Bracing of drive units

[tiroth]

I've seen a lot of examples of driver "bracing" in a manner similar to the pic below. More typically, I've seen this done with a shelf brace butted up to the driver.

What is happening here? The brace "pushes" against the motion into the box, it cannot "pull" the driver back when the motion is out of the box.

I would think that there is value in this because it certainly must provide some damping of any driver motion, and I would also believe there may be utility in preventing a in/out rocking motion from developing.

Is this a correct physical analysis? Are there any good ways of "grabbing" the driver in order to provide a true brace? Everything I've thought of seems poor from an engineering standpoint

[simon5]

If you glue the wood piece to the driver, you will provide bracing for both motions.

[Jim85IROC]

cutting the brace large enough that it's got some pressure against the driver once the driver is screwed into place should provide good motion damping in both directions as well.

[tiroth]

Thank you for the gluing suggestion, I'm sure a urethane glue would work well. I was hoping for a non-permanent mounting method though.

Jim, is there really damping in the "out" direction? Isn't the brace actually encouraging such a motion by applying outward pressure? Or is it that by forcing some flexion of the baffle outward, a greater force is required to produce additional flexion? (i.e. does the flexing of the baffle obey F=-kx or some higher order?)

[simon5]

Well, you know that glue is not that permanent, you can still scrap the wood and scrape off the glue... it's metal afterall...

[Jim85IROC]

Originally posted by tiroth
Thank you for the gluing suggestion, I'm sure a urethane glue would work well. I was hoping for a non-permanent mounting method though.

Jim, is there really damping in the "out" direction? Isn't the brace actually encouraging such a motion by applying outward pressure? Or is it that by forcing some flexion of the baffle outward, a greater force is required to produce additional flexion? (i.e. does the flexing of the baffle obey F=-kx or some higher order?)

Having the basket under a constant pressure will damp it regardless of the cone motion. It's more or less the same pricipal that govern's Sonus Faber's curved enclosures. Because the wood is always under tension, it is more resistant to vibration.

Think of a tuning fork that's ringing. If you touch it with your finger, it stops ringing, but you're only applying the force in one direction. But... you're applying enough that it's resting point is beyond the window of motion caused by the resonance.

Make sense?

[tiroth]

Hmm...yes, that is a good explanation. I still think that the initial outward impulse will not be damped or restrained (beyond that due to tension), but it does prevent a resonance from occurring (or at least forces it up in frequency and down in amplitude).

Thank you also for pointing out the Sonus Faber connection.