Volume control slider in subwoofer ubuntu 12.04

My laptop is a toshiba qosmio x770 with ubuntu 12.04 64-bit and when I installed it, subwoofer doesn't work, then I modified "sudo gedit /etc/pulse/daemon.conf", changing "enable-lfe-remixing=no" to "yes", "default-sample-channels=2" to "3" and "default-channel-map=front-left,front-right" to "front-left,front-right,lfe"
But when I tried to put subwoofer louder in sound properties, the subwoofer slider isn't active and the sound there is too low

Any ideas?
Thanks

I have the same problem, but it seems that the subwoofer is working, because using Pulseaudio-Equalizer, the bass sounds very well :O
Anyway, I would also like to know why I can't move the subwoofer bar in the Sound configuration.