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post #1 of 33 Old 02-11-2020, 07:34 PM - Thread Starter
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Best Way To Hang Backer Boxes?

Hello Everyone!

I've been following threads on here for years. It's been an amazing source of information and knowledge. Now that I'm doing my own home theatre build its time to post a question. Hence the title The DC-04 clip seems to be what is recommended but I can't seem to find a Canadian supplier for it. (Up until recently there was an outfit called 'CSR Building Services' that had them at 10 bucks CDN a clip but not anymore it seems.) There is also something called 'Resilmount Sound Isolation Clip' available up here that looks similar.

Are these clips worth the money for what they contribute? I can get a pack of 20 zinc corner braces for $6.99 One on each side of the box would isolate it from the joist. There would just be two contact points instead of one. I'm willing to spend money where it needs to be spent but if there's a cheaper alternative that's almost as good I could then take the savings and invest in more drywall and green glue

Thanks to anyone who takes the time and I look forward to hearing your answers.
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post #2 of 33 Old 02-11-2020, 07:36 PM - Thread Starter
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Sorry its actually the 'Resilmount Right Angle Bracket...'
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post #3 of 33 Old 02-11-2020, 07:54 PM
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Quote:
Originally Posted by Ronnie71 View Post
I can get a pack of 20 zinc corner braces for $6.99 One on each side of the box would isolate it from the joist. There would just be two contact points instead of one.

Don't do this. That is not what isolation is. Read the soundproofing master thread. DC-04 clips can be used various ways (check out the installation guide on PAC International's website) and I used them to decouple my walls from my joists with great results. The Resilimount products you reference definitely look promising as just from the look of it they appear to do the same things PAC Itl offers.



Also, what is your ceiling situation? Are you using drywall on your ceiling? I ask because it would be wise to decouple the ceiling from the joists and not just the backer boxes. And if you already did this, or plan to do this then Resilimount offers the decoupling hat channel and isolation clips you need. When you do this, you can hang the back boxes on the hat channel and not even attach to the joists. I've done this with my backer boxes and projector mount and couldn't be happier.
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post #4 of 33 Old 02-11-2020, 08:22 PM
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Just gonna share this bit of @BIGmouthinDC wisdom with you. If you are doing clips and channel to isolate your ceiling, this is the way to hang your backer boxes. The lip of the backer box is even with the bottom edge of the channel - so the drywall can be screwed to the lip.

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post #5 of 33 Old 02-11-2020, 08:28 PM
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Yeah, that pic inspired me and this is what I ended up with...can't hear these speakers at all from the room above:
The hat channel was 7/8" tall so the lip of the boxes were made flush with layers of 1/8" + 3/4" MDF.



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post #6 of 33 Old 02-11-2020, 09:34 PM - Thread Starter
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Yeah I was planning on using ISO clips and hat channel. I'm having the electrical work I'm doing inspected. I'm using lotus 9w super slim LED lights. My understanding is that the connection box functions as a junction box and those can't be covered so I was going to mount those into the backer boxes and put up clips and channel after first inspection. This looks like a great idea as I wouldn't have to guess how low to hang the boxes. If I go this route that means I'd have to have my clips and channel installed before first inspection as well, yes?
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post #7 of 33 Old 02-11-2020, 09:44 PM - Thread Starter
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I've actually heard good things about the IB-1 sound isolation clip but I'd have to order it from the States.Woth checking into anyway? I can't find any reviews of the Resilmount product but it seems to look like other similar clips. I might be going with that one by default.
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post #8 of 33 Old 02-11-2020, 09:48 PM - Thread Starter
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Just taking a closer look at the pics. Are they attached to the joists, resting on the channel or is there something else I'm not seeing?
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post #9 of 33 Old 02-11-2020, 10:09 PM - Thread Starter
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Right...hung on the hat channel! Guess I've got more work to do before the inspector comes.
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post #10 of 33 Old 02-11-2020, 10:41 PM
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Backer boxes are resting on top of the hat channel, screwed in from below (4 screws per box) through the top (skinny) flange of the channel, just to keep it from moving. In the attachments below I circled the screws mounting the boxes to the hat channel. You don't want to screw through the bottom flange since that protruding screw head could mess up your drywall install later.

