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.
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