Live/tracking room wall and ceiling design - angles.

Hey guys, First post here after a long time lurking. Amazing site, hopefully I've covered off all of the pre-requisites. Have just bought a place with a decent-sized 3-room garage/sleepout that's just itching to be converted into a control room, live room and vocal booth setup. I haven't started construction yet, when I move in I will be fixing the existing 'she;ll' etc first. I have done a reasonable amount of research about the construction process and materials to use over the last year or so, and have many books on the construction side of things,but the real questions I have are around the design of the live room. I will be building a 'room within a room' totally isolated from the external structure (other than the concrete floor) so can basically shape the room however is best within the space allowed (see picture). The ceiling is currently sloped just under 9 degrees (at the stud heights) for where the main room will be. From what I've read I would need to increase the angle of the internal structure to make it of any benefit - is there any angle (between 8 and 15 degrees) that would work best in this kind of space? Further to that, how would be the best way to angle the walls in that space so that it works out at the right total room volume, etc? I thought of originally having 2 of the 4 walls angled to eliminate flutter echo, (even having one wall come to a 'v' shape in the middle) etc but I'm not sure what method to use or where the walls should be placed. Any help here would be greatly appreciated! Currently the building is just the external shell with bare 2x4 framing inside for the two smaller pictured rooms, the larger of which will become the control room and the smaller becoming storage, as well as where the vocal booth will be housed. The budget as it sits at the moment is around $7000NZD which isn't much I know, but I am more than happy to chip away at it when I can if it's going to take more. Whatever yeilds a good, usable space! If there's any more information anyone would like please don't hesitate to get in touch here or by email ([removed]). Thanks so much in advance for your help! P.s. the posted measurements are the internal ones. Cheers! http://farm8.staticflickr.com/7204/6958626186_596ebc21c3_b.jpg tumblr_m2unhmJ9R01rq0td6o1_1280 by amatueraudio

Hey guys, Here's the first sort of 'concept' for what I'm wanting to do. As you'll see on the picture, the left hand and bottom walls are angled inwards at an angle of about 9 degrees. The ceiling is the same, sloping down at 10 degrees from its highest point. The internal structure has an airgap of around 8 inches from the wall housing the control room and storage room (both of these are not isolated from the building 'shell'). There are mineral wool bass traps in the corners as I'm sure a room like this will more than likely have bass problems. None of the dimensions are that close to being dividable by one another so hopefully the total volume, wall lengths and ceiling height will be OK. Any help would be greatly appreciated here. Construction won't start for a month or so - but want to get a decent idea of what I want to do before I start. Sketchup attached. Sorry about having to zip it (as well as my Sketchup skills haha) http://farm6.staticflickr.com/5325/6965257320_f96897c771_b.jpg Studiodraft4 by amatueraudio, on Flickr

Hey man, I recall that if you want to alter standing waves in your room, you need at least 12 degree angle, otherwise it's not effective. And I think that you really should splay maximum two of your surfaces (ceiling and one wall), because you are wasting your space, and you don't have a lot of it. It's easier and cheaper to treat room with two parallel walls then splay all of them. Secondly, do you really need small control room with vocal booth? Maybe you better off with larger control room and tracking vocals in live room? With your space, you can get pretty decent control room with good volume and splayed ceiling. Like this:

Hey Burst, Thanks so much for your reply and for taking the time to update the design! I see what you mean about the walls for the live room. Having the ceiling and one wall angled so that it ends in the control room (forming the angled slat wall of the control room) is brilliant. The only reason I was keeping that other room was so that there was some storage for drum kits, amps etc and so that the glass sliding door was not a part of the control room. A vocal booth is not a must ( in the live room with a Voxguard or similar would be fine I'm sure) but having storage would be a real benefit. The issue is, the control room's ratio (from what I can tell) is already less than ideal and shortening it's length would pretty much make it a square room with a splayed ceiling. Would you have any ideas on how to incorporate storage (enough to store say, a drum kit and a few amps) into anywhere in the build without having to shorten the control room or sacrificing symmetry? Would also want a way to get the glass sliding door out of the way haha. Thanks so much again! Hayden

No problems, Hayden! I know what it feels like when nobody is answering, my own thread is nearby and has zero answers :) LOL Regarding your question, maybe something like this would work: If you would want to go that way, make sure NOT to build airlock it that storage space, since you'll create third leaf that way. I mean, do not build more doors or walls on your way to control room. But to be honest, I wouldn't go that way if I were you. While I totally understand your desire to keep your room clean of unnecessary equipment, you are sacrificing volume of your live room (about 5.7 m3). Maybe it's easier and better to make some shelfs in your live room, lust beneath the ceiling, so you can place your stuff there, like this (note the shelf in top right corner): But, it's all really down to your personal preference and what type of music/records you are doing.

