Bowers & Wilkins HTM71 S3 black lacquered

Bowers & Wilkins HTM71 S3, the center channel speaker in the 700 S3 series

Reproducing a voice accurately in the middle of a busy soundtrack remains one of the most delicate tasks in home theater. The larger of the two center channel speakers in the 700 S3 series from Bowers & Wilkins tackles this problem head-on with a three-way design that separates the midrange and treble from bass duties. The expected result: Clear dialogue, whatever the scene.

Separating voices from the rest of the spectrum

A center channel speaker has an ungrateful role: carrying almost all of a film’s dialogue while the side channels handle the ambiance. The HTM71 S3 meets this constraint with a three-way design, where the midrange has its own driver instead of sharing the task with the bass. This midrange is also mechanically decoupled from the rest, which limits interference between woofer movement and voice reproduction.

The stated frequency response extends from 45 Hz to 33 kHz, with a maintained response of ± 3 dB between 50 Hz and 28 kHz. The 89 dB sensitivity (measured at 2.83 V at one meter) and the nominal 8 Ω impedance, with a minimum of 3 Ω, place the speaker in a category that works with most amplifiers. Bowers & Wilkins recommends power between 30 and 200 W per channel, a fairly wide range that leaves room depending on the size of the room.

A tweeter isolated from the cabinet

The brand’s most recognizable feature is found here: the tweeter housed in its own enclosure, mounted on top of the speaker. This “Solid Body” enclosure is milled from a block of solid aluminum, a mass that resists resonance better than a hollow structure. For this generation, the rear loading tube is longer and tapered in the manner of a Nautilus, filled with an absorbing material that dissipates the wave emitted behind the dome.

The dome itself measures 25 mm and uses carbon rather than the aluminum of previous generations. Its rigidity pushes the first breakup mode well beyond the audible band, which results in clean treble and precise effects placement. The tweeter is completely isolated from the cabinet by a damping gel connection, so that bass vibrations do not contaminate the high frequencies.

The Continuum midrange and its new suspension

At the center of the front panel, a 130 mm midrange driver features the Continuum diaphragm, that gray composite cone with which Bowers & Wilkins replaced its old yellow fiber cones. Its purpose: to avoid the abrupt behavioral breakups that color the sound when a conventional diaphragm leaves its comfort zone. The rendering gains in neutrality, especially on voices and instrumental timbres.

This midrange also uses FST technology, which eliminates the traditional peripheral surround, and a biomimetic suspension inherited from the 800 Diamond series. The latter replaces the fabric spider with an open structure that reduces parasitic air pressure and the coloration it causes. The aim of these choices is a readable midrange, without overstatement.

Two Aerofoil bass drivers and a profiled port

The bass relies on two 130 mm Aerofoil diaphragm drivers, a variable-thickness design: syntactic foam sandwiched between two layers of cellulose, thicker at the center and thinner at the edges. This profile provides rigidity where the diaphragm needs it without weighing down the whole, a condition for bass that is both deep and fast.

These woofers operate in a bass-reflex loading opened by a FlowPort with an aerodynamic profile. The port design smooths airflow at high volume and raises the threshold for turbulence noise. Bowers & Wilkins publishes its harmonic distortion figures, a transparency that is uncommon among manufacturers: below 90 dB at one meter, 2nd- and 3rd-harmonic distortion remains below 1% from 90 Hz to 22 kHz, and below 0.5% between 120 Hz and 20 kHz.

A refined cabinet with a curved front baffle

Compared with previous generations, the design has become slimmer. The cabinet is narrower and its front baffle slightly curved, a shape borrowed from the 800 Diamond series that limits wave diffraction on the edges and reduces internal standing waves. The midrange and bass drivers are housed in aluminum mounts that protrude from the front baffle, decoupled from the cabinet to contain vibrations.

Visible screws disappear in favor of a magnetic grille that can be fitted and removed without any visible markers. At the rear, a double pair of terminals allows bi-wiring or bi-amplification for those who want to separate the power supply for the bass and the upper part of the spectrum. The speaker measures 628 mm wide, 233 mm high including the tweeter, and 356 mm deep including the grille and terminal panel, for 17.5 kg, a weight that requires a solid support.

The evolution from the HTM71 S2

The move from the S2 to the S3 mainly comes down to the reorganization of the drivers. Where the previous model combined a 100 mm midrange and two 150 mm bass drivers, this version adopts a 130 mm midrange supported by two 130 mm bass drivers, while keeping a similar height. The decoupled carbon dome tweeter and latest-generation Aerofoil diaphragms accompany this change, resulting in a better-controlled frequency range and contained distortion.

Technical Specifications

Acoustic Configuration

• 3-way system with bass-reflex enclosure
• Aerodynamic profile bass-reflex port (Aerofoil Flowport)

Transducers

• 1 decoupled carbon dome tweeter, 25 mm
  • Rigid structure decoupled top-mounting (Tweeter-on-Top)
• 1 130 mm FST midrange driver with Continuum cone
• 2 130 mm bass drivers with aerodynamic membrane (Aerofoil)

Performance

• Frequency range: 45 Hz to 33 kHz
• Frequency response (± 3 dB): 50 Hz - 28 kHz
• Sensitivity: 89 dB SPL (2.83 V RMS, 1 m)
• Recommended amplification: 30 W - 200 W at 8 Ω (undistorted signal)

Impedance

• Nominal: 8 Ω
• Minimum: 3 Ω

Harmonic Distortion (90 dB, 1 m)

• < 1% from 90 Hz to 22 kHz
• < 0.5% from 120 Hz to 20 kHz

Dimensions

• Speaker only: 628 × 165 × 318 mm
• Height with tweeter: 233 mm
• Depth with grille and terminal: 356 mm
• Weight: 17.5 kg