why does the bass change on my velodyne dls-5000

When i plug in my lfe input from my sub out on my amp and then run a sub cable from my pre out to my line input why does bass change. I have the Arcam avr350 and when i use direct i loose the LFE so i want bass when i use this hense running a cable from pre-outs to line level in.
System:
Arcam AVR350
Pioneer elite bdp-sd05 blu ray player
Rotel rdx-1060
[2] Velodyne dls-5000's
[2] Klipsch rf82 rc 62 centre to rf52 bi polars