Mis à jour le 12 April 2019.
If you want to watch movies and series with three-dimensional sound, it is generally recommended to invest in a home theater system comprised of an AV receiver, a home theater speaker pack and a subwoofer.
But if you do not have enough space for a complete home theater installation or do not wish to have a speaker in every corner of your living room, this is not a viable solution. Some might even feel intimidated by the complexity of an AV receiver, due to their numerous and sometimes unclear functions, and possibly off-putting range of connectors.
Moreover, those who want to use their audio system primarily to listen to music in high-fidelity are generally facing a dilemma. They do not want to compromise on the quality of hi-fi restitution in favor of a multichannel configuration if they only occasionally watch movies. Besides, AV receivers are rarely as good as hi-fi amplifiers.
HDMI ARC and stereo surround sound
Companies manufacturing hi-fi amplifiers, amplifiers with an integrated DAC and connected amplifiers have been updating the design of their electronics to include an HDMI ARC connector. This is a way to enjoy a high quality stereo restitution with a TV, including multi channel soundtracks.
The audio return channel (HDMI ARC) may be used to transmit multi channel sound from a TV and video sources to a compatible receiver via a single HDMI cable.
Pioneer got the ball rolling with the Pioneer SX-S30D connected amplifier, rated at 2 x 85 Watts per channel. In a certain way, this amplifier is the stereo version of the slimline Pioneer VSX-S520 5.1 AV receiver.
Curiously, very few manufacturers of mainstream electronics followed suit, except for Onkyo who released the Onkyo TX-8270 stereo amplifier. HDMI ARC inputs are currently reserved for midrange to high-end stereo amplifiers. Amplifiers that fall into these categories are, for example, the Sonos Amp, the NAD D3045 and NAD M10, the Cambridge Edge, Lyngdorf TDAI-2170 and Lyngdorf TDAI-3400, or the Naim Uniti Atom and Naim Uniti Nova amplifiers.
The HDMI ARC connector is a simple way to connect an OLED TV or a 4K UHD TV to a stereo installation, using a reliable, tried and true, digital connection. There is no complicated installation required, a single HDMI cable is necessary to connect the amp’s HDMI ARC connector and the TV.
Stereo amp & HDMI ARC: what about the center channel?
Of course, experienced home theater enthusiasts know that in order to preserve the balance of the front stage and to ensure proper restitution of dialogues, a center speaker is an essential component.
Nevertheless, it is not always possible to place a center speaker right under the TV. Especially when the TV is placed on an AV cabinet. Even when the screen is on a TV mount, some people may not want to have a bulky center speaker on their furniture, not to mention that it’s not always easy to find the model that matches the front left and front right speakers.
It is also possible to use a pair of active stereo speakers fitted with an optical input, such as the KEF LSX Wireless.
The “phantom” center speaker
It is probably this very issue which motivated Sonos, the American speaker manufacturer, to pay particular attention to the sound spatialization performance of the Sonos Amp via its HDMI ARC port. This connected stereo amplifier benefits from an extremely effective digital sound treatment capable of creating a wide and deep soundstage.
When the Sonos Amp has to reproduce a convincing surround sound atmosphere, it creates a “phantom” center speaker, which simulates an actual center speaker. The voices are therefore well-centered and clear, even with only two stereo speakers, provided that the listener sits between the two speakers.
The limitations of the “phantom” center speakers and the solutions
When properly implemented, a phantom center channel is generally effective, as long as certain conditions are observed. Although still perceptible, the centering of voices isn’t quite as noticeable if the listener sits too far on the left or on the right from the ideal listening area. This is one of the two major drawbacks of not using an actual center speaker.
The second drawback is the fact that the voices themselves may be impacted, or even drowned out by loud sound effects. Nevertheless, this may be attenuated by investing in a subwoofer. By taking the low frequency sound effects (explosions, car collisions, gun shots, …) away from the main speakers, a subwoofer ensures better restitution of voices, which can then be clearly heard in the midst of sound effects.
Stereo amplifiers and HDMI ARC : what to think?
Will the HDMI ARC connector on stereo amplifiers find its audience? If it is accompanied by an effective delivery of voices and surround effects like it is with the Sonos Amp, then the answer is a resounding yes. Being able to enjoy a convincing three-dimensional sound restitution without the inherent clutter of a home theater installation, while preserving high-fidelity restitution for music might sound like a wager. It may even seem like a sacrilege for demanding home theater enthusiasts who cannot imagine anything but a multi channel system for listening to movie soundtracks.
Nevertheless, it is an appealing solution for audiophiles and for those who aren’t interested in a complex home theater installation. The only question is: will the HDMI ARC connector become a common feature for stereo amplifiers, amplifiers with an integrated DAC, and connected amplifiers? Not unlike soundbars, which almost always feature this type of connector.