Passive radiators, ext crossovers & subwoofers

Not sure if I'm understanding the question.

There's low pass and high pass components of a crossover. A sub, fed independently by interconnects, would only include the low pass filter, in which case the main speakers still receive full bandwidth. A separate active crossover, such as a NHT X2, includes both low pass and high pass filters. There are many ways to integrate a sub, including speaker level.

A passive radiator plays no part in your plans, except that it can be "tuned" or weighted (usually with blu-tack) to adjust the "Q".

In my understanding the passive radiator acts in the same way as a port, to relieve internal pressure inside the enclosure and to simulate a larger enclosure. This is probably a gross oversimplification but it is not driven at all by the amp and has nothing to do with what you are doing. If you choose 60 Hz as a crossover point that means that the speaker BEGINS to attenuate at that frequency and the rate of attenuation depends on the slope of the crossover [6 db, 12db etc.] So you will be getting response below the chosen crossover point, how much depends on your particular system.

Keep in mind the higher the frequency you roll off the low end the less effective the passive radiator becomes. The passive radiator will be out of phase with any sub you use so from my own experience you are better to blend a sub with the polks using the above mentioned velodyne or other bass management system and run the polks full range

To clarify,

The passive radiator (if properly designed) is designed to produce output mirroring the electrical input at the speaker's terminal - exactly like an active driver. If you attenuate any frequency at the input, a properly designed speaker - passive or active - will attenuate the output accordingly.

Good Luck.

Marty

Thanks everyone for your responses. This has been helpful.