Alright! Sorry for the late reply, preparing the exterior of the building took a little more time than I thought it would. I'm ready to begin construction now, I'm going with Bursts first idea (the one without the storage) and am going to have the left wall angled (as in the sketch up) at 15 degrees. The longer parallel walls I'll take care of with treatment. Im scrapping the idea of a separate vocal booth, going to just record vocals in the live room and use a voxguard, etc to tighten them up. Before I put wood to nail, does anyone else have any other opinions on this build? I would hate to start building a wall only to find out that it's not going to suit. I've searched other builds etc and I can't see anything wrong with this design but want to get something worth the money, so anyone's input would be much appreciated. The live room I want to be a good general purpose live room predominantly for tracking guitars and drums. I will be treating with panels along the parallel wall and will probably use ceiling clouds also as well as super hunk corner bass traps. Thank you all so much! Hayden

Before I put wood to nail, does anyone else have any other opinions on this build?

It would be good to see the entire SketchUp model fleshed out in more detail, with accurate dimensions, to be able to comment more completely. With only that basic floor outline, it's hard to say if it is a good design or not, or what could be done to make it better. In your original post, you asked about possible ceiling angles: 12° seems to to be the general recommendation for getting rid of flutter echo, so if you can angle the ceiling that much, it would help. However, that's the live room you were talking about, so angling might or might not be necessary, and flutter echo can also be dealt with absorption and/or diffusion (assuming the room is big enough for diffusion to be an option). Another option might be to slope only part of the ceiling and leave the rest flat with treatment. Live rooms have more options for shape / treatment than control rooms do.

Further to that, how would be the best way to angle the walls in that space so that it works out at the right total room volume, etc? I thought of originally having 2 of the 4 walls angled to eliminate flutter echo, (even having one wall come to a 'v' shape in the middle) etc but I'm not sure what method to use or where the walls should be placed. Any help here would be greatly appreciated!

The "V" option is a good one, as it does not eat up so much space. To deal with flutter echo between walls you can angle opposite walls 6° each (total of 12°). It might be an idea to angle two adjacent walls as well, to deal with flutter in both directions. Or once again, angle one wall and use diffusion / absorption on the adjacent wall.

I recall that if you want to alter standing waves in your room, you need at least 12 degree angle, otherwise it's not effective.

The 12° angling is the minimum for flutter echo, not standing waves. Splaying walls does not eliminate standing waves (room modes): it just moves them to a different frequency / location in the room. One point I did notice: there seems to be some kind of garage door or something on the top wall in your original diagram: What are your plans for sealing that? You didn't mention anywhere how much isolation you need, but I'm assuming that you need a fair amount, so that door will be critical for attaining decent levels. Anyway, if you post your updated model as it is now, then I'll take a look to see if I notice any potential issues. - Stuart -

Hey Stuart, Thanks heaps for the reply! I'll get to work tonight trying to get a more accurate model of the space I'm going to be working in and the idea of what I want to build. I'll do a bit of searching to find out how to get accurate measurements as well! As for the garage door, I was planning on Panelling it up with MDF/Plywood and insulating it (plugging gaps with expanding foam) as isolation in the control room isn't critical (very quiet neighbourhood, I monitor reasonably quietly. How would you approach sealing it up? The live room will be a true room within a room with double gyp board facing inwards, then unfaced acoustic insulation in the framing - totally decoupled from the external structure (apart from the floor) so hopefully that will be reasonably well isolated. The control room will only be a single layer of gyp board and regular insulation. Thanks heaps! Hayden

Hi again, I have redone the Sketchup model with more accurate measurements. I have attached the no frills model to give an idea of the internal space I am looking to create. The 'V' wall is 2 8 degree angles forming a point, but don't know if this will work/if it's worth it. The ceiling hasn't been included to see inside but the heights of the internal walls give you the idea. I know the ceiling angle isnt worth much from a flutter echo point of view, but just want to use every inch of space upwards that I can. If anyone has any feedback I'm really keen to hear it - I've wrecked everything and insluating the external structure today! Thanks a million guys

