5.1 Surround Sound Passthrough On TVs

Additional information

5.1 surround sound setup

‘5.1’ is the typical surround sound setup, and involves five (5) ‘regular’ speakers, and one subwoofer (which is the  ‘.1’ in '5.1').

The speakers are ideally positioned as follows.

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

To the sides: 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. 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 would not get with stereo setup (2.0).

You also benefit from having a dedicated subwoofer, as that provides deeper bass than you would get from regular speakers.

How 5.1 surround sound passthrough works

In a typical setup, multiple source devices will be connected to the TV via HDMI, a cable which can transmit both video and audio. With 5.1 passthrough, instead of needing to connect a separate wire from each source to the AV receiver for the audio signal to make it to the receiver, a single audio connection is established between the TV and the receiver. The 5.1 audio signal is transmitted via the existing HDMI connection from the sources and into the TV and then sent by the TV down the audio output and to the receiver.

Depending on the number of sources you have, and whether they all support the 5.1 signal types you want to use, this kind of setup can eliminate several extra cables, and without noticeable impact on sound quality.

5.1 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 that is deemed less important to the sound is removed from the signal. This does reduce the quality somewhat, but it’s important to note that compressed audio still sounds very good – good enough that the average person is not going to hear much difference between it and uncompressed audio.

With Bitstream, the audio signal (basically instructions telling the speakers what to do) is encoded (packaged) by the source device, and then sent to be decoded (unpacked) by the receiver, with the resulting information then telling the speakers what they are meant to play. This delivery method makes for a smaller signal size, and so it is 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 will not be able to unpack and play a given Bitstream audio signal.

At present, you must use a Bitstream signal if you wish to pass 5.1 audio through a TV. You can do this both via HDMI ARC and digital optical.

There are two main kinds of Bitstream signals. There is Dolby Digital 5.1, which is a very common audio format, found on DVDs, Blu-rays, and most streaming media, and is a bit more heavily compressed. The other is DTS, which is also a common audio format and is also found on most DVDs and Blu-rays. It is very uncommon with streaming media, though. It isn’t quite as compressed as Dolby Digital.

When to use DTS & Dolby Digital

You need to use either DTS or Dolby digital to pass a 5.1 signal through a TV. While DTS is somewhat preferable in terms of 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. Output audio directly from each source device and to the receiver. Output this audio via HDMI, and not optical.

PCM

PCM is an uncompressed audio format, which means it will theoretically have the best overall sound quality, as no information has been 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 receiver, and then on to the speakers.

Unfortunately, this makes for a signal that is more difficult to transmit. No TV seems to be able to pass a 5.1 PCM signal through to a sound system, so sending a PCM signal to or from a TV will downgrade the signal to 2.1 (two speakers + one subwoofer), thus eliminating the extra channels necessary for surround sound.

PCM 5.1 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 (one that outputs PCM 5.1) to the receiver. Note that only HDMI can transmit a 5.1 PCM signal. Digital optical is only capable of transmitting a 2.1 or 2.0 PCM signal.

When to use PCM

For 5.1 audio, use PCM sound only if you

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

How to get the best results

Here are the steps you need to complete to enable 5.1 passthrough on compatible TVs.

• Samsung:
  • Go to Menu > Sound > Speaker List and select ‘Receiver (HDMI)’ for HDMI ARC, or ‘Audio Out/Optical’ for digital optical.
  • Go to Menu > Sound > Additional Settings and set ‘HDMI Audio Format’ to ‘Bitstream.’
  • Go to Menu > Sound > Additional Settings and set ‘Audio Format’ to either ‘Dolby Digital’ or ‘DTS.’
  • For HDMI ARC, go to Menu > General and enable ‘AnyNet+.’

• Sony:
  • Go to Settings > Sound > Speakers and select ‘Audio System.’
  • Go to Settings > Sound > Digital Audio Out and select ‘Auto 1’
  • For HDMI ARC, enabled ‘Bravia Sync Control.’

• Vizio:
  • Go to Menu > Audio > and set ‘TV Speakers’ to ‘Off.’
  • Go to Menu > Audio > Digital Audio Out and select ‘Bitstream.’
  • For HDMI ARC, go to Menu> System and set CEC to ‘Enabled.’

• LG (For most TVs with 5.1 passthrough):
  • Go to Settings > Advanced > Sound > Sound Out and select ‘Audio Out (Optical/HDMI ARC).’
  • For HDMI ARC, go to Settings > General > Simplink and set it to ‘On.’

Related settings

• CEC: To enable HDMI ARC, you typically also need to enable a feature called ‘CEC.’ This makes it so that some commands sent to the TV, receiver, or source device can result in instructions being relayed to one of the other devices. For example, with CEC, powering the TV on might also power on the receiver, or pressing the volume up/down buttons on the remote will adjust the receiver’s volume output. Just be aware that this sort of thing may start happening with your setup.

Other notes

• For HDMI ARC: Make sure the TV and the receiver/soundbar are both connected by their respective HDMI ARC ports.
• For Digital Optical: Make sure the cable is firmly connected to each device. It should make a clicking noise when it gets plugged in.

Conclusion

5.1 surround sound passthrough allows a TV to accept a 5.1 signal and then pass it along to a speaker system. It’s not the most important feature, but in some situations, it can help cut down on the number of cables required for a surround sound setup. We test whether each TV can receive and pass both Dolby Digital 5.1 and DTS 5.1 signals to a 5.1 receiver. We also test passthrough over HDMI eARC of the Dolby Atmos and DTS:X object-based formats.

Different TVs require different settings to enable 5.1 audio, and the requirements differ slightly for HDMI ARC and digital optical. If you want 5.1 passthrough, be sure to get a TV that supports the feature for the signal type you use, and then make sure your TV’s settings are such that they will allow the process to happen. Above, we list some of the steps required for the more common brands.