johnnycamp5 Messages: 354 Registered: June 2015 Location: NJ
Grand Master
Most original JBL cones (and re-cone kits) have a pulp looking texture on the back side of them.
Also most are marked with a yellow or white crayon (keel) on the backside (JBL 2226H).
For use in two-way speakers, It used to be suggested to use official JBL re-cones.
Some other re-cone kits (non JBL) had a measured dip in the midrange frequency response.
If I recall corectly, in the range of +- 800Hz.
That's right in the wheelhouse of a 4pi.
You should probably try to make sure if they have been re-coned, they used genuine JBL re-cones.