Sony XEC-1000 Operating Instructions Manual page 9

System 2 shows the general 4-speaker system
with 4 amplifiers. In this system, set the SUB-
WOOFER INPUT selector of the XEC-1000 to
OFF and FRONT INPUT selector to the ON
position. If you want to get the more powerful
bass sound from the rear speakers, set the low
boost selector to the SUB & REAR position to
make the LOW BOOST contro! work towards
the rear speakers. For the FRONT and REAR
crossover point selectors, set them to the
FLAT position in this system.