Acoustic Research was a top of the line speaker. The company folded many years ago. The AR9 is a 40 year old speaker. IMO, you should save that $1K and buy a newer speaker. Here is the information on the AR9!
https://www.hifiengine.com/manual_library/acoustic-research/ar-9.shtml
https://www.hifiengine.com/manual_library/acoustic-research/ar-9.shtml