I’m fortunate to have reviewed in recent years not one but three different pairs of horn-loaded loudspeakers. My jaw dropped when I reviewed what would prove the finest loudspeaker to ever grace my home, the Volti Audio Rival. Second came a pricey but pleasing pair from handlebar-mustache king Gordon Burwell, the Burwell & Sons Homage. Then, at the urging of occasional Stereophile contributor Steve Guttenberg, I took on the fat-boy Klipsch Heresy III. As the Beatles used to say, I was dead-chuffed.

Horn-loaded speakers achieve what few conventional cone-only speakers can: reproduce the note-perfect timing, rhythmic energy, and blood-pulsing impact of the real event. With their high sensitivity ratings and low power requirements, horns deliver music faster, like a skier blasting off a jump at warp speed: There’s no drag, no lag, no confusion—just jumpin’ jiminy dynamics at practically every volume level.

Though horn-loaded loudspeakers began showing up in movie theaters as early as the mid-1930s, credit goes to Paul W. Klipsch for creating some of the earliest horn designs for home use. The biggest and most famous of these arrived in 1946: the still-popular Klipschorn, for which Paul Klipsch was awarded nearly two dozen patents.

Designed and manufactured in Klipsch’s Hope, Arkansas, factory, where the company’s manufacturing arm remains, the K-Horn has been in continuous production for over 70 years, a feat no other speaker manufacturer can claim. The three-driver K-Horn is, or was (footnote 1), open-back, folded-horn design. When the speaker is positioned tightly in a room’s corner, the floor and converging walls become part of the horn and contribute to low-frequency gain. Single-ended triode (SET) amplifiers are known for making K-Horns sing, and tube aficionados prize the speaker for a measure of efficiency—electrical sensitivity combined with impedance characteristics that ease drivability—that contributes to a lifelike dynamic range. Some of the same principles embodied in the Klipschorn—and, one hopes, many of its performance characteristics—are found in an old-new member of the company’s Heritage line, the Klipsch Forte III ($3998/pair). Introduced in 1985 as the Forte and relaunched in 1989 as the Forte II, this floorstander faded from the line but was reintroduced in 2017, just in time for a new SET renaissance!

Everything old is new again
The Forte III is a three-way design measuring 36″ high by 16.5″ wide by 13″ deep and weighing a solid 72 lb. The manufacturer’s specs include a frequency response of 38Hz–20kHz, ±3dB, a sensitivity of 99dB/2.83V/m, and an impedance described as “8 ohms compatible.” A newly designed steep-filter passive network crosses over at 650Hz and 5.2kHz. Tweeter and midrange drivers are, respectively, Klipsch’s new K-100-TI 1″ titanium-diaphragm high-frequency compression driver loaded with an ABS Tractrix K-79-T horn and a new K-70 1.75″ titanium-diaphragm midrange compression driver on a new Tractrix K-703-M horn. Down low, the Forte III’s 12″ K-281 treated-paper cone woofer, which uses a 3″ voice-coil, is supplemented with a 15″ KD-15 paper-cone passive radiator affixed to the cabinet’s lower backside. Constructed with a Santoprene/rubber surround, the passive driver works purely off the pistonlike air motion of the 12″ woofer, addressing frequencies below 65Hz.

“The radiator works the same as a port,” explained Klipsch’s principal engineer, Roy Delgado, a 30-year veteran of Klipsch Audio Technologies who initially worked under Paul W. Klipsch himself. “Because of the smaller air volume of the box, the drone (aka passive radiator) offers the advantage of allowing us to adjust compliance. If it’s done right, the drone extends the bottom end. Basically you’re creating a Helmholtz resonator. You cause the air to resonate at a certain frequency and that extends the bottom end. A drone does the same thing.”

At a time when the US is experiencing an outbreak of measles, the Forte III remains au courant by having—you guessed it—Mumps. Literally named for the swollen salivary glands they sort of resemble, Roy Delgado’s patented Mumps are curved 1″ ridges that round off the interior corners within the throat of the K-703-M midrange horn. The goal, according to Klipsch’s website, is “to improve coverage and control of the key mid-frequency band.”

“Studying various data,” Delgado noted, “I noticed that when the directivity index tends to drop, right before the horn starts to lose control of the coverage pattern, it beams, the coverage pattern becomes narrower and starts to wrap around itself like a cloverleaf effect, and the output comes down. I wanted the waves to stay in contact with the horn walls so that when they exit the horn that beaming is eliminated. Working with modeling clay, I noticed that the more clay I put into the corners of the horn, that tended to eliminate that beaming. Usually you avoid that by raising the crossover point, which isn’t the most efficient use of the horn. The Mumps allow me to use the horn in a wider bandwidth.”

Like versions I and II, the Forte III couples to the floor via a 1″ wood base to which four 1/8″-thick round metal footers are attached, one for each corner.

Setup
The Forte III is the most amplifier-sensitive loudspeaker I’ve reviewed: Careful upstream choices were essential. The Kuzma Stabi R turntable and 4Point tonearm/Hana EL cartridge handled analog; the Tascam CD-200iL CD player with BorderPatrol DAC SE spoke digital, connected by a lm run of Triode Wire Labs Spirit II interconnect. The Kuzma 4Point’s dedicated Crystal Cables tonearm cable connected to a Musical Surroundings Phonomena II phono stage, its signals flowing to either a Parasound Halo HINT 6 integrated amplifier, Shindo Allegro preamplifier with Shindo Haut-Brion power amplifier, or Schiit Ragnarok integrated amplifier, through a pair of Shindo interconnects. A lm pair of Triode Wire Labs Spirit II interconnects joined the BorderPatrol DAC SE to amplification. Auditorium 23 and Triode Wire Labs American speaker cables provided juice to the Forte IIIs.

You’d think a stout loudspeaker with two large bass radiators per cabinet would present a setup nightmare, but finding the optimum location for the Forte III proved rather easy. Firing the speakers almost straight ahead, with the grilles off, created the widest and deepest soundstage ever experienced in my Greenwich Village penthouse pad, with absolutely zero honk or nasal whine, common horn complaints. The Forte’s rear panel wound up two feet from the front wall.

Footnote 1: After 70 years, Klipsch is retiring the open-back Klipschorn. The most recent model, the AK6, has a fully enclosed basshorn to free users from having to snug their speakers into the corners; a review of the Klipschorn AK6 will appear in our pages later this year.