Aero, I think that once the calibration is doable then it doesn't matter how many LDRs are used so it opens the way to the series/shunt LDR config and if best sound is the target then it's worth having the option. I guess an experiment would be in order. I've seen it discussed that a very good resistor ($10) in the series position sounds as good as using a LDR there but this proves more expensive than using an LDR in this position. There is also an argument that the series/shunt LDR has a more steady impedance in the vol range.