Thinking of Magnepan ... finally!

Good point @ketchup, highlighting a mistake I hadn’t realized I made. Yes, a high pass filter must be used if one wants to relieve any loudspeaker the duty of reproducing low frequencies. That filter may be installed in between a power amp and the loudspeaker it is driving (in the speakers internal cross-over, aka high-level), but if it is instead installed in front of the power amp (aka low-level), the amp will ALSO be relieved of that duty (the point I was focused on). Doing so benefits both the amp and the speaker, a win-win.

A simple 1st order filter (just a single capacitor) may be soldered onto the input jacks of the power amp (on the amp’s interior), but a higher-order filter (which will create a steeper roll-off) containing more parts will require an outboard, active crossover. Some powered subs contain a high-pass output on their control panel, but that filtering is always (to the best of my knowledge) accomplished with an opamp or integrated circuit, not discrete parts.

A great budget-priced ($1500) 2-way crossover was for a while offered by First Watt---the B4, but is now available only as a DIY kit. It provides 1st/2nd/3rd/4th-order filters (6dB/12dB/18dB/24dB per octave), for frequencies ranging from 25Hz up to 6375Hz. And does so using discrete parts.

The B4 has two pair of outputs---low-out and high-out, and each filter may be configured independent of the other; the high-out may be 1st-order and the low-out 2nd, or visa versa. Very flexible, and the B4 a great cross-over for those wanting to bi--amp MG.6 and earlier Magnepan models. They have parallel crossovers, while the .7’s are series. Of course if used for subwoofer applications, that doesn't matter.

Oh, and by the way:

For anyone with a Maggie model that includes an outboard cross-over box, the First Watt B4 can be used in place of that box. While almost all other loudspeakers have cross-overs that included driver-compensation networks, the cross-overs in Maggies are purely "textbook" in nature: 1st, 2nd, or 3rd-order, with no driver compensation elements. The First Watt B4 is capable of creating the same filters are do the Magnepan outboard boxes, but in superior quality. Not to beat up on Magnepan, but everyone knows they use junk parts in their cross-overs.

So a local audiophile was gracious enough to invite me to his house to listen to his Magnepan-based system. His speakers are 20.7 driven by Audio Research amps. I'm planning to visit his home in 1-2 weeks. I understand that 20.7 is way outside what I'm planning to spend on Maggies at the moment, but at least it will give me a taste of what these speakers are capable of. Looking forward to the visit. 

The 20.7 is Large, but boy will it sound good,

i would say that in my experience, once you get to 1.7i and above, alot of the sound quality depends on how the speaker loads the room (and how loud one wants to listen)... i still have both the 1.7i and 3.7i and the size of the panels load my room very differently (17x22 well treated dedicated room) and i would imagine going to even bigger panels of the 20.7 and 30.7 would definitely be too much of a good thing... in fact i feel the 3.7i in my room can already overload the room in the midbass if i am not careful and i need to get the placement just right (and employ dsp control) to make them sound just right

there are those who have said that 3.7i has the true ribbon tweeter over the 1.7i quasi ribbon unit... i think both have absolutely outstanding treble, with the 3.7i having more treble energy - but i do not think the 3.7i resolves noticeably better than 1.7i