Efficiency Investigation of Subwoofer Driven Around Resonance Frequency

The need for efficient portable speaker systems has increased tremendously over the past 10 years. The batteries, amplifiers and filtering has all seen great improvements in efficiency leaving the speakers units as the most inefficient part of the system, mainly due to the large amounts of current drawn that ends up being dissipated as heat in the voice coil.

This paper will look at how you can design a speaker system to take advantage of the resonance of a speaker unit, since that is where the unit is most efficient and draws the least current. A subwoofer speaker system will be designed with focus on only driving the speaker units near their resonance frequency.

The tests found that with modern DSP it was rather simple to design a speaker system that operate in a very narrow frequency band around the speaker units’ resonance frequencies, which in turn ensured a very small current draw. This greatest drawback of this method is the increase in components needed, which drives up cost and complexity.