I have a GPA-rebuilt 604c which I find lacks bass, compared to 604-8K's, when mounted in a similar-sized and ported enclosure (actually that of Tannoy Arden's fitted originally to HPD-385's). The spider is quite a bit stiffer, ie the cone harder to move by hand pressure, compared to two un-reconed 604C's.
Is it necessary to break-in a recone, and if so how?
Thanks,
Jon Archibald