They also put each speaker though a 'quasi anechoic chamber' at the end of the line. I'm pretty sure Ian explained that here some time ago. What they did was build a small chamber on the line and calibrated it using a known reference speaker and measurements from the full chamber. As I remember it, this was a way to verify that the response of each speaker was as expected.

Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!