one room/mix room design

Hi All, After the last 4 months of well over 100 hours perusing this great forum and Rods book, I feel I am ready to hit up stage one, the design. Budget is $5K to $6K with all work being done by myself and friends. Before I continue, here is a layout for you: The purpose of this room will be for mixing. There will be no recording of drums, only direct guitars and acoustics .If recording amps, a ISO booth will be built somewhere down the track. As of now, I will be mixing only. I mix at the typical 85db approximately. After running some tests at various times of day and night, I have concluded that I will not be doing a room within a room for a variety of reasons. Number one, it would be overkill for my situation. The room will be built in a detached garage. Secondly, the width of the room will suffer considerably with a room in room approach. I am already a bit tight on width, and just dont want to pay the acoustic price of the extra width eaten up by double framing. Here are some shots of the space the room will be built in: Yes, its a single frame assembly much like a normal wall, so yes.....its a bit boring. After running SPL tests, results show I will get away with it. It will of course not be as quiet as it could be, but quiet enough. If I was going to be doing drums, it would be woefully inadequate. This way it will be cheaper, and most importantly I can have a considerably wider room as a result. You will see that I have to squeeze ever last inch I can out of the space to get a good volume and a ok ratio. I could have hit a better ratio, but I want the extra length in the room for the spaciousness. One major advantage is I will have enough room behind me for some diffusion on the rear wall. Another advantage of this is I get a nice little bass trap in the back of the room that will be screened off with a frame as indicated. Having had a number of near dead to dead rooms in the past, this time I would like the room to retain more high end. So in that vain, Im looking at John's side wall absorbers on the first reflection points between the mix position and the speakers.http://www.johnlsayers.com/HR/index1.htm There is some extra treatment not shown in the plan that I will be adding. Of course, a cloud over the mix position. And if needed, as it probably will be, trapping across some floor/ceiling corners. As I test and tune the room, additionally traps will be added as needed. Construction Details: My walls and ceiling will consist of the following: 90 x 45 stud frame 450mm OC, treated pine all round as the floor plates. Caulked all round, then caulked again, then one more time for the hell of it. One layer of 16mm MDF on the outside, and one layer of 16mm MDF and one 16mm layer of plasterboard on the inside with green glue in between. These layers will be installed as per Rod's book using backer rod and of course, more caulk. Fluffy pink stuff between the two surfaces as per standard. All of the framing will not be touching any of the garage structure in any way. In fact the kink at the end of the bottom wall in the plan is where the framing will need to take a small turn in order to get around one of the garage's support beams. Ceiling joists may be 2 x 6, the actual type of wood yet to be specified by my Structual Engineer. I did ask him if sistered 2x4's would work as joists spaced at 450mm OC with the expected load . If doug Fir was used he seemed to think this would be fine as it has much better deflection properties. This would be a better option if I can find the appropriate grade here in a 2x4. Flooring will be wood laminate over the concrete. Monitors being used are Quested H108's powered by a Hafler P3000 amp. These are thankfully front ported and not self powered, so I intend to flush mount them. The H108's have 8 inch drivers in them, so I am planning on making my baffles at least 40 inches wide. Wider if space permits. They will run from 1 foot from the floor to 1 foot from the ceiling. The extra foot either end to allow for more trapping at these crucial points. It will be mostly based on Barefoot's design, along with a couple of others that have nifty ideas on soffit/flush mounting as well. I am going to install a split system for the room, fresh air intake is still being sorted out. The garage is wired with 3 phase power so I should be good to go. The standard audio gear on one leg, lights A/C etc on another, and star grounding. So, there you have it. Any suggestions or ideas or problems I welcome feed back on. Thanks for your time.

WoW! :shock: Looks like you have it pretty much covered, and well thought out. You'll have a decently large room with enough volume and a decent ratio, and your treatment plan sounds like a good start. It's hard to add much to that! Just one or two comments:

I have concluded that I will not be doing a room within a room

Well, you kind of ARE doing that! You are building a new room inside the existing shell, so that does make it a "room in a room" already. Sure, the existing shell is giving you very little isolation, as it looks to be thin metal sheeting with large air gaps all over, but it is still there, and still constitutes an outer leaf to a certain extent, for better or worse. The question is, how badly will that interact with your new room?

90 x 45 stud frame 450mm OC, ... One layer of 16mm MDF on the outside, and one layer of 16mm MDF and one 16mm layer of plasterboard on the inside with green glue in between.

I'm a little concerned about that, as it sounds like you could be building a three-leaf system, but with a very thin outer leaf and two coupled inner leaves, where most of the mass is NOT on the middle leaf. For a three-leaf wall, you get best performance when most of the mass is on the middle leaf. I understand your reasoning here, but I think you could get a large improvement in isolation by doing two things: First, can you spare a half inch of space? I'm sure you can! That's about how much space would be taken up by using resilient channel across the studs on one side of your wall, before you put up the MDF (also consider switching that to OSB). It's about a half inch thick, but will greatly improve your isolation, so "not be as quiet as it could be" becomes "much quieter". In real terms, you could be gaining about 10 dB there. Well worthwhile, I think. Second, put more mass on the "middle" leaf, which is the single layer of MDF in your current plan. Maybe add a second layer of MDF (or OSB) there, with staggered joints, sealed, etc. If you can't afford the space to put it outside the studs, then put it inside the studs, using the "beefing up" technique you often see on the forum. That will gain you another few dB of isolation, since it puts more mass where it will be most effective. If cost is an issue here, then you could just move the layer of MDF that you had planned for the inner-leaf, to the middle leaf, so you'll end up with just a single layer of 16mm drywall for your inner leaf. Doing those two things will gain you plenty of isolation, making your "room in a room that isn't a room in a room" into a pretty nice place, I reckon! I love the extra space at the rear for bass trapping: I'd suggest hangers for that! And your room really is big enough that you probably can put some QRDs on the rear wall, as planned. That "kink" in the rear wall is not a problem. About the only question I have, is what you are going to do between the side wall modules and the speaker soffits? There's a gap there that definitely can't stay like it is. What did you have planned for that? But anyway, overall you sure seem to have figured this out nicely! :) - Stuart -

