Unit is in Great Condition!
This is the last equalizer to be made for McIntosh loudspeaker systems. The XRT26 was designed and produced without any requirements for an equalizer. However, because of customer complaints about the sound, particularly in Japan, the only way the system would be accepted was if an equalizer was included. The MQ109 was designed to correct, in part, the response of this system. However, instead of making the equalizer for use ONLY for the XRT26 and having no adjustments, it was decided to make it a more universal device that would roughly compensate for some room acoustics.
The frequencies are based on an earlier equalizer that I specified in the 1970's but it never went into production. The MQ109 center frequencies are selected to compensate for objectionable areas where the XRT26 has too much or too little output. These center frequencies are not adjustable. However, the amplitude and width of the frequency bands are adjustable and can boost or cut.