The Qs are multiplied against each other, which will give the loudspeaker an effective Q of 0.707. The advantage of this arrangement lies in the smaller enclosure needed for a higher Q loudspeaker alignment and the natural 2nd order highpass filter function of the sealed box enclosure adding to 1st order filter to make a 3rd order highpass filter with a -3 dip at the crossover frequency.
    To work best this 1st order filter must come before the power amplifier, as using a capacitor in series with the loudspeaker will not work due to the impedance spike at the speaker's resonance. The subwoofer's lowpass filter should be actively realized with an active 3rd order Butterworth filter. A further refinement would be to add an active 2nd order or 4th order highpass filter whose cutoff frequency would equal the Fs of the subwoofer. This would both work to protect the satellite speaker from excessive low frequency cone excursions and work to bring both subwoofer and satellite into the same phase relationships, as the subwoofer's own box resonance defines a highpass filter (2nd order for sealed boxes and 4th order for bass-reflex enclosures.)

     For most drivers that suffer from either limited power handling or limited frequency response, sharper cutoffs are needed. The 2nd, 3rd, and 4th order slopes both protect and isolate the drivers. Many audiophiles, however, distrust higher order filters, fearing the signal's phase reversals and complexity of the crossovers. Yet they do not realize that the speakers themselves bring phase aberrations because of resonances driver breakup at higher frequencies. For example, most tweeters have a resonant frequency between 800 to 2 kHz and all cone and dome drivers must flex once the circumference of the diaphragm becomes larger than the twice the wavelength of the frequency being reproduced. (Strictly speaking, for example, we should not let an 8 inch woofer extend beyond 1400 Hz; but we do so regularly.)
   Here is where active filters shine. As has been mentioned, the problem with using passive filters with loudspeakers is that they seldom function entirely to plan and this poor performance is due to the passive components falling short of their ideals.
    Inductors (chokes) are made up of long lengths of wire, which adds resistance. Capacitor also carry an ESR (effective series resistance) that upsets inter-relations within the filter. And loudspeaker drivers are anything but pure resistances. All of these failings add up to a filter that does not match its textbook model. On the other hand, the active filter can match its textbook template easily. Additionally, active filters can make do with only resistors and capacitors to define their poles. Doing without inductors is a relief in terms of money and space, as the lower the frequency, the bigger the inductor. And because the active filter presents an almost infinite input impedance to the frequency tailoring parts, high valued resistors can be used, which only require small valued capacitors to match. For example, an 8 ohm loudspeaker driver crossing over at 1 kHz requires a 20 µF capacitor, whereas a 10k resistor only needs a .0159 µF capacitor. In other words, active filters present a win, win situation. 

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