Because it was designed as a broadcast monitor the speaker is utterly unforgiving of poor source material. In particular the LS3/5a has a tendency to be slightly toppy and can sound dreadful (as it was designed to do) with sibilent sources.
The drive power recommended is 25W per channel but early versions had a nominal impedance of 15 ohms (falling in later models to nominally 11 ohms) and so an amplifier rated at 25W into 8 ohms is unlikely to be able to drive them properly. An under-rated amplifier not only sounds dreadful because it may frequently run into clipping when driving the very inefficient LS3/5a but is also likely to damage the tweeters. I have run my own pair happily for years from both a Quad 405-II (100W into 8 ohms) and a 100W home made MOSFET amplifier. The LS3/5a tells you when it is being overdriven! The B110 drive units make a very nasty cracking sound as they hit the stops which has you jumping to turn the volume down, no damage is usually done as a result.
The LS3/5a is not a "bookshelf" loudspeaker and needs to be used away from walls on stands. The BBC recommended that best stereo imaging would be achieved by turning the speakers in so they cross in front of the listening space. However the speaker was designed for use in confined spaces like outside broadcast vans. In these circumstances the listener will be very close to the speakers. In radio practice I have seen LS3/5as sitting on the top ledge of mixing desks. It was never intended for use in domestic HiFi systems. Many listeners report that they get good results in a domestic environment with the speakers facing directly forward. Try it both ways and see.
A bi-wired version was produced by Rogers in 1992 and possibly by other manufacturers. The crossover design lends itself very easily to bi-wiring but most LS3/5a owners dismiss it as a waste of time. Feedback from anyone who is bi-wiring would be very interesting. You can be sure that since the design was approved by the BBC a LS3/5a with the bi-wiring terminals strapped together will sound just as good as the normal version!
If you are lucky enough to have two pairs fun can be had by stacking them. If it is good enough for Quad ELSs it is good enough for LS3/5as! The 15 ohm impedance means the stacked speakers present an easy load to an amplifier. The only trade-off seems to be some HF beaming in the vertical plane. I have tried this briefly.
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