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PostPosted: Fri Aug 05, 2005 11:38 am 
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Location: Ottawa, Canada
I tried writing this as a big PDF document to attach to some questions I wanted to post, but it ended up being too big. Instead, I'll post it in bits here. Also, this way I can document progress, and further questions in one tidy spot. I hope this helps others in similar situations....

Last fall I moved into my new house, and I’m looking to convert a sizeable part of the basement into a combination rehearsal room/control room. I’ve pretty much settled on the one-room concept as opposed to a separate control/live room, simply based on the fact that I do not have much room to play with (less than 30’ X 15’, with a height of 8’10” to the bottom of the joists). See figure 1 for a top view of my basement as it currently exists. I’ve drawn in the intended locations of the various sections of my basement finishing plans. The area at the base of the stairs will serve as an office, with computer/desk, etc, and shelving. The closet in the lower right hand corner of the drawing will serve double duty as a place to stash kid’s toys and occasionally as an amp isolation booth. A second booth/closet will be located under the stairs…and will serve the same purposes. Although it’s probably possible to shoehorn a control room and a live room into the remaining space, I’d rather avoid the pitfalls associated with rooms that are too small (poor mode distributions, bass problems, excess volume in the live room). The last studio I had a share in was a two room, too small type, and I was never happy. The one room concept works for me since I like be right in the action, and for the most part I’m recording myself, or my band.


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 Post subject: Part II
PostPosted: Fri Aug 05, 2005 11:41 am 
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So, with that general layout in mind, I drew up the plan shown in figure 2. In consideration of wall thickness/construction details I have the following concerns:
• Kid’s bedrooms are on the second floor, near the front of the house (bottom of the drawing. I don’t expect to have a drum kit going while they’re sleeping, but I would like to be able to mix, and track guitars. And hey, if I can swing a kit during bedtime hours, even better!
• Family room/TV room is on the main floor at the back of the house, directly above the two HVAC lines in the figure. I’m sure my wife would like to be able to watch TV, or have a conversation at a reasonable volume (without having to compete with the band in the studio below).
• There is no door (and no plans for a door) at the bottom of the stairs (nor at the top). This means that noise that gets into the office area will carry to the main level (living/dining room).
• I’d like to reduce noise transmission from the furnace into the studio.

For wall construction I’d figured that in the areas adjacent to the office I should go with a double wall construction (with double drywall on each side) for best low frequency TL.

For the area adjacent to the closet in the lower right of the figure I’ve spec’d a double wall. Orinially I was going to go with a staggered wall here, and it shows that way on my sketches, but a double wall makes the cosmetics better for the other rooms, and heh, a little extra isolation isn’t going to hurt.

For the area adjacent to the furnace I’ve spec’d a double wall again, but wonder if I can get away with staggered stud construction to save on floorspace (those double walls do eat up lots of floor area).

For ceiling construction I plan on putting up resilient channel, and double drywall (5/8 + ½ inch). All walls (and ceiling joists) will have glass fiber fill for damping.


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PostPosted: Fri Aug 05, 2005 11:48 am 
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Given the wall constructions listed above (and shown in figure 2), that leaves me with approximately a 26’4” X 14’4” area. Considering the 8’10” ceiling, I checked out the mode distributions. See the modes in the figure below.

Overall, the mode distribution looks pretty good. There’s a hole at 30Hz because the room is so long compared to it’s width, but I figure it’s low enough not to cause too much trouble. The hole around 50 Hz is a bit more of a concern, but hopefully bass trapping can help damp the adjacent modes to make the hole less ‘obvious’. Other than that, the mode spacing looks pretty good.

The Bonello distribution is shown below. I’m not really sure how to read it, but I figure (from the spreadsheet) that if the red bar is taller than the blue it represents a problem frequency band. For my room design that occurs around 50 Hz, which corresponds nicely with my observation about the ‘hole at 50 Hz’ in the mode plot. The same is true for 25 and 31 Hz. I’m not really worried about anything below 40 Hz though….


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 Post subject: Part III
PostPosted: Fri Aug 05, 2005 11:51 am 
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Conventional control room design logic is to place the listening position at a distance 1/3rd along the longest length of the room. At the 1/3rd length position, the contribution from the first few axial modes is best balanced between peaks and nulls. For my room that’s about 8.5 feet or so. This leaves about 17.5 feet to the rear wall from the listening position. So, assuming sound travels 1 foot/ms, this means there’s an arrival time gap of about 35ms between the direct sound from the monitors and the first reflection from the rear wall. This is good, since reflections after 20 ms are perceived as discrete echoes, and are less confusing (so says Everest) than early reflections before 20ms.