Hey amatueraudio, Been reading through your thread...really love the size of the live room! However, do you not have plans for allowing sight lines between the two rooms? Seems like you might regret this later considering what a great sized space you have to work with. Even something simple could go a long way and not eat your budget too much (I understand laminated glass is expensive though). Just curious what your thoughts were on that. Looking forward to watching the progress! cheers Trevor

Hey Trevor, Thanks for having a look through! It's funny you should mention that I was thinking about this yesterday. The line of sight is tricky because of that storage gap between the two rooms. The gap serves two purposes, one to have unintrusive storage and the other to bring the room into a good ratio. I know a glazier who would be keen to work on this project so that shouldnt be too expensive, the question is placement and (if placed in the listening zone in the control room) how to treat it to keep the listening space as accurate as possible. I will do a little reading about it and see what I can find, cos you may be right - having a line of sight might help with keeping energy up, etc. Thanks heaps for your thoughts! Hayden

The line of sight is tricky because of that storage gap between the two rooms.

Gotcha...I didn't realize that space was for storage! Definitely a good idea to have storage in a studio so I would not sacrifice that aspect. However, I do think there is probably a way to have both storage space and sight lines. Have you tried moving the live room over towards the control room and using the space created on the left as a storage space? It would be equal in size to what you have now. You could still route cables around the air gaps of the live room if you had planned to put noisy mechanical equipment in the storage space. (that would be a simpler fix to your design...however, I've attached a completely different approach below) That would make it much more possible to place a double window between the two rooms. And since you say you have access to someone willing to help you out a bit, it would definitely be advantageous to incorporate some sight lines into the design. You will be glad you did! :D

having a line of sight might help with keeping energy up, etc.

You betcha! And not only that, but it makes for a much more enjoyable and professional space altogether! Sight lines are a huge part of most professional studios. Some of the best in the world literally have "walls" of glass! Such as this John Sayers design... Belair Studio Whatever you can afford would be well worth the effort IMHO. So yea, start playing around with the storage space and see what you can come up with. Also, it's hard to tell what's going on in the control room...are you planning to soffit mount the speakers? If done properly, soffit mounting is far superior to free standing monitors. Also, have you thought about shooting for an RFZ in the control room? Not completely necessary, but it can be far superior to a standard rectangular room if done properly. I've attached a rough RFZ design below...however I will say, there are many ways of achieving a "reflection free zone" in the space you have available. I just tried to keep it somewhat similar to what you had while also providing some sight lines. With this design, your first reflection would reach the ears approximately 17.5ms after the direct signal hits the ears (pretty darn good!). Considering the reflection has to hit the back wall (where you would place bass hangers/absorption) the signal would also be brought down in level (also good!). This type of design would be far superior to a rectangular control room where the first reflections are at the side walls between the mix position and monitors. Also, to keep the control room from getting too wide (and eating into your live room), there are two different angles at the front of the control room. The first one is pretty steep at 20º but only lasts for about 16" of wall space. The second one is only 12º and lasts for 4'3" which is where the laminated windows could be. I did this to achieve the RFZ within a narrower space. I'm sure it could be done even better but this is a start at least. :wink: No worries if you don't end up going the route of an RFZ...I just wanted to try my hand at a layout within the space you have available. Hopefully it gives you some further ideas regarding design possibilities. :) Note: I did not add drywall layers to the studs because I did not know what you were planning to use for isolation. This will change things very slightly. All of the walls are 3.5" to represent standard 2x4's. Also, in tandem with your design, the only "room within room" is the live room. I have to say that, like you, at first I didn't think I would need the extra isolation from external noise in my CR, but Stuart eventually convinced me otherwise. Are you REALLY sure there are NO possible noises that would enter your control room during a session?? Thunder, cars, big ass trucks, dogs barking, planes, domestic disputes next door, tractors, cows...??? :roll: you get the idea :lol: Mixing in a not so quiet room is never that much fun... Disclaimer: This design needs to be looked over by someone with more experience than myself in case there are problems in my thinking... Ahhh I think that's it for now...hope it was helpful. cheers Trevor Link to Sketchup file (dropbox download)

Forgot to mention...all of the acoustic treatments that I drew in are not accurate to what the rooms might need. It's just a rough guess. The dark grey areas are absorption panels/bass traps and the brown areas are slat resonators. Honestly, none of this can really be determined on an exact level until the room responses are measured...which means the rooms have to be built first! :D

Hey Trevor! Firstly I gotta say - wow man, thank you so much for the time and effort you put into this. I tell ya, there's a lot of love comin at you from the bottom of the world right now! To answer your questions:

Shybird wrote:

Have you tried moving the live room over towards the control room and using the space created on the left as a storage space? It would be equal in size to what you have now.

