Mic lines in close proximity to AC power conduit?

[oliverh]

Hello all! Let me preface everything I'm going to say by mentioning that I am currently awaiting delivery of Rod Gervais' book which I just purchased yesterday. I look forward to using it as an invaluable resource.

I'm looking to build a tracking space inside a 2-car garage attached to my home. I have not started any construction yet and am merely just in the beginning stages of research and learning, but am awfully close to wanting to start the ball rolling on this project.

The interior dimensions of the garage are approx 17' by 18.5' inside of unfinished 2x4 framed walls. It has a vaulted ceiling but the point at which a "ceiling" would otherwise be is at about 8'3" up from the slab floor of the garage. The vaulting goes up about another 6' or so from this "ceiling" level. It has a slab floor and is ground level.

The 2-car garage space shares a common wall with the house. The other side of this wall is a bathroom of approx 6'x9' dimension. I will have the luxury of using a bedroom inside the house as my "control room" and this bedroom space is just the other side of/adjacent to the bathroom that is sandwiched between the garage "tracking room" and the bedroom "control room." The bedroom measures approx 12'x12' roughly. I have essentially already converted the bedroom into a very functional control room in that I have treated it substantially with bass trapping material (a bunch of various GIK Acoustics products) and am rather satisfied at the moment with the acoustics of that room being tight and translating my mixes relatively well to other systems.

I am in the midst of having some custom cable bundles constructed in conjunction with respective wall plates they'll be soldered to for my tracking room. I've spent some time under the house recently, which has a raised foundation, investigating how exactly I will plumb my mic cables, speaker cables, Cat6, etc from the garage "tracking space" under the house and up into the bedroom "control room."

The slab garage floor sits approx 11" below where the subfloor exists for the rest of the house which is a nice feature since I've discovered that penetrating through the lowest vertical 11" of the existing garage wall gets me under the house allowing me to run electrical grey PVC conduit housing my mic line runs. I plan to make a separate conduit run dedicated to higher voltage speaker cable that will be at least approx 2' away from where I plan to drill into a 2x6 joist that sits atop the perimeter concrete foundation attached to the slab floor of the garage. This main hole for the mic lines will give me access that is most convenient for making the shortest run to the "control room" AND avoiding other plumbing that is nearby such as GAS, WATER, and to begin my question... AC Power in metal conduit.


So, my question about mic lines and their safest practical distance from AC power lines is two-fold:

Firstly, I'm wondering if there are any issues with me running the mic cable bundles throughout the tracking room BEFORE they arrive at the points where the conduit will run WITHOUT any conduit behind the inner walls of the tracking room? In other words, running mic lines in the air space between my dual-framed non-touching walls that I plan to build without any added conduit.... will this be OK? I assume these high quality cables I'm ordering will all be well shielded but in my research so far I've come across a pretty fair consensus that you should try to keep mic cables as far away as possible from AC power. Pretty sure my electrician will be using metal conduit for any added electrical outlets in the studio, but any advice here as to how much space I should keep between AC power for the room and the mic line runs (assuming they HAD to run roughly parallel)?

Secondly, this leads me to my next question pertaining to where I plan to be coming through the wall of my garage with the conduit on its way under the raised foundation of the rest of the house. The spot I've located where I want to punch through happens to come within a few inches of some metal conduit for AC power fed to the wall shared between the house and garage. You'll see what I'm talking about in the pictures attached here. One is a picture of the 2x6 joist I'm planning on drilling through for the mic line conduit and in the other I've drawn a red circle approximating the hole I would drill for the mic line conduit to enter. The good news is that while they would be close at this exact point in the picture, the AC power metal conduit veers off in a different direction from the run I plan to make for the mic lines. Think of a roughly "y" shape where two lines come close to converging but only momentarily. So this would be the closest the mic cable bundles and the AC power lines would be... at least that I can tell so far. Think I'll be OK? Or is this a legit concern for noise, EMI, etc.? Within the tracking room and under the house I'll certainly do my best to manually position any mic lines away from AC power to the best of my ability.

The second hole for the speaker lines run that is a couple feet away from this mic line hole location is further from the AC power conduit in question, but figured if I had to pick one to be closer to this existing AC power line, better that it be the one with mostly balanced cables? Am I crazy with that logic?

Otherwise I was going to combine mic/line level, Cat6, & MIDI cabling all into one conduit. Speaker lines then, of course, in their own dedicated separate conduit.

Do you think I'm OK for the mic line conduit to come this close to AC momentarily? Or should I avoid this and seek a different place to come under the house even if it's a lot less convenient?



Literally, warm regards from Los Angeles,

Oliver H.

[Speedskater]

Making some assumptions:
a] The AC wires are correctly connected (some low-budget electric jobs have the Hot & Neutral in switched lighting circuits following different paths). None of the wires go to things like air-conditioners that start big motors or compressors).
b] You are using a quality Shielded Twisted Pair (or quad) for the mic cables.

