Does the"quality" of jumpers affect the sound?

Anyone ever try wiring the positive to the tweeter and negative to the bass while using jumpers?

Yes, that is the best way to single-wire if you have to. Otherwise, whichever part of the speaker you connect directly to will sound noticeably better than the part that gets its sound via the jumpers. The + hi/- one low method results in the most balanced sound across the entire speaker.

Jumper quality matters, but it doesn't take much to have very good quality for such short pieces.

Notwithstanding the statements about jumpers making a difference and connecting at either the high or low side, cross wiring + to hi and - to low, cannot make any difference since the current is AC and effectively the + & - change continuously according to the frequency.

Try it and use your ears to determine what happens. You and anyone else who actually does the experiment, will easily hear the difference. It's not that subtle.

We are forced to do it here on a regular basis with the Linn Akurate speakers which have a true 5-way split crossover makeing them quin-wireable. When choosing the best way to hook up our two speaker cables, there are obvious differences depending on which drivers get the direct connection.

The point you make about AC has nothing to do with the reason that a direct connection sounds different from an indirect one. If we were talking about illuminating a light bulb, your analysis would be fine, but the sound we perceive through a stereo system is a much more complex animal. Lots of things matter (are perceivable) in audio that don't matter in other applications.

Does anyone have an opinion as to whether it is best to stick with one brand of cable for bi-wiring?

If your goal is making your speaker sound more coherent, then sticking to one brand of wire is a good idea. I would even recommend making sure that the two cables of a biwire set are very close in design or identical if possible. The importance of this will have a lot to do with the speaker you have.

If the speaker is a two-way design, where the crossover point occurs in the critical midrange, it becomes more important that the two cables are identical or very nearly the same. In a three-way, where the crossover point occurs at a much lower frequency, you can often get away with a less expensive cable for the bass. Be aware that three-way speakers with more gradual crossover slopes (1st order) or a somewhat higher crossover point between the midrange and woofer, will benefit more from a nearly identical or better quality cable to the bass. Or to put it another way, they will show the limitations of an inferior or vastly different cable design used in the bottom half of the biwire.

Clio09, check your specs again. That doesn't sound possible. The 3kHz sounds right, but I can't imagine that you'd have another crossover point up higher in the treble. I'd expect to see the second crossover point between the midrange and woofer at something like 300 hz.

Clio, in that case, you would want identical cables ideally or at the very least, two cables from within one line that are very similar.

Your crossover point occurs in the critical midrange where our ears are most sensitive. The last thing you want is to have a change in character where the tweeter hands off to the midrange. Identical cables will insure continuity in this critical region.