The LFE channel is a discrete channel. I have been measuring movie soundtracks for quite some time:
The 'subwoofer out' should be the lowpassed data from L/C/R/S channels + the LFE channel with its own lowpass, with the LFE channel weighted +10dB.
The Sherbourn 'subwoofer' crossover should only affect the LFE channel, per the manual. But it appears not to. The subwoofer out appears to be summed prior to the highpassing for the individual L/C/R/S, and then and only then is the 'subwoofer' lowpass applied by my unit. Which means, if you have all of your L/C/R/S crossovers set at 80, but your 'subwoofer' crossover at 200 (to prevent from losing info in the LFE channel, I have measured strong >120Hz signals in the LFE channel), the subwoofer out will contain information duplicated by the L/C/R/S, and too much midbass will result, which I have experienced. I have tried several times, and unless the crossover frequencies match, there is distinct overlap, and it does not sound right. Another error I wish I would have known about before I bought this unit.
I will have to measure to make sure, but I think I am correct.
The manual states only the LFE channel should be affected; in practice so far, this is not the case.
This unit has so much potential.