Then 2 inch clearance should work, but heck lets call it 6 inches to be on the safe side.

[Soundman2020]

Hi there Oliver, and Welcome!

Adding to what Kevin (Speedskater) said:

I have not started any construction yet and am merely just in the beginning stages of research and learning,

Excellent! That's a very, very smart place to be, for the next several months as you work on the actual design of the studio, in complete detail. Then you can start building.

but am awfully close to wanting to start the ball rolling on this project.

Patience... ! All I can say here is that if you want a really good studio, then the design phase will last a lot longer than the actual construction phase.

The interior dimensions of the garage are approx 17' by 18.5' inside of unfinished 2x4 framed walls.

Just to clarify: If you stand inside your garage right now and loo around you, then you see studs, and the distance across the garage from the face of the studs that you see on the left wall, to the face of the studs that you see on the right wall. is exactly 17.000 feet: Precisely 204.0 inches. While the distance in the other direction is exactly 18' 6.0", or precisely 222.0 inches. Correct?

Also just to clarify: You now plan to construct a new frame, within the garage, resting on the same slab, and you will have drywall on just one side of that new frame. Correct?

How do you plan to deal with the garage door?

I know that none of this appears to be pertinent to your questions, but bare with me; it is all related.

It has a vaulted ceiling but the point at which a "ceiling" would otherwise be is at about 8'3" up from the slab

In othere words, the bottom chord of the trusses (or underside of the joists) is exactly 99.0" above the surface of the slab? And your current plan is to put drywall on the bottom of those joists/trusses to complete the outer-leaf of your studio, then your new inner leaf will set a few inches below that. Is that correct?

The bedroom measures approx 12'x12'

In other words, it is square? And since I'm assuming that your house is built fairl standard, that implies an 8' ceiling? So how did you deal with the large modal issues that these dimensions imply, and what was the result? Have you done an actual acoustic response test in that room, using REW? If not, then please do that now, and post the results here. I suspect that you have issues that you are not aware of.

I plan to make a separate conduit run dedicated to higher voltage speaker cable

Speaker cable? Why are you running speaker cable between rooms? That implies that you have the amp in one room, and the speakers in the other room, which implies a large voltage drop and strange impedance, unless you use wiring that has a very large cross section and low resistance. It would be much better to put the amp in the room, right next to the speakers, with the shortest possible cable run, and just send line-level signals to the amp through your snake.

Firstly, I'm wondering if there are any issues with me running the mic cable bundles throughout the tracking room BEFORE they arrive at the points where the conduit will run WITHOUT any conduit behind the inner walls of the tracking room?

While it is might be possible to do that, it's something that I don't ever do in studios, for one simple reason: If you ever need to repair or replace a faulty cable, or run a new one, you would have to dig huge holes in your isolation walls to get at it. I always run conduit, even when it isn't really necessary, so that it is always possible to simply pull a faulty cable out and replace it with a good one, by just pulling it though the conduit. To be able to do that successfully, you need to use conduit that is quite a bit larger in diameter than the wire bundle you are using, and you need to keep all your bends gentle, smooth, and wide radius. You also need to be careful around the decoupling gap in the conduit, between the leaves of your wall, to make sure the gap is smooth enough and lines up well enough to allow easy pulling of cables.

I don't use metal conduit for this: I use PVC conduit, since it is easier to work with, and cheaper, and you can get it in fairly large diameters.

running mic lines in the air space between my dual-framed non-touching walls

I would not run individual mic lines: I would run a multi-conductor audio snake. You have many mic and line channels in one single cable like that.

Secondly, this leads me to my next question pertaining to where I plan to be coming through the wall of my garage with the conduit on its way under the raised foundation of the rest of the house. The spot I've located where I want to punch through happens to come within a few inches of some metal conduit for AC power fed to the wall shared between the house and garage.

I normally do the link across the air gap with two offset conduit sections, so that there is no mechanical connection between the leaves of the wall. Like this:

Conduit-isolation-1.png

Conduit-isolation-2.png

Conduit-isolation-3.png

The black "sleeve" is the rubber or canvas that is wrapped around the decoupling gap in the conduit. Do this for ALL your wiring connections, including electrical, if you need good isolation. You will also need to do something similar for your HVAC piping bundle, if you use mini-split system inside the room for that.

The second hole for the speaker lines run that is a couple feet away from this mic line hole location is further from the AC power conduit in question, but figured if I had to pick one to be closer to this existing AC power line, better that it be the one with mostly balanced cables? Am I crazy with that logic?

As I mentioned above, I don't normally run speaker lines between rooms. I run balanced lines, and place the amps as close as possible to the speakers.

Otherwise I was going to combine mic/line level, Cat6, & MIDI cabling all into one conduit.

