Building a viewing platform/stage---Need Help

Discussion in 'Home Theater Projects' started by Brett Loomis, Aug 3, 2001.

  1. Brett Loomis

    Brett Loomis Stunt Coordinator

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    I am building a new HT in Basement and want to build a stage/platform. Not sure if RPTV or projector but I do know that I will have 2 large towers and at least one sub, maybe two subs up front. The platform will be approx. 14' wide by 3' deep and beuilt using either 2x4's or 2x6's and then using 1/2" or 3/4" plywood or MDF.
    I am concerned about this platform/stage acting like an enclosure and causing muddy bass or resonating or adding unwanted noise. Please help me with construction tips and or sound/insulating ideas.
    Should I use 1/2" or 3/4" plywood or MDF?
    Should I screw and glue all cross-members?
    Should I insulate? pack tight or leave airspace?
    I want a rounded look to front of stage and envision the front center edge about 6" in front of the sides. How do I cut/draw a radius this large accurately?
    Platform and baement concrete floor will get heavy pad and carpet when done.
    Any and all tips/help/suggestions are appreciated as I am not a journeyman or master carpenter but I am good with tools and take instruction well!!!! Thanks a lot
    Brett
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    My system:
    Klipsch KLF-30's Mains
    KLF-C7 Center
    KSP-S6 Surrounds
    KSW-15 Front Sub
    KSW-100 Rear Sub
    Marantz SR-8000
    Toshiba SD-4205 5-DVD
    Mitsubishi VCR
    Mitsubishi 35"
    Pioneer PDF-1007 301-CD
    14 gauge Monster Cable
    Audioquest interconnects
     
  2. Bill Catherall

    Bill Catherall Screenwriter

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    I saw somebody here pack their front stage with sand. I had never thought of that before. I assume it was to take up the air space. I suppose polyfill would also work well, but I really liked that sand idea. Just make sure your subfloor and structure can support the weight.
    To draw a curve you can either trace a portion of a circle with a string tied to one nail, or you can trace out part of an ellipse. With the ellipse you nail down 2 nails and tie each end of a string to each nail, leaving plenty of slack in the string. The more slack you leave, the "curvier" the arc will be. Pull the string out taught with your pencil so you make a triangle shape between the pencil and two nails. Keep the string taught with your pencil and let the string guide you as you trace out the curve. The pencil should be free to slide along the string.
    Does that make sense or would a picture help?
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    Bill [​IMG]
    [​IMG]
     
  3. Bill Catherall

    Bill Catherall Screenwriter

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    Here's an animation of drawing an elliptical curve. I like this better than drawing a circular curve because the radius of the circle would need to be so large that it would make things more difficult. You can experiment with different spacing between nails and slack in the string.
    [​IMG]
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    Bill [​IMG]
    [​IMG]
     
  4. BobN

    BobN Auditioning

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    Once you have the arc traced out on the floor cut your joists to meet the arc. Depending on how tight the radius is you may want to place the joists in this section closer than 16" centers. once all the joists are laid out take a clear piece of 1x4 or 1x6, depending on size studs you are using, and on the opposite side of the face cut kerfs 1/3 to 1/2 the thickness of the material. (approx. 5/16 to 3/8 in depth) You will want to cut these about every inch or so. Make sure this piece of lumber has no knots if it does the board will most likely break when you go to bend it. Now that these kerfs are cut in the length of the board hold it so that the kerfs are facing the ends of the joists and bend it around your arc. Nail from one end to the other to avoid having a bubble in your arc. I would also use glue.
     
  5. Brett Loomis

    Brett Loomis Stunt Coordinator

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    Bill & Bob, Thanks a lot for the great tips. I love the string trick. Bob, how wide do the kerfs have to be?? Should I use a hand saw to control depth? Is that a good width? Anyone have an opinion on 3/4" plywood vs. MDF for the floor?
    Thanks again
    ------------------
    My system:
    Klipsch KLF-30's Mains
    KLF-C7 Center
    KSP-S6 Surrounds
    KSW-15 Front Sub
    KSW-100 Rear Sub
    Marantz SR-8000
    Toshiba SD-4205 5-DVD
    Mitsubishi VCR
    Mitsubishi 35"
    Pioneer PDF-1007 301-CD
    14 gauge Monster Cable
    Audioquest interconnects
     
