Optical vs Coaxial on a Soundbar: What the Words Mean

What optical and coaxial name on a listing

When a soundbar listing says "optical input" or "coaxial input," it names a physical port on the back of the bar. Optical, also called Toslink, uses a fiber optic cable with a square connector. Coaxial uses a single RCA-style cable with a round connector. Both carry digital audio as a stream of data, not as an analog signal.

On a listing, these words tell you which cables you can plug into the soundbar. They do not describe the soundbar's channel layout, its subwoofer, or its speaker drivers. A listing may name one, both, or neither. If a port is not named, the listing does not state that the soundbar has it. For more on reading listings, see how to read a soundbar listing.

What these inputs carry

Optical and coaxial inputs carry digital audio from a source device, such as a TV, a streaming box, or a game console, to the soundbar. The audio can be a stereo signal or a compressed surround signal like Dolby Digital. The exact formats a soundbar accepts over optical or coaxial are stated in the listing or the maker's page.

Neither optical nor coaxial carries the highest-bandwidth audio formats, such as the object-based audio used by Dolby Atmos on Ultra HD Blu-ray. For those formats, a soundbar needs an HDMI connection, specifically eARC. The HDMI 2.2 specification overview states that eARC "supports the most advanced audio formats and highest audio quality."

If a listing names optical or coaxial but not HDMI, the soundbar may still have an HDMI port. Read the full listing and the maker's page to see which connections are actually included. Compare the HDMI ARC vs eARC options to understand the difference.

Optical versus coaxial: what differs

The main difference between optical and coaxial is the cable and connector. Optical uses light to transmit data through a fiber optic cable. Coaxial uses an electrical signal through a copper cable. Both are digital connections, so they carry the same kind of data.

On a listing, the two names are not interchangeable. A soundbar with an optical input does not have a coaxial input unless the listing says so. A soundbar with a coaxial input does not have an optical input unless the listing says so. Check the listing for the exact port names.

For a TV connection, the choice depends on which port your TV has. Many TVs have an optical output but fewer have a coaxial output. If your TV has neither, you cannot use either input on the soundbar. Read your TV's manual to see which audio outputs it has. See soundbar connectivity options for a broader view.

How they compare to HDMI

HDMI is the connection that carries both video and audio. On a soundbar, HDMI ARC or eARC is used to receive audio from a TV. The HDMI 2.2 specification overview says eARC "simplifies connectivity, provides greater ease of use, and supports the most advanced audio formats and highest audio quality."

Optical and coaxial carry audio only, not video. They also have lower bandwidth than HDMI, so they cannot carry the highest-resolution audio formats. For a soundbar with Dolby Atmos, HDMI eARC is the connection that supports those formats. Optical and coaxial are more limited in what they can carry.

If a soundbar listing names both optical and HDMI, the HDMI port is the one to use for the most advanced audio. If the listing names only optical or coaxial, that is the connection you have to work with. Check your TV's ports to see which one matches. Learn about HDMI ARC vs optical to decide.

What to check before buying

Before you choose a soundbar, check the back of your TV to see which audio outputs it has. Look for a port labeled "optical," "digital audio out," or "coaxial." If your TV has an HDMI ARC or eARC port, that is the connection to use for the best audio format support.

On the soundbar listing, look for the input names. If the listing says "optical input" or "coaxial input," the soundbar has that port. If it says "HDMI eARC," the soundbar has that port. A listing that names no ports does not state which connections the soundbar has.

Also check what cables come in the box. A soundbar with an optical input may not include an optical cable. A soundbar with a coaxial input may not include a coaxial cable. The listing or the maker's page states what is included. For a complete setup, see soundbar unboxing setup checklist.

What this site cannot say

This site compares soundbars on stated details only. It does not have data on sound quality, loudness, or how a connection sounds. The choice between optical and coaxial is about which port your TV has and which audio formats the soundbar supports, not about sound quality.

For volume and hearing, follow the maker's manual and the guidance from the National Institute on Deafness and Other Communication Disorders. The NIDCD page on noise-induced hearing loss explains that sounds can be harmful when they are too loud, even for a brief time, or when they are both loud and long-lasting. Read that page for details.

What to pick for your situation

Questions

Is optical or coaxial better for a soundbar?

Neither is better in terms of sound quality. Both carry digital audio. The choice depends on which port your TV has. If your TV has both, either will work, but HDMI eARC is the connection that supports the most advanced audio formats.

Can optical or coaxial carry Dolby Atmos?

Optical and coaxial do not have the bandwidth for the highest-bandwidth object-based audio formats like Dolby Atmos from Ultra HD Blu-ray. HDMI eARC is the connection that supports those formats. Some soundbars may accept a compressed Dolby Atmos signal over HDMI, not over optical or coaxial.

What does a coaxial input look like on a soundbar?

A coaxial input is a single round RCA-style connector, usually orange or black, labeled "coaxial" or "digital audio out." It uses a cable with a similar connector on each end.

What does an optical input look like on a soundbar?

An optical input is a square or rectangular port with a small flap or cover. It uses a fiber optic cable with a square connector. The port is often labeled "optical" or "digital audio out."

Do I need an optical cable for a soundbar?

Only if the soundbar has an optical input and your TV has an optical output. Check the listing to see if a cable is included. If not, you will need to buy one separately.