Pete,
Happened on your question a while ago, and didn't answer it because I didn't know if you could use a "video" cable for your subwoofer.
I just happened to be perusing the HSU web site, and I clicked on a link in the forum which took me to a page on the HSU Australian web site. There, completely by accident, I came across this:
"There are a lot of different cable choices. These are open to both personal choice and how much you want or are willing to spend. As a rule of thumb we "do not" recommend that you waste your money on those fancy looking audiophile type cables for the limited bandwidth needed by a subwoofer.....................Being an active speaker means these low level inputs are subject to the cable becoming like a giant antenna, so we like great shielding especially if running it over 2-3 metres. Video cables tend to have good shielding, so these are very usable in our opinion and will deliver good results."
If you want to verify, go here, scroll down the page about half way, and you'll find the above under the heading "Cable Choice."
http://www.hsuresearch.com.au/Hsuvsothers.htm#Radio_Shack_SPL_Meters 
