Anyone using "jumper" cables?

The main cables carry the full signal to the woofer terminal. The jumpers transfer the mid and high signal to those units.The two crossovers are separate, hence the need for the jumpers. So since the bass signal will be removed by the crossover for the upper units the jumpers do not have to preform well in the bass area. It is their performance in the upper frequency area that is critical. In general terms this means that they can be of smaller gauge and lighter weight than the main cable which has to excel in all frequencies. My Cardas jumpers are a fraction of the size of the Golden Reference main cables and cost $120 as opposed to $2400. Since the main cables connect directly to the woofer terminals the jumpers will have no effect on bass performance. It is , of course, possible to connect the main cables to the upper drivers but if high power is being transferred from the amp the other is usual preferred. In that case the jumpers would be transferring the low frequency signal: the high frequency would be carried also but would be filtered out by the crossover and therefore irrelevant. In neither case do the jumpers act on BOTH crossovers, it is either/or.

Karmatogdral, Re your OP, The jumpers transfer/conduct the signal to the other section of the x/o. Among the more common metals, silver is the best conductor then copper then somewhere down the line brass. Magnepan even uses steel. They all conduct. These distances are very short, a matter of inches or less, which is why these companies use them. I'd love to see someone try and market an 8 foot pair of steel or brass speaker cables :-)

I would definitely try something made of silver or copper if only because it is a better conductor than brass. Silver may be too honest but who knows. When you do experiment, try the main cable hooked up to one set of post, then the other. Let your ears be the judge. Good luck.

Homegrown Audio Co. sells both all silver and a silver/copper hybrid jumper cable with a 30 day trial period. http://www.homegrownaudio.com/categories/Speaker-Jumpers/

Yes use them when my BMW does not start.

Karmatogdral,
If you own bi-wire speakers you basically have 2 ways to wire them, bi-wire cables or single runs with jumper. Experimentation should dictate which way you go for best sound. Also, you might discuss this subject with the speaker manufacturer to see if they have suggestions or recommendations.
One thing for sure though, the manufacturer supplied jumper plates are generally NOT the way to go.