RichardP Posted April 5, 2005 Share Posted April 5, 2005 I use a Quartet as my center speaker which sits on top of my 55" RPTV. The speaker weighs about 50 lbs., which is heavy enough to cause the top of the TV cabinet to sag. I thought about using a 1/4" sheet of tempered glass, but found it would cost about $65 and still may not prevent sag. My alternate plan is to build a shelf-like structure which will span the width of the TV top (50"wide X 12" deep) but contact only the left and right edges of the TV top on 1x2x12 or 2x2x12 "legs" or "skids" attached underneath the shelf. Thus the weight of speaker and shelf will be resting on, and supported mainly by, the TV's side panels, without resting on the TV's top center surface. My question is, what will be the stiffest wood product to use in this situation? I have looked at 1x12 pine, which flexes a little; laminated (edge-to-edge) 1x12 pine boards, which seem stiffer; and have also thought of glueing and screwing two such boards together. I also thought that a front and/or back "face" glued and screwed to the edge of the shelf would add stiffness. 3/4" plywood would seem very rigid, but I don't think I can get it locally larger than a 4x4 sheet (just shy of my 50" needed width). Are there any carpenters or engineers out there who could advise me? I cannot build an actual shelf on the wall, nor is there room to use an entertainment center "bridge" over the TV, so it has to be something that is not too heavy that can sit on top of the TV. Thanks in advance. Here is a crude text-character illustration: < speaker > xxxxxxxxxxxxxxxxxxxxxxxxxxx <--- 50"x12" x ? shelf xx xx <--- 1"x 2" (or 2x2) "legs" -------------------------------- <--- top of TV Quote Link to comment Share on other sites More sharing options...
T2K Posted April 6, 2005 Share Posted April 6, 2005 MDF Quote Link to comment Share on other sites More sharing options...
WMcD Posted April 6, 2005 Share Posted April 6, 2005 You could use the 1 x 12 as the shelf. Then add a 1 x 2 at the front and back to form what looks like a shallow inverted U as seen from the side (i.e. in cross section). The 1 x 2 s should be oriented long axis of the cross section up and down. In engineering, this is a channel cross section. You'll have to glue this up but I don't know if you have that sort of talent at hand. It is not too difficult even for a first time project. I'd position the 1 x 2 s under the shelf at the front and back edges rather than attached to the front and back edges. You see this type of structure under the top of a regular old kitchen table. This will add a very great amount of stiffness to the shelf. Consider a yard stick. If you use it as a "shelf" while it is laying on its broad side, it will flex like a diving board when a vertical force is applied. If you flip it on to its thin side, it is very stiff and inflexable to vertical forces. So you're adding this type of stiff structure. Home Depot should be able to fix you up with these sort of pieces and even cut them to the 50 inch length. Don't use MDF. If you do, the Thought Police section of the American Society of Civil Engineers will haunt you. Best, Gil Quote Link to comment Share on other sites More sharing options...
fini Posted April 6, 2005 Share Posted April 6, 2005 Journeyman carpenter here. Maybe I can help... Gil is right on, if you ar fixed on using wood. Basically, you'd be making the front and back edges thicker, and thicker is better (less flexible). You really have ZERO room for dropping legs down to the floor? That's hard to believe. I'd be extremely worried about relying on a few legs holding up such a huge speaker above your TV. Maybe I'm hyper-sensitive living in "earthquake country," but imagine that thing getting bumped off the TV. I mean, you aren't considering attaching the legs to the TV, are you? Perhaps you might consider some type of metal shelving, like that kitchen "Metro" shelving. It seems pretty stiff, and perhaps you could bring a couple of the legs down to the floor (depending on the size of the shelf, the shape of the TV back, etc.). See if you can at least get some sort of bracing connecting it to the wall behind. A few pictures would be extremely helpful... One note about the Metro shelving, and construction material in general. Typically, stuff comes in multiples of 2-foot lengths (the Metro stuff linked comes in 1-foot multiples). 50" is not a difficult size to manufacture in wood (although you'll be wasting 22" from a 6-foot board), but metal shelving would be a PITA to cut (and would require some other fabrication to make it work with the intended legs). So, see if 48" will work... Quote Link to comment Share on other sites More sharing options...
