Passive radiators, ext crossovers & subwoofers

All speakers will continue to produce sound (though rolled off) below the frequency you select on your x-over unit - at the rate specified by the x-over function. Whether a passive radiator or active driver, the input signal is attenuated by the x-over at the specified rate. If the speaker is dead-on accurate in-room (none are), you'll have the precise roll-off you selected.

In practice, the room is mucking up everything at these frequencies. I use a Velodyne SMS-1 sub controller to view (and corrrect for) room effects. I like this approach a lot and highly recommend it. Note: I also use an NHT x-1 to roll off my main speakers because I like it better than the internal hi-cut function in the SMS-1.

Marty

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