Hi Gordon,
I get that, and it almost certainly was an issue.
However, it didn't seem to stop folk (including me) revelling in the superb sound produced in that area of the room later, when the JBLs were swapped for Colin's Eddingdales, and the amps replaced with a combination of either my Croft preamp and Gary's valve amp, or the Radford.
That done, there were no 'suck out' issues whatsoever, and Steve's Pioneer PL-71 was thus allowed to show it's true potential. IMO, after your superb system, the sounds produced there were the next best we'd heard on the day - and that wouldn't have been possible if the issues in that part of the room were as bad as suggested
Marco.