Polk Signa S4

A capable and competitively-priced Atmos soundbar that delivers deep bass and immersive audio using an easy-to-setup system. The soundstage is understandably front-heavy, but the delivery is precise and detailed, making the Polk Signa S4 a great all-rounder for movies, music and games.

Introduction

The Signa S4 is a soundbar from the US manufacturer Polk, and builds on the success of the earlier Signa S2 and Signa S3.

This new model retains the same basic ‘bar and sub combo, but uses a redesigned wireless subwoofer and 3.1.2-channel speaker layout to deliver Dolby Atmos object-based immersive audio. There’s also an HDMI connection that supports eARC, Polk’s patented VoiceAdjust technology, and a choice of different sound modes.

Design

• Minimalist design, matte black finish and solid build quality
• Controls on the soundbar and well-designed remote
• No proper display on the soundbar.

The Polk Signa S4 uses a similar design to the company’s other soundbars, with a simple rectangular cabinet wrapped in black fabric. The look is unassuming, but that’s the point, allowing the Signa S4 to sit under your TV without drawing attention to itself. The subwoofer is also finished in matte black, and sits on large feet to accommodate the downward-firing driver.

The soundbar is intended for medium-sized screens up to 55in, and measures 1046 x 60 x 95mm (WxHxD). It offers a choice of stand or wall mounting, and includes a template and spacers for the latter. The subwoofer automatically connects wirelessly with the main unit, and measures 200 x 280 x 328mm (WxHxD).

There’s no proper display on the soundbar itself, just a series of five multicoloured lights in various configurations that you’re unlikely to remember. There is a recessed area around the back for connections, and some basic buttons on the centre of the top surface. These controls cover power on/off, source select, Bluetooth pairing, and volume level up/down.

Polk includes a well-designed remote control that, while a little small, is easy to use and offers all the necessary buttons in an intuitive layout. There are controls for power on/off, mute, input selection (TV – Optical/Aux – 3.5mm/Bluetooth), volume level up/down, bass level up/down, sound modes (Movie/Music/Night), and VoiceAdjust (1/2/3).

Features

• 3.1.2-channel speaker layout
• Dolby Atmos decoding
• HDMI connection with eARC
• VoiceAdjust technology
• Sound Modes: Movies, Music and Night

The Polk Signa S4 uses a 3.1.2-channel system to deliver Dolby Atmos, but also supports other Dolby formats such as Dolby Digital, Dolby Digital Plus and Dolby TrueHD. In addition the soundbar can decode PCM, but there is no support for any DTS format. The latter omission is strange given the, admittedly more expensive, Polk Magnify Mini AX does decode up to DTS:X.

The speakers are based around left and right forward-firing channels, each composed of a 25mm tweeter and 120 x 40mm racetrack midrange driver. There’s a full-range centre speaker, and a pair of upward-firing 66mm drivers that bounce sounds off the ceiling to create the overhead channels. The subwoofer uses a 5.9-inch downward-firing driver to generate infrasonic frequencies.

The connectivity is based around a single HDMI port that supports eARC (enhanced audio return channel), which allows lossless audio to be sent back from supporting TVs. If the TV’s HDMI is limited to ARC, the audio will be lossy instead. There’s also an optical digital input for TV’s without eARC/ARC, and a 3.5mm analogue auxiliary input. Finally, there is support for a wireless Bluetooth connection.

In terms of other features, the Signa S4 includes Polk’s VoiceAdjust feature, which uses patented technology to ensure the dedicated centre channel is clear and precise, so you can hear every word of dialogue. There are three different settings to raise the volume of voices, while leaving the rest of the soundtrack untouched.

Finally, there are three sound modes – Movies, Music and Night. The Movie mode emphasises the effects and bass to give film soundtracks more impact, the Music mode is designed to deliver a more balanced soundstage with stereo recordings, and the Night mode reduces the bass while increasing the intelligibility of the dialogue, allowing you to watch content at night without needing to raise the volume.

Sound Quality

• Effective height Chanels
• Solid bass performance
• Expansive delivery
• No DTS support

The Polk Signa S4 is good all-round performer that produces a decent front soundstage with a solid foundation of bass. The overall delivery is smooth, with a clean treble and well-defined midrange. The size of the soundbar gives the audio some width that helps with stereo imaging, and the dedicated centre speaker provides clear and focused dialogue.

The upward-firing speakers are also effective at generating the front overhead channels, although how effective will depend on your ceiling. The lower, flatter and more reflective, the better. The lack of rear surround speakers or rear height channels means the soundstage tends to fill the first third of the room, but the well-integrated subwoofer adds plenty of low-frequency impact to proceedings.

The result is a soundstage that has a genuine sense of scale, giving the sand storm in Dune far greater impact as you feel immersed in hurricane-force winds and dust. Despite the complex nature of the mix, the individual sounds of rocks scraping the canopy are well defined, and the dialogue remains clear and focused to the characters on screen.

The Stuka dive bombers attacking the beach in Dunkirk are another good example of this soundbar’s capabilities, with high-pitched screams that are free of sibilance, and deep bass rumbles that accompany the explosions. While Polk doesn’t disclose the amount of built-in power, it’s certainly sufficient to give this sequence the necessary dynamic range without distorting.

The toe-tapping tunes in The Greatest Showman benefit from the Signa S4’s inherent musicality, and the addition of the sub gives the opening track ‘The Greatest Show’ a nice low-end hit. This is a solid soundbar for listening to music, and pretty with games as well. The effects are steered precisely around the front of the room when playing Call of Duty, although the lack of rears means you’re never quite sure what’s behind you.

When dealing with non-Atmos soundtracks the Movie sound mode gives films a greater sense of presence, with width and height added to the mix, while the bass is more pronounced. The Music option is more balanced, resulting in a smoother overall delivery, while the Night mode suppresses the bass and dynamic range, allowing for all-night bingeing sessions. Finally, VoiceAdjust can be handy for anyone who struggles to understand dialogue when it’s mixed too low in a soundtrack.

The Signa S4 isn’t perfect, but you certainly won’t find a better performer at this price. The lack of any DTS support is disappointing and increasingly common these days, making this soundbar useless for anyone with a large collection of Blu-ray discs, and it’s a shame you can’t add rear speakers to expand the soundstage, but otherwise this is a cracking all-rounder.

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Sustainability

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As part of this mission, whenever we review a product we send the company a series of questions to help us gauge and make transparent the impact the device has on the environment.

We currently haven’t received answers to the questions on this product, but will update this page the moment we do. You can see a detailed breakdown of the questions we ask and why in our sustainability info page.