For room treatment I’m looking at probably some serious deadening of the front wall. Probably a 4” 703 panel array right across the front. The ceiling will also be deadened, but likely with 2” 703, possibly spaced out by 1-2” depending on room cosmetics (ie: how much headroom is left). Front walls near the mix position will likely have a set of slat absorbers to help tame the 1st harmonic of the axial mode acting across the room.

The speakers (ATC SCM50A active triamps…got a killer deal on them, and absolutely love em) will be mounted in false wall type soffits. They will sit on concrete block stands (filled with some type of damping material…sand if my slab can take the weight, otherwise, some kind of fiberglass). I’m not sure if I need to decouple the speaker from the stand, or the stand from the floor…might be hard with all that weight (the ATC’s are about 110 lbs each, and I’m sure that a concrete block stand will not be light). A double MDF panel wall will be constructed in front of the speakers, with the second layer having a bezel that mates flush with the edges of the ATC cabinet. I figure I’ll stuff the cavity with insulation, but install separator plates to keep the insulation away from the rear of the speaker cab (where the heatsinks are). The top will be covered in fabric for cosmetics, and to allow heat to escape (and for bass to be trapped). The planned installation is shown in the figures below….X-ray mode on the left. I will build an active shelving filter to compensate the monitors for the bass boost effect of the larger baffle from the soffit mount.


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PostPosted: Fri Aug 05, 2005 11:58 am 
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The graph below shows the results of the wall-bounce calculator. A 3dB bump at around 50 hz can be seen…maybe this will compensate a little for the hole at 50 Hz seen in the modal distribution chart.

The final result is something along the lines of the figure below…including some acoustic treatments. I will likely have a fair amount of absorbent up at the front of the room, and some slat resonators at either side of the mix position. Since doing my drawing I have changed my mind a little, and will build the wall adjacent to the furnace area a little closer to the furnace (top left in the figure). In my original plan I had left 2 feet of clearance to the back of the furnace, but will likely change this to more like 9 inches or whatever the building code minimum is…whichever is less. My reasoning for this change is that the room is looking a little cramped at the front

Door construction will likely be based on the BBC research, which suggests about a 5 cm thick composite door consisting of MDF, lead loaded vinyl, a glass fiber filled air cavity, and more MDF, and thin plywood facing on both sides.

The amp closet underneath the stairs will present somewhat of a challenge… I don’t expect to be using it too often, so it won’t receive the same level of attention as the rest of the room, but expect to use drywall to seal in glass fiber underneath the stair. Maybe I can use resilient channel underneath the main stair supports to hang the drywall on, and gain a little more decoupling. There will only be a single door into the closet, and this may be the limiting factor on the performance of the room (well, the ceiling is probably a big factor there too). The primary goal in this closet is to reduce the sound leakage up into the living area of the house from sound sources in the main studio room. After that, the secondary goal would be to achieve decent isolation between the amp closet and studio room (for live tracking…done when the kids aren’t sleeping).


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PostPosted: Sat Aug 06, 2005 4:54 am 
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Great stuff! I'm looking forward to future posts!

Exclamatorially:
Andre


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 Post subject: Framing completed....
PostPosted: Sun Aug 21, 2005 6:14 am 
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Okay, the framing is done now, and I've attached some photos.

Now I've got to lay my AC wiring and signal wiring to do before I proceed to drywalling.

Drywall is up on some the adjacent walls, and I've started acoustic caulking them...man thats nasty stuff if you get it on you. Basically need a solvent to get it off.

As you can see from the photos I've had the band setup in the room already, and can already tell that the weak link in my construction will be leakage through the HVAC system. I have lots of HVAC lines running in the ceiling, and two main truncs that cut across the room laterally just in front of the mix position. I'm going to need to build a big soffit for these, and will likely end up constructing some sort of truss structure to sit between the truncs to hold the weight of the double layers of drywall I intend on hanging underneath. I will likely have enough space to build a bit of a baffled plenum for the cold air return line, but there is no extra room for a similar approach to the hot/cool air supply line. Maybe I can go to a lined duct for these lines (shown in the photo attached)...dunno, gotta call an HVAC expert in to see.