RichardP Posted April 6, 2005 Author Share Posted April 6, 2005 Thanks Gil and Fini, very much. Gil, I see exactly what you are talking about, having the 1x2s attached underneath the main 1x12 instead of on the edge of it. Fortunately, that is within my modest woodworking skills. Here's one more question: do you think I should still try to have the shelf rest on the TV top only at the left and right edges, so no weight is in contact with the middle flexy portion of the TV top, or will this channel structure be so rigid as to not flex at all? Fini: I guess I am living dangerously, as I have never worried much about the speaker falling off the TV (and the speaker is even tilted down a couple of degrees with a 1x2 propping it up underneath in the back; speaker is on its side, of course). I don't have kids or others who would bump it, nor do I live in an earthquake area, and believe it or not, I have even rolled the TV with speaker out a foot or two to make/change connections in the back! I have thought about attaching a small piece of metal or something to the shelf front to form a small lip, so the speaker would not slip over the front edge if it got a big bump. Your suggestion of the metal shelving is a very good solution, but it just would not fit in with my decor that well. My room has a lot of natural wood moulding, and of course, there is a lot of that nice Klipsch walnut in all parts of the room. As far as this shelf goes, I found a textured spray paint that matches the dark gray of the Mitsubishi RPTV very closely, so it will look fairly unobtrusive. Thanks again for all your great suggestions. Quote Link to comment Share on other sites More sharing options...
fini Posted April 6, 2005 Share Posted April 6, 2005 Those metal shelves come in elegant black... Quote Link to comment Share on other sites More sharing options...
Joe Shmoe Posted April 6, 2005 Share Posted April 6, 2005 As Fini stated, I find it hard to believe you don't have room for a sheet of 3/4" plywood to run on either side of the TV. I thought of doing it that way myself. Then your just making somewhat of a box and sliding it back over the TV. Then you would probably need to just run some across the back to help stiffen in it up a bit. After thinking about it a bit I decided to just mount a shelf to the wall. You stated that maybe you cannot do that? Here's a pic of mine.... Quote Link to comment Share on other sites More sharing options...
T2K Posted April 6, 2005 Share Posted April 6, 2005 I would still use MDF. Although the modulus of elasticity of MDF is greater than that of various types of wood, were you to use 2 sheets boxing in 3 or 4 stringers along the length of the 'riser', the thing should be plenty strong. Sort of like a shoe box with 1 or 2 braces running the length of the thing. You could even use precut 1x2 oak strips butt jointed along the edges with 1 or 2 'stringers inside the box instead of MDF were you worried about the horizontal integrity of the thing(cost factors arise). For butt joints and screwing in the edge of MDF you should predrill all holes and use straight shanked screws to avoid splitting the edge of MDF. Also seal the thing, else those toxic fumes will kill you. I imagine you can buy all the MDF precut at your local Home Depot. It is cheap. A 3/4" by 16" piece of MDF shelving 6' length costs about $4, I don't know if the 1x2's come precut, I've never looked for it myself. They do have precut 1x2's in various types of wood although its more costly. Also, MDF just sounds better than other materials. Its stiffness and density yield good accoustical damping properties. Glued and screwed properly the thing should be strong enough to support your TV, and weigh just about as much. Keith (shade tree cabinet man) Quote Link to comment Share on other sites More sharing options...
fini Posted April 6, 2005 Share Posted April 6, 2005 ---------------- On 4/6/2005 4:03:19 PM T2K wrote: ...elasticity...wood...length...'riser'...the thing...strips...butt jointed...the box...horizontal integrity ...arise...screwing...holes...straight shanked......screwed properly... ---------------- My, my, my... Quote Link to comment Share on other sites More sharing options...
mike stehr Posted April 6, 2005 Share Posted April 6, 2005 I sense sexual frustration..... Quote Link to comment Share on other sites More sharing options...
T2K Posted April 6, 2005 Share Posted April 6, 2005 ---------------- On 4/6/2005 5:31:06 PM fini wrote: ---------------- On 4/6/2005 4:03:19 PM T2K wrote: ...elasticity...wood...length...'riser'...the thing...strips...butt jointed...the box...horizontal integrity ...arise...screwing...holes...straight shanked......screwed properly... ---------------- My, my, my... ---------------- My spouse got up smiling this morning while using those last two words. Keith Quote Link to comment Share on other sites More sharing options...
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