One of the goals of this project was to have a speaker that offered great sound quality, and as such, I put a little more work into the crossover than what you would probably fi nd in most other "music store" cabinets. I did initially test the design with a stock passive pro-sound crossover, which produced fair results, but I decided that a little more effort in the crossover design could deliver dramatically improved results.

My final passive crossover design includes a second order low-pass fi lter plus impedance compensation network on the woofer, which works with its natural roll-off and eliminates higher frequency hash. The horn driver also has a second order high-pass fi lter in addition to an impedance notch fi lter at the resonance frequency. Without the notch fi lter, I was getting excess excursion and distortion at the resonance frequency. This circuit really cleans up the sound of the high-frequency driver.

The net crossover point is about 2.5 kHz, though the drivers are slightly underlapped, meaning that the woofer rolls-off a little lower and the tweeter rolls-off a little higher. Note that because of the high power levels that this speaker will see, it is important that high wattage resistors are used, especially in the woofer impedance compensation leg. I chose to make a high-power resistor pack by connecting four 20-watt resistors in parallel.

This is an excellent opportunity to mention that biamplifying with an active 2-way crossover could be a very viable option for these drivers. Thanks to the woofer and tweeters' smooth frequency responses, a standard electronic crossover should work well. Not to mention that this approach would eliminate the crossover component cost and the need for high-power resistors. Just center the crossover around 2.5 kHz with about 10 dB of attenuation on the tweeter and you should be most of the way there.