There is much confusion surrounding the multitude of listening modes found on a modern home theater receiver, pre-amp or integrated amplifier: Stereo, PLII:Movie, THX Cinema, DTS-MAHD; which one is the right one? Does the “right” one change depending on what you’re watching? Below we explain the various listening modes, what they do, and what they’re designed for.
To explain the different modes, we first need to review how the audio gets to your receiver / Pre-amp. These can be broken down into Uncompressed or Compressed (note that compressed/uncompressed does not say anything about quality of the audio stream. In the days before digital music, audio was only transported uncompressed, over RCA cables. There was one cable for the Right channel and one cable for the Left channel. With the addition of multi-channel sound, the number of RCA cables expanded, but the concept remained the same; one RCA per discrete speaker channel. With the advent of Digital Music, a new format was created and named Linear PCM. This is the de facto standard for transporting uncompressed digital music over a single cable.
Compressed formats all exist digitally and they’re formats that you’re quite familiar with. Dolby Digital was the first major “brand” to market a compressed digital format in order to get high quality sound onto the tiny space available on movie theater film reals. The music is “compressed” and packaged at the source, transported over a cable (Toslink, Digital Coax, and HDMI) and then “expanded” by the receiver. DTS is another major name in the compressed audio battle that you’ve most likely heard of. They work differently from each other, but they perform the same purpose: Squeezing down the size of multi-channel audio so we can pass it to the receiver over a single cable. For example, a Toslink (optical) cable only has enough bandwidth for 2 channels of uncompressed Linear PCM digital data. But with Dolby Digital, you can move up to 6.1 audio through the same pipeline.
The important take away is that uncompressed audio sends a direct signal to the receiver, and compressed audio requires the receiver to “unpack” the audio before it can be sent to your speakers. The way it unpacks the file is out of our control, as it’s proprietary to Dolby or DTS, but what the receiver does with this unpacked audio IS in our control and is set by the various listening modes on the receiver.
We like to break down the listening modes into 3 broad categories: Direct, Licensed and proprietary. Direct are your basic modes: Stereo, 6 channel direct, Linear PCM: where the receiver simply passes along the signal from the RCA, or Digital source directly to the speakers. Licensed modes are the modes developed by Dolby and DTS and are licensed to the receiver manufacturer to use. Proprietary modes are those developed by either a 3rd party, or the receiver manufacturer: some examples are THX: cinema or Hall.
Note that the names will vary by Manufacturer.
Stereo – Output of audio to the Right Front and Left Front channel only. Suitable for audio recorded with 2 channels. CD’s are in this format as well as older TV shows. If you input a multi-channel source, you can select Stereo and the receiver will convert the multi-channel source into two channel audio for you.
All Channel Stereo – same as above, but clones the Front channels to the surround and rear speakers as well at the same volume. Not recommended as you lose the appearance of a front sound stage. There are better modes to select if you want “surround sound” from a two channel source.
Direct – Passes the audio stream to the speakers directly with no processing. Can be used with analogue and digital sources.
Mono – Outputs the same signal to the Right Front and Left Front channel only. Suitable for very old sources recorded in Mono.
Full Mono – Every speaker outputs the same signal regardless of position. Excellent choice for distributed audio indoors or outdoors.
Multichannel – This is the direct mode for Linear PCM sources. It will pass the signal through to the speakers unchanged.
Pure Audio – Many receivers and pre-amps now include a mode such as this; it’s the same as “direct” above, but turns off all video processing to try to create a lower noise signal. Generally not useful.
Dolby D, Dolby D+, Dolby TrueHD – These are the multi-channel Dolby sources found on DVD and Blu-Ray discs. In these modes it uses the algorithms developed by Dolby for their sound format and does not process the signal in any other way. Recommended for Dolby Digital Sources since you will receive the audio the way the source was engineered to sound. You cannot use Dolby Digital modes with any source other than a Dolby Digital source, i.e., DTS, Linear PCM, RCA, etc.
Dolby Pro Logic II – Dolby Pro Logic II attempts to analyse a 2 channel audio source, and expand it into a surround sound field. Excellent choice for TV shows or Movies with only a 2 channel audio stream so you can make use of all your speakers and get a surround sound experience. In practical use, this is very effective.
DTS, DTS 96/24, DTS Express, DTS-HD HR, DTS-HD MSTR – Similar to the Dolby Digital modes, these are the formats created by DTS. The receiver will decode the digital stream and otherwise not process the signal in any way. Recommended for DTS Sources since you will receive the audio the way the source was engineered to sound. You cannot use DTS modes with any source other than a Dolby Digital source, i.e., DTS, Linear PCM, RCA, etc.
DTS Neo:6 – Similar to Dolby Pro Logic II above, but developed by DTS. This is a way to get surround sound from a two channel source. Try both modes and see which one you prefer. There are no technical benefits of one over the other.
The proprietary formats are generally legacy formats, or it’s the receiver manufacturer trying to show that they have more features then another manufacturer.
These modes re-process the audio signal into something different from the original recording for various reasons. Generally not recommended.
Some examples with descriptions from Onkyo (as an example) are:
THX Cinema, Game, Movie, Music
Surround sound modes developed by THX.
Studio-Mix – Suitable for rock or pop music, listening to music in this mode creates a lively sound field with a powerful acoustic image, like being at a club or rock concert.
TV Logic – Suitable for TV shows produced in a TV studio, this mode enhances the surround effects to the entire sound to give clarity to voices and create a realistic acoustic image.
Orchestra – Suitable for classical or operatic music, this mode emphasizes the surround channels in order to widen the stereo image, and simulates the natural reverberation of a large hall
Game-Action – In this mode, sound localization is distinct with emphasis on bass
The best modes are those that send the signal to your speakers with the least amount of processing and duplicate the sound field the way the artist or recording engineer intended.
If you have a 2 channel source, Stereo is recommended for listening to Music. Dolby Pro Logic II and DTS Neo:6 are recommended for TV shows or Movies with only 2 channels.
For a linear PCM source (Digital output of CD player) Multichannel or “linear PCM” mode is recommended.
For a DTS or Dolby digital source (DVD, Blu-Ray, or Digital Video encoded with Dolby or DTS) the appropriate DTS or Dolby mode is recommended.
For outdoor or indoor distributed audio – Full Mono is recommended, as it will ensure the area is covered equally by the sound field.
The other formats on your receiver are not recommended as they add additional processing to your experience; however feel free to try out all the modes to see if they produce a sound you prefer.