Klipsch RP-640D

The RP-640D is the largest model in Klipsch’s Reference Premiere Designer On-Wall series, a range designed to hug the wall without sacrificing the sound reproduction of traditional speakers. Beneath its flat profile lies a six-driver configuration, the Tractrix horn, and the Cerametallic diaphragms found on the “classic” speakers in the Reference Premiere range.

An ultra-slim column format, made for the wall

The RP-640D first stands out for its silhouette. The matte black ABS cabinet measures 15.24 cm wide and only 6.10 cm deep: placed against a wall next to a flat-screen TV, it barely intrudes on the living space. The matte finish blends with contemporary screens and wall mounts, where a lacquered or wood-veneered speaker would attract more attention.

The wrap-around grille attaches magnetically and covers almost the entire front face and sides. Removed, it reveals the copper-colored diaphragms characteristic of Klipsch. With the grille on, the speaker blends into the decor. Without it, it shows its identity.

Two drivers, four passive radiators, and a horn

The driver layout is symmetrical: the 25 mm titanium dome tweeter, loaded by a 90° × 90° Tractrix horn, sits in the center. On either side, two 89 mm (3.5-inch) Cerametallic woofers/midrange drivers handle the reproduction of low and mid frequencies. Four passive radiators of the same diameter and material complete the assembly. They are what compensate for the absence of a traditional bass-reflex port: in a cabinet this slim, a conventional tubular port simply would not fit.

Cerametallic diaphragms are aluminum cones whose inner and outer surfaces are converted into ceramic through anodizing. The result is a cone that is both rigid and damped, limiting unwanted deformation (“break-up”) at the frequencies where the driver operates. It is a technology Klipsch uses throughout its entire Reference Premiere range, from floorstanding living-room speakers to in-wall models.

The LTS (Linear Travel Suspension) tweeter is also borrowed from the “cabinet” Reference Premiere speakers. The linear travel suspension keeps the titanium dome aligned throughout its entire excursion, which reduces treble distortion. Paired with the Tractrix horn, whose geometry concentrates high-frequency energy toward the listening area, it produces direct and detailed highs. The 90° × 90° horn disperses identically on the horizontal and vertical axes, an advantage when the speaker is mounted horizontally to serve as a center channel.

94 dB sensitivity: fewer watts, more output

The 94 dB sensitivity (2.83 V / 1 m) is one of the figures that sets the RP-640D apart in its category. To put that number in perspective: a typical on-wall speaker shows between 84 and 88 dB of sensitivity. Every 3 dB gain is equivalent to a doubling of perceived power. In other words, the RP-640D produces a high sound level with little input power.

In practice, this means that an entry-level or mid-range home theater amplifier is enough to run it under good conditions. Klipsch specifies 75 W continuous (RMS) and 300 W peak, at a nominal impedance of 8 ohms. These values are compatible with the vast majority of AV amplifiers on the market.

The frequency response extends from 55 Hz to 25 kHz (±3 dB). Reaching down to 55 Hz in a cabinet of this thickness is no small feat: that is the work of the four passive radiators, which increase radiating surface area in the bass without requiring additional air volume. A subwoofer is still recommended for the very lowest frequencies (below 50-60 Hz), but the RP-640D alone covers a sufficient range for voices, music, and a large part of movie effects.

Wall mounting or shelf placement, vertical or horizontal

Klipsch has provided two mounting options. Two four-position keyhole inserts, located on the back of the cabinet, allow direct wall mounting, vertically as well as horizontally. The speaker’s shallow depth ensures a discreet result, flush against the wall.

For those who prefer not to drill, a glass base is included. It attaches beneath the speaker and allows placement on a piece of furniture or a shelf, again in both orientations. It is a valuable option for testing positioning before committing to a permanent wall installation.

The terminal is a simple screw-type model that accepts bare wire or banana plugs. No bi-wiring here: just a single pair of terminals, which simplifies connection.

Possible roles in a multichannel system

The RP-640D can occupy several positions in a home theater setup. In vertical configuration, it works as a left or right front speaker, or as a surround. In horizontal configuration, it can serve as a center channel below a wall-mounted screen. This versatility is what makes the “D” (Designer) format appealing at Klipsch.

The series also includes the RP-140D (one woofer/midrange driver, compact format), the RP-240D (two woofer/midrange drivers, intermediate format), and the RP-440D SB, a passive three-channel soundbar. It is possible to combine these models to create a 5.1 system or more, entirely wall-mounted and visually consistent. The RP-640D, with its six drivers and lower frequency extension, is logically the best suited for the main channels (left, center, right) in medium to large rooms.

Technical specifications

Audio configuration

• Type: 2-way passive speaker with passive radiators
• Enclosure type: bass-reflex with passive radiators
• Tweeter
  • 1 x 25 mm titanium LTS dome
  • 90° x 90° Tractrix® horn
• Midrange / woofer drivers: 2 x 89 mm (3.5”) active Cerametallic
• Passive radiators: 4 x 89 mm (3.5”) Cerametallic

Performance

• Frequency response: 55 Hz – 25 kHz (±3 dB)
• Sensitivity: 94 dB (2.83 V / 1 m)
• Nominal impedance: 8 ohms
• Crossover frequency: 2200 Hz
• Power handling
  • 75 W RMS
  • 300 W peak

Design and materials

• Cabinet: ABS
• Finish: matte black
• Grille: removable magnetic (wrap-around)
• Klipsch high-efficiency technology (horn and rigid low-distortion cone)

Dimensions and weight

• Height: 72.39 cm
• Width: 15.24 cm
• Depth: 6.10 cm
• Weight: 1.7 kg

Connectivity and installation

• Single screw terminal
• Vertical or horizontal wall mounting
• Glass base included for placement on furniture

Key product highlights

• Ultra-slim format ideal for wall integration
• High efficiency (94 dB) compatible with low-power amplifiers
• Controlled directivity thanks to the Tractrix horn
• Discreet design for modern home theater installations
• Perfect solution for LCR fronts or wall-mounted surround speakers