Box is not touching the joists at all, to maintain isolation of the decoupled ceiling.

When you install the first layer of drywall, run a bead of acoustical caulk on the backer box flange, and screw the drywall to the backer box flange. Box becomes part of the decoupled ceiling.
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post #11 of 33 Old 02-12-2020, 04:34 AM - Thread Starter
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Thanks James! Wouldn't have noticed that if you hadn't pointed it out. If you don't mind my asking, did you use backers for any of your lighting or just speakers?
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post #12 of 33 Old 02-12-2020, 04:41 AM - Thread Starter
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Man, I really ought to try looking at these a little closer! It looks like you have lights in backers in the second pic, am I correct? If that's the case, the order to go in would be wiring, clips and channel, then backer boxes?
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post #13 of 33 Old 02-12-2020, 05:26 AM
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A clearer picture of Big's backer box attached.
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post #14 of 33 Old 02-12-2020, 05:37 AM
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didn't take...
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post #15 of 33 Old 02-12-2020, 09:45 AM
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post #16 of 33 Old 02-12-2020, 10:19 AM
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Quote:
Originally Posted by Ronnie71 View Post
Man, I really ought to try looking at these a little closer! It looks like you have lights in backers in the second pic, am I correct? If that's the case, the order to go in would be wiring, clips and channel, then backer boxes?
In this case I am just helping you find information - my theater build is within an existing bedroom that I didn't strip down to studs - no isolation. My can lights are in a soffit, and my overhead speakers don't have backer boxes.

But when I read your question, I knew BIG's picture of backer box mounted to top of channel would be the answer.

I imagine you would want to establish the locations for each speaker/light fixture and pull cabling to those areas before installing channel. Just seems easier that way. I don't know how folks are handling inspections, sorry.

Another BIG tip is to use a plumb bob or laser to transfer the locations of your backer boxes to the subfloor prior to drywalling. Once drywall is installed, you can transfer the marks from floor back to ceiling and know where to cut in.
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post #17 of 33 Old 02-12-2020, 12:30 PM - Thread Starter
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Thanks to everyone for taking the time! Very helpful stuff for sure. Exactly why I'm here.
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post #18 of 33 Old 02-12-2020, 12:41 PM
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Quote:
Originally Posted by James92TSi View Post
But when I read your question, I knew BIG's picture of backer box mounted to top of channel would be the answer.
The backerbox pic is definitely familiar but the picture of the can lights does not look like a BIGmouthinDC build because the clips are not staggered.


Quote:
Another BIG tip is to use a plumb bob or laser to transfer the locations of your backer boxes to the subfloor prior to drywalling. Once drywall is installed, you can transfer the marks from floor back to ceiling and know where to cut in.
Wisdom. And that is why we pay him to hang out here. Did you send your check this month?
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post #19 of 33 Old 02-12-2020, 02:05 PM
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Quote:
Originally Posted by ScottAvery View Post
The backerbox pic is definitely familiar but the picture of the can lights does not look like a BIGmouthinDC build because the clips are not staggered.
Correct, the first pic is from BIG/Jeff's photobucket (google image search "bigmouthindc backer box" for max results ), the second pic was shared earlier in this thread by tookoolkris, and I assume is of his theater build. I just wanted to highlight the screws fastening backer box to channel in each pic. The clips not being staggered is a good observation...
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Wisdom. And that is why we pay him to hang out here. Did you send your check this month?
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post #20 of 33 Old 02-12-2020, 04:03 PM
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The one picture is a backer box from one of my projects, the second of lights is not.
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post #21 of 33 Old 02-12-2020, 07:08 PM
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The second pic is from my theater build. The clips were not staggered simply for convenience. When I laid out the backer boxes and lights it didn't require as many extra clips for added support. In other words, many of the clip locations were strategically laid out to be exactly where I needed extra support for the backer boxes while keeping them spread out as far as possible (48").

