I just reread this thread after quite a bit of research... so much misinformation and I thunk on the internet, here is a continuation of this pattern, but with what I believe to be a better thunk version haha. Here is a "more correct"... maybe
D's came first- alnico- they handle the least wattage because of their surround- its paper- its basically like a continuation of the cone- this is the major reason a lot of people (not on this forum of course--for the most part at least) like the d's the best. This is by far the easiest JBL to blow. A lot of D's out there have what appear to be the original cones, but with non original surrounds. you know how the JBL factory recone kits are becoming rare, and i'm just talking about the E series factory recone kits. This used to be true of the D series recone kits, and a lot of people would use a K kit which had a completely different cloth surround that was more similar to the E kit.
K's came next- still alnico- handle more wattage with their cloth surrounds. I'm confused here by the evolution of this surround. apparently all K's have cloth surrounds. and i've read in some places that eventually they started treating the cloth surround that could handle even more power. I also believe all the E series have the treated cloth surround or at least a stronger more evolved cloth surround than the K series. later model E's at least.
Now come the E's- the ceramic magnets can handle a ton of wattage- and the surrounds are the most evolved JBL surrounds in terms of power handling.
Now sound, I have recently tried some different jbl's with varying degrees of originality. I like them all. If youre looking for a sound description of these speakers. check this forum, because these guys are chasing the JBL guitar sound and know their stuff. I do however believe that many JBL workalikes that are being produced sound good, and sound very similar to real JBL's. Maybe I need to get a pristine set of D's K's and E's in 12" and 15" and play them for hours and hours to really start hating the remakes. But the weber california's, even with their smaller voice coils, rock and the eminence commonwealth is a darn good substitute for an E series.
Today i got a chance to play a HUUUUUGGGE marshall ported bass cab (almost as tall as 2 4x12's and a lot deeper and wider) loaded with two JBL d140's with a highpass leslie (rotophase?) in between my pro reverb. That was one time I did not care about being insanely loud at a music store. wow. The d140's are a good option for people that dont want the icepick highs jbl's can be known for. they're a good deal more mellow