In passive circuitry, every component, including resistor and speaker driver characteristic, plays an role in the crossover frequency formula.
The analysis is as follow: From the woofer point of view, within the woofer band (assuming 20Hz to 400Hz), the woofer can be considered as resistive. The woofer crossover network is dominant as a first order low-pass function, since 1.03mH is inductor and woofer itself is resistor. The effect on 6.8uF and 3R3 resistor branch is small in this frequency range.
However, this woofer also acts as midrange to cover the frequency maybe up to 3kHz. The woofer impedance would rise as frequency increasing due to both coil inductance and mechanical compilance of cone. Also the sensitivity of woofer at low and high frequency is different. The 6.8uF and 3R3 branch forms a parallelling impedance with the woofer to control the woofer sensitivity approaching crossover point. Since there is 3R3 in the 6.8uF branch, in theory it is a zero (in terms of circuit theory), the overall system is not entirely a second order network, but still a low-pass function.
Additionally, even there would be much higher impedance at the woofer resonance frequency around 100Hz, the impedance is still resistive.
The 6.8uF certainly be part of formula in controlling crossover frequency. Only 7% change in capacitance value would not cause so much the crossover frequency shifting. The "capacitor sound" may be the issue. |