IT shouldn't be a problem, but I normally keep all analog audio signal cables in one set of conduit, and put all other cables, especially digital ones, in another conduit or set of conduit. You might also need other lines, such as telephone, alarm, cable TV, internet, intercom, CCTV, etc. Keep all of those separate from your analog audio cables, if possible. It's probably overkill for short runs like you are talking about, but once again, it's better to do everything possible now to keep out interference, because fixing it after the studio is built means tearing into carefully built and hermetically sealed isolation walls. For this same reason, I normally run a couple of extra empty conduit lines, for future expansion, or as spares when I find out after the room is finished and while I'm trying to pull cables through, that some clumsy workman put a nail through one of my conduits, and the cables can0t get through.... So try to think ahead, and plan for every possible eventuality that might happen after your walls are closed up and all of that becomes inaccessible. A few extra feet of unused empty conduit is dirt cheap, compared to the cost of tearing holes in your wall...


- Stuart -

[oliverh]

The interior dimensions of the garage are approx 17' by 18.5' inside of unfinished 2x4 framed walls.

Just to clarify: If you stand inside your garage right now and loo around you, then you see studs, and the distance across the garage from the face of the studs that you see on the left wall, to the face of the studs that you see on the right wall. is exactly 17.000 feet: Precisely 204.0 inches. While the distance in the other direction is exactly 18' 6.0", or precisely 222.0 inches. Correct?

To be even more precise, the width of the garage from 'stud to stud' is 17' feet & 1.5" inches. The depth is 18' feet & 8" inches and this depth measurement is stopping a couple inches INSIDE of where there is currently garage door track running vertically (more comments on this later).

Also just to clarify: You now plan to construct a new frame, within the garage, resting on the same slab, and you will have drywall on just one side of that new frame. Correct?

Yes. Have a question as to whether or not he base plate wall studs would need to be isolated with any material or would just be bolted into the existing slab as is? I have not received Rod Gervais' book yet, but roughly was expecting that I would insulate the existing outer leaf walls without covering them on the inside and then would use drywall on both sides of the new frame/inner leaf wall...? Some on the back in order to press insulation into the gaps and then drywall on the front for finishing? Or this is overkill perhaps?

How do you plan to deal with the garage door?

I plan to essentially build two walls inside of the existing garage door. I will remove the horizontal portion of the garage door track and psychically fasten the garage door to the existing framing of the garage structure. The first interior wall will be the "wall that never was built" and that could attach to the existing outer leaf framing of the existing structure, along with weather proofing, moisture flashing at the bottom of the wall, etc. And then, with an air gap, construct the second inner leaf wall as part of the room-in-a-room structure matching what I will be doing throughout the rest of the space.

It has a vaulted ceiling but the point at which a "ceiling" would otherwise be is at about 8'3" up from the slab

In othere words, the bottom chord of the trusses (or underside of the joists) is exactly 99.0" above the surface of the slab? And your current plan is to put drywall on the bottom of those joists/trusses to complete the outer-leaf of your studio, then your new inner leaf will set a few inches below that. Is that correct?

Yes, the bottom of the trusses is (to be very exact) 8' feet & 3.75" inches above the surface of the slab. And yes, inner leaf will match the similar shape of outer leaf truss construction but set a couple inches below/away.

The bedroom measures approx 12'x12'

In other words, it is square? And since I'm assuming that your house is built fairl standard, that implies an 8' ceiling? So how did you deal with the large modal issues that these dimensions imply, and what was the result? Have you done an actual acoustic response test in that room, using REW? If not, then please do that now, and post the results here. I suspect that you have issues that you are not aware of.

Give or take a few inches in each direction, yes, it's roughly 12'x12'. However, it's broken up with some built-in book shelving and a built-in desk on the side of the room, along with a closet space that I renovated into simply an open space that houses all my rack equipment. In other words, there is a bit of "break up" structure existing in the room that helps it not just be a bone dry square box. I have a lot of bass trapping going on in the room. 4 GIK Tri-Traps in the front two corners (2 in each corner), 2 GIK Monster Traps on wall behind monitors, 2 GIK 244 panels overhead as a "cloud," 2 GIK 244 panels flanking the mix position on the side walls, 4 more smaller square 244 panels - 1 angled where ceiling meets wall behind monitors, 1 on wall behind monitors, 2 on back wall of room.

I have yet to sine sweep the room with REW but would be curious to see what the results are. In my last room, I tore my hair out trying to get "linear response" only to finally realize that what still looked like messed up low end response curves after a lot of bass trapping was actually VERY good response when I showed it to a few acousticians at GIK.

I plan to make a separate conduit run dedicated to higher voltage speaker cable

Speaker cable? Why are you running speaker cable between rooms? That implies that you have the amp in one room, and the speakers in the other room, which implies a large voltage drop and strange impedance, unless you use wiring that has a very large cross section and low resistance. It would be much better to put the amp in the room, right next to the speakers, with the shortest possible cable run, and just send line-level signals to the amp through your snake.

