@Jerryfurry the old Peavey 1820 cabs were set up for bi-amping or full range as was the SUNN Coliseum head. I set the x-over in the SUNN Coliseum for 1000 hz. Ran from the high out on the back to the power amp in of the upper SUNN Concert and then speaker out from it to the 2-10's. Then low out on the Colseum was driving the 18" Black Widow.
It was a surprisingly loud and punchy rig. Covered up to medium sized venues without PA support. I ran my effects only through the 10's which left the low end still fat and thumpy. That cab was heavy and a real bitch for one person to move. Roughly 450 watts but sounded way bigger.