These electronic crossovers look good, I am considering going active;has anyone used them ? Suggestions for alternatives welcome. The Speakers are Spendor S 100s which would be tri amped with 6 identical mono amps.
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. . .

I would call Marchand if I was you. The owner has forgotten more about crossing over speakers than the collective brain trust here has ever known.

If he has made a crossover for your speakers before, he has a set of parameters worked up already. I think you will be surprised how simple it can be for Marchand to build something for you. Also, there can be several different modules they can suggest, very reasonably priced, to make adjustments.
I am now really confused. The reason why I don't buy or build active speakers of another brand [I have had some] is that I like the sound of the Spendors better and wanted to optimize it. They did make an active version but the company has changed ownership since that time. I will try to contact them as well as Marchand.
Excellent idea! I love those speakers too.
Happy XM44 owner here. Call Phil. I'm sure he could cook up something that would suit the Spendors!
Another happy XM44 owner here. Using four 300B monoblocks with my Tannoy 15" dual concentric.
Dusty & Jburidan - are you both using the Marchand XM44 because you've bypassed the internal xover within your speakers, OR are you using both the Marchand external xover PLUS the speaker's internal xover??? Care to elaborate?

I wrote:
>much of which the marchand products won't accomodate.

which was incorrect.

You can have shelving filters, peaking filters, notch filters, etc. but some one needs to know what you need and calculate component values. Most of that is listed in the manual.

Each channel of each way has 3 card-slots. Each card-slot connects to the pins of a dual op-amp.
Kevinzoe your proposed solution of using a Marchand to remove low bass from your mains to send to the subwoofers will work and is a very good idea. I am doing the same thing, but using a Behringer until my Marchand arrives.

BTW, baffle step compensation, notch filters, group delay, etc. are available for Marchand crossovers. They are drop-in cards.