I'm using 4 pole speakon cables to run out to the subs, which are a bit tricky to test, but given that when I run the two subs daisy chained (parallel), I wasn't having the polarity issue, I'm assuming they're good.
While that is probably true, it's not necessarily so. If your cable is wired backwards and your parallel speakon on the cab is wired backwards - they would now send the signal properly. That could account for the bad polarity when running with two sides of the amp vs. one. Bottom line - check every cable and check the input plates on both cabs.
So.... How do I test polarity off the amp, rack, and mixer? I'm putting money on the mixer, as it was a rebuilt Frankenstein we got from a service provider. The Amp was bought new and the drive rack was vgc second hand from someone that had used it without complaint... unless he was fibbing.
As always, many thanks in advance
To test the mixer, hook it all up and let it run. Now, unplug the Left output - did it get louder? If so, there's a problem. However, it's doubtful that is the cause. As far as the amp.....maybe a one in a million chance that it's wired backwards.
More than likely, as Grant mentioned, the problem is in the driverack. So, do these things....
1. Start fresh with a new program.
2. Do NOT use the automatic setup wizard
3. Set everything to CUSTOM
4. Make sure you are running a MONO sub.....regardless of whether the tops are stereo.
I'm pretty sure you aren't doing this since the GX7 can't run a parallel input - you have to be
running a cable to both the left and right inputs. Instead, you should run only one XLR from the
sub out of the driverack to the first channel of the amp, then daisy chain from the first input to
the second input with a short jumper or build a Y at the end.
5. Now set your crossover, limiter, etc.
At this point, my bets are on there being an incorrect setup in the driverack and your wiring scheme to the amp. Give that a try.