The Signa S4 is Polk Audio's first Dolby Atmos-compatible soundbar. With its wireless subwoofer and miniature remote control, it is above all simple and easy to use.
American audiophile brand Polk Audio is trying to make its mark with a number of hi-fi speaker references, but also home-cinema solutions, including the Signa S4 3.1.2 soundbar. Accompanied by its wireless subwoofer, this one trades the Signa S3's Wi-Fi connectivity and built-in Chromecast for Dolby Atmos compatibility and a longer design.
The Signa S4 is a nice, simple, no-frills soundbar that is made entirely of matte plastic shells. The front and upper sides - those housing the grilles protecting the speakers - are covered with an acoustic fabric preventing any image reflection on the bar. Its size (104.6 x 9.5 x 6 cm) also allows it to be easily slid under a TV without obstructing the bottom of the picture. The wireless subwoofer is made of painted wood and adopts a very rounded design in a contained size of 20 x 32.8 x 28 cm which allows it to be placed discreetly in a corner of the living room.
The finishing of the whole is very correct: the traces of assembly are certainly visible, but the general manufacture is particularly neat. For the rest, the Signa S4 can be hung on a wall thanks to the spacer system provided. An optical cable and an HDMI cable are also delivered with the bar to allow a quick installation.
The Signa S4's connectivity is rather sparse, but it provides the essentials and allows it to be very easily set up. On the right rear side of the bar we find an HDMI eARC input, an optical S/PDIF input and a mini-jack auxiliary input. In addition to supporting Dolby Digital and Dolby Digital Plus, the eARC allows audio streams such as Dolby TrueHD and Dolby Atmos to pass through... provided you have a TV that supports this standard. The bar is also capable of decoding DTS and LPCM stereo streams, but unfortunately does not recognize multichannel LPCM streams.
The Signa S4 also features Bluetooth for wireless communication. Unlike its predecessor (the Signa S3), it offers no network connection (no Wi-Fi or RJ45) and therefore no connected functionality.
Everyday use of the Signa S4 is child's play, especially because it is ready to use as soon as it is plugged into the mains. The small remote control provided is also a big help, as it has all the essential controls and no superfluous buttons. It must be said that the bar does not include any advanced settings such as an equalizer (except for the level of the subwoofer) or a calibration system. It is also compatible with the HDMI CEC protocol and can therefore be controlled through the TV remote control.
This simplicity can also be seen in the display, which consists of five LEDs on the front panel. Although it borders on the austere, the display is still sufficiently legible and understandable. It is unfortunate, however, that the lights remain permanently on, with no way to turn them off.
The Signa S4 is a 3.1.2 sound bar composed of a 25 mm full range center speaker, two 25 mm tweeters and two 120 x 40 mm midrange speakers for the stereo channels, and two 66 mm vertical diffusers. The cabinet is equipped with a 150 mm woofer and a bass-reflex port. The bar has 3 listening modes (Movie, Night and Music) and three levels of voice enhancement (VoiceAdjust).
Let's start with the movie mode. As its name suggests, this mode is particularly well suited to films and series, as it allows the scene to be extended horizontally in a rather surprising way. Indeed, although the bar offers a 3.1.2 format, it manages to reproduce lateral surround effects admirably without any dedicated speakers. Voices do sound a bit distant, but they're still intelligible enough that you don't have to keep adjusting the volume between quiet scenes and more action-packed ones. The use of VoiceAdjust is therefore without real interest, especially since to highlight the voices, this mode lowers the level of bass and treble, which distorts the sound a little too much.
The two vertical channels, dedicated to Atmos effects, are on the contrary a little disappointing. The verticality of the sound scene is very discreet and we can hardly feel the elevation of certain effects. Moreover, the bar permanently performs an upmix in Dolby Atmos, which cannot be deactivated, when it is in Film mode and creates a kind of reverberation that is hardly suitable for musical content, for example. Fortunately, the Music mode allows the bar to be transformed into a simple stereo speaker. The left and right channels are then completely independent, which gives a much more natural rendering to musical content.
The Signa S4 has a V-shaped sound signature emphasizing the bass and treble at the expense of the midrange and highs. The warm aspect is brought by the subwoofer which brings a good extension in the bass. Its cutoff frequency is however particularly high (200 Hz) and the crossover is rather abrupt. This creates a dichotomy between the bar and the cabinet: the instruments officiating in the low register seem to come from the cabinet while the rest comes from the bar.
The removal of the midrange and upper midrange creates a lack of presence and a distancing of the soundstage: many instruments, including voices, can indeed seem distant. The general precision is also rather average, with effects of overflows in the low frequencies and sibilance effects which are quite recurrent.
For its first Dolby Atmos compatible soundbar, Polk Audio signs a convincing Signa S4. The Dolby Atmos argument is far from being its greatest strength, but it manages to surprise with its bluffing surround reproduction. Its simplicity also plays in its favor because it is indeed very easy to handle. We would have appreciated the integration of a Wi-Fi connectivity, which is present on the Signa S3 model of the same brand.