"I did ask him if sistered 2x4's would work as joists spaced at 450mm OC with the expected load ." You have the head room, forget the "sistered" joists and use what the span requires...it's just way more easier...and stronger at the end of the day.

xSpace wrote:

"I did ask him if sistered 2x4's would work as joists spaced at 450mm OC with the expected load ." You have the head room, forget the "sistered" joists and use what the span requires...it's just way more easier...and stronger at the end of the day.

Yep, the more I have been thinking about , I tend to agree. Just do it the tried and true way and be sure. Thanks X.

Thanks Stuart! Most informative and raises some issues I hadn't thought of.

I have concluded that I will not be doing a room within a room

Well, you kind of ARE doing that! You are building a new room inside the existing shell, so that does make it a "room in a room" already. Sure, the existing shell is giving you very little isolation, as it looks to be thin metal sheeting with large air gaps all over, but it is still there, and still constitutes an outer leaf to a certain extent, for better or worse. The question is, how badly will that interact with your new room? It is indeed the question isnt it. Well, my initial reasoning was that the effect would be "small" given the flimsy nature of the thin metal walls. Of course , "small" does not mean much in itself with no real numbers or data. What I did consider is that I can probably live with a pseudo 3 leaf effect given that I will not be trying to contain any intense low end sources, such as drums.That established, I wonder how far do you actually go? What I mean is, should all the air gaps be sealed up as much as possible to make it a 3rd leaf , as much as it ever will be being so thin? Or do you leave it and let it leak to try and minimise the 3 leaf effect? Right at this moment, Im thinking I will seal it up, but I have more thinking to do on that. Your opinion here would be very helpful.

90 x 45 stud frame 450mm OC, ... One layer of 16mm MDF on the outside, and one layer of 16mm MDF and one 16mm layer of plasterboard on the inside with green glue in between.

I'm a little concerned about that, as it sounds like you could be building a three-leaf system, but with a very thin outer leaf and two coupled inner leaves, where most of the mass is NOT on the middle leaf. For a three-leaf wall, you get best performance when most of the mass is on the middle leaf. Ah ha nice one, I missed this in my thinking. Probably as I have been thinking of the proposed room as a simple two leaf structure and forgetting about the garage walls. Well, thats an easy fix....largest mass to the middle leaf...done and done. I understand your reasoning here, but I think you could get a large improvement in isolation by doing two things: First, can you spare a half inch of space? I'm sure you can! That's about how much space would be taken up by using resilient channel across the studs on one side of your wall, before you put up the MDF (also consider switching that to OSB). It's about a half inch thick, but will greatly improve your isolation, so "not be as quiet as it could be" becomes "much quieter". In real terms, you could be gaining about 10 dB there. Well worthwhile, I think. A half inch for up to 10db?? You had me at 10db.... :D The whisper clips I think they are called, seem to me to be preferred over RSC these days, would you agree? They claim better performance than the channel, and also less chance of shorting the system out as you can with RSC with one errant screw. I think I would lose a inch in total by doing the entire inside perimeter. But Im going to do this anyway. The trade off is well worth it as you say. Second, put more mass on the "middle" leaf, which is the single layer of MDF in your current plan. Maybe add a second layer of MDF (or OSB) there, with staggered joints, sealed, etc. If you can't afford the space to put it outside the studs, then put it inside the studs, using the "beefing up" technique you often see on the forum. That will gain you another few dB of isolation, since it puts more mass where it will be most effective. If cost is an issue here, then you could just move the layer of MDF that you had planned for the inner-leaf, to the middle leaf, so you'll end up with just a single layer of 16mm drywall for your inner leaf. I will at the very least arrange it this way, but hopefully also do a beef up" layer in between the studs. Doing those two things will gain you plenty of isolation, making your "room in a room that isn't a room in a room" into a pretty nice place, I reckon! I love the extra space at the rear for bass trapping: I'd suggest hangers for that! And your room really is big enough that you probably can put some QRDs on the rear wall, as planned. That "kink" in the rear wall is not a problem. About the only question I have, is what you are going to do between the side wall modules and the speaker soffits? There's a gap there that definitely can't stay like it is. What did you have planned for that? I was tossing up between hangers and a full fill. Hangers certainly would cost a bit less as I have the rockwool already to do it from my old place. A curious thing I have found in my research concerning this. I havent been able to find any real numbers, evidence or comparisons between hangers and a full fill for any given space. Maybe I have just missed it, but I have looked pretty extensively. I think I read someone say on a forum somewhere that having air surrounding each hanger as they hang, has some sort of beneficial effect with long low end waves....but that could have just been guesswork. Either way, hangers it is. Regarding the gap between the speakers and the side wall modules. Id have to check Johns plans, but I think he side wall module will cover the entire length between speakers and mix position, given an approximate 38% positioning.If not, a couple of extra 2x4 traps on either side will be easy to knock up. Thanks again Stuart for your thoughts, I will only be improving the room as a result so that is great.