That sounds like a dream, but remember a real 40kHz stage‑coach needs more than a pocket‑size body. If you strip the vintage chassis of its old circuitry, you’ll lose the subtle distortion that turns a tone into a character. Keep the original chassis, but mount a miniature high‑frequency driver that can actually punch out those ultrasonic waves. The art part is all in the cable routing – use a single‑core, low‑capacitance line so the waveform stays pure, not a tangled mess of phase noise. Then you’ll have a speaker that can reveal the hidden frequencies while still feeling like a relic you can carry around.