Omega Speaker systems,
Omega Speaker Systems
from Norwalk Connecticut all speakers between 94.5dB and 98dB efficiency, and are actually reasonably priced.
Japanese Audio
I've owned a few great low powered Japanese tube amps and wonder if anyone knows why this niche of low power class A and tube amps exists in Japan. Luxman, Leben, Airtight, Yamamoto, Almarro (no longer), SPEC, Accuphase to name a few. If your goal is building a low power amplifier, where does the inspiration come from? Did these brands spring up from western influence like other areas of Japanese culture or are there many unheard of Japanese high efficiency speakers?