Only 5 posts on the AVS forum ? That seems hard to believe
Before buying a VP180 I doodled up some (much less sophisticated than the Doctor's) calculations for comb filtering on each of the driver pairs and was actually pretty impressed with the results.
That said, I lived with a VP100 for several years (pretty much your common or garden D'Appolito array) and only heard audible comb filtering on a single track -- I forget which one, but it was a single-note-guitar-heavy track off Genesis' Nursery Cryme and was only clearly audible when I picked a stereo-to-5-channel matrixing option that pumped up the center channel volume.
Playing the same track with a VP180 resulted in less comb filtering effect, although since I can't remember which track it was I guess I have to go dig the CD out of my carousel and play it again upstairs on the HT system...
