The Klipsch Heresy IV are three-way loudspeakers introduced in 1957 and still part of the brand’s catalog. They combine traditional design with recent technical advancements and are one of Klipsch’s emblematic models.
The Heresy IV emerges from the workshops in Hope, Arkansas, where each pair is hand-assembled using methods that have changed little since the time of Paul W. Klipsch. The 20 mm-thick MDF cabinetry receives special treatment: the front and rear baffles are coated with a textured, damping resin, while the remaining panels are finished with real-wood veneer.
This construction exclusively uses matched veneer leaves sourced from the same tree. The wood veneers are arranged in mirror image, creating visual symmetry that distinguishes each pair. This “book-matched” technique ensures aesthetic consistency between the two speakers while underscoring their artisanal craftsmanship. Four finishes are available: aged oak, American walnut, natural cherry, and satin black ash—each revealing the wood’s natural grain with an authenticity that contrasts with standardized industrial production.
The removable slanted riser, a hallmark of the Heresy line, tilts the speakers by about 10 degrees. This natural incline directs sound toward the listening area—particularly relevant when the speakers are placed on the floor. The riser can be removed for installation in furniture or on dedicated stands, providing welcome flexibility for various listening setups.
The most significant change in this fourth generation is the adoption of bass-reflex loading, breaking with the sealed-box tradition that characterized the previous three generations. The rear port features Klipsch’s signature Tractrix geometry, with specially profiled internal flares to minimize turbulence. This modification lets the Heresy IV extend down to 48 Hz, versus 58 Hz for the previous generation—a substantial gain that meaningfully enriches the bass register.
The K-28-E woofer retains its 30.5 cm diameter but benefits from a composite-fiber cone whose rigidity ensures tight, controlled low-frequency reproduction. This driver operates up to 850 Hz, where it hands off to the new K-702 compression midrange.
The K-702 midrange is one of this generation’s major innovations. Its 44.5 mm polyimide diaphragm replaces the previously used titanium, offering, according to measurements, better linearity and reduced distortion. Coupled with the Tractrix K-704 horn, this driver reproduces the midrange from 850 Hz to 4500 Hz—the critical zone where most musical and vocal information resides.
The K-107-TI tweeter retains its 25 mm titanium diaphragm but incorporates a new wide-dispersion phase plug. This technical refinement improves the uniformity of high-frequency dispersion in the room, considerably widening the optimal listening area. Listeners are no longer confined to a rigid sweet spot to enjoy a coherent stereo image.
The compression drivers used for the midrange and treble operate on a fundamentally different principle from conventional direct-radiating transducers. A small-diameter diaphragm compresses air in a small-volume chamber before directing it through a phase plug into the horn. This architecture delivers significantly higher efficiency than direct-radiating drivers.
The horn acts as an acoustic transformer, matching the high pressure generated in the compression chamber to the lower acoustic impedance of the surrounding air. Klipsch’s Tractrix horn geometry optimizes this transition, ensuring efficient coupling over a wide frequency band. This technology, inherited from professional sound reinforcement systems of the 1930s, allows the Heresy IV to achieve a sensitivity of 99 dB for 1 watt at 1 meter—an exceptional figure in the world of domestic high fidelity.
This remarkable efficiency offers several concrete advantages. Low-power amplifiers—particularly tube amplifiers prized by many audiophiles—can drive these speakers with authority. A 10-watt amplifier is sufficient to achieve comfortable listening levels in a medium-sized room. This characteristic also enables faithful reproduction of microdynamics—the subtle level variations that bring musical performances to life.
The crossover network has been completely redesigned for this fourth generation. Klipsch drew inspiration from the architectures used in the Klipschorn and La Scala models, the brand’s absolute references. The crossover points, set at 850 Hz and 4500 Hz, were optimized to ensure harmonious integration among the three drivers.
Crossover components were selected for their quality, minimizing losses and preserving signal purity. Internal wiring uses AudioQuest Type 4 conductors with Star-Quad geometry, a configuration that reduces electromagnetic interference and preserves the integrity of the musical signal. This attention to technical detail—often overlooked in mass production—speaks to the uncompromising approach taken with these speakers.
The Heresy IV offers more placement flexibility than the larger models in the Heritage range. Their relatively compact format (630 × 394 × 337 mm with the riser) allows integration in moderate spaces while retaining a physical presence that hints at their dynamic capability.
The rear Tractrix port requires at least 30 cm of breathing room from the back wall to operate optimally. Placement too close to the wall can cause excessive bass reinforcement, altering the carefully balanced tonality. Distance from side walls also influences soundstage width and stereo imaging precision.
The dual aluminum binding posts accept large-gauge cables and support bi-wiring or bi-amping. This configuration lets audiophiles further optimize performance—for example, by using different amplifiers for the bass and mid/high sections, each tailored to its specific frequency range.
The most significant change is the shift from a sealed enclosure to a bass-reflex design with a rear Tractrix port. This evolution lets the Heresy IV reach 10 Hz deeper in the bass (48 Hz versus 58 Hz). The new K-702 midrange with a polyimide diaphragm also replaces the former titanium model, offering better clarity and less coloration in the midband.
Absolutely not. With 99 dB sensitivity, the Heresy IV ranks among the most efficient speakers on the market. A 10-watt amplifier is enough to achieve comfortable listening levels. This makes them particularly suitable for low-power tube amplifiers, widely appreciated for their musicality.
Their compact height (63 cm) and controlled dispersion make them suitable for small to medium-sized rooms. However, you should allow at least 30 cm of clearance behind the speakers for the bass-reflex port and avoid positioning them too close to walls, which could generate unwanted resonances.
When Paul W. Klipsch developed this compact speaker in 1957 to serve as a center channel between two Klipschorns, his colleagues pointed out that it violated his own design principles based on corner horns. He replied, “To hell with it—that’s exactly what I’m going to call it!” Ironically, the model became a great success in church sound systems.
The Heresy IV is the most compact of the Heritage lineup. The Forte IV offers deeper bass extension thanks to an additional passive radiator, while the Cornwall IV and the imposing Klipschorn deliver even greater dynamic capability but require larger spaces. The Heresy remains the ideal choice for those seeking the Heritage sound in a more domestic-friendly format.
A confined installation is not recommended. The Tractrix port needs breathing room to function properly. For built-in setups, the Cornwall IV with its front-firing ports would be more suitable. The Heresy IV is designed to be placed on its riser or on stands, with sufficient space around it.
Jérome
These speakers are astonishing for their size and the realism of the soundstage. Replacing big tower speakers, they fit in perfectly, and their vintage look is just gorgeous.
Comment from August 18, 2025 — Experience from August 07, 2025
Stephane
Dear Hi-Fi Friend, Regarding the Klipschs = Top Speakers powered by a Primaluna Evo 200 tube amplifier - Magnificent sound. Cabling: Wireworlds Oasis 8.
Stef from Belgium.
Comment from February 17, 2025 — Experience from February 06, 2025
Dylan
Absolument amoureux des Klipsch Heresy IV ! J'ai remplacé une ancienne paire d'enceintes colonnes Klipsch, et la scène sonore, la clarté et la qualité sonore globale de celles-ci sont incroyables. En plus, elles sont aussi belles qu'elles sonnent.
Comment from February 10, 2025 — Experience from January 30, 2025
