Live room treatment.

Hello from New Zealand! My friends and I are building a recording studio inside a double garage plus side room. We are at the stage where the live room construction is finished and acoustic treatment is being pondered. Unfortunately the local library is a bit short on the subject and we don't know what the hell we're doing! The room will be primarily used for pop/rock and jazz drums and also various acoustic instruments from the same genres. Its sounding good at the moment but the reverb is messy and long at high frequencies. I've attached a sketchup drawing with dimensions and info about materials. The drawings missing an approx 1.4m by 1m double glazed window in the middle of the 5760mm wall. Also attached a couple of older pictures of the live room. If anybody could recommend the next step I should be looking at or fire some critique at the designs it would be much appreciated. Thanks! Arie.

Hi Arie, and welcome! There's a lot of information that you didn't provide that might help folks to get a better idea of what it is you are trying to do. Maybe you could complete that. But I did notice a couple of things that caught my attention. From your description on the SketchUp image, I understand that all of the inner-leaf walls and the ceiling are single stud frames with a single layer of 13mm gypsum board on them? Is that correct? If so, then I guess that good isolation from the surrounding rooms is not very important for you? Or are there actually more layers of GB on there? Also, it seems like you built your floor on a wooden frame, with a thin plywood subfloor, without any insulation or mass filler in the cavity. Is that correct? Is there a good reason why you did that? My guess is that a structure like that will resonate quite badly at certain low frequencies. It's basically a drum head that you built. I'm not at all sure that your room will work as a live room like that, especially if you are talking about drum kits. Hammering away on a drum kit while it is sitting on a 13mm plywood subfloor over a 3 inch cavity, does not sound like it will do anything nice acoustically. If the cavity depth is what I suspect (around 3 to 4 inches), then the resonant frequency of that floor is almost exactly the same as that of the kick drum.

Its sounding good at the moment but the reverb is messy and long at high frequencies.

How can it be sounding good if you have serious resonance problems? :) It shouldn't have those problems anyway. The predicted overall RT-60 for a room with those dimensions is around 270 ms, which is reasonable. Your worst problem will be in the low end, where the RT-60 will be over 500 ms, but you say you have ringing in the high end? Once again, predicted times for those dimensions for everything above 3.5 kHz is in the range around 170 to 370 ms, which is long but not fatal. You shouldn't be getting flutter echo in there either, since you have non-parallel walls. How about if you measure the actual response of the room, and post a waterfall plot so the experts here can look at it? But before you do anything else, you might want to reconsider what you have done already, because it doesn't sound like it will be helping your acoustics much. It's not too late to fix it, either. - Stuart -

Hey Stuart! Much thanks for the reply. I will try and provide as much info as possible... I am building a studio with a live room, control and vocal booth. Ideally, what I want is a good sounding, reverberant general purpose live room, isolated as much as possible from the control room. External isolation is not key (but would still be nice!) as my neighbours are slightly deaf. Yes, the angled inner-leaf walls and outer walls are single stud frames with 13mm gib and insulation. The wall measuring 5200mm is single stud double 13mm gib (staggered joint? Hope thats the correct term...), and the wall measuring 5760mm divides the live room from control room and is essentially 2 layers of 13mm gib divided by insulation on a single stud frame with a 6x2 lentil (sp?). The spaces between the angled walls and original walls are filled with leftover carpet and excess insulation. The control room is the only room surrounding the live room. Isolation would be nice! Any suggestions regarding that are more than welcome. Regarding the floor, the cavities are stuffed with old carpet underlay. Do you think this is adequate? I'll research how to do a waterfall plot... Hopefully I'll get it up in a coupla days! Cheers, Arie.

One of the best ways to increase the usefulness of this room is to remove the flimsy plywood stage floor. You have a concrete slab underneath it that is already damped by the earth it lays on and is far far heavier and more solid then the pop-up cavity you have constructed. Like Stuart mentioned, it can act like a drum head and vibrate making as much noise as everything else around and on it. The concrete will take a lot more to excite it...it's the better choice for a floor. Good luck, Brien

Hey Arie. Glad to be of service!

