I have a couple of soundbars in my home, and both of them have a Dolby Atmos logo printed proudly on the box. So, as an audiophile, I assumed that meant I’d get immersive, overhead sound every time I pressed play, with no input needed. But getting a Dolby Atmos soundbar is only half the job; the other half is making sure it can actually receive the signal, and mine couldn’t.
The culprit was a thin optical cable I’d never thought to question, and the difference was evident the moment I swapped it for HDMI. During this operation, I learned that optical simply can’t carry Dolby Atmos, no matter what the box promises.
If you’re in the same situation, HDMI ARC and eARC are the fix, and you can make the switch in about ten minutes.
Optical cable and Dolby Atmos don’t go hand in hand
There’s a bandwidth problem
Optical audio is good, but it is old. You can get at most compressed 5.1 surround sound with an optical cable, which is quite good if you have a surround-sound speaker system. With advanced audio technology like Dolby Atmos, an optical cable isn’t enough. Dolby Atmos is a different kind of audio that treats sounds as objects that move around you in 3D, and that takes far more data than optical can carry.
Speaking of numbers, an optical cable has roughly 3-5 Mbps of bandwidth. Dolby Atmos can’t squeeze through that, as it needs more bandwidth. It only works in HDMI mode because HDMI eARC delivers much higher bandwidth, around 37 Mbps (double standard ARC HDMI).
While surround sound works well, it isn’t the best way to experience a movie meant for Dolby Atmos. The worst part is having a Dolby Atmos speaker but not utilizing its full potential. Before switching to HDMI, the audio felt flat. However, after switching to HDMI, I could hear rainfall near me and helicopters zooming past my head.
HDMI ARC and eARC fix it
But ARC means Atmos, but compressed
HDMI ARC (Audio Return Channel) has been around since 2009. It lets your TV send sound back to your soundbar through the same HDMI cable that carries video. So, no two cables. It’s also a big step up from optical. ARC can carry Atmos, but only in a compressed form, commonly known as Dolby Digital Plus. For most streaming, that’s already a real upgrade because not all content is available in Dolby Atmos.
If you want true Dolby Atmos, then HDMI eARC is your option. eARC stands for Enhanced ARC. It supports uncompressed 5.1 and 7.1, 32-channel audio, Dolby TrueHD, and Dolby Atmos. With around 37 times more bandwidth than standard ARC, that is the real difference between “Atmos-ish” and the real thing. So, if you’ve got a 4K Blu-ray player, eARC is how its lossless Atmos soundtrack reaches your soundbar.
To switch over, keep a few things in mind. Not every HDMI port can send audio back. Look for the port labeled ARC or eARC on your TV. Use the TV’s eARC port, which is available on most modern TVs and DVD players. Then plug the other end into the HDMI eARC/ARC output on your soundbar. In most devices, the first HDMI port is usually the eARC port.
There are also a few things that you need to toggle:
- You need to turn on HDMI-CEC.
- Set the digital audio output to Auto or Pass-Through.
- Turn on eARC mode, which some soundbar or TV menus require.
Menus vary by brand; look up your TV’s menu online.
What will you actually hear?
Streaming versus discs
Most streaming apps, be it Netflix, Hulu, Disney+, or Amazon Prime, deliver Atmos using Dolby Digital Plus. This is basically a lossy version of Atmos. If you want to enjoy true lossless Dolby Atmos sound, you’d get it on Blu-ray discs, which use Dolby TrueHD.
So will you hear a difference? There won’t be a night-and-day difference on every show. But you’ll still get real Atmos, something you won’t get over optical. When I played a movie with Dolby Atmos, I could hear footsteps approaching, a fight scene unfolding around me, and other scenes felt lively.
The best part is that you shouldn’t give up on your TV if it only has plain ARC. According to Dolby, you can get Dolby Atmos sound by plugging your streaming box or console into the soundbar’s HDMI input, then sending the soundbar’s HDMI output to the TV.
Get the best sound quality
If your soundbar supports Atmos and your TV has an ARC or eARC port, you’ve probably paid for something you’re not using. Notably, it costs nothing if you’ve already got an HDMI cable. Speaker placement and room setup matter a lot, and Atmos isn’t like magic on every soundbar. The better the soundbar, the better Atmos sound you will have. Still, it’s the easiest upgrade I’ve made all year.