I'm running speaker cable between the rooms so I can have someone play into a guitar amp in the control room and mic a cabinet in the live room. I would try to use the heaviest gauge cable practical to reduce resistance the best I can. Some level might be lost over the 25-30ft run, but it would likely be negligible as it relates to a guitar amp, from what I understand? If we're doing it with a combo amp, I would do as you say and use the Radial SGI interface system which converts Hi-Z instrument level to mic level & impedance for running long distance over XLR (unless you're possibly referring to me thinking i was going to run mixing monitor speaker cabling between two rooms?)

Firstly, I'm wondering if there are any issues with me running the mic cable bundles throughout the tracking room BEFORE they arrive at the points where the conduit will run WITHOUT any conduit behind the inner walls of the tracking room?

While it is might be possible to do that, it's something that I don't ever do in studios, for one simple reason: If you ever need to repair or replace a faulty cable, or run a new one, you would have to dig huge holes in your isolation walls to get at it. I always run conduit, even when it isn't really necessary, so that it is always possible to simply pull a faulty cable out and replace it with a good one, by just pulling it though the conduit. To be able to do that successfully, you need to use conduit that is quite a bit larger in diameter than the wire bundle you are using, and you need to keep all your bends gentle, smooth, and wide radius. You also need to be careful around the decoupling gap in the conduit, between the leaves of your wall, to make sure the gap is smooth enough and lines up well enough to allow easy pulling of cables.

I don't use metal conduit for this: I use PVC conduit, since it is easier to work with, and cheaper, and you can get it in fairly large diameters.

Excellent point! And yes, was planning on using PVC conduit between the two rooms and now would want to use it also within the main tracking room too.

running mic lines in the air space between my dual-framed non-touching walls

I would not run individual mic lines: I would run a multi-conductor audio snake. You have many mic and line channels in one single cable like that.

Yes, was planning on running snakes. I am currently looking into have several made custom, one for each wall plate in the room that I am looking to have. So they will be pre-bundled/harnessed mini-snakes running behind the inner leaf wall on their way to converge at the conduit exit for under the house.

Secondly, this leads me to my next question pertaining to where I plan to be coming through the wall of my garage with the conduit on its way under the raised foundation of the rest of the house. The spot I've located where I want to punch through happens to come within a few inches of some metal conduit for AC power fed to the wall shared between the house and garage.

I normally do the link across the air gap with two offset conduit sections, so that there is no mechanical connection between the leaves of the wall. Like this:

Conduit-isolation-1.png

Conduit-isolation-2.png

Conduit-isolation-3.png

The black "sleeve" is the rubber or canvas that is wrapped around the decoupling gap in the conduit. Do this for ALL your wiring connections, including electrical, if you need good isolation. You will also need to do something similar for your HVAC piping bundle, if you use mini-split system inside the room for that.

Good to know!

The second hole for the speaker lines run that is a couple feet away from this mic line hole location is further from the AC power conduit in question, but figured if I had to pick one to be closer to this existing AC power line, better that it be the one with mostly balanced cables? Am I crazy with that logic?

As I mentioned above, I don't normally run speaker lines between rooms. I run balanced lines, and place the amps as close as possible to the speakers.

Would love to not have to run speaker lines between rooms, as it's clearly not ideal, but have run into situations where artists would like the ability to tweak their amp in the control room while monitoring a mic'd cabinet in the other room. The compromise seems mostly negligible, I hope, when we're talking about a rather high-voltage guitar amp?

Otherwise I was going to combine mic/line level, Cat6, & MIDI cabling all into one conduit.

IT shouldn't be a problem, but I normally keep all analog audio signal cables in one set of conduit, and put all other cables, especially digital ones, in another conduit or set of conduit. You might also need other lines, such as telephone, alarm, cable TV, internet, intercom, CCTV, etc. Keep all of those separate from your analog audio cables, if possible. It's probably overkill for short runs like you are talking about, but once again, it's better to do everything possible now to keep out interference, because fixing it after the studio is built means tearing into carefully built and hermetically sealed isolation walls. For this same reason, I normally run a couple of extra empty conduit lines, for future expansion, or as spares when I find out after the room is finished and while I'm trying to pull cables through, that some clumsy workman put a nail through one of my conduits, and the cables can0t get through.... So try to think ahead, and plan for every possible eventuality that might happen after your walls are closed up and all of that becomes inaccessible. A few extra feet of unused empty conduit is dirt cheap, compared to the cost of tearing holes in your wall...

Good call, I do plan to run CCTV between the rooms over standard analog BNC cables... and sorta thought I could just run those wild on their own without conduit...?? I also plan to run Ethernet for both a WiFi extender and screen-share capability for controlling the control room computer. Again, was thinking I could just run that exposed under the house as I've done before for the rest of the house for general networking. And I guess I could keep the MIDI cabling outside of the analog conduit if I went with multiple conduit runs.. but no big concern there?

I also plan to have multiple Cat6 cables running to different points in the room that would be dedicated to headphone monitoring (Hear Tech's HearBack system) and that carries audio as well as power via PoE... so would running PoE deem them no longer "digital only" cables?

Whew! Ok I think that's all for now!

[Soundman2020]

Have a question as to whether or not he base plate wall studs would need to be isolated with any material or would just be bolted into the existing slab as is?