  6. Ted White

    Ted White Agent

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    Screw the kerfs. Use two layers of 1/8" tempered hardboard. Bends elegantly smooth and the two layers (more if you like)is as strong as hell.
    I've bent wood with kerfs and I've done the hardboard route. The hardboard is about as slick and easy as it comes. You can jump on that little edge when done, to give you an idea of how strong it is.
    Ted
     
  7. Ben Cannon

    Ben Cannon Extra

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    Hi There, the sand fill route is the best way, dense insulation if that is not an option.
    Two sheets of 3/4" MDF will make for an utterly unshakable, utterly damped floor. Do screw and glue all connections.
    Lastly, you might consider "floating" the floor on the subfloor of your house proper. This is done by essentially placing a sheet of genuine 1/4" rubber or neoprene or other material between your floor, and your new stage. Totally isolate one from the other, and now one cannot shake the other.
    This is the technique used in profesional recording studios (sometimes more than once for a 'double' or 'tripple' floating floor [​IMG]
    Enjoy!!!
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    [​IMG]
    Ben Cannon
    Dream With Your Eyes Wide Open, Inc.
    "Every man dies, not every man really lives" --Mel Gibson, "Braveheart"
     
  8. Brett Loomis

    Brett Loomis Stunt Coordinator

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    Ted, I like the hardboard idea a lot. I am very familiar with hardboard as it is used for a lot of trim parts in the auto industry (spare tire covers, package trays, etc.). I know this material well and it has excellent flexibility/strength balance especially for this application.
    Ben/Bill-the sand idea is a good one although it might end up being a mess given the size of this platform.
    Thanks again
    ------------------
    My system:
    Klipsch KLF-30's Mains
    KLF-C7 Center
    KSP-S6 Surrounds
    KSW-15 Front Sub
    KSW-100 Rear Sub
    Marantz SR-8000
    Toshiba SD-4205 5-DVD
    Mitsubishi VCR
    Mitsubishi 35"
    Pioneer PDF-1007 301-CD
    14 gauge Monster Cable
    Audioquest interconnects
     
  9. Ted White

    Ted White Agent

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    If the stage will have speakers directly resting on it, especially a sub, you'll want very dry playsand in it. That stage will resonate. The sand route isn't all that bad.
    Some particulars to consider:
    The 2x4 or 2x6 studs (joists, actually) that lay on your floor could use a little damping. I'd apply two beads of caulk (3/8") to the underside of these 2x4s where they contact the floor. Let the caulk cure before installing, perhaps a day or two. Apply a heavy bead of construction adhesive in an "s" pattern over and between the cured caulk beads when installing. Make sure the floor is very clean to get good adhesion. This little process will de-couple the 2x4s somewhat, so that their vibrations won't tend to transmit into the floor.
    After the glue is thoroughly cured, you're ready to fill with sand. Very dry playsand is what you want. Commercial sand is NOT safe, as it contains silica dust, a known carcinogen. Playsand has beed washed. Drying the sand might be a trick. I had a fan blowing on the piles, which I turned over to expose moist sand. This took a couple days, but ensured that the sand was really dry.
    The sand is leveled into the cavity of the stage. Clean off the top edge of the 2x4s. Construction adhesive is applied, and a 3/4" layer of plywood is screwed to the stage. Then apply a layer of 15 or 30 pound roofing felt, followed by a 1/2" layer of plywood. Another layer of felt and top it off with another layer of 3/4" ply.
    Does this sound excessive? Perhaps, but it will keep your stage from sounding excessive. The process itself is very easy, and the stage is sooooo solid. I'm entirely glad I did this.
    Ted
     
  10. Jim Sentry

    Jim Sentry Stunt Coordinator

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    Ted

    since my theater is in the basement and I would be building directly on concrete should I lay roofing felt or plastic down first to act a vapor barrier. I ask because concrete takes so long to truly dry out so withhout the barrier won't the sand eventually become wet.

    Also, I know my concrete floor is not perfectly level and since I will be using 2x4's 16" o.c. I will need to somehow nail the joists to the floor.

    What do you think.

