The twelve-element line array had been touring for six months. Reviews were generally positive, but every venue produced the same complaint from the second row of the balcony: thin, phasey sound with no body. Everywhere else sounded fine. The crew blamed balcony acoustics. Different balcony, same complaint, every city.

I measured the array's combined response at the balcony position. The transfer function showed a severe comb filter pattern with nulls every 340 Hz — characteristic of a path length difference of approximately 2.9 milliseconds, or about one meter. One meter is, by complete non-coincidence, the height of a single array cabinet.

Cabinet number seven — dead center in the array — was wired with reversed polarity. The NL4 connector at the rigging end had pins 1+ and 1- swapped. This single inverted cabinet was cancelling with its neighbors at the precise angle that projected to the balcony seating area. At other angles, the path length differences from the inverted cabinet were different, and the comb filter pattern shifted to frequencies where it was less audibly objectionable.

The crew had been chasing this problem for six months, across thirty-seven venues, blaming room acoustics each time. The fix took ninety seconds with a soldering iron.

The Moral: Repeating problems across venues aren't venue problems — they're system problems. SonaVyx's transfer function with coherence analysis would have identified the comb filter's periodicity and implied the physical cause on day one, not month six.