The shot for the Mid/High crossover is a passive implementation. Even though It sounds nice to have a full active setup for the JBL L300, it would require three amplifiers. I don't have 2 tube SET amplifiers that I like at this point, so this will start with a passive crossover for my low-powered SET amplifier.
The picture above, sketching the distribution of components for a prototyping passive XO section. You also can see above the active crossover that will split LF and MD at 800hz.
The first shot is easy, I start with the Nelson Pass crossover design from this article https://www.firstwatt.com/pdf/art_l300.pdf. I only need the MF and HF sections.
For the mid-section, I don't need the high pass filter, since that will come filtered from the active section at 800hz and 24db/oct, but I may consider placing a DC capacitor for DC protection.
I started with the Nelson Pass crossover and striped out the high pass sections. I ended up with the following circuit. I also simulated the response to make sure I removed the right elements.
The picture above, the original Mid from the Pass's crossover redesign and my version stripped of the high pass section. The original crossover has L-pads for the High and Mids but I am only using the high L-pad since the Mid one level can be controlled from the active XO.
I expect a long period of listening, measuring and modifying so I am building a board where I can switch components with ease.
<picture of components>
The final first prototype.
<insert final pictures when ready>
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