For fresh air supply, I think I have a solution. Home Depot carries a 300 CFM fan with a reasonably low noise level that I can mount in the adjacent furnace room, and duct through a couple 90deg bends (home made MDF duct was what I was planning here). This will force air from the furnace room into the recording room. The furnace (high efficiency) is ducted to the outside through 8" flex hose. The hose is brought right to the center of the furnace and not ducted directly to it, so I assume that this is to provide adequate fresh air to the furnace area. I beleive that with the fan mounted in the furnace area, I will simply draw more fresh air from the outside....hopefully that pipe will be enough to handle both the 300CFM fan plus the furnace requirements (again, HVAC expert will be required to answer this). I'm hoping that this will result in a slight overpressuring of the recording room, and will force the stale air out the HVAC air return lines. If not, then I need to consider how to get the stale air out of my recording room....ugg more things to consider, and more holes in my precious room.

Oh, and a fortutious discovery...the office room (the L shaped room with the stairs) makes for a great reverb chamber. It's particularly diffuse and currently with no carpet down has a long reverb time, which can be varied by opening the closet door. Very cool. Now I need to drop some signal lines in this room so I can use it as a reverb chamber if need be.

Cheers,

Kris


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PostPosted: Sun Aug 21, 2005 9:45 am 
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drfrankencopter wrote:
For fresh air supply, I think I have a solution. Home Depot carries a 300 CFM fan with a reasonably low noise level that I can mount in the adjacent furnace room, and duct through a couple 90deg bends (home made MDF duct was what I was planning here). This will force air from the furnace room into the recording room. The furnace (high efficiency) is ducted to the outside through 8" flex hose. The hose is brought right to the center of the furnace and not ducted directly to it, so I assume that this is to provide adequate fresh air to the furnace area. I beleive that with the fan mounted in the furnace area, I will simply draw more fresh air from the outside....hopefully that pipe will be enough to handle both the 300CFM fan plus the furnace requirements (again, HVAC expert will be required to answer this). I'm hoping that this will result in a slight overpressuring of the recording room, and will force the stale air out the HVAC air return lines. If not, then I need to consider how to get the stale air out of my recording room....ugg more things to consider, and more holes in my precious room.

Oh my. Maybe I'm overreacting here (wouldn't be the first time), but I'm very uncomfortable with the idea of sucking air from the furnace area into a mostly airtight room. :shock: What kind of furnace is this? Is there risk of carbon monoxide poisoning? :shock:

If you haven't already been watching my thread closely lately, you may want to give it a visit, starting at page 18. Follow me as I come up with ideas and then shoot them down, finally to (hopefully) settle on a system that I believe will work well for me.

I'm by no means "the answer guy" on this topic... But I do have some scrapes and scratches from having failed a number of times on paper, so hopefully you (and others) can benefit from that.

--Keith


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PostPosted: Sun Aug 21, 2005 10:59 am 
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Sharward, I share your concern, and that's why I will have an HVAC specialist in to reafirm, or entirely shoot down my idea. But, I can answer a few of your questions:

As far as what type of furnace, its a new high efficiency type that's direct vented to the outdoors. It doesn't breathe in household air, and is exhausted directly to the outside. In order to supply the air for combustion, a seperate duct is brought right to the the area between the send and return ducts at the furnace. This duct is connected to the outside, and is for intake purposes, not for exhaust. Assuming (and this is the key) that this pipe is big enough to handle the additional 300CFM flow that I want to draw from it, then my plan should draw additional fresh air, while not affecting the combustion of the furnace in any appreciable way.

Some furnaces are installed without the fresh air supply pipe, and these will draw air from the surrounding area, and won't work well when confined to a small room...these will result in inefficient combustion and possibly carbon monoxide products, but mine has been installed with confined space in mind.

Again, I'm no HVAC expert, and we'll see what the pro's have to see when they see my plans.

Cheers,

Kris


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PostPosted: Wed Aug 24, 2005 12:34 am 
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Hey Dr. F., Cool project. Just noticed this thread after posting in this one about my own "one room" studio project (read my comments in that thread for more on my place).

I'm curious to hear how things turn out for you, especially your results with filling the ceiling cavity - I'm about to do the same thing. Per Ethan Winer's advice on his Acoustics forum, the results should be to basically make the ceiling into an acoutically invisible "cloud" - at least as far as bass and lo-mids are concerned.

