Captain,
At the rear panel of the M80s, where the speaker cable connects to the positive and negative terminals, there are two sets of speaker posts linked by gold straps. These must make electrical contact between the upper pair of binding posts and the lower pair in order for the crossovers to function properly. You only need to connect the speaker cable to one pair of the binding posts. Please check those carefully.
In recent M80s, the v3 series, we've eliminated the dual sets of binding posts (except on special order) as they may cause malfunctions when the links are knocked out of place. We only added the "bi-wirng" sets of terminals as a marketing tool (both Ian and I believe there are no audible benefits to bi-wiring) and we had enough problems with customers not realizing that the two sets must be connected for the M80s to function properly that we decided to eliminate the extra bi-wiring set of terminals.
No super tweeter should be required for the M80s. They have extended and very detailed treble response that is highly praised by musicians, enthusiasts, and other owners. Clearly, there is something malfunctioning in your setup. The thin speaker wire should not affect the high frequencies; it just wastes power because of increased resistance. If it were ridulously thin, it could affect response, but I do not think that is the situation.
Regards,
Alan
