Ready to frame - please take a look.

Hi all, I have sorted out all electrical and mechanical design including insulated plenum and silencers. I have suppliers for LED recessed lighting, Green Glue, Genie clips, 1" - 4" rigid, acoustical fabric, etc. My contractor has demo'd the space and we're ready to frame. I have worked my studio design from John Sayers' "small-studio.skp" to accommodate a larger control room and a bit larger live room. Being a basement studio, the ceilings will be isolated with the Genie Clips and incorporate two layers of 5/8" drywall with Green Glue between. Front and right-side interior walls are "inside-out" 5/8" drywall with Roxul and walls between control room and live room are reversed to form 5/8"-stud-insulation-4" air space-insulation-stud-5/8". I am happy with the level of isolation using these materials. I have done my best to make a usable SketchUp file (a lot of work when you're learning the program at the same time) and include some jpgs in this post. The zipped file is too big it seems. The outside dimensions are: Control Room - W 12' x L 18' x H 7.5' Live Room - W 11' x L 12' x H 7.5' I was planning on following John's wall treatment in the "small studio" file but modified for a larger space. What I would really appreciate is your expert opinions on control room wall treatment and how to arrange rear trapping and diffusion as well as the use of slat walls. There are dozens of designs on the forum and elsewhere so I have tried to use methods from some of those designs. I have seen, and do like, the idea of building a client bench (filled with insulation) between the rear bass traps. Of course, with trying to absorb so much info from so many sources, it's easy to become overwhelmed and make mistakes...so, I'm a little nervous and acquiesce to the collective knowledge base. The questions are: 1. Should I use insulation batts or construct hangers in the rear bass traps and what is the best way to calculate the dimensions and angles for their construction? 2. Would it be better to build a "V-shaped" diffuser between the rear bass traps, or maybe a slat wall, instead of a client bench? 3. Should I follow the original design and apply slats to the complete right side splayed wall (about 9.5') and around the sliding doors or maybe partial slats and partial fabric? 4. And very importantly, any recommendations, modifications or suggestions on the overall plan. Thanks in advance, Alan

bouche wrote:

1. Should I use insulation batts or construct hangers in the rear bass traps and what is the best way to calculate the dimensions and angles for their construction? 2. Would it be better to build a "V-shaped" diffuser between the rear bass traps, or maybe a slat wall, instead of a client bench? 3. Should I follow the original design and apply slats to the complete right side splayed wall (about 9.5') and around the sliding doors or maybe partial slats and partial fabric? 4. And very importantly, any recommendations, modifications or suggestions on the overall plan.

1) use hangers. built using Homasote or similar and wrapped with insulation. put them on a 15° angle relative to the front opening. 2) you could go either way. i'd would tend to think using that space for more bass trapping would be good and then add the diffusion on top of that. 3) i would go with all slats but consider dividing the cavity space in quarters - split in the middle both horizontally and vertically to improve efficiency of the unit on the right side. matching slats on the door side. 4) overall looks like some nice work. remember the ceiling plays a very big role and you could go with a number of clouds and various angles and sizes to the clouds to manipulate that space. in the live room, some of John's slat boxes or some polys along with bass trapping and/or slats across the corners. what are your plans for ventilation?

Thank you very much Glenn, I'm not sure if we can get Homasote here in Toronto - was thinking of mdf originally. Can't find any information on actual dimensions of the bass corner traps or size and quantity of hangers. Just kind of guesstimating from designs that I've found here and elsewhere. Also, are the hangers the full height of the trap or is the trap split in the middle with hangers below and batts above? It seems hard to predict what frequencies they will actually trap if not calculated correctly. Re the space between the rear traps, my thought was that the bench could act as another trap with diffusers above. I intend to do more research on that one. Interesting approach to "quarter" the space behind the slat wall. I suppose that would help treat certain low frequencies. I have never seen a design where the space behind the splayed walls sealed, however. How is that possible without coupling to the existing walls? I was concerned that having that much slat area on the walls might cause the room to be too live in the higher frequencies - do you see that as a problem? As far as the HVAC goes, we are replacing the existing galvanized plenum run with an industrial insulated plenum 6" x 18" which will allow 7' height for the completed ceiling. From the plenum, 6" ducts will feed into the to-be-fabricated silencer boxes in each room and the same for return air. That should give us adequate isolation and good air flow. Thanks again. cheers, Alan

If not homasote, then some other low density fiber board should be ok. The hangers should occupy as much space as possible in a given section. So full height or half height depends on the space available. You could try the bench idea and if it turns out you need more it should be straightforward to replace it. You need to seal the slat cavities really well. Yes, you don't always see what happens behind the slat walls but in this case (or really any long slat wall) you want to partition it to improve efficiencies.

gullfo wrote:

You need to seal the slat cavities really well. Yes, you don't always see what happens behind the slat walls but in this case (or really any long slat wall) you want to partition it to improve efficiencies.

Appreciate the feedback, Glenn. Can anyone point me to some information on "sealing cavities" and "partitioning" behind slat walls? As it is, the long "splayed" slat wall is about 9.5 feet, is constructed inside out with 5/8" drywall on the outside, and has to be prebuilt on the floor and then raised into position and sway braces attached at the top plate. I can't envision how to "seal and partition the cavity" behind such an assembly. Another wall or layer of mdf would then give me a 3 leaf system - and that couldn't be good. And if someone could offer a means to calculate the dimensions for the rear bass traps and diffusers, that would be really helpful. Otherwise, I guess I'll just have to do some guesswork from the other (many and varied) designs and hope it works when the studio is built. cheers, Alan

vertically it's as easy as adding panels from the angled wall to the isolation wall. horizontally on the inside out-wall, you would have to create some cut-away panels that fit into the studs so you might want to skip that.

gullfo wrote:

vertically it's as easy as adding panels from the angled wall to the isolation wall. horizontally on the inside out-wall, you would have to create some cut-away panels that fit into the studs so you might want to skip that.

