The Monitor Audio MA1 Series II was released in 1975. Employing a KEF 139 bass driver, this speaker was known for its full and effortless bass reproduction. The Monitor Audio MA4 was designed using an Isophon tweeter and fulfilled the need for high power, medium sized system of extended response and low colouration. The bass and mid-range came from a 220mm KEF B1039 unit, with a 33mm high power voice coil. The MA3 Series II and MA7 were known for their open sound whilst the MA5 Series II was commended with it’s tight bass reproduction. The MA3 Series II was a full three-unit system and could handle 100 watts of power. The drivers consisted of a mid-range that was a bextrene coned unit and an elliptical bass driver. The HF driver was a special version of an already establish design, employing a 25mm polycarbonate dome.