Yeah I'm totally open to that, I could still have that 'v' wall over the left-hand side and just double--door on the right. You're totally right, that'd allow a line of sight pretty easily (even if the corresponding part of internal control room wall is angled at 8°-12°)

Also, it's hard to tell what's going on in the control room...are you planning to soffit mount the speakers? If done properly, soffit mounting is far superior to free standing monitors.

I was thinking about this, I have 7" monitors (BM5a MKii) and dont know whether their size/design would lend well to soffit mounting? Totally open to it though.

Also, have you thought about shooting for an RFZ in the control room?

Yeah, you can't see it in the control room but I was looking at angling the walls for around half the room covering the mix position. It was going to simply be angling the side walls at 8° away from each other back towards the rear of the room (as well as potentially going with a 12° ceiling slope from the mix position to the rear of the room).

Are you REALLY sure there are NO possible noises that would enter your control room during a session?? Thunder, cars, big ass trucks, dogs barking, planes, domestic disputes next door, tractors, cows...???

I'm confident on this one. I live in a pretty quiet back section in a quiet suburb away from main roads, not under any flight paths, no train tracks, etc. and we have about one thunderstorm a year. I think the only domestic dispute would be caused by me asking for the money from my fiancée to build a room-within-a-room for the control room! Fortunately I'm building the live room before moving on to the control room, this gives me time to take in all the brilliant advice! I'm definitely going to move the storage over to the left and move the v wall there as well. Also going to shoot for the line of sight as well! Here's a link to the more fleshed-out model I did to get an idea of what I was going for if you're interested: https://www.dropbox.com/s/qw736cggv8o6tfd/traps.skp Thanks so much again!

Hey amatueraudio... Sorry for not checking in for awhile...hope everything is going well. A couple things I would like to comment on:

I was thinking about this, I have 7" monitors (BM5a MKii) and dont know whether their size/design would lend well to soffit mounting?

From everything I've been told, by Stuart and many other professionals here on the forum, almost all monitors can benefit from a soffit configuration. Now in some cases (possibly yours), I would imagine you might be spending more on the soffits than the monitors are even worth :shock: ...so that is something you would have to think about. However, I can assure you that even your monitors will provide a more accurate sonic reproduction in a proper soffit in comparison to a free standing setup. Do they have controls on the back for adjusting the bass response? That would be necessary.

Yeah, you can't see it in the control room but I was looking at angling the walls for around half the room covering the mix position. It was going to simply be angling the side walls at 8° away from each other back towards the rear of the room (as well as potentially going with a 12° ceiling slope from the mix position to the rear of the room).

Ok, that's great that you have some angles, but have you ray-traced to insure that your angles are actually providing a proper "reflection free zone"? There are no "magic" angles...ray-tracing is an absolute must so that you know exactly what is going on. The "magic" of 12º is really only applicable to flutter echo (either one wall has to be at least 12º or two opposing walls at least 6º each). However, that only helps to eliminate flutter echo, but is not the same thing as an RFZ.

Fortunately I'm building the live room before moving on to the control room, this gives me time to take in all the brilliant advice!

OK I really REALLY hope I'm not too late...you really shouldn't build anything until you have complete designs for EVERYTHING!!!!! The only time studio building becomes a complete and utterly irreversible disaster is when people get trigger happy with their hammers and nails in hopes that they can just "GET ER DONE"...that is a VERY unwise path to go down and makes for way more headaches, more wasted money, and a final product that really might not do what you want it to do. If the design phase is done properly, there would be no way you could just go ahead and build the live room before the control room is designed and ready to build too!! They go hand in hand. You really can't have one before the other...and honestly, the control room design is more crucial to have figured out before the live room design since the control room has so many more issues to take into account. The live room kind of DEPENDS on how the control design turns out. Am I making sense here?

Also going to shoot for the line of sight as well!

