I just upgraded the crossovers in one of my speaker pairs. I've had these Mission Argonauts for years, the drivers and cabinet are in good condition, I and don't use this set up enough to justify spending much. The speakers are sealed towers, 2-ways, with a Mission "Super Elliptic Impedance Transformed Tweeter" and two Mission 8" woofers.
I asked Danny about upgrading the crossovers and keeping the cost moderate. Sending a speaker to him to design a new crossover would be the best, but not worth the freight cost. I mailed a crossover to him, he measured the values of the components, and supplied new parts. Danny was very aware of the costs and gave me some options in that regard.
The tweeter got a new Alpha-Core copper foil air-core inductor replacing a wire-wound iron-core coil. A Sonicap Gen 1 capacitor bypassed with a Sonicap Gen 2 0.1uf cap, and the re-used wire-wound resistor completed that crossover.
The woofer got an Alpha-Core inductor, an Erse cap with the Sonicap bypass (good quality and lower cost than a Sonicap cap), and the re-used resistor.
For about $100 these speakers sound GREAT. I did the first one and gave the Mrs. (no audiophile!) an A-B comparison against the original. She said, "the old one sounds muddy." Danny described the difference in the new crossovers as being able to hear the space between musical notes. Very true. I even think I could hear a detail in a low note on a violin string where the bow alternately grabbed and lost the grip on the string--which of course is how a bow makes a violin string make sound. The clarity is wonderful, and the imaging improved...imaging and sound stage are a result of timing nuances, aren't they, and the caps are about timing.
By the way, I could assemble GR-Research speakers in Parts Express cabinets for people as well as routing the front baffles. No CNC stuff, just a router and a Jasper circle cutting jig. I need to build my own Neo 2X speakers first. For my other system that gets more use, I'll have Neo 2x and a Rythmik/GR sub--if I ever get around to making the sub cabinet.
Ken
