Ah, okay, it's passive you want. The purist way to high-pass filter the signal going to your power amp and speakers, to relieve them of reproducing bass frequencies (a worthwhile objective imo), one that has been used since the DIY 1950's, is to install a single capacitor (the value of which is determined by 1- your power amp's input impedance, and 2- the desired x/o frequency) on the inside of your power amp, on it's input jacks. This will create only a 1st-order, 6dB/octave filter. That is the way to incur the least damage to the signal, both by the use of but a single part---a capacitor, and by removing the need for an extra inter-connect---no x/o box necessary. The formula for determining the capacitor value required for your application can be found all over the 'net.
What I have heard from other Magneplanar Tympani owners on the Planar Speaker Asylum, many of whom use Marchand active x/o's in their systems, is that the active Marchands are actually better sounding than the passive ones. How can that be, you ask? Aren't passive parts more transparent than an active circuit? Look at the parts inside those passive Marchands---the parts necessary to provide a higher-than-1st-order filter. Nasty, ugly sounding things, worse than the parts in an active circuit.
Speaking of ugly sounding parts---all Marchands contain Opamps (except the tube model, one presumes). The First Watt B4 is completely discrete---all resistors and capacitors, no Opamps, no IC's. The B4 provides 1st-2nd-3rd-4th order (6-12-18-24 dB/octave) filters from 25Hz to 3200 Hz, in 25 Hz increments. Incredible! Unfortunately, it is available unbalanced/RCA jacks only, so may be unsuitable for your system.
