my personal playground

hi guys, first time poster here but i've been a lurker for a while. i've been reading this forum with great interest and im starting my own little room next week. i will be dividing my kitchen space so i can have a dedicated space for practicing/tracking drums and mixing. id really like to have separate tracking and control rooms but its not possible due to my space limitations. the new room will be an irregular trapezoid and im planning to build a room within room using the inside out method. the internal wall lengths are 4m, 4m, 5m and 1.5m. the room will be 2.5 meters high. the outer walls are 6" CHB with grout and the 4th outer wall will be constructed with light steel framing with 2 layers of 5/8" gypsum. the outer ceiling is 3 meters high and is made from 4" thick concrete. the floor is also a concrete slab but not isolated nor floating. for the new inside walls, im going to use 2x3 lumber which is actually called 2x4 here (local wood is always undersized). i might probably use 2x3 also on the ceiling but i dont know if this lumber can carry 2 layers of 5/8" gypsum with a span of 4m. the concrete floors will be covered with hard wood over a vapor barrier. i will be using single super door and there will be 2 windows: one is fixed looking over the kitchen and the other one is a regular sliding window that opens to the garage. AC will be a 1HP mini split (no need for heating) and will be installed above the garage-facing window. the space is pretty small so budget is not a problem. my sketchup isnt quite finished on the inside room because i dont know how the room will sound. id rather do actual room acoustic measurements after all the walls are up and decide what slat resonators and other acoustic treatments to use. i also did not include the outer walls so you will be seeing the pink fiberglass as the outermost layer but i will have 3" of air between my inner gypsum wall and my outer CHB wall. i do have a few concerns: 1. i want to soffit my krk rp8 g2s but the space is just 1.5meters wide. the space will be very tight but its no different from how i setup my monitors now which is also very close to my monitor. is there a size requirement for soffits? is it even worth doing given my space constraints? i can always put the monitors back on stands. the lcd screen will be wall mounted and all my recording gear, cpu and keyboard will be on a rolling rack. 2. my maximum ceiling span is 13.2 feet and i did mention using ceiling joist from 2x3 . i tried using several ceiling joist calculators and im not getting a consistent answer. im using philippine mahogany which is roughly as hard as pine (based on janka rating but of course im not aware of the exact pine specie to compare against). im getting only a max span of 8 feet so id probably be using a 2x6 for the joist to make the 13 feet. i do have enough room as i still have 0.5 meters between my outer ceiling and my inner ceiling. from a DIY perspective, 2x6 frames are just to heavy too lift even if i invite a couple of big friends hence my attempt at making 2x3 lumber work. any thoughts?

Welcome! It's definitely an interesting space. while tight it looks like you've angle the soffits appropriately for the space. Lookup some topics on soffits to see how to construct them and use that space behind for your bass trapping. Plan on some additional bass trapping in the back corners of the room as well. Are the soffit and speakers as shown to scale? If so they should be ok from a size perspective. The ceiling is tricky. You could possible split the ceiling span using 2x8 (10?) beams and run your 2x3 off that. Using a layer of OSB to strengthen the ceiling before putting on the drywall layers. Since you have a lot of space left overhead, you could put the ventilation ducts up there. If in doubt get a structural engineer to review and comment.

thanks glenn! yes i will be putting bass hangers on the soffit as well as vents. kindly check on my ceiling-1.jpg illustration and let me know if this is what you meant. i also had this crazy idea of just adding a frame to support the longest ceiling joist on the 8' position then add rectangular bass hangers inside. the new frame will be covered with cloth. i still dont know much about bass hangers and i was wondering if they have a tuning requirement, like a specific size and shape for a frequency, or can i make triangle-shaped ones as long as i can make them big?

here's my idea of adding triangular bass hangers above the mix position. im going to hide them by adding an angled false ceiling covered with cloth.

ceiling-1 is the idea. on the hangers - also consider them in the back of the room and possibly behind the soffits if you have enough space.

right then, ceiling-1 it is and i do have an engineer friend coming over to do the load computations on the ceiling and improve on the framing design. i have also been calling around for suppliers of fiberglass blankets and the only density i can buy around here is 2pcf 50mm x 1.2m x 15m rolls. if i put 2 layers of 50mm blankets on top of one another over the concrete walls, does it still rate as 2pcf or is it now 4pcf? im going for maximum low frequency attenuation. thanks for the help Glenn! paolo

oh forgot to mention that my build should be starting in 2 to 3 days. just waiting for the lumber and gypsum order to be delivered

you won't increase the density (32Kg/m3) by increasing the depth - but if you double layer it and compress it to 50mm, then you are close. use the 2x layers - 100mm wherever you can. on the hangers, you can use lighter insulation (15-18Kg/m3). same for pockets of air in the corner absorbers and in the wall (between walls).

understood. i doubled my order for the 50mm blankets... but things arent really going according to plan lately. i had to return all the lumber i ordered as more than 70% are so crooked (bent and twisted) that i wont even attempt to use them. half of the gypsum were also delivered. i may have to change my design to use light steel framing for the inner room and not do inside out walls. inner ceiling will be a problem as light steel framing cant support loads and i also have doubts if the walls can support my mini split AC.

due to material problems, im forced to finally use light steel framing. i will not be able to build inside out walls anymore and the 4th concrete wall is going up now... since i already have a concrete ceiling that is 6" thick, will adding 'air', 4" of 2pcf insulation, hat channels and 2 layers of gypsum be enough to match the STC ratings of the inside walls? will i still get good isolation? i know hat channels dont offer much isolation but im still looking for RC-2 equivalents here or isolation clips to hold the hat channel. i will use sway braces for the light steel frame walls as the top part will not be bolted to the ceiling.

most available isolation clips should readily support 2x drywall. check out kinetics noise and pacific international for sourcing the clips. regular hat channel by itself will not provide the isolation.

finally found a local distributor of isomax clips. while my order is still being processed, im looking at windows with good stc ratings. i had pvc windows recently installed in my kitchen and storage room. the storage room window is about 2'x2' with ordinary 1/4" (or probably less) float glass. i did a very unscientific measurement of the isolation being provided - i used 2 condensers, i placed one outside the room and another one inside then played my kick drum while recording both mics. i just subtracted the peaks on the level meter and got a 22db difference. is this promising? i read somewhere here that there are windows capable of 30db isolation. i was thinking of buying another pvc window for the drum room then somehow replace the float glass with 1/2" laminated glass to reach 30db. i can always build wood frames with laminated glass for the window but it would be nice to match the look of the other pvc windows.

:shot: vs window http://www.youtube.com/watch?v=RiWBUg9XQNc

in this case, you might consider build a very heavy internal window (say 5/8" glass). worst case, you might have to replace the exterior window with another heavy window (1/2").