Running cables under carpet. Any great methods?

I need to run a subwoofer cable under the carpet. I managed to do a 4-5 foot run, but now I am being asked to move it to the other side of the room. Anyone have any brilliant ideas without pulling up the floor covering?
Thanks, John
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If you can lift the two locations of entry and exit of the carpet without causing damage. Rent or borrow an electricians fish tape or better yet the fiberglass stiff fish rods to push a string through the pull the cable back through. But make sure it is not in a traffic area as repeated crushing from foot steps will eventually damage the cable and cause a short. If the new location is not crossing a traffic area, e.g. hallway, adjacent room etc., you may consider tucking the cable under the baseboard trim, I have found that a coax can usually fit in that space.
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Pulling up the carpet IS a pain in the ass and I would avoid it unless you know someone, (or want to pay a carpet install guy), to lay it back down all nice and neat, tucked properly at the edges/under the baseboard/on the tackstrip. You can really make things look crappy if your "carpet-laying" skills are as bad as mine were. I did it once, made a friggin' mess, had to call the "PROFESSIONAL" to come fix what I had screwed up.
However, depending on the length of your cable run, you might have success with one of those "electricians" fish tapes as Theo suggested. The big issue doing it that way is getting the leading tip of it slid under the carpet without jamming-up and snagging on the padding. You gotta make the cable go inbetween the underside of the carpet and the top surface of the padding. Don't try and get the cable under the padding, it's a disaster and besides, the padding is usually glued down to the subfloor. It'll be a frustrating mess. I ended up doing 2 things to insure success: (1) just spend a few extra dollars and call the carpet guy to lift up, and correctly re-install the carpet. You'll be glad you did. And (2) use good quality cable right off the bat. Don't be skimping, using cheaper shit just to save some cash. If you're anything like me, you'll end up wanting to tear the "bargain" cable out and replace it with another one, (which I did 4 times in a 10 year period), and that's a pain. Depending on whether you plan to run the sub line leval? or speaker leval? you'll want to go with FLAT stuff. I have used Analysis Plus, and Nordost. Both worked well. Both have many different "levals" in their lines, so you wouldn't have to sell your firstborn, or auction off one of your body parts to own a high quality subwoofer cable! And the fact that they are FLAT cables means your carpet will look less stupid, or bumpy and bulged-up where the cable runs. (Things like that matter in my house 'cause my lovely wife can't bear the sight of wires the size of garden hoses running across the floor). As for going wireless? I personally do not like wireless subs, Had one once, seemed to have issues with occasional signal loss and interference. Maybe something was wrong with the transmitter module? But I didn't hang on to it long enough to figure it out. Dumped it less than a month after buying it and went the Wired route, never looked back. Good luck with your installation.
Yeah, fish tape is the easiest. If this isn't flat wire, which I'm suspecting it is not, you may have to make runs in and out of a corner rather than going straight across the room. Don't want to create a mole tunnel in the middle of the room.
There is underlay under the carpet that is stapled to the floor so using a fish tape may be difficult . The last time I went the full route and removed the carpet and underlay and routered out a trough in the plywood next to the wall , this worked out very well , the better half decided it would be a good time to have new carpeting installed , so the project cost a little extra but we were both happy when it was done . I have also ran cable along the corner and had custom baseboard made to cover it .

The main problem with running cables under a carpet is damaged to the cables. People will step on the spot and the cables can get damaged over time. It is best to put the cable under both the carpet and the padding. If you just put the cable under the carpet there will be a bump where a crease can form. You can try a fish tape but fiberglass rods are the easiest. They won't bend and get stuck as easily. I was a custom cable installer for more years than I care to mention so I have done it a few times.

The way I did my cables was to run it through the basement. I did a small wall fish about a foot to the basement on each side. Then I ran the cables down through the wall to the basement and up the other wall. But it all depends on what your floors are made of. I have original Victorian hard wood floors that I did not want to damage. If the floor is just plywood then I would not be that concerned.
Yeah, I figured its gonna be tough. There is no basement in my home. It is upstairs, but there is no way to go between the floors with all the fire blocks and such. I have contemplated trying to shove it between the edge of the carpet and the base board but there are two places that need to cross doorways.
I did use the fishtape on my original instalation accross the one doorway. It was a bear as the tape wanted to go everywhere but where I wanted it. But I did get it through eventually.
Thanks for the input. Perhaps I can sweet talk my way into keeping it where it is. I dont know which chore would be the harder one! Regards to all, John
Martinmobile: Awesome response.
Ebm: What, you want me to hang the wires from the ceiling?
Ha ha!
Thanks, John
Here is a simple answer to your question.

Best of luck!
Many times, if you pull the baseboards you will find gaps to simple push the cable into. As Elizabeth suggested a router will make it easy. You are working on the back sides of the baseboards any way.

1 piece of advice: After removing the baseboards, pull the nails all the way through instead of pushing them out and splitting the wood. Then, just buy new finish nails.
Hey that idea with the custom baseboard Tmsorosk suggested IS a really slick way to do it, provided you aren't using any big 'ol fat cable. It will be costly though. I had that done last April 2010 when the wife and I ripped out all our (ugly, dirty, smelly, 18 year old) carpet from "hell". We put in Oak hardwood floors throughout, and custom made 4 1/2" tall solid oak baseboards. We had the flooring contractor router a channel on the backside of the B.B. and then neatly tucked a 40 foot long run of Audioquest Diamond X3 interconnects (xlr connectors) into it. Once the B.B.'s were installed it looked super clean!
Problem was, it DID cost us a chunk 'o change to have that done. Like $2500 for the custom B.B., another couple hundred bucks for the "extra" router work, and of course the labor to install the whole shootin' match. So we ended up spending over 3 grand when it was all said and done, albiet NOT all just for the subwoofer cable. But pricey none the less. Probably would have been easier to try out the "wireless" option again? Aaronmadler has a great answer with the Outlaw Audio link. And it's very reasonably priced. Go check that out. If I had bothered to do my research prior to putting in new wood floors & custom B.B.'s, I might have gone that route, and saved a bunch of money! (money better spent on new music, good Scotch, import beer, and cigars!)