Choice of Amplification

The LS3/5a was designed by the BBC primarily for outside broadcast use where space is at a premium, although in practice they are used in many different broadcast environments including control rooms and edit suites.

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 solid-state 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.

Many LS3/5a owners prefer tube amplification and excellent results have been achieved with Quad IIs, Radfords and Leaks. Rogers comissioned Audio Note to design a tube amplifier, the Rogers E40a, for use especially with LS3/5as and AB1 subs. The E40 also gives excellent results when driving LS3/5as without subs.

Position

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, perhaps only 1 metre from the 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 the best results in a domestic environment with the speakers facing directly forward. Many owners enjoy listening in the nearfield, with the LS3/5as placed approximately 2 metres apart, positioned well down the room, the listening position being equidistant at around 2 metres from the speakers. Under these circumstances an extraordinarily deep three dimensional sound stage can be produced.

The LS3/5a is not a "bookshelf" loudspeaker and needs to be used away from walls on stands. Good results have been achieved with the Foundation, Partington and Linn Kan stands.

The NSM Audio web site provides useful information on setting up a pair of speakers for stereo and their instructions for loudspeaker positioning work very well with the LS3/5a.

Bi-wiring.

Several bi-wired versions of the 11 ohm LS3/5a were produced by companies including Rogers, Harbeth & KEF. The crossover design lends itself very easily to bi-wiring but many LS3/5a owners dismiss it as a waste of time. 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!

For a clear explanation of bi-wiring take a look at the Home Cinema Guide site

The AB1 Sub Woofer

The AB1 was designed by Andy Whittle when he was Technical Director at Rogers and LS3/5a owners are polarised in their opinion of it. Some don't like them at all, while others, including myself, can't live without using a pair with the LS3/5as. Rogers originally intended the LS3/5a to be stacked on top of the AB1 and spikes are provided with them to do this to make mini-towers. It was thought at the time that because the drive unit in the AB1 fired vertically it would have little effect on the performance of the 3/5a when used as a stand. Experiments have shown that a significant improvement in quality can be achieved by seperating the LS3/5a and AB1. I first saw and heard this positioning used by Jo Ki in Malaysia in his system and have come to call it the "Ki Method", although it may be that the idea was thought of elsewhere as well. Jo has actually wired his LS3/5as and AB1s in parallel and not in the conventional way as shown in the diagram. The + terminals on the AB1s and LS3/5as are wired together as are the -ve terminals. In theory this gives a bump in the bass because the LS3/5a is no longer rolled off. In practice Jo's system sounds superb, the best LS3/5a system I have ever heard.

In the Ki Method each LS3/5a is placed on its own dedicated stand with the AB1 approximately 6 inches (the width of a CD case) behind it, the two connected using jumper wires. The improvement in sound stage as a result is awesome and I now always use this as my preferred method. When I talked to Andy Whittle about this he admitted that perhaps they got it wrong in believing the AB1 made a good LS3/5a stand. In my experience it makes a great bass extender but a lousy stand!

I have replaced the reversible electrolytic capacitors in my own AB1s with audio-grade polypropylenes and therefore use the conventional system of running the LS3/5as through the AB1 crossover. Information on this can be found in the DIY external crossover article.

Stacking

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.

Please email your tips to Paul Whatton for inclusion here.