Hi. I just bought a new Eltax Liberty Power Tower speaker with built in powered subwoofer. But there's no sound from the subwoofer.The red light on the sub amp is turning green when my Denon avr 4308 is turned on.I've set the Lfe+Main on my denon. But still no sound in 2 channel mode. Has anyone got this problem with these Eltax speakers?