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The Cynosure

Cynosure
Design Goals
Driver Selection
Enclosure Design
Enclosure Assembly
Crossover Design
Conclusion
Parts List
About the Designer
- Crossover Design -

As established in the goals section, the crossover design is an integral part of the success of this speaker. I employed a somewhat unique approach to the crossover, namely what could be called a 2.5.5 way design. Basically, the outermost drivers operate up to about 200 Hz, the middle drivers operate up to about 700 Hz, and the innermost drivers operate up to about 2 kHz where they cross to the tweeter. This approach allows all of the drivers to work together at the lowest frequencies for maximum low-end extension, while only the innermost work at higher frequencies for maximum dispersion.

To achieve the desired impedance, the speakers are wired with two drivers in series, and then each of these pairs in parallel. The outer two drivers are in series with each other, the middle two are in series, and so on. The net result is an impedance of 5.33 ohms, which once some inductor DC resistance is added results in a nominal impedance of 6 ohms. This impedance combined with the high overall sensitivity should work well with any home theater receiver, even if it is rated for an 8 ohm minimum center channel. The tweeter crossover is a second order high-pass with a very small padding resistor that reduces the output by a couple dB. This design is unique in that the tweeter is connected in reverse phase compared to a "normal" two-way design. The result is excellent off-axis response in the horizontal domain-- far superior than what would be expected.
Frequency Response Chart

Crossover Schematic