LP12 suspension susceptible to acoustic feedback

If you have a concrete floor than you don't need a wall shelf. Just the a good solid stand will do. But I would tie the elephant up out back when playing records as mine used to want to dance and he might bump the TT stand.
It was sad when he died. Plumber told me I should have buried him instead. Even if it worked for the goldfish, I know now that buriel was the way to go.

Since the beginning of time, or at least as long as the Sondek has been
around Ivor Tiefenbrun and Linn dealers have recommended only a light and
rigid shelf below the LP12 for best sonic results.

I understand testing a theory because so little is absolute yet, when the
designer and builder calls for a specific foundation, maybe there is something
to it.

There is not a TT on earth made to withstand "When I place the
arm/cartridge on a (stationary) LP, the entire arm board and arm rest
resonates to light finger taps, and the sound emerges as rather loud thuds
through the speakers, at normal listening levels.' this is not a valid test of TT
resonance mismanagement... sorry.

Personally I have found most suspension TT's to give excellent results with
the same (a light rigid shelf).

The Ikea Lack is such a table.

Happy Listening!

R f Sayles is absolutely correct!