Definitely a good idea!! :D Once again, sorry for such a delayed reply...I hope everything is going well in your design process. Cheers Trevor

Hey guys, Had an alternative design idea for the live room. Instead of having the far wall coming to a 'v' point, simply having the far wall angled at 12 degrees. Since this is built inside the isolation shell, I'd basically have the wall as slats over Rockwool. My hope is that the hard surfaces reflecting at the angle will reduce the flutter echo between this set of paralell surfaces as well as giving the room a little 'character'. The openings between these slats would hopefully help with some bass control (a la Helmholtz Resonator) as well as prevent an air lock (definitely want to avoid three leaves at this end of the room). Would also look to put a door at the wider end of the space created at act as storage. Big question is, which of these two do you guys think would be a more effective way of dealing with this set of parallell surfaces? I wonder if the 'v' wall with 2 sets of 6 degrees coming to a point will be less effective than the single 12 degree angle in the pic beI will be treating the ceiling with diffusion at one end and absorbtion on the right-hand third of the ceiling space. The two paralell walls length-wise will have flutter dealt with by 1D QRD's mounted in the middle, taking up 90% of one long wall. Appreciate any ideas before diving in here... Really want to do the right thing. Thanks heaps!

Had an alternative design idea for the live room

That seems to wasting a lot of space in the top left corner. And while the angled slot wall will help with flutter echo, it won't do anything for the modal response of the room, since the shape of the true inner leaf is still a rectangle. The slot wall is just treatment inside that, and does not affect the hard boundaries of the room.

The openings between these slats would hopefully help with some bass control (a la Helmholtz Resonator)

Well, yes, that is a slot wall, so it could help, but the depth seems way too large to me. What size slats and gaps are you using there, and what frequencies are you tuning the slots too? Slot walls are more useful for broad-band mid-range treatment, and usually don't work effectively enough at very low frequencies to be useful.

as well as prevent an air lock (definitely want to avoid three leaves at this end of the room).

I'm not sure I understand what you are saying: What is the relationship between an air lock and a third leaf? They are two different, unrelated things. A third leaf is just a large relatively massive panel over an air gap. The gap does not have to be sealed in order to have a three-leaf effect. Air is plenty springy enough to still get the effect without the air gap being sealed.

Would also look to put a door at the wider end of the space created at act as storage.

That will need to be sealed very carefully. Unlike a 3-leaf system, a Helmholtz resonators DOES have to be sealed air-tight in order to work. So the rear, sides, top and bottom of that space behind the slats must be sealed totally air tight, and so must the door. If you open the door, the entire slot wall will stop working. And that won't work as a storage space either: if you put things inside, then you re-tune the slots to different frequencies, so you will change the room response. Each time put something inside that "storage" area, or take it out, the room response will change.

Big question is, which of these two do you guys think would be a more effective way of dealing with this set of parallell surfaces?

What is the issue that concerns you with the parallel surfaces? If it is just flutter echo, then that can be treated in other ways. And if it is the modal response of the room, then that wall won't make any difference since it does not change the room boundary, as it is a slot wall. - Stuart -

Again, thank you SO much for your input here. Having someone coming back with your level of insight is just so valuable and I appreciate it very much. To answer your questions:

Soundman2020 wrote:

That seems to wasting a lot of space in the top left corner. And while the angled slot wall will help with flutter echo, it won't do anything for the modal response of the room, since the shape of the true inner leaf is still a rectangle. The slot wall is just treatment inside that, and does not affect the hard boundaries of the room.

The top left corner will act as storage for drum/guitar cases etc. I agree there are probably more effective ways of having storage, but I figured this might have been a 'two birds, one stone' sorta thing with the angled wall. With the modal response, the dimensions of the true inner leaf calculate out to be fairly decent down to 60hz.

Well, yes, that is a slot wall, so it could help, but the depth seems way too large to me. What size slats and gaps are you using there, and what frequencies are you tuning the slots too? Slot walls are more useful for broad-band mid-range treatment, and usually don't work effectively enough at very low frequencies to be useful.

Based on pure room mode calculations (23L x 14W x 7.9ft H), I'm going to need to work on 30-60hz. I'd be looking to measure the room before actually tuning anything. I was hoping that the sheer size of the resonator would make more effective at lower frequencies. Based on what you're saying I might actually be better off just keeping that wall flat and using combinations of large membrane bass traps for low end control and diffusion to take care of lengthwise flutter echo.

I'm not sure I understand what you are saying: What is the relationship between an air lock and a third leaf? They are two different, unrelated things. A third leaf is just a large relatively massive panel over an air gap. The gap does not have to be sealed in order to have a three-leaf effect. Air is plenty springy enough to still get the effect without the air gap being sealed.

