oops: Speaking just of the clouds - what would you guys suggest with regard to height, angle, and hard top or open top in my silly room? I'm anticipating adding a good deal of broadband absorption in either scenario (with or w/o the false wall) - I realize changing one wall will not magically fix all of my issues - so I'm game to put some time and effort into this project assuming it will end up being a worthwhile return on investment... I'm heading out to the room on Saturday, so I'll have hard dimensions and a rough RTA next time I post back. I'm hoping to get the false wall placement/plan all figured out with your help, and then present my findings to the owner on Sunday (time and your input permitting) - then cross my fingers. With any luck, I'll be able to tackle this next weekend (3-day weekend!). I'm getting really excited about this project (I'm sure this is old hat and a bit "amateur" to you pros :wink: ) I'll chat with you nice folks later 8)

Boy - I was off on the ceiling height - It's only 11'5" !!! My mistake :oops: I swear the owner told me it was higher - but I should have known it was lower. The room is actually 19' x 19' x 11'5" . I'll recap the currently installed acoustic treatments that the owner already had up: 2 adjacent walls have thin 1" foam covered with the plastic tarp material - one of these walls also has the huge mirror. 1 wall has 2" thick "pyramid" type foam (not covered with plastic). The last wall actually has EGG CRATES covered with the plastic crap (wow!). I'm going to ask the owner if I can at least remove the egg crates from the wall, and treat the exposed mason/brick wall with more appropriate panels. I attached numerous RTA plots below from different locations and from 2 different source speaker locations (reference the file name for the mic location). The peaks and nulls are drastic to say the least (35dB variance). So, knowing the actual dimensions and RTA measurements of the room, where would you recommend I place a false wall? Considering it's only ~12' high, I will take it to the ceiling. Thanks - and have a good weekend! 8)

Friendly Bump. I apologize for assuming the room had higher ceilings - I feel like a doofus! :oops: Anyways, I'd like to make a proposal to the owner soon, and I'd like to have all of my ducks in a row when I speak to him. Any suggestions on the placement of the false wall knowing the hard dimensions of the room and seeing the RTA response? Will one false wall really start to tame some of those peaks and nulls (with appropriate broadband absorption)? Would more aggressive membrane bass traps be another option to consider (in addition to broadband absorption) seeing how drastic the peaks are at 40Hz and 60Hz with a big dip @ 50Hz and other serious issues around 65-120Hz? I'd bet simply removing the egg crates and plastic from that one wall and treating it with 4" OC703 panels would do wonders in itself with regard to the timbre of the room, and let some of the "air" back in. If the owner doesn't go for the false-wall build out option, then I will at least press him to allow me to remove the stinking egg crates, and go to town on the wall and corner panels. I realize this won't help my severe < 200Hz mode issues, but if the false wall is out of the question, then I'll need to do something to get the room close where I want it... Thanks again for your valuable time! 8)

Any suggestions on the placement of the false wall knowing the hard dimensions of the room and seeing the RTA response?

One way of figuring it out would be to look for a known good room ratio that is close to what you already have, then work out how much you'd need to adjust one wall to get to that ratio. Tat will help with your mode spread. You could also then splay (angle) that new wall to deal with flutter echo. How much to angle it? Good question. In a control room, walls are splayed 6 degrees on each side, for a total of 12 degrees differential, but that is in order to get a good reflection free zone, as well as helping with flutter. So 12 degrees would work, but something less might work too. Perhaps one of the acoustic experts can help you out with the minimum angle that you'd need to splay.

Will one false wall really start to tame some of those peaks and nulls (with appropriate broadband absorption)?

