The Fs averages between 175Hz and 200Hz. So typically you shoot to cross it an octave above that or with a steep enough slope to have the output down about 20db before hitting it's Fs.

Chris> "Is what I beieve about a crossover correct ?"

I think you pretty much have it figured out by now.

Chris> "But what would putty have to do with the roll off ?"

Adding or taking away mass to a PR changes the Fs of the PR and changes the tuning frequency of the box. It will alter the bottom end of its range. It will not alter the upper end of the range.

Also changing the mass a gram or two at a time is like changing the port length of a port by a fraction of an inch at a time. You won't hear a change.