Orion and LX521.4 owners are sophisticated enough to have knowledge of all the following, but for others:
There are a few well known benefits to be had by using an outboard active line-level crossover in place of a passive speaker-level one. A main one is keeping the bass frequencies out of the amp that is driving the midrange and tweeter drivers. That is why bi-amping without inserting a line-level x/o before the two power amps doesn’t provide the same degree of improvement as does sending a filtered signal to each amp. Keeping the bass frequencies out of the amp reproducing the mids and highs allows the m/t amp to produce less distortion, and leaves much more available power for the midrange and tweeter drivers.
My Magneplanar Tympani T-IVa loudspeakers came with a pair of outboard passive speaker-level crossover boxes, each box placed inline between one channel of a single stereo (or dual mono) power amp(s) and it’s designated speaker. So even though the bass, midrange, and tweeter drivers are seeing filtered signals, the power amps are not. A single stereo amp driving all three drivers---woofers, midrange, and tweeter---reproduces all frequencies.
The Tympani crossover creates a 3rd-order (18dB/octave) high-pass filtered signal at 250Hz for the midrange/tweeter panel (the mid-tweeter x/o is located at 3kHz, the two drivers not worth separating), and a 2nd-order (12dB/octave) low-pass at 400Hz for the woofer panel. Those are referred to as textbook crossover filters: they create their assigned slopes only. To actively bi-amp a Tympani, the stock speaker-level crossover is simply replaced by a line-level x/o that can provide the same textbook filtering. Doing that allows the Tympani to achieve a higher level of sound quality, and Magnepan recommends it in the speaker owners manual. I purchased a First Watt B4 to use with my pair of Tympani T-IVa, the B4 being perfect for the job. Excellent design and build, and reasonably price ($1500 retail).
Linkwitz obviously believed in loudspeakers having an active line-level crossover. But his loudspeakers incorporate crossover filters far different from textbook filters. The filters he designed for the two above models do more than just create simple high-pass and low-pass slopes; they also include parts that provide tailoring of the response of the drivers within their respective bandpasses. Line-level textbook filters cannot provide that tailoring, and Linkwitz resorted to using digital processing to do his filtering on the two models being discussed.
His friend and neighbor Nelson Pass (designer/maker of the First Watt B4, of course)---knowing that digital filtering was not going to be well received in Asia---asked Linkwitz if he wanted him to create an analog x/o for the LX541. Like the Asian’s, I do not want all my source material to go through digital processing.
Danny Richie is also against digital filtering, and that is one reason he eliminated the Orion’s complex stock digital x/o and created his own speaker-level one. The filtering required by the individual drivers could not be done at line-level in the analog domain, so Danny created speaker-level filters that not only replicated the stock digital filters, but also "corrected" what he considered to be imperfections in the speaker’s performance. Whether one prefers the stock performance of the Orion, or Danny Richie’s Modified one, is a matter of personal opinion.
I long ago realized planars are my preferred loudspeaker design, but at least the Linkwitz are open baffle dipoles ;-) . I much prefer large sheets of mylar over dynamic cones for my loudspeaker drivers. Danny uses cones, domes, and magnetic-planar drivers in his loudspeakers, and imo is a master designer. Don't let his good ol' boy demeanor fool you: he is very sophisticated and knowledgeable.
