When I got a set of L100s I was mesmerized by the sound.Thought it sounded real good and it did to my ears.As I moved to different music and speakers(specifically east coast sound,classical and jazz and alnicos)I found my JBLs not only the L100 but other JBLs in my stable to be almost unlistenable at times.Was ready to chuck the lot but found that JBLs can make some music sound unbelievably good at times.It does to some music what my other speakers cannot do.Anybody feel polarized by JBLs?
I a pair of 4412A's in my office studio and listen to them for 6-10 hours a day w/lossless files from Itunes/apogee duet/Mac G5/various amps.
They are very easy to listen to at all volume levels and I never suffer from "fatigue" (unless the original source material was poorly recorded.)
They are set up as near field monitors (the way God and JBL intended) and I absolutely love them.

Also use have a set of older 4312A's I listen to upstairs with a Accuphase P300/Sony TA2000 or Pioneer SX-1250. They are postitioned about 8 feet apart and 8 feet from the couch on 10" Lovan stands (away from the walls). They also sound wonderful to me and are very neutral with good punchy bass.
IMHO JBL monitors are pretty hard to beat if you use them as they were designed to be used and are very easy to listen for extended periods of time.
Just my opinion of course and, hey they're my ears....
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Accuphase: P-300 amp
Classé: Cap-151
Harman Kardon: HK730 / 930
Hofi: Integra 5.1 Amp / Xara CD transport
Kenwood: KA907, KA-801 / KT-615
Marantz: 2230, 2240B, 2270, 2285B, 2325, 4240, 4270, 4300
Parasound: HCA 2200II AMP
Pioneer: SA-9500II / TX 9500II, SX1250, SX1010, SX980, SX950, 9930
Sansui: 9090 / 990DB / AU717
Sony: TA-3200 TA2000x2, and 2000F Pre-amp/amp, STR-6065, 7065
Yamaha: CR-1020 / 2020 / 3020
Speakers: Pioneer HPM-1500's, HPM-900's, Klipsch Heresy II, Forte II's,
KG-2's--JBL 4412A / 4312B / S-38's, Ohm Model L, Norman Labs Model 8's Advent /1 + "New" Large & KEF 103.2's