If this is specifically related to π Speakers, as you've indicated you want to do this to a Theater four π, then you'll want to modify the values in the tweeter compensation circuit. Remove the bypass capacitor and possibly increase attenuation. The Theater four π uses a 10dB attenuator; Change the values to 12dB, 14dB or whatever desired. There's a chart showing what resistors to use in the crossover document.