I'd be curious if the designers of your preamp and amplifiers don't think they could integrate a simple high pass filter without significantly compromising the performance. The passive networks needed to create the filtering at speaker level, while still fully analog, have their own limits of linearity, interact significantly with the speaker's load, and will even change their interaction with big dynamics. For many systems, the best high pass filter is the acoustic one created by an appropriately sized sealed box... Which I suspect is the way your MM7's operate.
To be clear, I'm largely agnostic on the methods of executing a crossover... so long as it works in an objective manner and a desirable result is had.
well.....actually......the darTZeel NHB-18NS does, in fact, have the facility to power a low frequency circuit. it has provisions for tri-amping each with it's own preamp output. according to the provisional manual, all three outputs are separately buffered, and optional built in filters can be activated for bi-amping or tri-amping purposes. I don't use mine that way myself as my speaker system, the EA MM7's, provide the bass towers the signal from the speaker terminal of the main towers so the purity to the main tower is not compromised. and when the signal is taken from the speaker terminal, the character of the main amp is carried through to the bottom octave amplification. using a separate crossover upstream of the main amp, you have to then work to get a consistent amplifier character.
this picture shows the back of the old version of the preamp; the -3- BNC outputs in the bottom right (BNC 50 ohm darT outputs) are the same on the new version. it would be cool to tri-amp using 3 sets of 458's.
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