A favor/question for anyone with Atrium45s

jimmyhc

Hi,

I'm thinking about trying to mount a pair of Atrium 45s on my limestone masonry exterior. Has anyone else tried this?

I think I've found a reasonable 3/8" Rawl bolt for mounting in limestone. My question for you atrium owners out there: how large is the mounting bracket opening at it's largest point? From the pics I can see there is a large opening which shrinks down to a smaller one at both ends of the mounting bracket. Is the large end of the opening 3/8" or close to it?

Thanks very much!

disneyjoe7

Not sure about the 45's but I own the 55's with Stucco for exterior then plywood in the section of house which I will install them. I my case I was going to use a toggle bolt with a washer under screw head 3"x 1/4" toggle. If it was Stucco over Cinder block then lag bolt 2"x 1/4 with a washer.

So what you're asking there a "T" shaped hole for the screw where the hole is larger in middle of "T" for screw. So the speaker could be mounted left / right or down.

Hope that helps some.

disneyjoe7

WELCOME to Club Polk


Sorry I went straight to question first.

jimmyhc

Hi,

Thanks for your response. In this case I believe it's solid limestone (at least I hope I don't drill all the way through it into the house!) The bolt which will be sticking out from the stone is a rock-climbing style bolt, 3/8" in diameter.

So, what I'm trying to find out is if the mounting bracket opening, which is shaped kind of like a cross, is about 3/8" at its largest point (see attached figure, hopefully). If you haven't already hung your 55s, I'd be curious if you could measure that and let me know (approximately) how large it is.

Thanks,
J

disneyjoe7

I can check first thing in morning for ya, but I think you're ok with a 3/8" bolt / screw if you wish. I'm going with a 1/4" with a small fender washer, but again I think a 3/8" would work also.

jimmyhc

I pulled an Atrium 45 off the display at Fry's and measured the mounting bracket holes. I think it's gonna work out - they are almost a perfect 3/8" at the center. If I ever buy these and put them in, I'll try to post a pic.

-J

disneyjoe7

Checked myself because I will be doing the same for some porch speakers. A 1/4" toggle bolt won't work too big, and a 1/4" Tapcon screw is to large also. The head of these fasterns are too large to get into larger hole of "T" also the shaft of the bolt is too large to get into the end of "T" to sit correctly. I will use a 3/16" or a tad smaller for mine.

In-short 3/8" is way too large.

Desert Audio

I'm thinking he meant 3/16" not 3/8".

3/8" = OVERKILL.

jimmyhc

Hi Desert Audio,

I am really talking about a 3/8" bolt It is typically used for rock climbing, and is specially designed to expand and fill the hole it's placed in when the bolt is tightened down. 3/8" is pretty much the smallest diam. bolt you can get for this purpose (I'm drilling into pure limestone.)

I got the Polk people to email me a CAD drawing of the back of the Atriums. The mounting bracket diameter is marked as 0.42", essentially perfect (I think) for what I'm attempting to do.

I'll let you know how it turns out when I finally get these.

disneyjoe7

Jimmy,

I took some pictures which I post when I get home for ya, I'm thinking anything over 3/16" will not work. Besides being overkill it just won't work.

jimmyhc

Well, in spite of Disney Joe's advice that it wouldn't work I went ahead and hung the speakers using the 3/8" bolts in limestone masonry. They sound great. I'm attaching a few pics so you can check it out for yourself!

First pic: Here is the 3/8" carbide-tipped masonry drill bit, and one of the 4 RAWL 5-piece bolts I used.

Second pic: a shot of the hole after it was drilled in the limestone. This hole extends about 2.5" into the limestone exterior.

Third pic: Here's a shot of the bolt after it was hammered into the hole. These bolts are designed to be completely removable, so you can take them with you if you ever move.

Fourth pic: Here's the mounting bracket after I drilled a second hole and added a second bolt. I could have swung from a rope off there, assuming the speaker bracket would have supported it

Fifth pic: The final product, with speaker wire and j-box cover painted to match the house exterior.

This was an extremely easy project, and the Polk people were really helpful in sending me the speaker mounting bracket dimensions so that I knew my hardware would work.

-J

duksbak

Wow that looks great!

Didn't sound like too hard of a DIY project. Great pics too!

disneyjoe7

Glad it worked out for ya, I still think 3/8" bolt is a bit over the top... But it looks great.


Rock on

jimmyhc

Yeah, you'll get no argument from me that 3/8" is more bolt than is necessary. Unfortunately, this is the smallest diameter bolt of this type that is available.

On the other hand, if my house is destroyed by a tornado, that mounting bracket will probably still be attached to that rock somewhere in the next county.

F1nut

Nice job!

disneyjoe7

jimmyhc wrote: »

On the other hand, if my house is destroyed by a tornado, that mounting bracket will probably still be attached to that rock somewhere in the next county.

Funny LOL

adam2434

Just curious - would a couple standard lead or plastic anchors and screws have worked too?

I've mounted speakers to brick and concrete using anchors with no issues at all. Not sure about limestone.

jimmyhc

adam2434 wrote: »

Just curious - would a couple standard lead or plastic anchors and screws have worked too?

I've mounted speakers to brick and concrete using anchors with no issues at all. Not sure about limestone.

Hmm...yeah they probably would've worked just fine. Even though I don't see any for limestone specifically, they can be used in solid concrete and probably would have been plenty strong. I guess one advantage of the sleeve bolts is they are specifically designed to be easy to remove.