Sunfire MK IV User Manual page 13

Using the line level high-pass outputs
If you are using a
preamplifier which does
not have a sub/LFE
output, you can send its
left and right front output
into the subwoofer's Line
Level inputs and then
connect the subwoofer's
High-Pass outputs to the
inputs of your amplifier.
The subwoofer will play
the low frequencies and
your amplifier and front
speakers will play the
frequency range above the
subwoofer's fixed high-
pass crossover point.
The signals coming out
of the subwoofer's high-
pass outputs are not
affected by any of the
controls. They are just a
copy of the signals going
in except that the low bass
is filtered out. This uses
the subwoofer's passive
crossover network, rather
than the active network
and controls.
User's Manual 13