Not too sure how much this will help with isolation though. Lots of flanking to deal with at my place, also due to HVAC (which I'm not about to redo). I've also got two little kids on a 2nd floor, so my solution has been to create decoupled drum and amp risers (detailed in another currenly active thread in the Studio Construction forum, which I'm too lazy to link to right now :) ).

Love to hear more as it progresses.

Adam


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PostPosted: Wed Aug 31, 2005 12:14 pm 
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Hi AjD.... I'm going to put drywall up over the ceiling though. Double layers on RC. I need that for isolation to the upstairs. For acoustics in the room I will build ceiling absorbers. I prefer the sound of a dead ceiling...makes a room sound bigger/taller than it really is.

Just about done my acoustic caulk of the framing and some walls. Moving on to electrical...had to put in a junction box to make my life easier for wiring this sucker up.

I'm still not sure how to get my outlet boxes (plastic, and fairly well sealed) flush with the outter wall. I may need to just hold them in place for now, and install them permanently when the 1st layer of drywall goes up. Not sure if that meets code though (but I can't see why not as long as its affixed to a stud, and wired properly).

Just had a SPL meter in the basement. As it sits, with Rockwool up on the walls, and no drywall up I have 35 dB (C weighted) SPL. Quieter than I thought. Its about 53 dB when the air conditioner/furnace fan is on.

Should be nice and quiet by the time the drywall goes up!

Cheers,

Kris


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 Post subject: AC wiring plan....
PostPosted: Thu Sep 01, 2005 11:41 am 
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Ok, here's the AC wiring plan.

There will be 3 seperate circuits, each fed by 15 Amp breaker via a junction panel:
1. Feeding the studio gear (preamps, computer, compressors, monitors)
2. Feeding the additional outlets in the room(s) (amps, synths, floor lamps, PA)
3. Feeding the wall sconces via a double pole switch (2 switch locations, 1 near entrance, 1 near mix posn)

I will also have track lighting supplied via existing wiring (shared with other household circuits).

Each outlet will have a seperate ground wire leading back to the junction box, and then coming back to the main safety ground. Its a star system to the junction box. Wire throughout to be Romex 12-2. I'll be trying to keep the AC lines high in the wall, and any audio lines that I run will be low in the wall.

I'm not exactly sure how to handle the outlet boxes just yet. The ones I bought have nice gaskets around them, and should make for a fairly well sealed enclosure. BUT, they have a flange on them that seems set up for 1/2" drywall. How do I handle the 2 layers (5/8" and 1/2")? They have little screw holes to let me attatch the flange directly to the stud face, maybe I can just tack them up in place to get my wire lengths, then put up my 1st layer of drywall, and affix the boxes to the studs through the flange then. Not sure here.....

Cheers,

Kris


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PostPosted: Thu Sep 01, 2005 3:39 pm 
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Pretty nifty boxes, if you were going to use a single layer of rock... :roll:

I don't have a solution for you, but I will say that I'm sure that using those boxes, putting multiple layers of rock on the wall, and then putting outlets into the boxes with an extra layer (or two?) of rock in the way is not to code and not safe. In other words, the opening of the box needs to be flush with the surface of the wall inside the room.

Another thing I learned recently is that not tightening down the screws on the outlet (or switch), allowing the item to "float" off the box a bit so that it fits snugly into the wall plate that covers it, is also not to code and not safe. Even though it may look nicer, that's a no-no.

I'm most certainly not an expert when it comes to electrical... I just know of some things not to do... :roll:

By the way, you may want to consider upgrading your outlet circuits to 20 amp. You'll probably not need it, but the cost difference is minimal. You only have to bump your wiring up to 12 guage (from 14 guage), albeit 12 is harder to manipulate with your hands.

FYI, don't miss these threads:--Keith :mrgreen:


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PostPosted: Thu Sep 01, 2005 4:02 pm 
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it's not unheard of in "normal" remodeling to add a layer of drywall to an existing wall, and i think there are box extenders made for this purpose. they may be called mud rings, or that may be something different. but it's the same idea. whether there is one that will work for 2 layers i don't know. but anyway i think there is a legal way to extend boxes.


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PostPosted: Thu Sep 01, 2005 4:08 pm 
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Dan Fitzpatrick wrote:
. . . i think there is a legal way to extend boxes.

Yeah, I think so too -- thanks for mentioning that. If anyone sees such a product, please post details! :-)


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