<!-- Image with unknown copyright status removed: right|250px|thumb|Dynaco Stereo 70 -->
Dynaco was an American hi-fi audio system manufacturer popular in the 1960s and 1970s for its wide range of affordable, yet high quality audio components. Founded by David Hafler and Ed Laurent in Philadelphia, Pennsylvania in 1955, its best known product was the ST-70 tube stereo amplifier. They also manufactured other tube and solid state amplifiers, preamplifiers, radio tuners and bookshelf loudspeakers. Dynaco was liquidated in 1980, and the trademark is now owned by Radial Engineering Ltd.
Early company history
In 1950 David Hafler and Herb Keroes started a Philadelphia-based company called Acrosound to build and sell audio-quality output transformers, primarily for home electronics hobbyists. A modified aperiodic bass reflex design using SEAS speakers in a handsome wood cabinet, the A-25 sold for $79.95 each in 1969 making it competitive with much more expensive loudspeakers. The patented aperiodic (essentially non-resonant) woofer design utilized a highly damped vent instead of a reflex port, whose acoustic resistance is very carefully controlled. The resistant venting action lowered the "Q" of the system and reduced impedance variation near resonance in the A-Series speakers. Dynaco followed the A-25 with the slightly larger A-35, which featured a dual-chambered, non-vented design in a walnut-veneered cabinet with even greater transparency and fidelity. Over time, Dynaco marketed a wide range of loudspeakers, ranging from the small A-10 model to the floor standing A-50 series. After some 30 years, these loudspeakers still command good prices in markets such as eBay, and are a testimonial to their quality.
Concurrent with A-25 production, Dynaco introduced the QD-1 speaker adapter which synthesized 4-channel sound from the stereo amplifier output. This "Dynaco patent" required a single resistor and a threeway potentiometer for the two rear speakers, generating phase difference signals for a feeling of ambience. The system worked best when the stereo sound had been recorded via two bidirectional microphones on the same spot. When microphone set-up changed to the use of multiple directional microphones and multitrack tape recording and postprocessing (i.c. in the CD era), the QD-1 was less effective.
Dynaco became a wholly owned subsidiary of Tyco, Inc. in 1969. David Hafler remained with the company a few years longer, but left in 1974 to join Ortofon, manufacturer and importer of high-end phono cartridges. In 1977, Hafler founded the Hafler Company, continuing the tradition of high quality but inexpensive kits and assembled hi-fi gear.
In the late 1970s, Dynaco released a short-lived set of new loudspeakers developed by Ed Laurent, the Phase III. The speakers were well regarded by the audiophile community, but their introduction was apparently too late to make any strong impression in the marketplace, and Ed Laurent left shortly afterward to join SEAS Corporation. After Dynaco closed its USA operations, its former Canadian subsidiary released the Dynaco A-150, A-250, and A-350 speakers, all manufactured in Canton, Massachusetts.