Axiom Home Page Forums General Discussion Advice from Axiom Owners Full Metal Bracket: sheet rock mounting?

I have the following problem: the spaces where each of my (soon to arrive) M22ti's go is between a built-in cabinet and a window. The space is about 16", and there is no stud in the wall.

I'd like to mount the M22's with the Full Metal Bracket. Ideally, I'd just put in hefty sheetrock mounts and be done. But the 16lb weight of the M22's out on a 2.5" lever arm (the full metal bracket) worries me. I'm afraid the torsional load might result in ripping a big chunk out of the sheetrock. Has anyone else encountered this problem?

One possible solution would be to put a 16x3" piece of maple (matches the builtin) on the wall vertically so that it would hide behind the speaker. I would mount the bracket to that. If I remember my freshman-year engineering statics correctly, that would do a much better job of reducing the torsional load on the sheetrock. And, from what I've read on the web, sheetrock can easily hold a 16lb load directly--especially with 3-4 screws.

Advice? Experiences?

thanks,
Robert

I would mount the maple piece first. As you had noted sheetrock can with stand quite a bit of load. A couple of the newer self tapping drywall anchors would work, they come in large enough capacities, but the maple strip behind the speaker would also be a nice touch.

Drywall anchors will not work. I tried using them when mounting a pair of M2i's and they pulled right out.

They work fine when mounting the bracket for the QS8's, but that's because there are 5 mounting points and the QS8's hug the wall very, very closely.

Sounds like you've got it engineered right to me. If you just use the FMB, I would think you'd end up with quite a dent in the drywall, at least. If it were me, I'd do as you suggested and mount the wood pieces first to spread the load over a wider area. Should look nice, too. Post pictures when you're done!

For optimal support I would suggest a stilt, similar to the kind that hold up tilt up walls in new construction. To do this you'll need to angle a 2x4 45 degrees down and away from the bottom of your speaker and onto the floor. In order to keep the stilt in place you'll need 6" piece of 2x4 to use as a stop that will be nailed at the foot of the stilt using 2" concrete nails. (to avoid excess work, predrill some holes in the floor, don't worry about carpet, it won't hurt most drill bits). Now ideally, you'd want to break out the foundation where the stop will be and pour a 1'x1'x1' footing with anchor bolts comming out of the concrete, but that might be over kill, unless you decide to upgrade to bigger speakers in the future. Now, if your not married, then congradulations, you're done!! If you are married, you can extend your marrage by about a month or two if you paint the stilt a color that matches or accents your wall. That's it. I'm glad I could help!

How are you at patching drywall, you could cut a square out of the dry wall insert a piece of wood in behind a section of 1x6 about 12-16" long would do fine. The 1x6 is also used as the backer to screw your cut out piece of dry wall back in, fill the holes some paint and you now have wood and a good load bearing surface to attach the FMB too.

IF you use good heavy duty nylon or metal Zip-its in the drywall, you should be fine. They have held a ~50 lb screen on the wall in my living room and 18 lb JBLs in the bedroom on mounts not to different from the FMB. See here http://lawn-and-garden.aubuchonhardware.com/screws_anchors_nuts_and_washers/anchors_lag_screws_hollow_wall_screws/zip-it_anchors_with_screws-728519.asp. Target sells a really strong nylon one. Home depot has bulk metal ones.

Are the 18lb JBLs you describe out a bit from the wall on the brackets? My primary concern is that with the speaker's center of gravity out another 4-5", the torque on the FMB will be pretty significant.

I'm not experienced with drywall repair, and we just had the inside of the house painted this week! (After I drilled the holes for the surround speakers.) The only other option is the strip of maple mentioned above, but it seems rather permanent.

Robert

I encountered a similar situation when mounting my VP150 with FMB to sheet rock with no stud. In theory some compression-spreader-type dry wall anchors (aka hollow wall anchors) will hold it. However this varies depending on dry wall thickness, distance from stud, and probably environmental factors like humidity. Also the heavier-duty anchors may not be compatible with FMB -- screw diameter may be too large for the FMB screw holes.

Make sure you don't use a simple plastic expansion anchor. Use some type of spreader anchor (toggle bolt, molly, etc) that expands behind the dry wall. For details see http://www.naturalhandyman.com/iip/infanchor/infanchor.shtm

My HDTV was beneath the VP150, so I decided not to risk it. My options were concealing a board behind the VP150 that spanned to the closest studs, then mount the VP150 to the board, or shifting the entire speaker, TV, etc. to the right 8" to hit the stud (which I ultimately did).

In your case you can't move L/R. While the right type of hollow wall anchor could probably hold an M22 via FMB, in general I'd suggest using a board behind the speaker to distribute the load, as you described. I'd still use spreader type hollow wall anchors to hold the board. It's better safe than sorry in situations like this.

Great link, thanks!

I already bought toggle bolts, I've just been debating on adding the board. It's certainly the safest thing to do. Since we have 16-month-old twins (boys, no less), I think that I'll go for safety over wall preservation. I imagine the FMB with toggles would likely hold, but not with the weight of a toddler attemping pull-ups on it...

Robert