TAS Legacy: Thiel CS5 Loudspeaker

Equipment report
TAS Legacy: Thiel CS5 Loudspeaker

When Thiel launched its ambitious new flagship, the CS5, at the 1989 CES, the company stated its technical requirements as “tonal fidelity, spatial fidelity, transient fidelity, and dynamic fidelity,” and the design goals as “uniform and extended frequency response, time response accuracy, phase response accuracy, low energy storage, and low distortion.”

The driver complement for the massive five-way CS5 was three 8" long-excursion drivers with dual-layer Kevlar diaphragms, a 5" midrange driver operating from 400Hz to 1kHz, a 2" metal-dome upper-midrange driver handling 1kHz to 3kHz, and a 1" metal dome for frequencies above 3kHz. Two of the three woofers were dedicated to reproducing the bottom two octaves, while the third was a mid/bass driver in its own sub-enclosure that crossed over to the midrange at 400Hz.

The CS5’s massively complex crossover used 87 “elements” implemented with 114 discrete components. According to the Thiel white paper, “most of the components are used to provide a high degree of response shaping…32 of the elements are used to ‘fine tune’ the time response of the system.”

How fine-tuned was the CS5? Thiel’s design goal for the CS5 was no more than 0.5dB of octave-averaged variation from 200Hz to 10kHz. Thiel also allowed for only a 0.5dB in-production variance. The use of Kevlar drivers moved the cone’s first resonance higher in frequency (vital when rolling off the driver at only 6dB per octave). Moreover, Kevlar’s resonance was more predictable than that of other cone materials. This allowed Thiel to notch-out in the crossover energy at that resonance frequency. According to Thiel, “There is usually one resonance which, being very pure and predictable, can be removed electrically with circuitry that also automatically removes energy storage and phase shifts of the resonance.” The crossover’s complexity in part gave the CS5 a reputation for needing to be driven by a very powerful amplifier.

Thiel also devoted a lot of engineering effort to reducing energy storage in the drivers, crossover components, and cabinet. The baffle was cast from a marble-polymer material, and weighed 65 pounds. The enclosure was built from 1" MDF. The CS5’s drivers used a cast or machined magnesium or aluminum instead of stamped steel for the basket.

In February, 2018, former 30-year Thiel employee Rob Gillum announced the creation of Coherent Source Service to provide service for all Thiel speakers made by the company between 1977 and 2012. Coherent Source Service has stocked parts for nearly all legacy Thiel speakers, and will provide Thiel warranty and non-warranty service for customers worldwide. Full speaker and cabinet restoration are available as well, with prices quoted based on condition.