The LFE channel is not the same as bass. The LFE channel is used by DVDs for low frequency effects such as explosions, earthquakes, and airplane flyovers. Some preamps allow you to direct bass output to the LFE channel, so that all bass is redirected to it. If you could do this, then you would get a response when playing musical material out of your subs. Otherwise, you should send the right and left channels to the subs if the subs have a high-pass filter in them that you can use to roll off the high frequencies that are being fed them. Another alternative is to feed the left and right channels to an outboard crossover, that would allow you to feed only the low frequencies to the subs. Since frequencies below 100 Hz are non-directional, your subs' performance would improve if you fed both left and right channels to each sub and used a crossover frequency of 80 Hz for the subs.
Why aren't my subs turning on?
I have a pair of Von Schweikert VS-3/S subs. Auto-on appears to be the only option, but they do not turn on unless I manually turn them off and then on? They are being fed from the line level (called LFE) outputs of an SMS-1. One to each sub. Both were purchased used from diff owners; hard to believe that they both are independently defective in the same way. They both play when I run the auto-eq frequency sweep. I am sending same question to VS, but your thoughts would help. TIA.