Usually it's just bolted into the slab, but with several beads of good quality caulk under it, to create a good seal. You only need rubber seals if your slab is very uneven, pitted, cracked, gouged, or otherwise in a pretty bad state such that the sole plate wont sit flat and leaves large gaps under it, or if you need very high levels of isolation.

was expecting that I would insulate the existing outer leaf walls without covering them on the inside and then would use drywall on both sides of the new frame/inner leaf wall...?

If you put drywall on BOTH sides of your inner-leaf frame, then you'll have a three-leaf system, which potentially REDUCES your isolation, as shown here:

2-leaf-3-leaf-4-leaf-STC-diagram--classic2-GOOD!!!.gif

That shows three different scenarios: On the left is what happens if you put drywall on both sides of both frames: You only get around 35 dB of isolation (yeah, it says "STC-44", but STC is not decibels, so ignore that). The middle scenario is what you propose: Outer leaf with sheathing on just one side, inner-leaf with sheathing on both sides. And you get a 10 dB boost, to maybe 45 dB, but that's still not very good. The final diagram, on the right, shows how you should do it: Sheathing on only ONE side of each frame, for another 10 dB boost, to maybe 55 dB.

So even though the wall system on the left and the wall system on the right both have exactly the same building materials and exactly the same total thickness, the way they are arranged on the version on the right gives you one hundred times more isolation (20 dB).

Not intuitive, but very true. Only ever build two-leaf isolation systems. Never 4 leaf! And 3-leaf only if you have no other choice, but then you compensate for the lost isolation with more mass and larger air gaps.

I plan to essentially build two walls inside of the existing garage door. I will remove the horizontal portion of the garage door track and psychically fasten the garage door to the existing framing of the garage structure. The first interior wall will be the "wall that never was built" and that could attach to the existing outer leaf framing of the existing structure, along with weather proofing, moisture flashing at the bottom of the wall, etc. And then, with an air gap, construct the second inner leaf wall as part of the room-in-a-room structure matching what I will be doing throughout the rest of the space.

You have the basic idea right, but here too you need to avoid three-leaf and four-leaf systems.

Here's the way I normally deal with that situation:

PKNCUS-Garage-Door-Isolation-Plan-01.png

PKNCUS-Garage-Door-Isolation-Plan-02.png

PKNCUS-Garage-Door-Isolation-Plan-03.png

PKNCUS-Garage-Door-Isolation-Plan-04.png

PKNCUS-Garage-Door-Isolation-Plan-05.png

PKNCUS-Garage-Door-Isolation-Plan-06.png

Of course, you first need to lock down the door itself to the wall, so it cannot move! That's not shown in the above sequence, for clarity, but here's one way of doing that:

PKNCUS-Garage-Door-Isolation-Plan-10.png

However, it's broken up with some built-in book shelving and a built-in desk on the side of the room, along with a closet space that I renovated into simply an open space that houses all my rack equipment.

So the room is not symmetrical? Have you done a test to see how far off that is? In other words, comparing the acoustic response of the left speaker to that of the right speaker?

In addition, the items you mentioned wont have any real effect on the modal response of the room, which is the key. Sound waves are only affected by objects larger than the wavelength, and considering that the wavelength for typical modal problems in small rooms is measured in dozens of feet, a desk of bookshelf is way too small to have a major effect.

I have yet to sine sweep the room with REW but would be curious to see what the results are.

Great! Get out your sound level meter, use that to calibrate your sound system and REW to 80 dBC for each individual speaker (then you will automatically get 86 with both of them on), and run three tests: Left speaker only turned on, right speaker only turned on, both speakers on. Upload the resulting MDAT file to a file sharing service, such as Dropbox, then post the link here.

I tore my hair out trying to get "linear response" only to finally realize that what still looked like messed up low end response curves after a lot of bass trapping was actually VERY good response when I showed it to a few acousticians at GIK.

Wellll... maybe. But was it as good as this?

www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=20471

That shows what can be accomplished by very careful design and very careful tuning. I wonder what the folks at GIK would say about that?

I'm running speaker cable between the rooms so I can have someone play into a guitar amp in the control room and mic a cabinet in the live room.

You do not need speaker cable for that! It looks like you are not thinking this through. Just put the amp in the live room, along with the speaker, and mic it there.

Some level might be lost over the 25-30ft run, but it would likely be negligible as it relates to a guitar amp, from what I understand?

Perhaps, but do the math to find out for sure:

ILoss = 20* log [ (Rload / (Rload + Rcable) ]

For a 40 foot run assuming 4 ohm speakers impedance, you'd need 12 gauge or larger. It's not just voltage loss that you need to be worried about, but also things like damping factor, impedance mismatch, and things like that.

Good call, I do plan to run CCTV between the rooms over standard analog BNC cables... and sorta thought I could just run those wild on their own without conduit...?? I also plan to run Ethernet for both a WiFi extender and screen-share capability for controlling the control room computer. Again, was thinking I could just run that exposed under the house as I've done before for the rest of the house for general networking. And I guess I could keep the MIDI cabling outside of the analog conduit if I went with multiple conduit runs.. but no big concern there?

