Klipsch Forte IV Auburn (pack of 2)

The Klipsch Forte IV is a three-way loudspeaker positioned between the Heresy IV and the Cornwall IV. This model, the fourth generation of a series launched in 1985, blends traditional design with contemporary acoustic refinements while preserving the sonic character of the Heritage series.

Handcrafted construction that defies time

The Forte IV loudspeaker continues a manufacturing tradition dating back to 1946, when Paul Wilbur Klipsch founded his company in a modest shed in Hope, Arkansas. Each unit is still assembled by hand in this very town by craftspeople, some of whom have been honing this expertise for decades. The 19 mm MDF cabinet features a real-wood veneer applied using the book-matching technique: veneer sheets are kept in their cutting order and arranged in a mirror image to create striking visual symmetry.

The Auburn finish (American mahogany) stands out for its warm hues ranging from deep brown to coppery highlights, especially pronounced when natural light reveals the wood grain. This shade is noticeably darker than American walnut while remaining warmer than black ash. The Salt and Pepper grille cloth, a subtle blend of gray and white threads, lends a discreet touch of modernity to this neo-vintage aesthetic.

Each pair is carefully matched (grain-matching) using veneer panels sourced from the same tree. The two speakers travel together through the factory and receive consecutive serial numbers, ensuring perfect visual and acoustic coherence. This artisanal approach partly explains the substantial weight of 32.7 kg per speaker and their imposing dimensions: 90.81 cm high, 42.24 cm wide, and 33 cm deep.

Acoustic architecture subtly reimagined

The Forte IV’s three-way configuration hides significant innovations behind a familiar appearance. The new 44.5 mm K-702 compression driver with a polyimide diaphragm replaces the previous model and is the most substantial change in this generation. Mounted on a Tractrix K-703-M horn featuring Klipsch’s patented Mumps technology, this midrange provides a more uniform polar dispersion of mid frequencies, considerably widening the listening sweet spot.

The K-100-TI compression tweeter retains its 25.4 mm titanium diaphragm but now benefits from a wide-dispersion ABS phase plug. This seemingly minor change transforms high-frequency reproduction by offering roughly 20 degrees wider horizontal dispersion than the Heresy IV in the critical 500 Hz–1 kHz region. The K-79T horn that houses it maintains its 15 cm × 10 cm dimensions, optimized for controlled directivity without harshness.

Bass relies on a 30.5 cm K-281 woofer with a fiber-composite diaphragm, supported by a rear-firing 38 cm KD-15 passive radiator. This hybrid configuration, introduced in 1985 on the original Forte by engineer Gary Gillum, achieves bass extension down to 38 Hz without requiring an oversized enclosure volume. Unlike a traditional port, the passive radiator operates via acoustic pressure generated by the active woofer, offering superior low-frequency control and avoiding port chuffing.

Sophisticated crossover that changes the game

The crossover network is the most profound transformation in this fourth generation, even though the crossover points remain at 650 Hz and 5.2 kHz. Roy Delgado, Klipsch’s chief acoustic engineer for four decades, completely reworked the topology, drawing inspiration from the steep slopes used in the legendary Klipschorn and La Scala. This approach minimizes overlap between drivers, thereby reducing interference and distortion.

The new circuit uses premium components and asymmetric attenuation slopes: the high-pass filters indeed adopt steep slopes in line with Paul W. Klipsch’s philosophy, while the low-pass filters for the woofer and midrange retain gentler slopes. This hybrid architecture, the result of meticulous optimization, partly explains why the Forte IV sounds more refined and coherent than its predecessor.

The solid aluminum input terminal accepts thick-gauge cables and supports bi-wiring or bi-amping. The robust, versatile binding posts reflect a design intended to last for generations. This build quality is evident throughout the product, from the structural adhesives used in assembly to the oversized mechanical fasteners.

Acoustic performance balancing power and finesse

With a sensitivity of 99 dB for 2.83 V at 1 meter, the Forte IV belongs to the rare category of very high-efficiency speakers. This exceptional efficiency enables a continuous sound level of 116 dB with just 100 watts, while maintaining perfect compatibility with low-power amplifiers. A 2.5-watt single-ended triode tube amplifier is theoretically sufficient to produce a comfortable listening level in a medium-sized room.

Frequency response extends from 38 Hz to 20 kHz (±3 dB), with a notable characteristic in the 2–4 kHz region that appears slightly recessed compared to typical Klipsch standards. This less aggressive upper midrange paradoxically allows for more comfortable long listening sessions, even if some purists may miss a touch of vocal presence. The nominal 8-ohm impedance hides a measured minimum of 3.1 ohms, requiring an amplifier stable with complex loads.

The soundstage unfolds with remarkable breadth, far exceeding the speakers’ physical boundaries. This generous spatialization is accompanied by greater depth of field compared to the Forte III, creating a three-dimensional sonic bubble that is particularly convincing on live recordings. Dynamics, a longstanding Klipsch strength, preserve micro-contrast even at low volume, making late-night listening especially rewarding.

Positioning and acoustic optimization

Contrary to popular belief, the Forte IV tolerates relatively close placement to the rear wall. Klipsch recommends spacing of 5 to 25 cm, with the rear passive radiator requiring a minimum of 2.5 cm to operate properly. In practice, placement about 90 cm from the rear wall often provides the best tonal balance, avoiding midrange masking without sacrificing bass extension.

Optimal spacing between the two speakers ranges from 1.8 to 4.5 meters depending on room size, with toe-in toward the listening position recommended to maximize stereophonic image coherence. This pronounced orientation compensates for the horns’ natural directivity and broadens the sweet spot—particularly beneficial when multiple listeners share the listening area.

Medium-sized rooms (15 to 25 m²) are a perfect fit, unlike higher-tier Heritage models that demand more generous volumes. Acoustic treatment remains secondary thanks to the controlled directivity of the horns, which minimizes unwanted reflections. A simple rug between the speakers and the listening position is generally enough to optimize reproduction.

Technical specifications

Acoustic configuration

• 3-way horn-loaded loudspeaker, 30 cm woofer
• K-702 polyimide midrange on Tractrix Mumps horn
• K-100-TI titanium tweeter with phase plug, wide listening area
• 38 cm passive radiator for deep bass

Acoustic performance

• Frequency response: 38 Hz–20 kHz (±3 dB)
• High sensitivity: 99 dB @ 2.83 V / 1 m for optimal efficiency with low power
• Power handling: 100 W continuous / 400 W peak
• Maximum sound pressure level: 116 dB continuous
• Nominal impedance: 8 ohms

Drivers and transducers

• K-281 woofer: 30 cm composite cone
• KD-15 passive radiator: 38 cm
• K-702 midrange: 44 mm compression driver with polyimide diaphragm
• K-100-TI tweeter: 25 mm compression driver with titanium diaphragm
• Crossover frequencies: midrange 650 Hz / treble 5.2 kHz

Connectivity and amplification

• Dual binding posts for bi-wiring/bi-amping
• Maximum flexibility for amplification configuration

Construction and dimensions

• 19 mm medium-density fiberboard (MDF) cabinet
• Dimensions (H × W × D): 90.81 × 42.24 × 33 cm
• Weight: 32.7 kg
• Robust design assembled with the finest adhesives and fasteners

Available finishes

• Black ash (black ash)
• American walnut (American walnut)
• American auburn
• Red oak (red oak)

Manufacturing and design

• Handcrafted in the US, mirror-matched wood veneers
• Matched pairs for visual consistency
• Built to last for generations