The combination of both will do good things. Based on your new (accurate!) dimensions, your major issues should be at 29.7 Hz, 42.1, 49.1, 57.4, 59.5, 66.5, 77.1, 82.7, and 89.2. But that's only up to 90 Hz., where your room modes stop being the dominant factor. Beyond that there are still multiple recurring pairs of modes all the way up the scale. Looking at the graphs, your 49 Hz problem is very prominent (at least, it looks like roughly 49 Hz on all of your graphs), which is your 0,0,1 mode. This is a height-related mode, so moving the wall is not going help with that one. Angled clouds should do something, but that one might need a tuned trap to deal with it, since it is so prominent on all your graphs. I'm guessing that you took all the measurements at roughly the same height above the floor? Which was roughly at your head height? All of your other major modal issues are pretty clear in those graphs, in different places. Some in one graph, some in another, but they are all there: Look how the biggest dips and peaks line up pretty much spot on those predicted frequencies. Since all of those other ones are related to walls in one way or another, building a new angled wall should help. Lots of bass trapping will probably help too, I reckon. But I'm curious about those apparent dips on all of the graphs around 1.8 kHz, 4k, 6k and 10k. I'm curious as to where those come from, since there doesn't seem to be a reason for that from the room dimensions. I'm wondering if those are artifacts form that foam/plastic on the walls? Or the carpet? Or maybe artifacts of the speaker / mic / system you used to measure the room response? Perhaps the speaker has a cross-over or response issue, or something in the room is sucking energy out around those frequencies, consistently, all over. Whatever it is, you probably should try to identify it, and fix it if it is a room problem. The room will sound strange like that, with a muffled mid range and "holes" in the mid highs and highs. If it is room-related, then maybe some kind of broadband treatment for that are would help. The rest will most likely even out somewhat with the basic treatment, then you can measure again and see what still needs to be done, more accurately.

Would more aggressive membrane bass traps be another option to consider (in addition to broadband absorption) seeing how drastic the peaks are at 40Hz and 60Hz with a big dip @ 50Hz and other serious issues around 65-120Hz?

I think I'd leave specifically tuned treatment for a last resort. I'd go for fising the geometry first (new splayed wall), plus massive bass trapping in all the corners you can get to, plus some broadband stuff for the mids/highs (maybe one of John's famous slot walls?), then see how it goes with that, and carry on to deal with more specific issues, if they are still troublesome. At least, that's my take on it, from my limited understanding of acoustics. Perhaps one of the real experts here can chime in with better advice.

I'd bet simply removing the egg crates and plastic from that one wall and treating it with 4" OC703 panels would do wonders in itself with regard to the timbre of the room,

Sounds like a good plan to me! Egg crates actually do have an effect on acoustics (see Rod's book), but the effect is unpredictable and not pleasant, so they certainly do have to go!

If the owner doesn't go for the false-wall build out option, ...

... Then how about building a bunch of 11 foot 4 3/4 inch gobos, and lining them up all along one wall, at an angle, butted up really tight to each other ?? :) It wont be the same as a "false" wall, of course, but it would do SOMETHING at least! Anything has to be an improvement on what you have right now. Build them with a really solid back (plywood, MDF, etc) and some combination of absorption / broadband slots in the front... They would be movable, and you could even build them on wheels, and shift them around as needed for special situations . . . My 0.02 - Stuart -

Soundman2020 wrote:

Angled clouds should do something, but that one might need a tuned trap to deal with it, since it is so prominent on all your graphs. I'm guessing that you took all the measurements at roughly the same height above the floor? Which was roughly at your head height?

Yup. I had the mic a bit lower at the Drum Area, but the rest of the RTA's were taken at standing head height. So knowing my revised height, would you say I should raise the clouds and put a hard back on them as previously mentioned?

Soundman2020 wrote:

But I'm curious about those apparent dips on all of the graphs around 1.8 kHz, 4k, 6k and 10k. I'm curious as to where those come from, since there doesn't seem to be a reason for that from the room dimensions. I'm wondering if those are artifacts form that foam/plastic on the walls? Or the carpet? Or maybe artifacts of the speaker / mic / system you used to measure the room response?

I'm thinking it's the pre-existing treatment. I was going to use my Dynaudio speakers, but I decided to use the cheaper Mackie 824 as my source which should be relatively flat, and I used a DBX RTA mic. Could some of those upper frequency issues be due to the drum gobo in the middle of the room (the back side is mostly exposed plexiglass, but the side facing the drums is covered with heavy moving blankets). To make it worse, the exposed plexiglass on the drum shield reflects back into the large mirror on the wall! I'm planning on covering both sides of the plexiglass gobo with 703 panels, and leaving the top 10" of it un-covered plexiglass so I can still see out of my drum area. I'll also plan on dealing with the rest of the mirror. Speaking of the mirror - Would having a heavy blanket approx 3-4" off the mirror cause any of the higher frequency issues you mentioned (nulls in those areas)?

Soundman2020 wrote:

I think I'd leave specifically tuned treatment for a last resort. I'd go for fising the geometry first (new splayed wall), plus massive bass trapping in all the corners you can get to, plus some broadband stuff for the mids/highs (maybe one of John's famous slot walls?)