My personal "rule" is to put everything in conduit. You never know when Murphy's Law will strike you, and according to that law, the only cable you did NOT put in conduit, is the one that will fail... Conduit is cheap. So use it any place that you will never have access to again, after the studio is completed.

I also plan to have multiple Cat6 cables running to different points in the room that would be dedicated to headphone monitoring (Hear Tech's HearBack system) and that carries audio as well as power via PoE... so would running PoE deem them no longer "digital only" cables?

Well, they carry both analog (power) and also digital, so that still makes them digital.

As I mentioned, you probably won't have any issues with interference and hum getting into your system, but it's still good to do whatever you can to minimize even the vague possibility.

- Stuart -

[oliverh]

Wow thanks so much for all the input so far, Stuart. Hugely appreciated. I've been making my way through Rod's book page by page, skipping around a little to bigger points of interest, but one question I have so far that I don't quite understand a way around is the fact that my 2-car garage space that will be my starting structure includes truss bracing (I think that's what it's called?) that forms an "X" shape across where a flat ceiling would otherwise be in the structure, along with some horizontally mounted scabbed-together scrap lumber that also runs along the same plane as the "X." Obviously I'm not a construction expert by any means, but I have to assume these are necessary to keep the vaulted part of the roof structure from pushing downward into the 4 walls' interior? In other words, these beams are required to stay? Or are they? Were they just put in as bracing to complete the construction and then left? Also, a reminder that my garage is attached to the rest of the house, in case that was of any benefit for not needing these beams.

Firstly, I desire to have a somewhat vaulted inner room built within this garage structure if at all possible. Secondly, these trusses aren't very attractive. But I don't see how I will be able to build around these beams other than building a flat ceiling for my inner room if they have to stay? I'd love to find a way to keep a non-flat ceiling for the final shape of the independently framed interior room ceiling... one that follows the similar angles of the existing roof but just an interior framed version of it, even if I have to make some compromises and/or move the positioning of these truss beams upwards a bit? I have to imagine these trusses are rather common in garage construction... or are they? I've just never really paid much attention to them until now when I have this very specific idea in mind of building a studio inside it.

I've attached several pictures, not super ideal, but I think the few camera angles will illustrate what I'm talking about. It just seems like an awful lot of wasted vertical space if I can't utilize the upper part of the vaulted ceiling structure. Plus I would think it would help with reflections a bit and also, it just looks cooler.

Please ignore all the miscellaneous debris, fluorescent lighting, garage door opener, and temporary sheets of plywood hanging around everywhere in the rafters. The previous owner had all sorts of extra lumber going on, for storage I assume, which I plan to remove.

Ideas?


Also, on a related but different topic pertaining to the previous post in this thread...

Since I have a slab floor in the garage, you mentioned that I could bolt the base plate studs for the interior wall framing straight onto the floor with use of caulk to help seal it. The floor seems like it's in pretty good shape and is rather flat, so hoping that caulk would indeed suffice for sealing the base plates. However, you mentioned it really depended on how much isolation I needed. One of the primary purposes of this studio will to be able to record loud rock drums. So, obviously somewhat subjective, but I live on a quiet cul-de-sac street with neighbors about 10 feet to one side of this structure and about 40 ft to the other side.

Rod's book mentions that there are some neoprene products available for isolation of base plate studs and I've also seen mention of a thin layer of fiberglas insulation being placed underneath for a similar effect. Assuming airtightness is achieved with caulking, how much increase in isolation (in dB?) can really be attained using this approach over wood-to-slab?

Lastly, it seems pretty unanimous that a slab floor doesn't really need floor floating and this makes sense. However, Rod's book also mentions a degree of success with a modified floating deck constructed of 1" of 703 rigid insulation with two layers of plywood covering that and that this helps with barrier to impact sound transmission to rooms below your floor. Perhaps a silly question, but since there is no room below me to isolate from, would this help me in isolating impact sound from reaching my neighbors or inside my house, particularly if a loud rock drummer is playing?


Kind regards,

Oliver

[Soundman2020]

structure includes truss bracing (I think that's what it's called?) that forms an "X" shape across where a flat ceiling would otherwise be in the structure, along with some horizontally mounted scabbed-together scrap lumber that also runs along the same plane as the "X." Obviously I'm not a construction expert by any means, but I have to assume these are necessary to keep the vaulted part of the roof structure from pushing downward into the 4 walls' interior?

I'm not a structural engineer either, so you should hire one to get a true qualified opinion, but I'm not convinced that the "X" in those photos is structural. Perhaps it is, and there's something I'm not seeing in there, but I don't see a real purpose to it, and even if it is necessary, it is also probably possible to replace it with something else, higher up. You might even want to consider re-doing your trusses, to get even more room up there: I've done a couple of places where that helped. Ask your structural engineer about modifying those trusses to make them into collar-tie trusses, with the collar raised as high as possible.

