Complex sentence: In 1981, Quad introduced the ESL-63 as a successor to the ESL-57; it attempted to address, amongst other things, both the deficiency in bass reproduction of the ESL-57 and its extreme directionality at high frequencies.
Split into simpler sentences: In 1981, Quad introduced the ESL-63 as a successor to the ESL-57. It attempted to address both the deficiency in bass reproduction of the ESL-57 and its extreme directionality at high frequencies.