Slackware has driver for this sound emulation included. See if you installed alsa packages. If you did then:
$su -
$alsamixer
Configure bars with arrows, enable or disable service with "m" key.
When done ESC
#alsactl store
P.S. If you have 5.1 speaker system, be sure that LFE channels bars are all way down and [off]. LFE channel is to generate 5.1 emulation matrix on 4 speaker systems.