I am building a studio with a live room, control and vocal booth.

OK, maybe you could complete your SketchUp model with the positions of all of those, in 3D, with accurate construction details of how your walls, ceiling and floor are built. The reason I suggest you do that urgently, is because from your descriptions and the photos, I strongly suspect that what you are doing is not going to accomplish what you are hoping it will do. For instance, I see what look like roof trusses inside your "finished" room, which implies that your outer leaf and inner leaf are mixed up somehow, and even worse that they are coupled. You also say: "wall measuring 5760mm divides the live room from control room and is essentially 2 layers of 13mm gib divided by insulation on a single stud frame". Well, that wall is not going to provide much isolation between the rooms. My guess would be in the region of an STC 30-something rating, which is pretty much the same as a normal house internal non load-bearing wall. The kind you'd find between the living room and dining room for example, or between two bedrooms. The level of isolation from that wall is not going to be enough to be able to mic a drum kit in the live room (LR) and be able to hear exactly what the mics are doing on the monitors in the control room (CR). There will be so much bleed of the drums coming through the wall that you'll never be able to be certain of what you are hearing. I'd strongly suggest that you might want to re-think that wall. It should be two separate stud frames, with at least two layers of 16mm drywall on the LR side of one frame, and another two layers of drywall on the CR side of the other frame, and the cavity in between filled with insulation. In other words, going from one side to the other of the entire wall, you would have: two layers of 16mm drywall - stud frame - cavity with insulation - stud frame - two layers of 16mm drywall. That should get you an STC of at least 60, which means that, subjectively, it will be about eight times quieter than what you have now.

The spaces between the angled walls and original walls are filled with leftover carpet and excess insulation.

The carpet is not doing anything useful for you, and in fact is probably doing some harm. It is most likely creating some amount of flanking between the two leaves, if it is packed in tight and touching both sides. Ordinary carpet doesn't have a lot of uses acoustically (although it does have some), and stuffing a wall with is isn't one of them! Ditch the carpet. Also you say that the wall is filled with "excess insulation". That sounds like you just put a bit of leftover stuff in there. In reality, the entire cavity should be filled with insulation, either mineral wool or fiberglass (the usual pink fluffy stuff). At the very least you need a four-inch (12cm) depth of fiberglass that completely covers the surface of one leaf of the wall, between the studs.

Regarding the floor, the cavities are stuffed with old carpet underlay. Do you think this is adequate?

