Troy, that's a bit clearer now, and as Dave commented, what you're proposing is similar to what can happen now. If the mains/sub crossover would be set at 60Hz the mains would be rolled off at 12dB per octave below 60Hz, while the sub would be rolled off at 24dB per octave above 60Hz. So, there's a blend of the mains and sub in the crossover area and as the frequency got lower the mains would do less and less, while as the frequency got higher than the crossover set the sub would do less and less.

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Enjoy the music, not the equipment.