ADC 450A (1971)
Little is documented about the ADC 450A beyond a few period reviews and a big advertising campaign. What the record shows is a two-way speaker system that ADC sold with the tagline “NEW, TRANSPARENT AND BEAUTIFUL.” The slogan ran in multiple issues of Audio and HiFI-Stereo throughout early 1971.
High Fidelity (April 1971, p.46) published a full lab and listening report. The reviewer found signals in the 20-25 Hz region less evident than in most speakers. Beyond 800 Hz, where the tweeter took over, response continued to beyond audibility, with an audibly evident slope beginning around 14.5 kHz. Directional effects did not show up until above 5 kHz, and even then the sound stayed amply dispersed. Tones above 10 kHz were still well spread. The review also included measured harmonic distortion figures at 80 Hz and 300 Hz across a range of output levels, but the exact numbers are fragmentary in surviving copies.
HiFI-Stereo (January 1971, p.34) called the 450A a “high transparency” speaker system, a phrase ADC used prominently in its early advertising for the model. No other specifications have turned up in surviving sources - no driver sizes, impedance, sensitivity, crossover details or cabinet dimensions. Production years appear to center on 1971, with no evidence of an extended run.
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