Bass leaves after amp warms up?

What?...

Audioquest Comet biwire speaker cable
Bananas

From the AQ website:

Comet is an exceptional Single-Biwire cable. When the halves are separated at the speaker end, the double quad-helix design turns Comet into a true double-biwire set thanks to the magnetic autonomy of each quad-helix. On its own, one quad would be a little light-weight in performance as it is biased towards treble finesse. The other quad is more forcefully biased toward the bass. Together they form a completely optimized full range design, but when separated the Comet becomes a maximum performance double-biwire in a single cable.

Whatever that means.

Fishing, I still find myself uncertain of the meaning of your description of the connections. I think you are saying (correct me if I'm wrong) that what you WERE doing was:

1)Connecting the "red treble" banana plug of the cable to the red binding post of the high frequency part of the speaker.

2)Connecting the "black treble" banana plug of the cable to the black binding post of the low frequency part of the speaker.

3)Connecting the "red bass" banana plug of the cable to the red binding post of the low frequency part of the speaker.

4)Connecting the "black bass" banana plug of the cable to the black binding post of the high frequency part of the speaker.

In other words, you were interchanging the connections of the two black banana plugs at the speaker end of the cable.

If that is correct, like Dan (Drubin) I don't see how that would cause the bass to be fine for an hour or so, and then mostly disappear. JJ offered a clever theory, but looking at the description and photos of the Comet at the AQ site I don't see anything suggesting that the gauge of the treble wiring is extremely thin, which it would have to be for a resistance rise due to heating to become significant.

Regards,
-- Al

If speakers were connected out of phase, bass would be impacted from the get go, not more so over time. That could have just been a perception that it got worse over time. Whatever. If it sounds good now, take a note on how to wire correctly so you can do it again if needed. Reds to + and blacks to - in all connections from amp and into speakers should do it!