1983 Klipschorn Speakers * Signed by Paul Klipsch himself * AK-3 Prototype ?

A legend says that Paul Klipsch himself sometimes worked on the assembly line to build or sign either prototypes or special orders for customers. The pair of Klipschorn speakers that we have for sale appears to be one of the latter. Both speakers bear his signature and are dated May 25, 1983.

This pair of Klipschorn speakers is in perfect working condition. They have the AK-3 crossover, which makes us think they might be a prototype since the AK-3 didn't become standard on the Klipschorn until 1989.

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The Klipschorn

The Klipschorn, or K-Horn, loudspeaker is the flagship product of Klipsch Audio Technologies. It was patented by founder Paul W. Klipsch in 1946 and has been in continuous production in the company's Hope, Arkansas, plant since then—the longest run in speaker production history. Although the Klipschorn's basic design is more than seventy years old, it has received periodic minor modifications. 

The Klipschorn's large (51” H (129 cm) x 31” W (79 cm) x 28” D (72 cm)) enclosure houses a three-way design: separate drivers—the woofer, the squawker, and the tweeter, respectively—handle the bass, midrange, and treble portions of the sound signal.

Two rectangular horn lenses coupled to compression drivers handle the midrange and treble, while a 15” cone woofer is mounted in a folded bass bin compartment below. The folds open at the rear of the horn cabinet structure, utilizing the room walls and floor as continuations of horn structure, thereby increasing the effective length and size of the horn, thus lowering its cut-off frequency and, likewise, its lowest usable tone.

The body of the speaker cabinet forms a horn. The “K-Horn” shape is like a baseball diamond: the pointy rear is open and exposed, the flat front covered with a wood panel and the top enclosed in cloth. The speaker sits in the corner of two adjoining walls, using the walls and floor boundaries as extensions of the horn. Technically speaking, the K-Horn's folded bass "corner horn" can be described as a bifurcated trihedral (floor and two walls to form the trihedral corner) exponential wave transmission line.

This design results in extremely high efficiency. One watt RMS produces a 105 decibel at 1 meter sound pressure level (SPL), which is approximately 14–20 decibels higher than conventional speakers. Such sensitivity requires less amplifier power to achieve the same loudness. (Paul Klipsch demonstrated that the Klipschorn could reproduce concert-level dynamics powered by as little as 1 watt per channel.) The K-Horn encourages the use of low-powered amplifiers. The growing popularity in the audiophile community of single-ended valve (vacuum tube) amplifiers has sparked renewed interest in the Klipschorn and other highly sensitive Klipsch models.

Utilizing the room walls and floor boundaries as extensions of the bass horn helps extend the speaker's frequency response down into the 35 Hz range, considerably lower than would be possible otherwise. Because of the folded horn, the woofer cone moves no more than a few millimeters.