Audiomatica is pleased to publish a new interesting paper written by Joe D’Appolito on subwoofer design: “Model-Based Active Equalization of Closed-Box Subwoofers”.
Quoting Dr. D’Appolito’s own words:
“Early in my career at Snell I began to look at sealed-box subwoofers. One of the problems with them is equalizing response down to 20 Hz for home theater application. I looked at several approaches. There was, however, one model-based approach by Linkwitz. He developed a biquad op-amp circuit to do the job, but the circuit topology was not at all obvious and component calculations were very complex. Multiple iterations were required to get reasonable component values. Also the circuit did not cover all possible fsa and Q combinations. The state-variable-filter approach put forth in my article is much simpler and more intuitive. This work was actually done around 2006 or 2007. It was only recently that I thought it might be of interest to the DIY community.”