Danley first gained notice in the 1980s with his novel servomotor-driven subwoofer systems used to reproduce very low frequencies in concert tours and theme parks.
[2] In 1979, a co-worker recommended a job offering nearby at Intersonics, a contractor to NASA, supplying hardware for rocketry research.
The inventions include a high-powered acoustic levitator, a sonic-boom generator used by BBN Technologies, and a multi-enclosure Flow Modulator loudspeaker system used by Georgia Tech Research Institute and NASA for vibration tests on rocket payloads.
[2] Danley designed a variety of models including W bins, seeing the most success with the folded horn BassTech 7 subwoofer which performed very well.
[6] Clair typically used a dozen Danley subwoofers as the lowest element of a 5-way system, to fill the bottom octave.
The BassTech 7 drive unit was essentially a cube holding two opposing 15-inch woofers, both connected to a central servo motor by way of shafts and flexible belts.
The enclosure included Danley's patented cooling fan powered by a DC-rectified portion of the audio signal, kicking in only at high voltage levels.
Additionally, the servo design greatly reduced the common problem of power compression, in which a driver heats up and sound output drops.
A turning point was the Space Shuttle Challenger disaster in 1986, which damped the mood and the business climate in the aerospace industry, and brought delays and cancellations of contracts.
[2][3] Around 1986 a request came in to Intersonics from Cornell University for a low frequency subwoofer loudspeaker intended to reproduce elephant vocalizations in Kenya.
Dr. Joyce Poole and Katy Payne of the Amboseli Elephant Research Project asked for a custom loudspeaker that would fit inside a sport utility vehicle, and provide strong output down to 14 Hz.
[9] Based on this, another subwoofer model produced by ServoDrive was the Contrabass in 1987, similar to the Pachyderm 6 but with a smaller enclosure and half the number of passive radiators.
To save the firm, Danley teamed with Bradford Skuran, a guitarist he had played with in his youth, to form a new company: Sound Physics Labs (SPL).
In the late 1990s, Danley designed the SPL-td1, his first trapezoidal "top box" intended to deliver the mid- and high frequency sounds to complement a subwoofer.
[12] Further modifications to the SPL-td1 concept came with the SPL-td2 providing improved phase/time linearity, the smaller and lighter SPL-runt, and the larger SPL-trik containing nine drivers.
Danley's conceptual design (he never built one) was given freely to the public domain, and proved to be influential as the first DIY folded horn subwoofer.
Previously, Hedden had been the owner of dB Audio & Video, an A/V contractor who was the largest distributor of SPL loudspeakers.
At frequences such that the wavelength is twice the distance to the taps, the waves routed inside the cabinet to exit through ports in the horn combine positively with direct sound from the front of the driver.
Danley designed the Matterhorn to meet a military specification, to produce a low frequency sound in the range of 15 to 20 Hz, to be measured at 94 decibels at a distance of 250 meters.
[20] The Jericho Horn was praised in 2017 when four of the large enclosures were used for DJ sets at the Temple stage at Glastonbury Festival, along with 22 boxes of DSL TH-118 subwoofers.