>>Has anyone replaced the cheap speaker wire terminal with a better one
that uses higher-quality connections, like the banana plug? If so,
where did you find the right size terminal and was the upgrade
Yes, I did this yesterday. While it is too late to help the original poster, perhaps this reply will help others who are looking for an answer.
I replaced the broken (and yes, very "cheesy") terminal strip on my ProMedia 2.1 (not sure about the GMX designation) subwoofer with a higher-quality terminal strip. The replacement I found at a local electronics supply house was a Philmore Terminal Strip, Push to Insert, No. 1979. This is made in Taiwan and cost me $2.95.
Unlike the original Klipsch part, which mounts from the inside, the Philmore unit bolts on from the outside, covering the original opening.The bolt holes on the Philmore strip are close enough to the original that no drilling was required. Just insert one bolt on either side and tighten with a washer and locking nut.
The Philmore strip has four terminals. There are only three wires connecting the older part. So once you remove the wires from the intermediate circuit board that connects to the Klipsch terminal strip, you connect two of the wires to the two + terminals; connect the remaining wire to one of the - terminals, and use a jumper wire from that to the other - terminal.
With my particular unit, I believe the white, green, and red wires reconnected like this:
+ - - +
W, G G, R
After acquiring the parts and removing the back cover of the subwoofer to access everything, it took about 20 minutes to replace and resolder the terminal strip, then a few minutes more to reassemble and test.
The new terminal strip is much more robust. Not sure though what types of connectors it will handle, but it did work with the heavier-duty cables that Klipsch sells.
Hope that helps. ...pt