These unique looking speakers are housed in a bass reflex enclosure constructed out of black granite. The enclosure size is 15L and tuned to 45 Hz. The drivers, G17REX/P woofer and Seas 27 TFFC tweeter are from Seas. The crossover is second order at 2500 Hz. See the project page: DIY Granite Loudspeakers with Seas Drivers for more information.