Phitek Systems manufacture a wide range of commercially successful personal audio delivery platforms all of which include active noise control. The transducers in these systems include miniature electro-dynamic actuators and electro-static sensors, which are close-coupled into assemblies small enough to operate in the ear. This paper reviews some aspects of transducer function within an active control system, with particular emphasis on frequency response, dynamic range, linearity and self-noise. However, it is the main purpose of the paper to illustrate how the demands imposed by these objective criteria are exaggerated and exacerbated in the context of practical volume manufacture for the consumer market. The additional complexities of sample-to-sample variance in transducer performance are considered from the perspectives of system impact, quality control and manufacturing yield. Finally, examples of how system performance can be compromised by transducer handling during manufacture are presented.