The AB1 and other Sub Woofers for the LS3/5A
The LS3/5A was designed by the BBC for non-critical nearfield monitoring in small spaces and does not have an extended low frequency response. But given the high level of popularity among domestic music lovers, inevitably there have been many attempts to use a subwoofer with it.
Some have worked well and some less so. The LS3/5A has a bass “bump” to give the listener the impression that there is more bass than there actually is, and this can make it difficult to integrate a subwoofer. Other users have complained that subwoofers destroy some of the magic of the LS3/5A.
I have had good results with a pair of small REL active subwoofers which have adjustable crossover frequency, level and phase. Two certainly works better than one!
The classic LS3/5A bass extender is the AB1 which was designed by Andy Whittle at Rogers using the B110 SP1228 driver as used in the 11 ohm LS3/5A.
Although originally intended that the LS3/5A would stand on top of the AB1, Jo Ki has done a considerable amount of experimentation interfacing the LS3/5A. He much prefers to use them with the LS3/5A on a stand and the AB1 behind it. This has come to be known as Jo Ki’s Method. The AB1 has an integral crossover but Jo also prefers to connect both speakers in parallel.
Build a pair of bass extenders inspired by the AB1. Andy Whittle kindly supplied information about his design to help home constructors.
Harbeth Bass Extenders
Harbeth made a LS3/5A bass extender which appears to be similar to the AB1.
Rogers L35B and Reference Monitor System
The bi-amplified Rogers Reference system was manufactured from 1978 and consisted of a pair of Rogers L35B 150-litre aperiodic low-frequency enclosures, together with a pair of standard Rogers LS3/5A speakers and the Rogers XA75 electronic crossover amplifier. Few were sold. In 1978 the selling price was £837.56 which is about £6,000 at today’s prices. More photographs can be found on the Japanese HiFido web site.