Bottlehead Forum
Other Gear => Speakers => Topic started by: glynnw on October 09, 2011, 11:19:14 AM
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I want to experiment with mounting speaker drivers using a "squishy" (or some such) material sandwiched between the driver and the mounting board. Some 12" x 12" squares of sorbothane are easily available but what thickness would be recommended?
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You'll probably have to experiment. Vibration isolation works least well when the material is in compression, which you have to do for speaker mounting. Finding the right balance of gasket material stiffness, strong enough mounting screw pressure to hold the driver in place, and loose enough to provide isolation, is not going to be obvious.
Be aware that it is very easy to short-circuit the isolation. If the mounting screw head touches the speaker frame, then it conducts all the vibration force into the cabinet and the gasket does nothing. If you put a rubber washer or gasket between the screw head and the driver, notice that it should be stiffer than the gasket material, in proportion to the ratio of areas bearing load - again, difficult to assess. Next, you can worry about the screw shaft touching the driver frame - wrap that screw, or slide it into a rubber hose of appropriate size and stiffness.
Back when I was playing with speakers, it was not unusual to glue the speaker to the box with silicone RTV caulking. You can, with moderate difficulty at least in theory, pry the stuff off if you need to get back into the box. In practice that's a fairly frustrating task, so try to get it right the first time if you go this way!
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My midranges are "floating" in some really mushy urethane gaskets that PB cast for me. He made an ABS baffle that holds the contraption against the cabinet baffle. Only the ABS panel is screwed to the cabinet, the other parts float. The difference when we did this was remarkable, the midrange became much cleaner.
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Now that is interesting. Makes me wonder how many speakers actually address this. On the bass drivers for my speakers there is a rather stiff poly-foam like material that separates the driver housing from the cabinet. Seems like it may accomplish what you are talking about. But the mid only has a wimpy foam that just crushes to the cabinet. The tweet has nothing at all. These drivers are all mounted on 1 1/2" stock using 3/4" long button head type screws. The weight of the bass driver has to be at least 20 lbs, so unless I tighten the screws down very snug I feel they're may be a problem there. Glynn, have you decided on a material to use yet. I like Doc's idea but will have to think about how to actually do it.
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Hey Doc, any chance you could send along a picture of the "contraption"?
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I am thinking of just doing the Fostex driver in the Basszillas, using sorbothane, perhaps 1/8" thick.