Glenn...I must admit that I really don't understand if these cavities are supposed to be connected to the existing walls - is that what you mean by "isolation wall"? And "sealing the cavities" is bewildering as well as the outside walls are not going to have any drywall on them - just insulation. As I mentioned, I've never seen anything like this in any other designs here or in Rod's book. Just can't wrap my head around this. I have reduced my Sketchup file to 365 kb, so I'll include it in this post to see if someone can take a look at it and see if I'm off track on my design. I'd really appreciate it if I could get some advice on the rear traps and what to do for rear diffusion between them. That would help us immensely to get going with the framing this week. My HVAC guy is coming to replace the plenum and do the required ductwork and then we'd like to start the walls. Thanks in advance, Alan

you can build out boxes in the wall to create the sealed cavities, or use the walls to do it. either way the key concept is you need sealed air spaces behind the slats to make them function correctly. the simplest way is to add plywood panels that extend from the slat frame to the isolation wall, top to bottom, to divide the cavity and caulk it.

gullfo wrote:

you can build out boxes in the wall to create the sealed cavities, or use the walls to do it. either way the key concept is you need sealed air spaces behind the slats to make them function correctly. the simplest way is to add plywood panels that extend from the slat frame to the isolation wall, top to bottom, to divide the cavity and caulk it.

Hi Glenn, I get that the cavity must be sealed. If you look at the jpg close up of the slat wall and existing basement wall (and the attached jpg photo), you can see that it is just framing - we took off all of the drywall to leave just the framing and insulation up against the concrete basement wall ( must have vapour barrier on the basement walls!!!). If I connect the slat wall to the existing wall with plywood, I can't see how that makes a sealed cavity as the framing is not "sealed" to the concrete foundation wall. Surely sound would leak out the back even if the top. sides and bottom of the plywood were all sealed. (Yeah...I have to build a trap door for the water meter into the slat wall) I'm supposing that your response would be to construct a sealed plywood wedge cavity complete with plywood back behind the slat wall and possibly divide that cavity into four. Yes? To all: I'm hoping someone...anyone can chime in and answer my rear trapping and diffusion questions and, if I'm really lucky, take a look at the Sketchup file that I posted earlier and give some feedback. Ductwork finished this evening. Fingers crossed on design questions. Please gurus, wise men and experienced builders of all things audio ...lend me your wisdom. Let the framing begin. Thanks, Alan

i think you'll have to box it in then since the framing is open.

gullfo wrote:

i think you'll have to box it in then since the framing is open.

Thanks Glenn, That's what I thought. However, with these short answers you're assuming that I know what I'm doing - I don't. Mon dieu...I just took all of the drywall off of those studs after seeing photos of Silva's studio build on John Sayers' site!!!!!! (see below) So now I have to ask the dumb question that my contractor is going to ask me: can the back section of plywood be attached to the existing stud frame - or does the cavity have to be a free standing structure attached only to the slat wall? Should we just put drywall BACK on the framing? How did Silva get away with not "sealing the cavity" behind his slat wall??? Surely John blessed the design if it's on his site. I dunno. This is a very frustrating process. I was hoping for more feedback on this forum. I scour this forum's previous posts and topics for hours each day looking for answers and I can' help but notice that others seemed to have had pages and pages of help and comments through every step from first drawings to completion, and I can't even get to the point where I'm ready to put the first 2x4 in place. Some do it one way...some do it another way...but they all get helpful feedback. I'm still having to guess-timate the dimensions of the rear traps and diffusers. You can only tell so much from photos. Like they say - it's all in the details. I would really, really love to have some.

you can attach it to the frame since your frames aren't doing any of the isolation work.

gullfo wrote:

you can attach it to the frame since your frames aren't doing any of the isolation work.

That sounds good. So I will instruct my guy to build a 3/4" plywood, wedge-shaped, sealed cavity with the backplate attached to the existing framing on the concrete outside wall -divide it into 2 compartments - and then we will add the framing for the splayed wall, seal the cavity where it joins the splayed wall - add one layer of 3" roxul insulation to the back of the cavity - friction fit a layer of 1" rigid to the splayed wall framing - apply the fabric - then screw the alternating pattern of wood slats onto the assembly. I've seen mention of glueing the slats as well as screwing, but I don't know if that would be effective over fabric. My God...let's hope it works. Next - a build diary. Thanks so much Glenn.

toe nailing, toe screwing (not sure if that came across properly :mrgreen: ), using metal or wood pegs, or simply gluing are the various method folks have used. i prefer just to nail it through and cover with putty - definitely if painting them. you can also cut out slots on panels on MDF or plywood so it mounts as a single unit or as many panels as needed.

heh-heh...Thanks for the giggle. I think I like your idea of nailing (since we have the nail gun) and filling with putty. Now about the frequency calculation. I've downloaded the Helmholtz excel file from John's site. How is this used for a slat wall? Does one predetermine the frequencies to be treated and then say, divide the number of slots by that and install accordingly? Or just use the following formula and hope for the best? The slat formula that I've seen around here is: 100mm (4") - 50mm (2") - 25mm (1") alternating slats 2.5mm (1/16") - 5mm (1/8") - 10mm (3/8") alternating gaps Room size calculation at 16' L x 12' W x 7.5' H indicates that following are my resonant frequencies: 35-38 Hz 70 - 75 Hz 105-115 Hz 140-145 Hz I'm presuming that the bass traps will take care of the lower range and that I should design the slat wall to treat frequencies from 140 Hz and up. I really appreciate all of your help.

the slat/slot formula you selected is a good option to create a broadband effect.