Did a bit of reading on this, please forgive my ignorance! I meant more that I was trying to avoid creating a three-leaf system by removing a lot of mass (hence the gaps in the slot wall) meaning that I could reflect some sound back into the room (hard slats) but at an angle preventing flutter echo.

That will need to be sealed very carefully. Unlike a 3-leaf system, a Helmholtz resonators DOES have to be sealed air-tight in order to work. So the rear, sides, top and bottom of that space behind the slats must be sealed totally air tight, and so must the door. If you open the door, the entire slot wall will stop working. And that won't work as a storage space either: if you put things inside, then you re-tune the slots to different frequencies, so you will change the room response. Each time put something inside that "storage" area, or take it out, the room response will change.

THAT is crucial - thanks a lot for pointing that out. Problems from having the storage area not isolated from the resonator seems so obvious now that I think about it - but a big design oversight that could have made it to the construction phase. Thanks again.

What is the issue that concerns you with the parallel surfaces? If it is just flutter echo, then that can be treated in other ways. And if it is the modal response of the room, then that wall won't make any difference since it does not change the room boundary, as it is a slot wall.

[/quote] Definitely flutter echo is the concern here. I've worked in a few rooms this size and not liked them to be honest. Untreated, flutter echo is terrible and the room is very messy and undefined, acoustically. With superchunk trapping and 703 panels on even one wall, the room became rather lifeless. I really want to try and avoid absorption on walls wherever possible as I find that a lot of absorption kills the character of the room very quickly. The ceiling height is a hair under 8 feet so absorption on the ceiling is the only real option - so already a lot more absorption going on than I'd like ideally. Angling the wall I hoped to eliminate flutter echo between the west-east walls while still keeping some of the vibe. The room is 23 feet long I'm guessing that diffusion on one wall would be OK to avoid flutter echo while giving it a somewhat 'live' feel. The room is going to be used predominantly for tracking drums and guitar cabinets. I'd really appreciate any ideas here - the only thing that can't be changed is the placement of the wall sepeating the live and control rooms and the height of the rooms. Other than that I'm still at a stage where anything is a possibility!

With the modal response, the dimensions of the true inner leaf calculate out to be fairly decent down to 60hz.

I¿m not sure I'd agree with that! Did you take a look at the Bonello graph for those dimensions? That ratio also fails one of the three critical tests used by the BBC, ITU, EBU and others for predicting if a room is usable as a studio.

Based on pure room mode calculations (23L x 14W x 7.9ft H), I'm going to need to work on 30-60hz.

Actually, there's nothing at all in the range 30 - 40 Hz, one at 40, a big gap, then a pair almost together at 47 Hz and 49 Hz, and the next one is at 63 Hz. I would take a close look at that, and see if you can't find a better ratio.

I was hoping that the sheer size of the resonator would make more effective at lower frequencies.

Not necessarily. Each slot is tuned to a specific frequency, or a range of frequencies if the depth varies. On the other hand, each mode peaks at a specific location in the room. If the slot that is tuned to that frequency happens to fall at a null for that mode, then nothing happens. It would only be effective if the slot is located at the pressure peak for the mode. So you'd have a lot of work to do to figure out where in the room mode peaks, and then try to get a slot close to that location and tuned to the right frequency. If not, then you won't be treating the modes. Yes, size does matter (!) here: In general, a larger acoustic device will have more effect than a small one, but the caveat is: it needs to be in the right place. For example, you could make your entire rear wall a slot wall, tuned to 71.5 Hz, thinking that you had found the perfect way to treat your 0,0,1 axial mode... but it would do practically nothing at all, since that is a vertical mode, happening between the ceiling and the floor, not involving the rear wall. So even though the device would be very effective, in reality it would be useless due to being in the wrong place. Slot walls and all other pressure-based devices are hard to position, since they have to go at the pressure peaks, which are not easy to locate. Absorbers, on the other hand, are easy to position, since, even though they are velocity-based, they will always be most effective if located in corners as that is where all modes must terminate. If you space an absorber away from a wall or across a corner, then it is always effective, since you are guaranteed to be hitting at least some of the velocity component of ALL modes, not just some of them. Slot walls are more useful for general treatment, not specifically for modes. So a slot wall in your room would actually be a great idea, but built properly and tuned to useful frequencies, but in the mod range. I'm not even sure that you would be able to tune it effectively to the frequencies you mentioned for bass trapping: Did you figure the dimensions of the slot, slat, gap and depth that you would need for 24, 40, 47, 49 and 63 Hz? Sounds like that would be rather hard to do with a slot wall...

