Swap left and right connections at the back of AMP. Does the “crack” move to the other channel?

Unfortunately the same speaker still cracks when switching connections. Using 16 gauge. Perhaps moving to 14 will help?

We’ve learned that it’s the speaker or speaker wire, not AMP.

Clean the connections at the back of the speakers. A first test would be to jostle the wires while playing music. There should be no response to this. Somewhat more trouble would be swapping speakers, but this would give you an excuse to clean the connections. As you move the speakers listen for any rattling inside.

Normally, for short runs, unless there is a proven issue with the wire, replacing #16 with #14 will not accomplish much. With your 100ft run you may notice a slight improvement in sound quality. 

Sure sounds like a wire problem, not wire size though. More a bad connection, cut or shorted wire.

If replacing the wire to get better sound I’d go up at least two steps so # 12 and even then it would be a small improvement and the size wouldn’t impact the cracking.

(non-https site)  http://www.roger-russell.com/wire/wire.htm#wiretable

I’m not familiar with these speaker’s terminals. Some speakers will not gracefully accept #12.

I’ve seen that a lot on other connections, the solution is a short, 2-3 inch pigtail of the largest size accepted or trimming a few strands from the too large wire.

When going with trimming I untwist the end and trim from the center and then re-twist. That avoids exposed sharp trimmed ends and looks a bit neater.

Nothing I can find gives connector info, just # 16 or larger.