It made day and night difference for me for my passive subwoofer. The internal amp on my decade old PSB subsonic 6i subwoofer died. I was using a radio shack PA250 amp to drive the sub. Initially, I used a two feet long 18 gauge speaker wire to connect. The sound was recessed. Then, I used a three feet 14 gauge speaker wire. The bass was immediately fully. I was able to use some bass testing sound on youtube to measure the difference. Then I picked up a long contractor grade extension cord from my neighbor's trash bin. I cut a pair of three feet long, and striped three wire (black, green, white) on each end, and combine with a mono price
Open Screw Type
banana plugs. Then the subwoofer made another day and night difference in extension and output.
Doubling speaker wire works well for any speaker can produce decent sound below 100Hz or all subwoofers. For most stand mount speakers, the difference may not be heard by human ears.