Bluesound node 2 subwoofer output (volt)

I have the problem with my bluesound node 2 and subwoofer output. I have enabled the subwoofer output and the main speakers are playing very nice but the subwoofer has almost no output. It is an active subwoofer so I opened the gain of my subwoofer amp and I have to fully open the gain in order to hear a little bit of bass coming out of the subwoofer, how is this possible? My setup is as follows: -OTL e130l tube mono block amps -Audio physic Yara subwoofer -Philips AD9710 fullrange main speakers.