Well if your jumper cable is of lower quality than your speaker wire (or just different), it seems logical that the high post (to the mids & tweeter) was not getting as good of (or the same) signal as the low post to the bass. Also, since you are not going to notice as big of a difference in the bass as in the mids and treble, connecting the wire to the top post should be noticeable. In the best of worlds the jumpers should be the same cable. Using jumpers is not bi-wiring. Bi-Wiring is all the way from the amp to the speakers. You'll need that second wire you're saving for.
Bi-wire-top post, bottom post, why a difference?
I use mapleshade jumpers between the 2 peerless drivers that cross over at either 900 or 1000 to the 30" newform research ribbons..the acoustic zen satori[single wire] was always running to the bottom speaker lugs...I could only afford one good wire at the time. Sunday I connected the satori to the second set of lugs. Please note the ribbons are connected to the cabinet' top by their own jumpers[mapleshade]....I wasn't quite ready for the improvement I hear in the sound...in fact I still have to replay cds to make sure it is "better" and not merely different. Better clarity and blossoming of voices into the space between me and the speakers. Larger if you will, while depth seems enhanced. Is this an indication these speakers should be biwired? I'm toying with getting a short run of bolder cable[affordable] to see if this is the case. Any thoughts on the above? Oh, the rest of the system is a krell pam3. sim4070se, nopariel cd, roxan zerxes, ac matric ic and ixos ixotica ic. and absolute power cord. Monster and panamex conditioners. Thanks in advance. Bluenose