Probably not. While that might damp the cavity slightly, it isn't really the damping that is the problem. It is the fact that you have a cavity with a thin membrane over it. Your floor is basically a resonant chamber, and it appears to be tuned to roughly the frequency of a kick drum. That room is going to be extremely "boomy" when you play the drum kit in there, and probably also the bass guitar. If the floor resonates at, say, 80 Hz, then it will also resonate at the harmonics of 80 Hz, at lower levels. So you will resonance problems at 160 Hz, 240 Hz, 320 Hz, etc. From your description it seems that each of the walls has a different construction technique and a different level of isolation. But the sound waves don't care about that, and they'll just take the easiest path in or out. Basically, if you have three walls the roof and the floor all with STC 60 rating, and one wall with STC 30 rating, well that means that all you get is STC 30. You wasted time, effort and money on the other fives sides. So if you have a great wall directly between the CR and the LR, but the side walls and the ceiling are poor, then sound will just "flank" around your fantastic wall as if it wasn't there. A chain is only as strong as the weakest link. Studio isolation is only as good as the weakest wall. You should build your studio so that all of the walls have the same level of isolation, which usually(but not always) implies the same construction method all around. I'm absolutely certain that what I'm telling is not making you happy at all, and I really hate to be the bearer of bad tidings like this, but from what I can see, your room is not going to accomplish what you are hoping it will accomplish, due to multiple questionable design issues. I am sincerely, deeply hoping that you are not like many other folks that I've seen pass through this forum in a similar situation to yours, who don't like what they are told here, think the posters here that try to give them good advise are just smart alecs who are out to ruin their day. Those builders can't seem handle the fact that they might have screwed up, and that what they though was a great plan for their wonderful studio, was actually not so great after all and twas turning into acoustic garbage. I've only been on this forum for about six months, and I'm no expert, but during that time I've seen a few folks come along, post like you did asking for advice on one area of their build, only to learn that there are serious issues in other areas that need addressing first. And then they never post again. I can only assume that they were not prepared to do what it takes to correct the problems, and I always wonder just how bad their studios ended up. I'm hoping that you are not like that. The big advantage you have is that, in your case, you are not too far advanced yet, and going back to fix your problems at this stage would only be sad and disheartening, but it would not be too much of a major disaster, which it WOULD be if you get to the final finished studio and then find that it is an acoustic nightmare. Thankfully, others do heed to the advise they get here, do knock down walls, ceilings and floors they just finished, do fix their problems, and do end up with successful studios. I hope you are one of those, and not one of "the others"! At this point, continuing with your build without fixing the issues that seem to be there from what you already posted, would be foolish, IMHO. Adding acoustic treatment would be wasted money, since it is not going to fix the underlying problems. You would probably end up adding so much treatment in a misguided attempt to fix the unfixable, that you'd waste a huge amount of money on that, and still end up with a studio that sounds like the inside of dumpster full of scrap carpet, with a kid's toy drum set inside... Better to spend that same money, plus some time and tears to fix the underlying issues first, THEN worry about treatment. So, if you really are concerned about building a good studio that actually can be used for what you want, then I sincerely hope that you at least take the time to build a detailed, accurate SketchUp model of what you have at present, for the experts here to look at and tell you if you actually do have the problems that i suspect you have, and if so, how to fix them. Sorry if I come across as a jack-ass or smart-alec (you wouldn't be the first to call me that!), but I like to call it like I see it, and I only hope that others here will do the same for me in my build. Folks here tend to be like that. If they see you just did something dumb, then they'll tell you: "Did you just do ZZZZ? That was really dumb!". And that arrogant attitude issue is exactly why I'm here, and exactly what I want for my build! If I do something stupid, then I want to know about it so I can fix it, and I don't care if you bruise my ego or injure my pride when you tell. Just tell, me damn it! Be brutal! Get my attention! That's the kind of friends I want looking over my shoulder as I build, and that's the kind I found here. All that matters is that my studio turns out to be the very best that it possibly can be, so who cares if the comments that got it that way stung my pride a bit? I reckon it's far better that you hear the truth up front, bluntly and to the point, rather than that you carry on blissfully, thinking that you don't have any major problems, and the little ones can be fixed with some patches of carpet on the walls and a few egg crates on the ceiling. So please take what I posted in the spirit that it was intended: Not to criticize what you did, nor to laugh at your mistakes, but rather just to warn you that I think you screwed up with some of what you built so far, with the intention to help you fix it now so that your studio actually does turn out to be a success, instead of an embarrassing catastrophe. To warn you that I'm not 100% sure on how much you screwed up, and how serious it might be, since I'm not a professional acoustician (just an avid learner with a thirst for understanding stuff in order to build my own studio right). But I do know that if you post your detailed, accurate SketchUp model here, and ask questions about it, that you will eventually get really good advise from some of the best studio designers in the business, and your build will be infinitely better for heeding what they say. - Stuart -

Cheers for the replies! I'll measure up tomorrow and attach a better sketchup model. Learned a lot from your post Stuart. Regarding the floor, would it be worth filling the cavities with sand or should I just plop the plywood straight down on the concrete?

For instance, I see what look like roof trusses inside your "finished" room, which implies that your outer leaf and inner leaf are mixed up somehow, and even worse that they are coupled.

