Marchand

They are respected line-level crossovers. Some models are available in tube and solid-state versions.

Note that

1) Many cross-overs incorporate compensations for baffle step, rising response with increasing frequency, and driver resonances.

2) Many cross-overs combine drivers' acoustic roll-offs with electrical transfer functions to produce the final slopes.

3) Many cross-overs get the flattest response by compensating for the phase shift cause by their acoustic center location or band-pass functions with asymmetric cross-over slopes and points.

much of which the marchand products won't accomodate.

Without measuring the transfer functions from your existing passive cross-overs you don't know enough about what's going on to do as well with an active solution.

The other thing to note here is that #3 is a compromise for the inability to implement affordable speaker level delay networks.

People monkey with asymmetries until they get acceptable response over a given vertical window.

Ideally, you'd use symmetric slopes and delay the driver with phase lead using all-pass networks.

Obviously, this requires measurement capabilities.

If the goal is to realize the gains of multi-amplification and not to embark on speaker design as a hobby, you'd be better off buying active speakers which suit your tastes or building a respected active design that's known to work well.

Drew - thanks for your very informative responses. At the risk of hijacking Stanwal's thread, let me ask a related question: If one wants to remove the low bass from the main speakers (which in my case has the woofer crossed over at 80Hz) and send it instead to a pair of subwoofers, then would an active or passive Marchand unit be fine? My thinking is that all of the factors in you first post above wouldn't come into play with the main's woofer as it'll be removed and replaced with the subwoofers. . .