Hi ewilburn54,
Thanks for posting on the Community!
If you're trying to use a 3rd party active subwoofer with the Soundbar 700, it will not work as the system is only compatible with the Bass Module 700 or 500. The 3.5mm connection on the soundbar was designed to be used with the bass modules mentioned previously if there were any issues with the wireless aspect.
Warm Regards,
Tony A - Community Support