The 11 Ohm Crossover
After 1987 all LS3/5A crossovers were manufactured by KEF and supplied as complete boards to the manufacturers. This was because when a speaker fell out side specification there had been disagreements between KEF and the licensees each blaming the other for the problems! With KEF supplying both drive units and crossover this source of conflict was resolved.
This example is from a Harbeth 11 ohm LS3/5A but all manufacturers should look similar.
Greater consistency of B110 manufacture and a smoother response meant that the new crossover could be simplified, eliminating the costly autotransformer used in the older version. Matching of relative sensitivity between the B110 and T27 was now achieved with a resistive ladder.
In 1990, at the request of the manufacturers who believed it would make the LS3/5A more attractive to consumers, the BBC approved a minor modification to the crossover PCB to allow a bi-wired option. The condition was that the loudspeaker must still meet the BBC specification with the terminals strapped.