Mixed up? They're definitely physically coupled to each other by the roof trusses and concrete floor.

My guess would be in the region of an STC 30-something rating, which is pretty much the same as a normal house internal non load-bearing wall. The kind you'd find between the living room and dining room for example, or between two bedrooms.

Haha, pretty much.

It should be two separate stud frames, with at least two layers of 16mm drywall on the LR side of one frame, and another two layers of drywall on the CR side of the other frame, and the cavity in between filled with insulation.

Ok... thats quite a mission. I see where you're coming from though. Definitely want to hear things through the monitors, not the walls! What do you think would be the best STC rating I could achieve with the single stud wall frame?

At the very least you need a four-inch (12cm) depth of fiberglass that completely covers the surface of one leaf of the wall, between the studs.

. Ah ha, I have this! I suppose I can splash out on some cheap insulation to fill the rest of the gap, but will it be ok with the air gap? All good Stuart, I appreciate the advice. I don't have the time or money to get everything perfect but I'm more than willing to fix the big problems with the studio.

Mixed up? They're definitely physically coupled to each other by the roof trusses and concrete floor.

If the outer leaf and inner leaf are coupled to each other mechanically (excluding the floor), then you have a problem: Your isolation will not isolate well. If there is any solid mechanical link between the inner leaf and outer leaf, then that creates a flanking path for sound to bypass your isolation. That seem to be the case with your build, since your inner leaf walls appear to be connected to your outer leaf trusses.

Ok... thats quite a mission. I see where you're coming from though. Definitely want to hear things through the monitors, not the walls! What do you think would be the best STC rating I could achieve with the single stud wall frame

? With a single leaf stud-frame wall that has a single sheet of drywall on each side and insulation in between, you might get STC-36 if you are lucky. Put another layer of drywall on each side, and theoretically you might make STC-42, once again if you are lucky. Probably more like 39 to 40, in real life. On the other hand, put the exact same two layers of drywall on the outsides of a double stud wall with insulation, an you will get STC-63, which means that it will be more than four times quieter (subjectively), or roughly one hundred times less power transmission through the walls (objectively).

. Ah ha, I have this! I suppose I can splash out on some cheap insulation to fill the rest of the gap, but will it be ok with the air gap?

Yep! Put as much insulation as you can in that air gap, completely covering one of the surfaces. Adding insulation into the gap of a single stud wall will buy you maybe 3 dB of isolation. Adding it to a double-stud wall will get you about 10 dB of extra isolation. Well worth it! - Stuart -

Hey again Stuart, cheers for the reply. Just spent my easter weekend ripping up the floors and filling the cavities with sand. Feels a lot more solid for starters. Got the power on connected as well, and the heaters and lights are on, woo! Haven't had time to update the sketchup model. That and more photos to come... Are there any ways to reduce the coupling without ripping out the roof truss? Thanks.

Hey guys, quick update. Filled the cavities with sand, unfortunately, the ply flexed and compacted the sand making a 'scrunch' noise whenever you stepped on the floor. We ripped it up the 12 mm ply again and put down 20mm pinex, then glued n' screwed the 12 mm down. Far more sturdy now and the room is less 'boomy'. I'll be filling the wall cavities with insulation tomorrow morning. Hopefully it will get us some more isolation because at the moment there is far more noise leakage than I originally thought. It seems a lot is leaking through the ceiling. Does anyone have any tips on ways I can treat noise leakage externally? We have doors in now and I agree that another wall between the live room and control is necessary. Unfortunately I won't be able to tackle it for a while. Also, I've been pressured to take a band in earlier than I wanted to. Are there any other major flaws I should be looking at before I start tracking drums? Included a rough updated sketchup model...

Ah, another quick question... Would it be beneficial to put together some ceiling clouds and bass traps in the corners? I see lots of people using ceiling clouds but their ceilings are parallel with their floors, mine are sloped. Cheers! C_S

Colonel_Sanders wrote:

Are there any ways to reduce the coupling without ripping out the roof truss? Thanks.

