The Klipsch Heresy IV are three-way speakers introduced in 1957 and still featured in the brand’s catalog. They combine traditional design with recent technical advances and stand as one of Klipsch’s most iconic models.
The Heresy IV emerge from the workshops in Hope, Arkansas, where each pair is hand-assembled using methods that have changed little since the days 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 faces are finished with real-wood veneer.
This construction uses exclusively matched veneer sheets sourced from the same tree. The veneer leaves are arranged in mirror image, creating visual symmetry that distinguishes each pair. This “book-matched” technique ensures aesthetic consistency between the two speakers while highlighting the artisanal character of their manufacture. Four finishes are available: distressed 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 range, tilts the speakers by around 10 degrees. This natural angle directs sound toward the listening area, particularly relevant when the speakers are placed on the floor. The riser can be removed for installation in a cabinet or on dedicated stands, providing welcome flexibility for different listening setups.
The most significant change in this fourth generation is the adoption of a bass-reflex enclosure, breaking with the sealed designs that characterized the previous three generations. The rear port uses Klipsch’s signature Tractrix geometry, with specially contoured internal flares to minimize turbulence. This modification lets the Heresy IV reach down to 48 Hz, versus 58 Hz for the previous generation—a substantial gain that greatly 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 transducer reproduces the critical 850 Hz to 4500 Hz range, 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 change improves the uniformity of high-frequency dispersion in the room, significantly widening the sweet spot. Listeners are no longer confined to a rigid listening position to enjoy a coherent stereo image.
The compression drivers used for the mids and highs operate on a principle radically different from conventional transducers. The small-diameter diaphragm compresses air in a low-volume chamber before directing it toward the horn through a phase plug. This architecture achieves considerably 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 impedance of the surrounding air. The Tractrix geometry of Klipsch horns optimizes this transition, ensuring efficient coupling across a wide frequency band. This technology, inherited from professional sound reinforcement systems of the 1930s, enables the Heresy IV to achieve a sensitivity of 99 dB for 1 watt at 1 meter—an exceptional figure in the world of home hi-fi.
This remarkable efficiency brings several concrete benefits. Low-power amplifiers—especially tube amps favored by many audiophiles—can drive these speakers with authority. A 10-watt amplifier is enough to achieve comfortable levels in a medium-sized room. This characteristic also allows faithful reproduction of microdynamics, those 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 employs 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, reflects the uncompromising approach adopted for these speakers.
The Heresy IV offer greater placement flexibility than the larger models in the Heritage line. Their relatively compact format (630 × 394 × 337 mm with the riser) allows integration in moderate spaces while maintaining a physical presence that hints at their dynamic capability.
The rear Tractrix port needs at least 30 cm of breathing room from the back wall to perform optimally. Positioning too close to the wall can cause excessive bass reinforcement, upsetting the carefully balanced tonality. The 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 gives audiophiles the option to 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 switch from a sealed enclosure to a bass-reflex design with a rear Tractrix port. This evolution lets the Heresy IV extend 10 Hz deeper in the bass (48 Hz versus 58 Hz). The new K-702 midrange with a polyimide diaphragm also replaces the previous titanium model, offering better clarity and less coloration in the midrange.
Absolutely not. With 99 dB sensitivity, the Heresy IV are among the most efficient speakers on the market. A 10-watt amplifier is sufficient for comfortable listening levels. This makes them particularly suitable for low-power tube amplifiers, widely appreciated for their musicality.
Their compact format (63 cm tall) 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 placing 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 noted that it violated his own corner-horn design principles. He replied, “To hell with it—that’s exactly what I’m going to call it!” Ironically, the model went on to be highly successful in church sound installations.
The Heresy IV are the most compact in the Heritage lineup. The Forte IV offer 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 remain the ideal choice for those seeking the Heritage sound in a more domestic-friendly format.
Installation in a confined space is not recommended. The Tractrix port needs breathing room to work properly. For built-in setups, the Cornwall IV with its front ports would be more suitable. The Heresy IV are designed to be placed on their risers or stands, with sufficient space around them.
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