A note about the lights: I live in the Chicago area and around here all electrical is routed through metal conduit and can't be moved without having to re-pull wires -> this makes it especially difficult to build a backer box. The lights in my build are pre-construction and attached to wood supports. I would have done remodeler lights if I hadn't gotten $3000 of pre-construction lights+trim for free. Anyway, building boxes around metal conduit is a no go (not sure if anyone on these boards that has done it). At one point I had an idea to make the box in two halves and then join them together around the conduit which would have been a nightmare. I instead opted to surround my lights with tenmat covers which help seal in the sound a bit, but not as much as the backer boxes we are talking about. Most people have romex in there walls and this isn't an issue.

I think if you check out MinHeadroom's Adult Cave build, he went as far as making backer boxes light switches and outlets, as others have I'm sure:
https://www.avsforum.com/forum/19-de...ic-feet-4.html
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post #22 of 33 Old 02-12-2020, 07:25 PM
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Quote:
Originally Posted by James92TSi View Post
Backer boxes are resting on top of the hat channel, screwed in from below (4 screws per box) through the top (skinny) flange of the channel, just to keep it from moving. In the attachments below I circled the screws mounting the boxes to the hat channel. You don't want to screw through the bottom flange since that protruding screw head could mess up your drywall install later.
As a follow-on to this. Another thing I did, which was a tip from others, was put acoustical sealant on the lip of the box before drywalling so there are no gaps between the box and drywall. Then run a screw through the drywall into the lip on the 4 sides of the box to prevent any possibility of the box separating from the drywall and producing vibrational chatter.
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post #23 of 33 Old 02-13-2020, 05:08 AM
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In a clip and channel system each clip is intended to hold around 30 lbs, so I throw up an extra clip for each backer box near one of the corners.
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post #24 of 33 Old 02-13-2020, 11:21 AM
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Thanks all who've contributed to this thread!

Additional question/clarification: Are you all simply drywalling over the backer box, and then cutting in and installing a renovation / old work recessed light can?
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post #25 of 33 Old 02-13-2020, 11:47 AM
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Thanks all who've contributed to this thread!

Additional question/clarification: Are you all simply drywalling over the backer box, and then cutting in and installing a renovation / old work recessed light can?
Yup! That's the simplest approach.

Pre-wire romex into the backer box with plenty of extra length. Drywall over the backer box (caulk and screw the first layer of DW to the backer box). After DW, cut in for the light fixture, grab your Romex and pull it out, make the connections, and install the old work can.
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post #26 of 33 Old 02-14-2020, 06:52 AM - Thread Starter
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This is really going places Would someone mind giving me an abbreviated explanation about why the zinc corner braces I mentioned at the top of this thread (one on each side of the box attached to the joist) isn't a good idea as opposed to the much more pricey DC-04 clip? The backer box would still be floating except for an extra contact point. I get the logic behind resting the backer on the channel. It would seem to to be the best solution. I'm only giving consideration to braces because I'd be able to get the wiring and the rough in inspection over with sooner (thus saving me the cost of extending my permit) and I wouldn't be as rushed putting in clips and channel. (I'm finding things are taking a lot longer because I've never done them.)
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post #27 of 33 Old 02-14-2020, 08:10 AM
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It boils down to an undocumented difference in isolation of a solid zinc corner clip and a resilient clip. I don’t think anyone can tell you what the net difference is going to be in the overall project result.
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post #28 of 33 Old 02-14-2020, 06:01 PM - Thread Starter
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Did the channel actually have holes you could use to screw in the backers or did you have to add those? (The hat channel I've seen pics of seems rather smooth)
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post #29 of 33 Old 02-14-2020, 09:08 PM
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You use self tapping screws for metal channel either sheet metal screws or fine thread drywall screws. When you spin them and push tight they create their own holes.
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post #30 of 33 Old 02-15-2020, 06:12 AM - Thread Starter
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Thanks a lot BIG! If you don't mind my asking, what are the dimensions of the backers you typically build? (Allowing of course that different situations will cause this to vary.) I used the Sound Company manual for the sample box I built. I'd rather make them before purchasing/installing channel however I'd wait if that's preferred.
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