Firstly, I desire to have a somewhat vaulted inner room built within this garage structure if at all possible.

With raised collar ties, that would be possible:

BEFORE: (Look familiar?)

OWCAUS--ORIGINAL-roof-inside-SML-ENH.jpg

AFTER: (Raised collar ties, sistered rafters, new ridge beam)

OWCAUS--FINAL-roof-inside-SML-ENH.JPG

That's for one of my customers in California. We then put drywall on the bottom of those trusses, to create the middle leaf, and built the actual rooms below that, each with it's own ceiling. If you were to do something like that, you'd be able to raise your inner-leaf ceiling to follow that.

But I don't see how I will be able to build around these beams other than building a flat ceiling for my inner room if they have to stay? I'd love to find a way to keep a non-flat ceiling for the final shape of the independently framed interior room ceiling...

Done! See above...

I have to imagine these trusses are rather common in garage construction...

Yes, and it is common to modify them for studios, as above. We got a structural engineer to take a look, and OK this plan, which he did. As long as you get a qualified, certified structural engineer to sign off on it, then you can do something similar.

However, you mentioned it really depended on how much isolation I needed. One of the primary purposes of this studio will to be able to record loud rock drums. So, obviously somewhat subjective, but I live on a quiet cul-de-sac street with neighbors about 10 feet to one side of this structure and about 40 ft to the other side.

So you need to get out your trusty, proper, good-quality hand held sound level meter, set it to "C" and "slow", then do some tests, and come up with a number! (In decibels...)

Rod's book mentions that there are some neoprene products available for isolation of base plate studs and I've also seen mention of a thin layer of fiberglas insulation being placed underneath for a similar effect. Assuming airtightness is achieved with caulking, how much increase in isolation (in dB?) can really be attained using this approach over wood-to-slab?

You are tailing about products such as Isosil, I think:

Isosil-anchor-bolt-decoupling-isolation-collar-and-pad.jpg

They work, but once again, I'm not convinced you would need such a thing, unless you have a need for very high isolation.

Lastly, it seems pretty unanimous that a slab floor doesn't really need floor floating and this makes sense. However, Rod's book also mentions a degree of success with a modified floating deck constructed of 1" of 703 rigid insulation with two layers of plywood covering that and that this helps with barrier to impact sound transmission to rooms below your floor.

Right. Rod extends the "drum riser" concept to the entire floor, and if you check carefully, he does say that it is not a proper floated floor, just a partially decoupled floor. It's better than trying to "float" a lightweight deck on untested rubber pucks (which does not work), since Rod's method does actually disconnect the mechanical impact sounds in the deck from the sub-floor below (which rubber pucks don't), but it's still not as good as a correctly floated floor. I'm not sure if Rod as ever actually tested how much extra isolation that gets, but it's not a huge amount. However, it is worth it if you have a bad situation and need a little extra boost. I'm not sure that's your situation at all, though. Until you get your "number"... .)

Perhaps a silly question, but since there is no room below me to isolate from, would this help me in isolating impact sound from reaching my neighbors or inside my house, particularly if a loud rock drummer is playing?

Id your garage slab connected to your house slab, directly? DO they join? Is your slab connected to your neighbor's slab? If so, then a drum riser platform would probably be the way to go:

GLENN-example drum riser 2.jpg

GLENN-example drum riser 1.jpg

Glenn designed that, and it works really well. I suspect that you'd be better off with that than with trying to do your entire floor, ... unless your number is really big!

- Stuart -

[oliverh]

With raised collar ties, that would be possible

Yes, and it is common to modify them for studios, as above. We got a structural engineer to take a look, and OK this plan, which he did. As long as you get a qualified, certified structural engineer to sign off on it, then you can do something similar.

Thanks so much for your insight on this! Much appreciated. Will look into this with my contractor.

Is your garage slab connected to your house slab, directly? DO they join? Is your slab connected to your neighbor's slab? If so, then a drum riser platform would probably be the way to go:

Love this idea for the drum riser! Seems like a very cost efficient way to help further isolate from the floor what will likely be the loudest thing in the room without having to do this treatment across the entire square footage of the room. And yes, I suppose theoretically the slab of the garage does touch the house's foundation, albeit likely poured at different times but they touch. And yes, albeit separate in theory, the slabs on my property are adjacent to the neighbor's (see attached pictures of the side of my house/garage where there studio will go and where the walkway resides - my garage is the brown one). The walkway separating the two properties is attached to the neighbors garage slab, thereby connecting it to my garage slab it seems? The two properties are divided by a cinder block wall.

