Fidue a71 in ear hifi dual driver sound isolating earphones fidue a71 in ear hifi dual driver sound isolating earphones have been built using 2 separate dynamic drivers a 10mm woofer and a 68mm titanium dynamic driver the barrel type driver housing is tough and durable making them great for regular use dual dynamic drivers the barrel type casing of the a71s have been specially designed to fit 2 dynamic driver units in each earphone a 10mm woofer and a 68mm titanium dynamic driver this d