Hi Rudy,
interesting !
Speak of the devil and the devil shows up!
Do we all have 2415s
My 4425 are from 1988 and really originally fitted ,nothing was changed.
Only a few weeks ago,my best friend bought another pair of 4425.He screwed open his 4425 with same result.
Phaseplug with holes ,like mine.Exactly the same.His 4425 are stamped 1989.
Both have the same original titanium D8R2416 fitted.I'm not 100% sure but the coils looks like alu.
One of his diaphragms doesn't fit exactly on the driver-plate.There was a little space and he had problems to center the diaphragm exactly.
We noticed this before,because the Horn produced a "farting" sound by playing Bass-Sinus signals.These farting sounds comes out of the Horn-Front.So he covered the little hole on the back site of the diaphragm.The noise has gone.
In two days he will receive his Radians,then i will check his Drivers again...
Edit: The difference between 2415H & 2416H is =The 2415 have a higher DCR (4.5 vs 3.2) and the holes.
Ok, then JBL must have matched the crossovers for these (early 4425) Versions
here is a pic from my crossover: