The production crew was ready to throw out a perfectly good speaker. 'It's blown,' declared the stage manager. 'No output.' They demonstrated by turning it on alongside the adjacent cabinet. Indeed, the combined output from the pair was thin, hollow, and missing most of the low-mid frequency range. It sounded like a blown driver.

But when I disconnected the adjacent cabinet and listened to the 'broken' speaker in isolation, it sounded fine. Full range, good output, no distortion. The driver wasn't blown. The crossover wasn't damaged. The speaker was perfect — it was just wired in reverse polarity to its neighbor.

When both speakers played together, the out-of-phase relationship caused cancellation in the frequency range where their coverage patterns overlapped — roughly 200 Hz to 2 kHz. This removed the vocal presence region, leaving only the extreme highs (where the speakers' directivity was narrow enough that they didn't interact) and the extreme lows (where the wavelengths were long enough to partially survive the cancellation). The resulting sound was so degraded that 'blown driver' was a reasonable first guess.

I swapped pins 2 and 3 at one XLR connector. Both speakers now summed constructively. The level jumped. The mids reappeared. The stage manager looked at the previously condemned speaker with the expression of a man who just realized he almost threw away a three-thousand-dollar cabinet over a two-cent wiring error.

The Moral: Before condemning equipment, check polarity. SonaVyx's problem detector includes a polarity checker that identifies reversed connections instantly — because the most expensive repair is replacing equipment that was never broken.