External Crossovers for the LS3/5A

inside external crossover

 

I had some spare KEF SP1003 B110 and T27 drive units sitting on the shelf for over 20 years and when Stirling Broadcast introduced their range of reference cabinets I decided to construct a pair of 15 ohm LS3/5As in Stirling Reference cabinets with external crossovers.

The LS3/5As have no crossovers inside and instead the 15 ohm crossovers version FL6/23 were bought from Falcon Acoustics in the UK, and mounted in pair of boxes along with the crossovers for my AB1s. These Falcon crossovers are identical to the ones used in the Goodmans LS3/5A and the components are matched very tightly. Six pairs of 4mm terminals are provided on the front of the external crossover boxes to allow them to be configured for use with both "ordinary" LS3/5As and my new pair.

Keith Snook also describes a method of mounting the LS3/5A crossovers externally on his web pages.

external crossover

It is inevitable that a comparison will be drawn between my own external crossovers and the Cicable crossover. But they are quite different beasts. My own project uses a standard crossover taken out of the hostile environment within the LS3/5A cabinet. The superb Cicable crossovers on the other hand have been completely re-designed for the LS3/5A. The Cicable casework is somewhat better than mine too!

The big red capacitors are polypropolyne replacements for the reversible electrolytics used in the standard AB1 crossover. For information about this part of the project please see my article on building a pair of AB1s

Thanks to Doug Stirling at Stirling Broadcast for supplying the superb reference cabinets, baffles, sealing strip and felt and to John Bell at Royal Hi Fi for the tweeter grilles. The LS3/5A shown here was photographed before the tweeter grille was fitted and it is sitting on a Linn Kan stand.