Can the SBL paxo be recapped/serviced?
To answer my own question, I emailed Naim and was told...
1. The SL2 "crossovers are no longer available new from us'.
2. Naim "can no longer service SBL crossovers - some of the components are no longer available"
What the general consensus? How long can a SBL crossover last till it deteriorates to a point where it affects the performance of the SBL.
The capacitors are the main components that may deteriorate over time (though not all do). Whilst the original ones might not be available, there are plenty of good audio capacitors around (at a vast range of prices), and it is possible to buy matched pairs to ensure both channels are identical. So, if the crossovers get to a point where they don't sound right it would still be possible for someone competent with a soldering iron to re-cap. There could be subtle differences in the resultant sound compared to the original - marginally worse, or better, depending on the precise original and replacement cap values (e.g. A cap value of 15.3μF may have been specified and one of nominal value 16 used but testing and selecting one with an actual value of 16, and unless that info is known the replacement may have a slightly different capacitance, also there might be tiny differences from other qualities of a different brand of cap) but undoubtedly better than with caps that have changed significantly in value or failed completely.
Resistors should be OK unless they've been driven heavily enough for overheating (which may visibly show) - they will be easy to source replacements. The inductors are more difficult, however unless there has been catastrophic overload (e.g. a failed power amp) then they should last forever.
As for how long they last, when I recapped my 40 year old IMF monitors a few years ago on the assumption that they would have degraded but gradually so un-noticed by me, there was a marginal change but by no means radical and I can't say whether it was an improvement. BUt it will very much depend on the original caps.