DDJ 400 to Behringer B210D low end is indistinguishable. Can’t hear anything in headphones either.

I hooked up my one Behringer B210D to my DDJ 400 with a RCA to 1/4 “TRS?” and I can hear the song clearer after one minute but the lower end @ the beginning doesn’t stand out like on my iphone and laptop. Is it because my cable is 15ft(only thing I messed up on I think) making me lose signal or is it something else? What brand cable do I need and what type of connection gives the highest quality sound for this specific setup? I turn all my knobs down to lower volume but I hear low static when plugged in and not playing music. Would hooking up to my Scarlett 2i4 interface improve output? Please help a new producer/dj follow his childhood dream, thank you!