Don't rip out the truss build beneath or around it. For best isolation the only physical connection to the outer shell should be the concrete floor. Or in your case a sand filled floor. You will need bass traps!

Definitely won't be ripping of the roof truss! So far I've stuffed one wall insulation. I 'think' it helped, but theres still massive sound leakage through the ceiling. I'm thinking of sticking at least another layer of Gib on it. For basstraps I'm thinking of using 'Pink Batts Silencer' insulation. Will this be as good as the OC703 insulation everyone on here is using? Getting ahold of 703's a no go in NZ. Heres some limited info on it... http://www.pinkbatts.co.nz/images/old_i ... 0Range.pdf Cheers! C_S

Found these as well... http://autexindustries.com/retrieve-file/jaDpvVc.pdf Acoustic panels made by 'autex'. Come in 50mm (2 inch) sizes. Any advice from anyone? Cheers, C_S

Hey Colonel_Sanders Use Roxul 590 in place of owens corning 703 for you bass traps. Available from Forman insulation http://www.forman.co.nz/upload/pdf_documents/ds_039_roxul%20ind%20slab%20590.pdf http://www.forman.co.nz/about_building.php

Hi Colonel - if you put your approximate room dimensions into the reverb calculator http://johnlsayers.com/Pages/Reverb_Calc.htm you will see it matches your observations. The verbtime is longer in the higher frequencies but as you say , because of the angled walls and ceilings there are no resonances as you've observed. Also the 13mm drywall with insulation behind it is acting as a low frequency panel absorber which is why your low end is sounding ok. The floor will be fine - the carpet underlay will suffice and act like any insulation would. Some engineer like drum kits on resonant surfaces so they actually build risers like yours exactly for that purpose ( Bruce Swedien of Thriller fame comes to mind) here's a drum setup of his. I would use the calculator to calculate the surface area of 703 required to bring the high end verbtime down to match the lower frequencies and add it accordingly till you are satisfied.

Thanks for the replies! Wow john, cool tip. My floors no longer resonant though, nice and solid. Cheers luke! They only had Roxul 223 instock, so I loaded up on that and built 4 super chunks for my live room. What other treatments can I add to the room? Its sounding great, but to be honest, I don't know what great sounds like :lol: I'm thinking ceiling clouds over the where the drums will sit, and possibly panels behind the drums on the walls. Any suggestions? Cheers, C_S

I think the ceiling cloud would be a good idea as the ceiling reflections are the closest and shortest. Add that and see how it sounds.

Thanks John. Just got some more rockwool today. Away we go!

Hello again! Got my bass traps, ceiling clouds and wall panels installed and I'm loving the sound of my drum recordings. But now my live room has lost some of the kick ass reverb that it once had, and its a bit stifled. Is there a way to make the live room more live without removing any acoustic panels? Cheers, C_S

You could wrap your bass traps in plastic, to reflect some of the highs back into the room. Or put thin wood veneer over them, to reflect even more highs and mids too. Did you measure the room, to see where you are lacking reverb now? I'd suggest that you should not treat it until you understand exactly what the problem is, then treat ONLY that problem. - Stuart -

famous bands from the 60s and 70s used to record drums on castles with no acoustic treatment. So , theorically, if you want a LIVE room sound, just add some difussion and leave you large space do its thing This is gonna sound contradictory with our way of thinking here and sometimes you gotta break the rules, but a well known producer from the states told me once: If you want attitude and character on a drum sound , leave the room do its thing , If it sounds fucked up, leave it like that, you want it fucked up On my experience basis, you need to listen to the drums first in your room before making decisions. And that don't even count for measuring it with a software! Just listen how your drums sound in that room, and then start making decisions IMHO

Add slats to your bass traps. Or make them reversable reflective/diffusers on one side and absorbent on the other. then you can choose. :D

post some pictures too!!!