Based on what you're saying I might actually be better off just keeping that wall flat and using combinations of large membrane bass traps for low end control and diffusion to take care of lengthwise flutter echo.

I'm not a big fan of diffusion, to be honest. Yes, diffusion does have its place, but the distances you need to be able to use diffusers are so large as to make them impractical for small rooms and low frequencies.

Definitely flutter echo is the concern here. I've worked in a few rooms this size and not liked them to be honest. Untreated, flutter echo is terrible and the room is very messy and undefined, acoustically. With superchunk trapping and 703 panels on even one wall, the room became rather lifeless.

Not if done correctly! Yes, I agree that flutter echo is unpleasant. In fact, it can make a room unusable. But if you have been in a room with superchunks and absorption on the walls, and the room sounded dead, then the room was badly done. The idea is to design it to be live. That kind of is part of the meaning of "live room"! So a live room that sounds dead is a misnomer to start with, and badly designed. Clearly, it has way too much absorption in the high end. But that could easily be fixed by placing 6 mil plastic over the superchunks, and by locating the side absorbers correctly, and covering the correct amount of surface area. There are equations and methods for figuring all this out, so all I can suspect is the rooms you have been in that sounded so bad, were not designed correctly by someone who used the equations and techniques, and then tested and tweaked the room. About the only thing worse than a resonant room with lots of flutter is a totally dead room. Neither is much use, so the trick is to avoid all that, design it correctly, build it correctly, testing all along the way, and tweaking as needed at each step.

I really want to try and avoid absorption on walls wherever possible as I find that a lot of absorption kills the character of the room very quickly.

Once again, I agree that absorption DONE WRONG on the walls can kill it. Absorption done right is the goal. The Sabine equations and EBU guidelines are very useful here: So is REW, for testing and tweaking.

The ceiling height is a hair under 8 feet so absorption on the ceiling is the only real option - so already a lot more absorption going on than I'd like ideally.

I doubt it! :shock: To achieve good acoustics, that room needs 556 sabins of absorption. The ceiling area is 322 square feet, so even if you could by such a thing as "perfect absorption", the ceiling only accounts for 57% of the total absorption you need. Probably more like 40%, in the real world with real absorption. You are still going to need another couple of hundred square feet of absorption on the walls. If you do superchunks in all four vertical corners, that would add another 100 or so sabins, but you are still about two hundred short. Two full panels (4' x 8') of 4" 703 on each of the four walls, staggered to NOT be opposite each other (in other words, each panel faces blank, hard wall on the other side) would get you in the ball park. And I would cover the superchunks with plastic anyway, so they would be responsible for less absorption in total. Or you could do one of the walls as a slot wall, slightly angled, with more absorption on the opposite wall, so you have one side of the room a bit more live, and the other a bit more dead. I would also put a few gobos in there, so you can modify the acoustics as needed, either locally or globally as needed, by wheeling them around and exposing either the hard side or the soft side, as needed. You could even get fancier still, by building variable acoustics into the walls, such as large hinged or sliding panels that can be moved to reveal a lot more absorption, or a lot more hard surface. There are many options for a live room. But obviously, as you say, a "dead" live room is a pretty lousy place to record, so it needs to be designed well. - Stuart -

Stuart, you are THE MAN! Thank you so much, youve saved my skin again on this one.

Soundman2020 wrote:

I¿m not sure I'd agree with that! Did you take a look at the Bonello graph for those dimensions?

I totally made a fundamental mistake there - I looked purely at weightings, etc. and totally ignored the importance of the Bonello graph! You've saved me again here, thanks! I’ve revisited the ratios here, and given that I’m stuck with a width of 14.76 and a height of 7.81, the best length seemed to be 19.03. This means I have a few feet at the end of the room that I could either: A.) have as storage provided I could maintain an isolation shell or b.) keep the isolation shell at the original length and build an internal wall inside the isolation shell to bring the length in to 19ft. This means not having an extra door In the isolation shell, however This would create a 3 leaf at one end, but it would need to be a hard boundary to improve the modal response. Here's the Bonello:

Not necessarily. Each slot is tuned to a specific frequency, or a range of frequencies if the depth varies. On the other hand, each mode peaks at a specific location in the room. If the slot that is tuned to that frequency happens to fall at a null for that mode, then nothing happens. It would only be effective if the slot is located at the pressure peak for the mode. So you'd have a lot of work to do to figure out where in the room mode peaks, and then try to get a slot close to that location and tuned to the right frequency. If not, then you won't be treating the modes.