As far as bass trapping, you are just referring to putting up 45* corner absorbers wherever possible? I'll have to read up on slot walls as I'm not very familiar with them. Your suggestion with a large moveable wall (essentially a glorified Gobo) might be an option as well if the owner won't let me do the entire wall. So basically, this would be a 2-leaf wall with a solid/rigid back, and a slotted front - and then the interior is filled with 703? Thanks for the continued information. I'll work on some angles and dimensions for a proposed false wall ASAP. For now it's off to work... 8)

Losely, I believe I'd need to offset the wall by approx 4' to obtain approx 12 degrees offset at a 19' run. Does that sound about right? So - the wall will start pretty much at the corner (minus the thickness of the stud and leaf) and then end up approx 4' 6" in (leaving approx 14' 6" of useable room by the splayed area). The corner also has a small column at the wall that pertrudes approx 4"-6" on each side - so I'd likely be able to make the wall start flush with the column if thatmakes any sense (see crude pic below - Columns are Black - false wall is Grey - and not to scale :roll: ). I'd love to get more feedback on my current clouds, and if I should raise them and add a solid top to them? That is a very easy modification by comparison :) Thanks a million! 8)

Sorry in advance for the relentless posts. I just spoke to the owner, and while he didn't say "no", I didn't get a good feeling. He wants to meet with me the next time I'm at the room - so that will likely be on Saturday. I guess he wants to see exactly what I'm talking about - and I can understand that... I'd love to get some feedback on my current proposal of the approx 4' 6" offset wall (see crude pic above). This would actually kill 2 birds as this is also the wall that has the egg crates on it - so I'd just leave the egg crates and plastic up and cover them with the new wall. I'd also love to get your thoughts on raising the clouds and placing a hard top on them. I believe the "Hard Top Cloud" concept is only recommended if the clouds are relatively close to the ceiling and angled appropriately (12 degrees or more). With my NEW dimensions of 19' x 19' x 11'5", I can easily get my clouds closer to the ceiling if this sounds like it might be more effective at controlling my ceiling modes which seem to be pretty apparent at standing ear height (as Soundman succinctly pointed out). I read up on Super Chunks, and I will likely suppliment "checkerboarded" broadband absorbtion with super chunks in the corners. Slat Walls and Slot Resonators seem like they might be a bit too finniky for a first-timer to nail off the bat unless you might motivate me to investigate further. I do still plan on mixing and matching 703 and 703FRK to help keep some of the highs in the room, and I might put some generic wooden "slats" in front of the Super Chunk treatments to give a bit of reflection back into the room. Any reccomendations on the ratio of FRK vs non-FRK? Maybe 1/2 and 1/2 (every-other-panel)? Anything sticking out like a sore thumb? (besides ME!!!) Again, I can't thank all of you enough for your valuable time and priceless knowledge. I'm hoping to realize a marked sonic improvement once I'm done. 8)

Anything sticking out like a sore thumb? (besides ME!!!)

:) :!: Hey Randy, no problem!

I'd love to get some feedback on my current proposal of the approx 4' 6" offset wall (see crude pic above).

It looks OK to me, as a rough idea. Design details will have to be fleshed out, but the basic idea looks fine. Another idea that just occurred to me is that you could split the wall into two, so it angles first "out" then "back again", so you don't loose so much depth at the far end. That should work fine too, but might complicate your construction. Just an idea.

I'd also love to get your thoughts on raising the clouds and placing a hard top on them.

That sounds good to me too. Once again, it would be good to see the design details, but the idea is good in principle.

I read up on Super Chunks, and I will likely suppliment "checkerboarded" broadband absorbtion with super chunks in the corners.

sounds like a plan to me!

Slat Walls and Slot Resonators seem like they might be a bit too finniky for a first-timer to nail off the bat unless you might motivate me to investigate further.

Not so hard to do, really! And they are well worth while. Follow John's simple design and dimensions, and you can't go wrong. They are very good. (Is that enough motivation??? :) )

I do still plan on mixing and matching 703 and 703FRK to help keep some of the highs in the room, and I might put some generic wooden "slats" in front of the Super Chunk treatments to give a bit of reflection back into the room.

It is probably easier to do that with plastic sheeting over the wool. The plastic reflects back some of the highs, but lets the lows through. So the theory goes, anyway... Good luck with your Saturday meeting! - Stuart -