Frank,
With very few exceptions, you really don't want to use two completely different models or brands of cables for biwiring. You want the two cables to be identical or at least very similar in character. I believe that the reason you like the sound better with the otherwise unnecessary jumpers back in is because what you are doing is blending the two cable's sounds together. By defeating the split crossovers for biwiring and running two speaker cables you are really just shotgun wiring your speakers with two different cables and averaging their sound across the whole speaker.
The advantages of true biwiring are not as important as having consistent and coherent sound from the top to bottom of your speakers.
I would wager that if you had two identical sets of whichever is your favorite cable, say the Stage III Vacuum Ref., you would like the sound much better with them biwired properly (with the jumpers removed).
With very few exceptions, you really don't want to use two completely different models or brands of cables for biwiring. You want the two cables to be identical or at least very similar in character. I believe that the reason you like the sound better with the otherwise unnecessary jumpers back in is because what you are doing is blending the two cable's sounds together. By defeating the split crossovers for biwiring and running two speaker cables you are really just shotgun wiring your speakers with two different cables and averaging their sound across the whole speaker.
The advantages of true biwiring are not as important as having consistent and coherent sound from the top to bottom of your speakers.
I would wager that if you had two identical sets of whichever is your favorite cable, say the Stage III Vacuum Ref., you would like the sound much better with them biwired properly (with the jumpers removed).