Slot walls are more useful for general treatment, not specifically for modes. So a slot wall in your room would actually be a great idea, but built properly and tuned to useful frequencies, but in the mod range. I'm not even sure that you would be able to tune it effectively to the frequencies you mentioned for bass trapping: Did you figure the dimensions of the slot, slat, gap and depth that you would need for 24, 40, 47, 49 and 63 Hz? Sounds like that would be rather hard to do with a slot wall...

Yes that’s certainly beyond what I’m capable of… and perhaps beyond what a slot wall is capable of as well!

I'm not a big fan of diffusion, to be honest. Yes, diffusion does have its place, but the distances you need to be able to use diffusers are so large as to make them impractical for small rooms and low frequencies.

Fair enough! I've heard it do amazing stuff to really small spaces when tuned to mid-high frequencies. I know a guy who built a series focussed around the 1k mark and it was magic for making drums 'breathe' somehow. The room was already good, but adding this 1D diffusion on one wall about 10 feet from the kit made a massive difference to what the kit was doing. I would wait til I had actually measured the room and (more importantly) heard it. Before going on this.

Not if done correctly! Yes, I agree that flutter echo is unpleasant. In fact, it can make a room unusable. But if you have been in a room with superchunks and absorption on the walls, and the room sounded dead, then the room was badly done. The idea is to design it to be live. That kind of is part of the meaning of "live room"! So a live room that sounds dead is a misnomer to start with, and badly designed. Clearly, it has way too much absorption in the high end. But that could easily be fixed by placing 6 mil plastic over the superchunks, and by locating the side absorbers correctly, and covering the correct amount of surface area. There are equations and methods for figuring all this out, so all I can suspect is the rooms you have been in that sounded so bad, were not designed correctly by someone who used the equations and techniques, and then tested and tweaked the room. About the only thing worse than a resonant room with lots of flutter is a totally dead room. Neither is much use, so the trick is to avoid all that, design it correctly, build it correctly, testing all along the way, and tweaking as needed at each step.

Once again, I agree that absorption DONE WRONG on the walls can kill it. Absorption done right is the goal. The Sabine equations and EBU guidelines are very useful here: So is REW, for testing and tweaking.

I have a few materials here, MHoA, Rod Gervais’ brilliant text, as well as Newell’s Recording Spaces, etc but would love to know if you have any suggestions on good resources on this as I don’t feel I understand this well enough. How much absorption and where to place it is obviously important to understand thoroughly!

To achieve good acoustics, that room needs 556 sabins of absorption. The ceiling area is 322 square feet, so even if you could by such a thing as "perfect absorption", the ceiling only accounts for 57% of the total absorption you need. Probably more like 40%, in the real world with real absorption. You are still going to need another couple of hundred square feet of absorption on the walls. If you do superchunks in all four vertical corners, that would add another 100 or so sabins, but you are still about two hundred short. Two full panels (4' x 8') of 4" 703 on each of the four walls, staggered to NOT be opposite each other (in other words, each panel faces blank, hard wall on the other side) would get you in the ball park. And I would cover the superchunks with plastic anyway, so they would be responsible for less absorption in total.

I can actually build panels into the ceiling in such a way as almost all of it would be covered, if that would be best. I’ve heard that absorption on a low ceiling can make a room sound ‘taller’ which is very appealing. I suppose once the ceiling is taken care of, adding and removing panels and letting the ears be the judge is the next move. I’d definitely cover the bass traps in plastic if I indeed went with superchunks rather than larger membrane bass traps.

Or you could do one of the walls as a slot wall, slightly angled, with more absorption on the opposite wall, so you have one side of the room a bit more live, and the other a bit more dead.

This was exactly the sort of idea I’d love to go with. How slight an angle would work well, and where would it be best placed in the revised room size?

I would also put a few gobos in there, so you can modify the acoustics as needed, either locally or globally as needed, by wheeling them around and exposing either the hard side or the soft side, as needed.

[/quote] Yeah, that’s definitely on the cards. I figured I’d hear what I was dealing with before deciding on how many/what size etc. Thanks so so much again, you're making a world of difference here!