    Thanks

    Jim
     
  11. Scott-C

    Scott-C Supporting Actor

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    I'm also curious if it makes sense to line the inside of the stage with plastic prior to filling with sand, to prevent any leakage. What do you guys think?
     
  12. Scott-C

    Scott-C Supporting Actor

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    Some more questions:

    1. I apologize if this sounds stupid, but what is a kerf? I have not heard that term before and don't quite understand that part of BobN's post. Can someone further explain the cuts that would need to be made?

    2. I've heard the stage should not be directly attached to the walls. Should there be insulation or something between the sides of the stage and the front & side walls of the home theater? Would someone care to explain more about this?
     
  13. Bob Nowaskey

    Bob Nowaskey Auditioning

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    Scott, as far as the plastic lining. I would do this in the basement more for the potential moisture problem than for leakage. I would frame out the base and then lay 4ml or 6ml poly over the studs(joists) then fill with sand voids will be taken care by the weight of the sand. after filling all the bays you could slit the plastic down the center of the joist if you are going to glue and screw the flooring or subfloor material or not even bother cutting the plastic if just screwing. Again the plastic should be used to make sure moisture from the concrete floor is not wicked up into the sand (this could eventually rot the framework or cause a mold problem. As far as the kerfs are concerned. In my earlier post I said use a clear piece of 1x material. This is good if the platform is to be stained or painted plus you use less material i.e. only a 1x4 or 1x6 for the size platform. If you are going to carpet use 1/4 inch plywood.(more expenxise or less managable because you have to rip it to the appropriate size. I would be careful about using narrower material as it may flatten out when conforming to the curve. Anyway a kerf is used to remove a sawblades width of material 1/3 to 1/2 way through the backside of the lumber to be curved.(makes it easier to bend) The reason for using clear lumber is that if you have a knot, this would be a critical point where instead of a bend the board would snap. A kerf is made by setting your sawblade to the appropriate depth and then vertically scoring the backside of the face of the lumber to be bent. This needs to be done about every 1/2 to 3/4 inch. A lot of work but it works. Feel free to ask anymore questions.
     
  14. Robert Mee

    Robert Mee Agent

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    How about Scott's question about not attaching to the walls. What do you fill the void with? Do you carpet upto the wall or leave the gap?
     
  15. Pam W

    Pam W Stunt Coordinator

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    Ben,

    What do you mean by dense insulation? Our HT to-be is over our garage and my husband is concerned about the weight of the sand. Thanks for the help!
     
  16. Dave_Olds

    Dave_Olds Stunt Coordinator

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  17. Pam W

    Pam W Stunt Coordinator

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    Dave,

    Thanks for the information! Husband is digesting it as I type...
     
  18. Brett Loomis

    Brett Loomis Stunt Coordinator

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    Pam/All- Check out my photo's below at my HT link. they include the entire constrcution process from framing the walls and building the stage to custom cabinets, equipment, projector, stadium seating and movie posters. Lots of pics of my stage/proscenium.

    Total construction time was 4 1/2 months. I started on Labor Day 2001 and watched the first DVD at the end of January 2002.

    Thanks Ted and Bill for the great tips!!
     
  19. Pam W

    Pam W Stunt Coordinator

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    Thanks, Brett.
    We have been studying your HT construction site and are finding it to be very useful to us. We will soon be breaking ground - oops - I mean drywall - for the Wheeler Home Theatre![​IMG]
     
  20. Brett Loomis

    Brett Loomis Stunt Coordinator

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    Thanks Pam! Good luck and let us know your progress/results with photos if possible.

    IMO- Sand in the stage is overkill and extremely work/labor intensive, and risky if used in a 2nd floor application (over a garage or above a basement). I filled my stage with insulation and sound deadeners used for automotive interiors and my stage is dead-thud quiet.

    Just my opinion, I am not criticizing those that used sand, I considered it and decided against for several reasons including residual moisture, logistics of getting it from the store to my basement, and finally the thought of selling my home and removing or worse yet, some realtor, lawyer-type suing me for some frivolous BS lawsuit claiming sand caused ants, termites, rodents, cancer...insert some frivolous claim here) For the record, I live in a brand new home and no bugs or rodents of any kind (yet) inside!!
     

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