On a new unrelated note, as I'm reading through Rod's book, I've spent some time recently on the chapter about HVAC needs. I feel like I am likely going to go the ductless mini-split route for my space (and additionally with a 2nd blower in the house for the 'control room'). I understand the importance of the need for fresh air, but I'm a bit confused as to how to provide that to the room using an AC system like this. Other than simply opening the door to the tracking room occasionally, how do I get fresh air into the room while keeping it essentially sound-proofed still? This has been a real head-scratcher for me. I have seen diagrams of little baffle boxes that might help with keeping air flow quiet and I presume this also deflects sound from entering/exiting your room... but I guess I'm a little confused as to how to implement this, and where... and how to make sure it's not coupling a decoupled wall construction throughout my room somehow?

Additionally, if I'm going to build an iso room within the main tracking space in my garage, would it make sense to simply create a intake and outtake with a near-silent fan on the outtake (highest volume, lowest speed possible) that allows conditioned air from the main space into the iso booth? I've seen a few jury-rigged ways to go about this, but since I might be going ductless for the main room, I'm wondering if using an S-bend ducting type system just for exchanging air from the main space into the iso booth and exhausting out of the iso booth into the main space would make the most sense for a simple solution that still maintains a fairly high amount of isolation sound-wise?

Any insight is super appreciated, as always. Thanks.

[Soundman2020]

The walkway separating the two properties is attached to the neighbors garage slab, thereby connecting it to my garage slab it seems?

The walkway is not structural, and probably has no foundations, so I'd consider renting a large angle grinder or concrete cutter, and running it up the edge of the property line, to disconnect you from the neighbor. Cut a slice out there, maybe 1/4" wide or so. Maybe fill it with a highly flexible joint filler compound (soft, rubbery), to prevent water leaking down and back under the walkway. Get a local contractor (better still, a structural engineer) to take a look at that, and tell you if it is feasible.

I feel like I am likely going to go the ductless mini-split route for my space (and additionally with a 2nd blower in the house for the 'control room').

A mini-split heats / cools / dehumidifies, but it does not ventilate. You also need a ventilation system, in addition to the mini-split. And you need silencers on the ventilation system, to block the sound while allowing the air through.

I understand the importance of the need for fresh air, but I'm a bit confused as to how to provide that to the room using an AC system like this.

Simple answer: you don't! A ductless mini-split does not ventilate. So you need a ventilation system IN ADDITION to the mini.split. Two different things that work together.

Other than simply opening the door to the tracking room occasionally,

That's not a solution at all, actually, since it wont work. Opening the door of an acoustically isolated room does nothing at all to ventilate it. Since the room is sealed absolutely airtight, just opening the door does nothing. The air won't move, because there's nowhere for it to go, and nothing to drive it! No pressure differential and no path. Which is why you need a ventilation system.

how do I get fresh air into the room while keeping it essentially sound-proofed still?

You need two ducts for each room. One duct brings fresh air in, the other duct takes the stale air out. And you need a fan to drive that: The fan can be either on the supply duct or on the exhaust duct. To stop the sound getting in/out while still allowing the air in/out, you need something called a "silencer box". Examples:

http://www.johnlsayers.com/phpBB2/viewt ... 0&start=45
http://www.johnlsayers.com/phpBB2/viewt ... 9&start=74
http://www.johnlsayers.com/phpBB2/viewt ... 25&start=2
http://www.johnlsayers.com/phpBB2/viewt ... 42&start=5
http://www.johnlsayers.com/phpBB2/viewt ... 61&start=0
http://www.johnlsayers.com/phpBB2/viewt ... 5&start=98
http://www.johnlsayers.com/phpBB2/viewt ... &start=157
http://www.johnlsayers.com/phpBB2/viewt ... =2&t=13821
http://www.johnlsayers.com/phpBB2/viewt ... 8&start=44
http://www.johnlsayers.com/phpBB2/viewt ... 2&start=16

You need one of those on each duct for normal isolation, but if you want high isolation then you need TWO of those on each duct: one on the outer-leaf penetration, and the other on the inner-leaf penetration.

Of course, the fan does NOT go inside the room: it goes on the far end of the duct, as far away from the room as possible.

I have seen diagrams of little baffle boxes that might help with keeping air flow quiet and I presume this also deflects sound from entering/exiting your room...

Right. The multiple 90° turns inside the box force the air to flow around the "baffle" plates, that stop the sound from getting through. One way to think of it is that the sound can only travel in straight lines, but the air can go around corners... (It's actually not really true, and it's much more complicated than that, but it's a useful way of getting your head around the concept.)

but I guess I'm a little confused as to how to implement this, and where... and how to make sure it's not coupling a decoupled wall construction throughout my room somehow?

Your silencer box is installed at the point where the duct needs to go though the wall. For high isolation, you have one silencer box on the outer leaf of your wall, and another on the inner leaf, with a flexible duct or sleeves joining them inside the wall, between the leaves.

that allows conditioned air from the main space into the iso booth?

Not really, ant likely not allowed by building code. Generally, you are not allowed to suck stale air out of one "habitable space" (room) and supply it as sole source of the "fresh" air for another habitable space.

Before deciding how to do the HVAC ducting and silencers, you first need to define how much isolation your studio needs, as a whole.


- Stuart -