Rob wrote:

Phil Allison wrote:
"Arny Krueger"

The cone works against a relatively large mass - the speaker and its
enclosure.


** The mass ratio of a whole speaker box to the woofer cone is around 500:
1, or more.

The conservation of momentum principle ( Newton's "every action causes an
equal and opposite re-action" ) requires that the momentum of the moving
cone and whole box remain equal and opposite. So, the box moves about 0.2%
of the cone's movement in the opposite direction.

Typical woofers move at most 6mm forward and back when producing the lowest
bass frequencies.

The box, in compliance with Newton, then moves 12 um back and forward.

12 um = 0.5 thou = one quarter the thickness of a page in the phone book.



Why bother with spikes and cones at all?
Because it sounds better.
Only in sighted evaluations.


** Of course.


IME it doesn't always work like that. My Dynaudio 1.1s sit on some
stands with a smallish top plate. After an hour of fairly spirited
listening, they'd moved about 4cm forward. I'd usually use blutack for
that reason - it's all in the movement of air.

Actually it's down to 'microvibrations'.

Graham