Re: [CAD_CAM_EDM_DRO] re:Re: Active damping

> I wonder how well it would work with a liquid in there rather than a

solid,

> perhaps mud.
>
> Sand filled panels have been used in loudspeaker cabinets for many

decades,

> by Wharfdale (?).
>

Yes it was Wharfdale.

As far as mud, etc anything with a good loss tangent would work if
mechanical impedances are matched. Mud can be a colloidal suspension with
thixotropic and pseudoplastic properties.The philly system also requires a
good impedance match as they mention. But the impedance of the steel is
pretty high and reactive (springlike) below the first system pole. It takes
a pretty stiff damping material. To first approximation the force required
to move the damping material would need to be about the same magnitude as
the spring force of the steel for the same deflections. Ideally that would
result in the maximum energy transfer to heat in the damping.
That is a simpification but puts it into perspective at least.The forces
will be 90 degrees out of phase.

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.rabun.net/~leswatts/wattsfurniturewp.html