Before bonding to the spacer and film, the final layer, called stators are thoroughly cleaned with isopropyl alcohol and in an ultrasonic cleaner filled with “various other fun chemicals.” As a result, everyone has really clean glasses at Warwick!
Finally, each driver is carefully tested in a specially built chamber. The driver slots into a jig, which sits at the mouth of that measurement chamber for complete consistency. These plots are used to create matched pairs of transducers which are then tested again as a final headset on “Bob” the mannikin. At present, this is batch building in very low numbers. It’s one stage up from prototyping. But the process is designed to be scaled up, and part of the custom-making process is about working up ways to increase production by as much as a hundredfold.
This is very much a research and development lab, as well as a manufacturing facility. The development facility has its own anechoic chamber although not a huge one, but nevertheless this anechoic chamber didn’t come cheap and shows the level of commitment to audio design and development Warwick Acoustics is prepared to expend.
Like any ongoing project still in its earliest years, improvements happen on a regular basis as the technology becomes more mature. In Warwick Acoustics’ case, this has meant marked improvements in reject rates during the manufacturing process. This is entirely understandable; what begins as a laboratory experiment held together with electrical tape and crocodile clips quickly becomes a more practical proposition, and as the technology and the technologists who develop it learn better ways of making the transducer, so it becomes less likely to be rejected. For example, a small change in the layout of the honeycomb-like surface over the HPEL (High-Precision Electrostatic Laminate) electrostatic membrane almost halved the number of rejects
Ultimately, the limited-run, hand-built nature of the Warwick Acoustics transducer is not sustainable in the automotive industry, and it will need to be successfully production-engineered to be produced in greater numbers. But they have the expertise in house to make that jump when the time is right.