Very few manufacturers use electrically powered patch coils as was characteristic in the earliest designs. For instance, the shape of the pole piece affects the magnetic interaction between the voice coil and the magnetic field, and is sometimes worn to modify a http://www.gracedigitalaudio.com/lp/outdoor-wireless-speakers/outdoor-wireless-speakers.html driver's behavior. As well, a 'shorting ring' or cap is sometimes absorbed near the magnetic gap to reduce adverse distortion effects of high existent in the call coil.
The lowest-priced speaker systems and most drivers are manufactured in China or other low-cost manufacturing locations. Although the manufacture of drivers beat become largely commoditized, the fabrication and sequential sale of finished speaker systems still carries high profits. Partly for this reason, manufacturers are increasingly combining power amplifier electronics (a typically lower cleanup item) with finished speaker systems to fabricate powered speakers with an overall exceeding corner store value.
