No matter which AV receiver you have - Onkyo, Yamaha, Denon, Sony - each will have a number of audio processing modes for you to choose from.
DTS Neural:X, Dolby Atmos - maybe Dolby TrueHD? If you've just bought yourself a shiny new receiver and are flicking through the manual, it won't be long before you come across these terms.
Unless you have taken some time to study home theater surround audio formats, you might be somewhat confused by all these audio types. Don't be too downhearted, it's not too bad once you give it some thought.
In this article, I will look at the various AV audio formats and audio modes you get on your equipment. Let us try to understand the difference between them all.
The first issue to be clear about when I talk about home theater audio types is the difference between audio encoding and decoding. Once you get this straight the subject becomes much clearer.
Audio encoding is the method that stores the audio on a DVD or Blu-ray disc. For Blu-ray discs, there are seven supported codecs:
With the new Ultra HD Blu-ray specification, there have been two new optional audio codecs added:
You won't find all these formats on every Blu-ray disc. But if you look on the back of the box you will see which soundtracks are available for that disc.
The important thing to understand is that these are the encoded formats. Something needs to decode this audio before you can hear it.
Very simply, audio decoding is the process of reading the digital data and turning it into audio that you can hear. If your hardware doesn't support the decoding of a particular audio format, then you won't be able to play that version of the soundtrack.
The main soundtrack on a DVD or Blu-ray disc will always be a mandatory audio type that all hardware will support. So, you will never be in the situation where you cannot hear the sound from a disc that you buy. I think you'll agree, this is a good thing!
For more detailed information on all these codecs, go to the article on understanding Blu-ray audio codecs.
The decoding process is usually done by the AV receiver, which will have audio decoders built-in.
The specifications of the AV receiver should include details of the AV audio decoders it has. This will allow you to know which Blu-ray soundtracks it will support.
To decode the audio on your AV receiver, you should set the audio output of the player to 'bitstream'. This means it sends the encoded data to the AV receiver for it to decode.
If the receiver has a DTS decoder, then it will accept a DTS 5.1 soundtrack and play it in 5.1 surround sound. The front panel display should show 'DTS 5.1' (or similar) when it detects the incoming signal.
Likewise, if a receiver has onboard decoding for Dolby TrueHD audio, then it will be able to receive this signal type directly from a Blu-ray player. It will decode it and then send the audio to the speakers.
The alternative is that the DVD/Blu-ray player decodes the soundtrack. Rather than the AV receiver.
This is an important point. If your AV receiver doesn't support the decoding of a particular format on the disc, it may be that your Blu-ray player does.
The player can decode the soundtrack, and then send the audio to the AV receiver as LPCM (also known as PCM). All AV receivers will be able to play this back. It will sound exactly the same as when the AV receiver does the decoding.
In this case, the audio output settings of the player should be set to PCM. Some brands may use a different term.
Before you buy an AV receiver or Blu-ray player, you can check which audio decoding it supports. Then you can be sure of the Blu-ray soundtracks you will be able to play.
By the way, if you are looking for a new AV receiver at the moment, you might be interested in my article on the best AV receivers in 2018. Or you might not!
So, what has all this got to do with audio sound modes? Well, your AV receiver will support many listening modes. Some manufacturers call them different things. Denon, for example, uses the term sound mode.
Some of these listening modes will involve the direct decoding and playback of the encoded audio from the disc. For example, there might be a Dolby Atmos mode. The AV receiver will often automatically select this when it receives a Dolby Atmos bitstream from the player. If not, you can manually select the Dolby Atmos sound mode.
As well as onboard decoders, AV receivers will also come with further audio processing options. Often called DSP, or Digital Signal Processing. These extra audio processing features add extra playback options.
You may not notice a difference between these. There is a fine line between an AV receiver decoding a signal and processing a signal. This is because AV receivers make the process transparent, with as little intervention from the user as possible.
So, when you play a soundtrack that is directly decoded by the AV receiver, the receiver will detect and playback that audio stream.
For example, the AV receiver detects an incoming DTS:X signal. The front panel display will show as ‘DTS:X’, and the audio is sent to the surround speakers using this format. It will usually default to the playback mode for the audio type.
However, on your AV receiver, there will also be other forms of audio processing - or listening modes. You can use these to tell the receiver how to play back the audio. Therefore, the audio is processed after decoding.
In the example of DTS:X above, I can change the ‘DTS:X’ listening mode to a different one. To ‘All Channel Stereo’ for instance. This would play the DTS:X soundtrack in stereo around all the speakers in your system.
I’m not sure why you would want to do that, but, you could!
The most common use for the 'All Channel Stereo' mode would be when you are listening to stereo audio. This will play the stereo audio image around your surround sound speakers.
Many AV receivers also allow you to set a default sound mode for a particular input. You would set this to how you would like to play the audio from this input. You might set the receiver to always play stereo TV audio using DTS Neural:X. This will use all your surround sound speakers even though the incoming audio is only stereo. It creates a pseudo surround sound mix.
However, you can change these listening modes at any time to suit the type of audio. To make sure you hear music through the traditional 2 front left/right speakers, you might switch to a stereo listening mode. Or, you may feel adventurous and select Dolby Surround to hear this stereo music track as 5.1 surround sound.
You will only be able to select some listening modes for certain types of audio. The manual will tell you which audio input formats work with which listening modes.
I thought it might be useful to take a closer look at a couple of AV receivers to see which audio modes they have. It’s easier to understand how it all fits together this way.
Look out for the sound modes which are decoders for a specific audio format, and the DSP modes which allow you to alter what you hear in the room. Bear in mind, different makes and models may have different processing modes. Also, some DSP modes will only be available for certain sources and sound types.
The following is a list of the listening modes on the Onkyo TX-RZ820 AV Receiver. This is a fairly high-end AV receiver which is THX certified. This means it comes with some THX listening modes which aren’t available on all models:
Denon uses the term 'sound modes' in their documentation. Although they mean the same thing as listening modes with the Onkyo receivers.
If you look at what the Denon AVR-X4300H AV Receiver offers, you can see that it has many of the same options regarding decoders. One major difference is it will support Auro-3D if you perform an upgrade. There are fewer DSP modes than the Onkyo, but enough choice if you enjoy experimenting with these settings.
Yamaha has their own angle when it comes to decoders and DSP. The list of decoders is similar, but they have quite a few DSP programs under the banner of Cinema DSP. The idea is you apply a Cinema DSP program to the audio you are listening to, and it will try to recreate that audio as if you were in a particular hall, room or space.
The higher-end models also have Cinema DSP HD³, which uses more reflection data for an even more realistic effect.
These are the sound decoders and programs that come with the Yamaha RX-A3070 AV receiver:
There are many audio listening modes available on an AV receiver.
Some of these are the result of decoding the audio directly from the disc, and some are there to process the audio to suit your speaker setup. If you take a little time to understand the various options you have, then you will be able to get the best out of our receiver and speaker system.
If you want some more information on the different types of audio formats, go to the guide to surround sound formats for more details.
Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has worked as a sound, lighting and audio-visual engineer for around 20 years. At home, he has spent more time than is probably healthy installing, configuring, testing, de-rigging, fixing, tweaking, re-installing again (and sometimes using) various pieces of hi-fi and home cinema equipment.