I'm new to this forum having just joined this morning. It looks like a great place to gather information on JBL loudspeakers. I'm looking forward to participating here.
I've owned a pair of JBL L-100 Centuries since the late seventies that I purchased used. I'm assuming my version was the earliest as the centers of all three drivers are in line with one another.
The high frequency driver is the one with the round metal surround. I'm not sure what model this is but would it benefit from a foam surround ring?
A lot of craziness (diffraction?) seems to be going on behind the speaker grills as the speakers sound better with the grills off. With them off, the depth of the sound stage is increased as well as definition. The original foam was removed from the grills long ago and recently I purchased a set of grill inserts on eBay to finish off the refinishing of the cabinets. I removed the original screen that supported the foam to try and improve the sound though they still sound better with the wooden frames and speaker cloth removed.
BTW, does anyone know why my model doesn't have a tube extending into the cabinet from the port? Seems like a crude way to do a port tuning.
And if anyone is interested, here is a list of equipment connected to the L-100's:
Pioneer A-77X integrated amplifier
Sony 620 ESII CD player
Pioneer PL-71 turntable with Stanton 681 EEE
Behringer 8024 Ultra Curve Pro for room eq (modified with new Pioneer FC power supply capacitors and Pioneer bi-polar capacitors elsewhere)