Super efficient at 96db make these a treat with even flea watt amps. I drive them with 3.5watts of beautiful tube power. They are a concentric design with a tweeter mounted in the woofer similar to Tannoy & Kef. The imaging sharp and soundstage is huge These speakers were custom built for me by Frank at Coherent, google for details about Frank's hand built, Canadian speakers. Sensitivity at 96db/1watt make them very easy to drive. Rare and beautiful. https://wallofsound.ca/audioreviews/speakers/review-the-coherent-model-8-a-speaker-for-real-life/#prettyPhoto