That is the i/o for stereo and triamped... Unseen is the Minidrive in the lower rack - I have to get rid of that monster shock rack and get another normal rack on wheels ... Damned rack weighs 70lb by itself...
The i/o panels are the Middle Atlantic UCP system. With fan it's about $150 per rack. I could have done it cheaper but it's a very nicely thought out and constructed system. My splurge...
The XLR and single speakon is i/o for the spare amp channel in each rack. The speakon by itself is slaved to the subs. Normally my tops are on poles over the subs. I jump to the sub with a 2 wire speakon from the top. The separate sub output is for when I can group subs in another location like under center stage. Then I just run a dedicated line from each rack to the sub cluster.
Nice thing with this setup is that you can't plug the speakers in wrong. The single point of failure is getting the mains input and subs input backwards and even then there is a super steep feely filter on the tops. So I bring up the subs first and if I hear thump, I'm good to go. Stereo... Actually I run mono aux fed subs and while top tops are theoretically stereo, its really parallel mono. I just like the ability to audition each side independently of the other.
This is as clean a cable system as I have been able to come up with. It means that once the stacks are placed, I can spin the cabling out to someone else and concentrate on the snake... Which in and of itself presents 20x8 points of failure...
Riis, you really should give the Audiopile.net folks a go. Trust me, for the products they sell, you won't go back to parts express... Cables, Bulk Cable, connectors, racks, rack parts, snakes... They are small and give great service with sharp pricing.