Our TV Input Tests

Audio Passthrough

Before we get into the individual tests, let's first talk about the different connections you can use for audio passthrough. There are three types of connections: Enhanced Audio Return Channel (eARC), ARC, and Digital Optical. ARC and eARC both use HDMI cables, and eARC is simply a newer version of ARC that allows you to pass lossless audio from DTS:X and Dolby Atmos signals. These are audio formats that produce a more life-like sound experience with additional height sound, making objects seem like they're moving in the room around you. As for ARC and Digital Optical, they both support Dolby Digital and DTS audio formats, and the only difference is the type of cable you're going to use. Additionally, eARC is backwards compatible with ARC, so if a TV supports eARC, we know ARC also works on it.

Additional Information

5.1 surround sound setup

A 5.1 surround sound setup is a traditional speaker setup ideal for Dolby Digital and DTS formats, but newer audio formats use more speakers. Below you can see a 5.1 setup and where each of the speakers are positioned. Keep in mind that if there are setups with more speakers, the concept remains the same as 5.1, and you'll be adding more speakers to this configuration:

In front: It has one speaker to the left of the TV, one in the center (either just above or just below the screen), and one to the right. For the most part, these handle dialogue and the sound of on-screen action.

To the sides: There's one speaker each to the left and right of the seating area. These are mostly for playing sound from action occurring to the side and rear of the camera’s point of view.

Subwoofer: Should be placed on the floor to the side of the TV. It plays deep bass.

All six speakers receive and play their unique audio channel, and having five speakers in different places each playing different sounds, adds a sense of space and direction to the audio that you don't get with a 2.0 stereo setup. You also benefit from having a dedicated subwoofer, as that provides deeper bass than regular speakers.

Other surround sound setups

5.1 isn't the only available option you have for a surround sound setup. There are other formats like 5.1.2 or 5.1.4 for Dolby Atmos signals, which add height speakers to introduce sound above you, and a 7.1 setup, which adds two more surround sound speakers next to you. You need to find which one is best for your room and viewing habits because even if 7.1 seems like an improvement over 5.1, if you have a small room, the surround sound from the four side speakers will overtake dialogue from the front speakers.

Surround sound signal types

There are several different kinds of audio encoding used to deliver surround sound in a video. The three most common are Bitstream formats called Dolby Digital and DTS, which are both compressed, and then PCM, which is uncompressed.

Bitstream

Bitstream audio is compressed, meaning information deemed less important to the sound is removed from the signal. It does reduce the quality somewhat, but it’s important to note that compressed audio still sounds good enough that you won't hear much difference versus uncompressed audio unless your ears are well-trained.

With Bitstream, the audio signal is encoded (packaged) by the source device and then sent to be decoded (unpacked) by the receiver, with the resulting information telling the speakers what they're meant to play. This delivery method makes for a smaller bandwidth size, meaning it's easier to send multiple channels of audio. It also means that a receiver needs to have the ability to decode a particular Bitstream audio format to play it. Without that ability to decode the signal, a receiver can't unpack and play a given Bitstream audio signal.

At present, you must use a Bitstream signal if you wish to pass audio through a TV. You can do this both via HDMI ARC and Digital Optical. There are two main kinds of Bitstream signals, which is what we test for: Dolby Digital and DTS. They're designed by two competing brands; while Dolby Digital is a bit more compressed than DTS, the two formats are very similar.

When to use DTS & Dolby Digital

You need to use either DTS or Dolby digital to pass a signal through a TV. While DTS is somewhat preferable in audio quality, Dolby Digital is more widely available.

• Use DTS in your setup if you only watch Blu-rays or DVDs.
• Pick Dolby Digital if you also watch streaming videos. It's important if you output audio directly from each source device and to the receiver.

PCM

PCM is an uncompressed audio format, which means it will theoretically have the best overall sound quality, as no information will be removed to facilitate transmitting the signal. PCM is sent unencoded by the source, meaning the full, unpacked instructions for what sounds to play are sent directly from the source to the receiver and then on to the speakers.

Unfortunately, this makes for a signal that is more difficult to transmit. For most TVs, sending a PCM signal to or from a TV will downgrade the signal to 2.1 for two speakers and a subwoofer, thus eliminating the extra channels necessary for surround sound.

PCM can work with a receiver that supports the format, so if you want uncompressed sound, you’ll need to forego passing the audio through your TV and instead output the sound directly from the source to the receiver if the source outputs PCM. Only HDMI can transmit a PCM signal as Digital Optical is limited to 2.1 or 2.0 channels.

When to use PCM

For audio, use PCM sound only if you:

• Output audio directly from each source device to the receiver.
• Output this audio via HDMI and not optical.

How To Get The Best Results

For each brand, there are specific settings needed when you use eARC, ARC, and Digital Optical connections. You can consult the settings page in each review to see how to enable it. Even if we didn't test your specific TV, the same settings apply across a brand.

Related Settings

• CEC: To enable HDMI ARC, you typically also need to enable a feature called CEC. It makes it so that some commands sent to the TV, receiver, or source device can result in instructions relaying to one of the other devices. Simply put, you can control multiple devices with one remote. For example, powering the TV on will also power on the receiver, or pressing the volume up/down buttons on the remote will adjust the receiver’s volume output.

Conclusion

Surround sound passthrough is important if you have a receiver or soundbar and want to use the least amount of cables possible in your setup. With audio passthrough, you can connect your sources like a gaming console and Blu-ray directly to the TV and pass high-quality audio to a receiver using a single HDMI connection. It allows you to use fewer cables, and you can still take advantage of HDMI 2.1 and VRR support that the TV has.

We use the passthrough test to see which audio formats the TV can pass and over which connections. There are two main types of audio formats, Dolby and DTS, and if you watch a variety of content from streaming apps and Blu-rays, it will be important that your TV can pass both formats.