rsdio writes: If anyone is building a subwoofer crossover, this is a great article! Nice use of opamps too.
The linearity and high power-handling capability of modern low-frequency loudspeakers have made it easy to electronically extend the bass response. This extension is especially useful in second-order systems like a closed box, where cone excursions are limited by the box.
Many such circuits are available, but the most popular today is the so-called Linkwitz equalizer intended for complex-pole systems in which Q > 0.5. The circuit neutralizes the original response by compensating the original poles with zeros, and then creates a new highpass response as specified by the designer. Like the original, the new circuit provides a 2nd order response.