HDMI ARC vs Optical – Which Connection is Better?

So, you’ve just bought a new A/V receiver or soundbar. Congratulations! But now it’s time to make all the connections, and you’ve got some decisions to make. Life wasn’t always this complicated.

In the olden days, when dinosaurs ruled the earth, a simple coaxial cable got the job done for all connections. But we’re no longer technological cave men. Instead, we have a ton of accessories, like Blu-Ray players, game consoles, cable boxes, and A/V receivers.

Thankfully, HDMI has taken on the role that coax used to occupy. You’re just running more cables. But when it comes to A/V receivers or soundbars, you can run into some issues. Specifically, standard HDMI doesn’t support two-way audio transmission.

So if your signal comes through your receiver and into your TV, it can’t run back out again. For that, you’ll need to use an HDMI ARC (Audio Return Channel) cable. Alternatively, you can use a fiber optic cable, usually referred to simply as optical. Which one is best? Here’s a quick overview.

HDMI ARC and Optical Basics

HDMI ARC and optical cables both share the same purpose. They both transmit multi-channel audio from one device to another. So far, so good. The only significant difference in terms of function is that an optical cable won’t transmit video. But this shouldn’t be an issue, since you’ve already got video on your HD television.

The main difference between HDMI and optical is in their material construction. HDMI cables are primarily made of copper, which is a standard material for any electronic cable. Copper is cheap, it’s easy to produce, and we’ve been manufacturing with it for centuries.

On the downside, it’s susceptible to electromagnetic interference. Optical cables, on the other hand, are made of fiber optic strands, which are made of glass. These are relatively expensive to manufacture. However, they transmit the signal via light, rather than an electrical current. This makes them impervious to outside interference.

We shouldn’t have to mention this, but we will: make sure your equipment is compatible. For example, some soundbars don’t support HDMI sound. If your TV doesn’t support optical sound, you’ll need to run an optical cable directly from your source.

This might seem like a good workaround, but it’s actually not. Since the signals are travelling on separate paths, the audio and the video might be out of sync. In other words, before you buy a soundbar or A/V receiver, make sure it will work with your TV.

Audio Quality

For most home entertainment systems, optical cables are going to get the job done. They support surround sound with up to 5.1 channels. That’s good enough for any soundbar. But what if you’re an audio nut, and you use a 7.1-channel surround sound system?

In that case, an optical cable isn’t going to get the job done. Also, optical cables don’t even support TrueHD, DTS HD, or Dolby Digital Plus. That’s quite the limitation for a more advanced soundbar, much less a full stereo system.

The problem is that while optical cables are virtually immune to interference, they have a limited capacity. To get the most out of your powerful stereo system, you’re going to need an HDMI ARC connection. HDMI ARC supports virtually any sound format. You get support for Dolby Atmos, Dolby Digital Plus, TrueHD, and DTS HD. This will get you the best possible quality from your Blu-Ray discs or a modern game console.

The one major feature HDMI ARC doesn’t support is 7.1-channel surround sound. For that, you’ll need a further update. HDMI eARC – the “e” stands for “enhanced” – is capable of 7.1-channel surround sound. It also provides even higher bandwidth.

Most modern televisions, even expensive ones, output compressed sound at lower quality than the input. This can limit your sound quality regardless of whether or not you’re using HDMI ARC. HDMI eARC uses Ethernet technology to output at the same quality as the input.

In other words, you can enjoy rich, uncompressed audio without any jury-rigging or latency. Only a handful of devices currently support eARC technology. If you want to go this route, check your hardware specs carefully before you buy.

Video Quality

Video quality only applies to HDMI cables, but it’s still worth mentioning. The reason is that not all HDMI cables offer the same quality. If you need 4K video, an HDMI 2.0 cable will get the job done. However, you’ll be limited to 60 frames per second.

On the other hand, an HDMI 2.1 cable will offer 120 frames per second in 4K. You can even watch 8K video at 60 frames per second! This is essential for most VR systems.

In addition, there’s an obvious secondary point to be made relating to video. Because an optical cable isn’t compatible with video, it means you need more cables. Buying an optical cable and a cheap HDMI cable can be costlier than investing in a quality HDMI ARC cable.

Cable Length

Depending on your needs, cable length may or may not be an issue. If your TV and A/V receiver are right next to each-other, it’s a non-issue. Moreover, if you have a custom media room or whole-house audio system, it’s a significant issue.

Before we go on, we should point out that you should always use the shortest possible cable for your application. Regardless of cable type, you’re going to see some loss of signal the longer the cable is.

That said, video signals typically degrade faster than audio signals on HDMI. The reason is that the video uses the vast majority of the bandwidth. There’s also less tolerance for signal loss for video than there is for audio.

Knowing that, if you’re running separate cables to separate speakers, you’ll want to use the same length cable. The reason for this is that different cable lengths can skew the signal. The bigger the difference, the harder time your A/V receiver will have detecting the proper clock signal.

An HDMI cable has a maximum run length of approximately 15 meters (about 50 feet). The reason for this is twofold. First off, there’s the interference issue we already talked about. However, that’s not the whole story.

The other problem is that an HDMI signal uses an extremely low voltage, only 5 volts. As a result, even a high-quality cable with very low resistance can only carry the signal so far. After 15 meters, there’s going to be noticeable degradation.

Optical cables, depending on their quality, have a maximum length of 10 to 30 meters (about 33 to 99 feet). The reason they still have a maximum length is that no material is perfectly transparent. Eventually, the light signal will start to degrade.

The Case for HDMI ARC

The best case for HDMI ARC cables is if you have an A/V controller or soundbar. Simply put, you’ll get better quality audio than you would with an optical cable. This alone makes HDMI ARC a clear favorite.

In fact, HDMI ARC also enables CEC technology. We haven’t talked about this much. CEC allows you to use the same remote for all your HDMI ARC-connected devices. With that in mind, if you’re not using an external set of speakers, a standard HDMI cable might be a better option.

The Case for Optical

The best case for optical is if you have compatibility issues. For example, you might have an older A/V receiver or soundbar that doesn’t support HDMI ARC. In that case, optical may be your only choice. However, optical is a better choice for long runs.

If you’re wiring an audio system for your entire house, it’s definitely a better option. Finally, an optical cable is advisable if you’re getting a lot of electromagnetic interference. Of course, in that case, you should probably check your equipment to see what’s causing the interference.

Final Verdict

As you can see, both of these technologies have their own applications. To begin with, HDMI ARC is the best choice if you want the absolute best audio quality possible. It supports all the latest audio formats, and lets you use the same remote for all devices. Moreover, it helps you eliminate tangled cables and clutter.

On the other hand, optical cables still offer decent sound quality. Not only that, but they’re immune to interference, and they’re suitable for very long runs. At the end of the day, which type of cable you need will depend on what you’re looking for.