I'm going to move my AVR to a different location in my home theater room and so I will need a much longer sub cable. My current cable length is 3m and the new one will be 12m. After reading around the forum I decided to try a coaxial cable which I already had laying around. So I fitted it with RCA connections and plugged it in. The result was a very noticeable drop in bass. I can compensate for that by increasing the volume on the sub but I think it doesn't sound as good as before, although not by much.
The coaxial is currently 14m because I didn't want to cut it before deciding about using it. It's marked RG6U 75ohm. I don't know much about those numbers so I just want to know if there are other cables I should be looking at for 12m.

I use RG-6 quad shield for my 55ft (16.7meter) sub cable. I have no problems at all with my sub's volume. Just turn it up a little to compensate for the extra length.

The only difference between my cable and yours is the outer jacket. Yours is certified for underground burial. That's what the U stands for.

-Robert

monoprice.com 50ft 75 ohm RG6 sub cable, about $8.00 i have 2 running my MFW15's and they work great!

thanks!