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In the Forum: Horn-Loaded Speakers
In the Thread: Midbass Horns and Real Estate.

Post Subject: Proper structure stiffeningPosted by miab on: 1/29/2010

The proper way is little more involving but doable as I believe you don't mind customizing structure as you will probably be in the new house for good or a very long time. Sister joists PL glued and screwed to original joist (wood or engineered( full thickness, no i beam)) or equal distance between the existing, with a polyurathane foam sprayed full depth of cavity between. Moisten the undercarriage of the floor above with fine water spray for a couple days before to allow all wood to accept a little moisture into the grain before spraying the polyurathne. It will 'glue' everything together. From the top, if you have carpet/hardwood, rip it up and glue and screw (every 6") 3/4" FIR plywood onto existing plywood/plank boards. It's a good idea to screw every 6" existing plywood/plank floor into old and new joists below before new Fir plywood on top. Then finish floor with whatever you like (ie. preferable carpet). For extra measure you could plywood the underneath of joists with fir plywood again.
After all this 1 or 2 new crossbeam structure (Post and beam) should be placed at a 1/3rd distance from existing post beam supports, tighten upwards and then tightenend again after some time. Yo can actually affect resonance of floor above by manipulating the post/beam tightening. Hopefully you have access underneath and not too much electrical wires or plumbing or ductwork running through/under the existing joists. You might need the appropriate trade in to disassemble the utility until the new sisiter joists are in.
After this you will think and feel you are on a concrete slab. It sounds like much work but could be done in 2 days with proper planning from utility trades.

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