Even though the individual components are tested during the assembly process, the entire speaker is tested at the end as a completed system.
A run of ElectroMotion ESLs awaits final testing. The ElectroMotion ESL is MartinLogan's lowest-priced electrostatic-panel-based hybrid design, yet it goes through the same testing procedures as the more expensive models. The ElectroMotion ESL sells for $2200 USD per pair.
Each speaker is placed on a platform and tested for various electrical and acoustical properties . . .
. . . including phase and polarity.
Every speaker must receive a passing grade for all tests before it moves on to cleanup and packaging.