For sale is a rare and hard to find vintage subwoofer Parasound model BPI-A60 Perfect Image powered subwoofer which was designed for MUSIC reproduction in good working condition.
The current concern with providing the best possible deep bass has spawned subwoofers -- speakers specially designed for the rock bottom of the audible range. One of these is the Model BPI-A60, by Parasound, a company based in San Francisco. This bass-only speaker contains its own 60-watt amplifier and reaches all the way down to 20 hertz, just about the lowest musical frequency. Because low bass is non- directional, a single subwoofer can handle both stereo channels. The Parasound`s subwoofer can work with any pair of normal speakers to handle the upper range. OWNERS OF SOMEWHAT BASS-DEFICIENT SPEAKERS MAY WONDER WHETHER TO REPLACE THEIR SPEAKERS WITH MODELS HAVING A DEEPER REACH. But to many listeners, parting with a loudspeaker is like parting from an old friend. They have grown accustomed to its character and foibles; and unless the old speakers are clearly flawed, listeners tend to like what they are used to. To replace a cherished speaker just for the sake of better bass is a step that many audiophiles hesitate to take. Luckily they have another option. They can bolster the bass by adding a so-called subwoofer to their present speakers. A subwoofer is a speaker specifically designed to bring out the lower notes that lie beneath the reach of most regular speakers. It lends a sense of weight and magnitude to passages where cellos and basses play in octaves, adds conviction to the thud of a drum, and creates an almost tactile sensation of pulsing force in passages involving the deep pedal notes of an organ. To put these matters in numerical terms, most smaller loudspeakers cut off their response around 60 Hertz, and even full-sized floor-standing speakers usually do not reach farther down than about 40 Hertz. This ignores the bottom segment of the musical spectrum, which lies in the region of 30 to 35 Hertz, 32 Hertz being the low C of a pipe organ. Subwoofers assure that this part of the musical spectrum is reproduced without diminution. It is not necessary to have a subwoofer for both left and right channels to maintain the stereo effect. Below a certain pitch - roughly 100 Hertz - bass frequencies are nondirectional: you cannot tell exactly where the sound comes from. Consequently, signals from both left and right channels may be combined in a single speaker in that part of the frequency range. The middle and upper frequencies are directed to separate left and right speakers, and the necessary separation of frequencies between the subwoofer and the other speakers is accomplished by a frequency divider, which is built into the subwoofer. This subwoofer designed as add-on units to almost any existing speaker system to assure adequate power for those deep bass thrusts. It has both speaker and line inputs with level control and variable low pass crossover from 60 to 200 Hz.