"Rob"

The dust cap (if that's what it is) does have slots, but I can't see if
there's anything lodged inside.


** The " dust cap " or "dust dome" is fitted right in the centre of a cone
and is glued to the inner party of that cone - if part of that gluing
comes adrift, the cap can make loud, hammering noises when the cone is
driven at low frequencies.

The "dust cap" is also part of the sound radiating surface and cannot have
holes in it that would pass air when the cone moves back and forth.

Sometimes there are visible holes in the top part of the voice coil former,
near where it attaches to the cone, that you can easily see with the driver
removed.



...... Phil