In this final article of the four-part series, Andy Lewis expands upon the Back EMF concepts hinted at in the previous three articles in this series. This article explores the Electrical and Newtonian filters and their intersections, observations on reactive parallel filters as pertains to Back EMF and energy losses. The theories can be applied to virtually all areas of loudspeaker design.
I hope you have enjoyed this series on Back EMF. As I stated up-front, I really don’t see anything in this article series that would directly benefit a loudspeaker designer. I had just never seen anybody examine this activity. The important lesson to be taken from this article series applies not just to Back EMF, but to virtually all areas of loudspeaker design. There are many areas of loudspeaker design that involve frequency-dependant (complex) arithmetic. Back EMF is a filter. Bass enclosures are filters. Crossover networks are filters. Moving-coil drivers are filters.
An understanding of, and ability to perform, calculations using complex numbers can empower a designer in many ways. I developed my skills using complex impedance information in an effort to design accurate passive crossovers using fewer components, for my own selfish ends. My efforts were successful, and my passive crossovers are very good.
I never would have noticed how Back EMF behaves had it not been for this work on passive crossovers. An understanding of complex impedances and reactive filters enabled me to figure out how Back EMF behaves, and increased my understanding in other areas, as well. aX
This article was originally published in audioXpress, November 2018
Read Part 1 of this article series
Read Part 2 of this article series
Read Part 3 of this article series
Read the article now available online here