This is possibly the coolest music video ever made!
The outgoing Commander of the ISS singing "Space Oddity". In space.
The most successful speaker Epicure Products ever built, and for good reason, was the EPI 100. Using just an eight inch woofer and tweeter that were designed from scratch to work together, it provided a seamless, balanced musical experience in a small package, and at a very low price. (The epicure 10 is essentially the same speaker as the EPI 100.) The EPI 150 used the same parts, but took advantage of the capability of the woofer to achieve lower frequency extension when used in a larger cabinet, for those who didn't mind giving up some more space for them. The Genesis I, 1+, 1 and 10 worked from the same principle with similar drivers. Guess what? My HUMAN 81 and HUMAN 81+ do too!
This project, then, includes a variable. The volume of the cabinet can be anywhere from one half to as much as two cubic feet, and you can experiment creatively with cabinet shape and dimensions, given the range of "opinion" expressed by these wonderful forebears to your project.
The crossover used by EPI and HUMAN is just a single ten microfarad capacitor (I'd recommend using a high quality film type capacitor) in series with the tweeter. The Genesis I also added a shunt coil of 0.47 mH, and the Genesis 10 used 8.2 uF shunted by a 0.9 mH choke coil - these "second order" networks are intended to decrease the power "seen" by the tweeter below the roll off frequency. Since this comes with a penalty in the linearity of the phase response, I prefer to use the single capacitor design myself.
The K-81E is a special edition of this kit, intended for rebuilding first generation EPI speakers such as the M90, M100, M110, M150, etc. The tweeter is built on a 5" diameter faceplate (the PRO 002 ME1), and the input terminal/crossover/wiring assembly is built on a board that is screwed inside the rectangular opening in the original cabinet (the ACC 004 A).
The K-81AP is similarly a special version, intended for rebuilding the Advent Prodigy tower speaker. The tweeter is built on a custom faceplate designed to match the original mounting location and cutout, and the input terminal/crossover/wiring assembly is built on a cup that matches the rectangular opening in the original cabinet, after the through-hole is enlarged somewhat.
Interior dimensions in inches, volume in cubic feet:
Stock bracing: None (except HUMAN models). I recommend adding at least one brace front to rear at the point between the woofer and tweeter cutouts.
Driver position: Offset from center of cabinet face, tweeter a different distance from the top than the sides, drivers as close together as practical.
The HUMAN 81 Kit includes:
2 PRO 005 woofers
Here are some photos of 81 kits people have built: