Cone tweeters were popular in older stereo hi-fi speakers designed and manufactured in the 1960s and 1970s as an alternative to the dome tweeter (which was developed in the late 1950s). Cone tweeters today are often relatively cheap, but many of those in the past were of high quality, such as those made by Audax/Polydax, Bozak, CTS, JBL, Tonegen and SEAS. These vintage cone tweeters exhibited very flat frequency response, low distortion, fast transient response, a low resonance frequency and a gentle low-end roll-off, easing crossover design.
Cone tweeters have the same basic design and form as a woofer with optimizations to operate at higher frequencies. The optimizations usually are:
Typical of the 1960s/1970s-era was the CTS "phenolic ring" cone tweeters, exhibiting flat response from 2,000 to 15,000 Hz, low distortion and fast transient response. The CTS "phenolic ring" tweeter gets its name from the orange-colored edge suspension ring that it made from phenolic. It was used in many makes and models of well-regarded vintage speakers, and was a mid-priced unit.
Various materials are used in the construction of compression driver diaphragms including titanium, aluminium, phenolic impregnated fabric, and , each having its own characteristics. The diaphragm is glued to a voice coil former, typically made from a different material from the dome, since it must cope with heat without tearing or significant dimensional change. Polyimide film, , and glassfibre are popular for this application. The suspension may be a continuation of the diaphragm and is glued to a mounting ring, which may fit into a groove, over locating pins, or be fastened with machine screws. The diaphragm is generally shaped like an inverted dome and loads into a series of tapered channels in a central structure called a , which equalizes the path length between various areas of the diaphragm and the horn throat, preventing acoustic cancellations between different points on the diaphragm surface. The phase plug exits into a tapered tube, which forms the start of the horn itself. This slowly expanding throat within the driver is continued in the horn flare. The horn flare controls the coverage pattern, or directivity, and as an acoustic transformer, adds gain. A professional horn and compression driver combination has an output sensitivity of between 105 and 112 dB/watt/meter. This is substantially more efficient (and less thermally dangerous to a small voice coil and former) than other tweeter construction.
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