The widespread compatibility of today?s AV receivers with immersive home cinema formats (Dolby Atmos and DTS) has spurred a revolution in post-processing and upmixing technologies used for 5.1 surround sound installations. Gone are the days of Dolby Pro Logic and DTS Neo, eclipsed by entirely revamped technologies from Dolby and DTS.
Dolby Pro Logic II/IIx and DTS Neo:6
These two audio post-processing techniques share very similar operating principles. Both are also relatively outdated, although certain amplifiers lacking Dolby Atmos compatibility still implement them. Dolby Pro Logic II and DTS Neo:6 separate the stereo signal emitted by the source (TV, Netflix, etc.) by extracting sounds which are redistributed over all available channels. In this way, a stereo signal is transformed into a 3.0 – 5.1 multichannel soundtrack. This aging technology is lackluster in terms of dynamics, and the sound produced by the surround speakers is not free of artifacts, especially with highly compressed stereo signals (TV or set-top box, for example).
The new Dolby Surround
Since 2014, Dolby has totally revamped its Dolby Surround technology. The current iteration is a far cry from the Dolby Surround post-processing technology used for Laserdiscs and DVDs. This former version of Dolby surround processed the stereo signal to create a third rear channel that was then added as a mono signal to the soundtrack diffused by the 2 surround speakers. This process subsequently evolved into Dolby Pro Logic technology (interpolation of a center channel), which has today been surpassed by Dolby Pro Logic II (stereo surround sound). Consequently, the original Dolby Surround technology is simply no longer integrated into Dolby Atmos certified AV receivers.
There is a very simple reason for this: Dolby did not want ceiling speakers and upfiring speakers to be exclusively used to play Blu-ray discs with a Dolby Atmos soundtrack. To this end, the current iteration of Dolby Surround post-processing technology is capable of sending a stereo, 5.1, or 7.1 signal to ceiling speakers, but it can also upmix the same signal for 4, 5 or 7 standard speakers. More efficient than previous iterations, the new Dolby surround technology offers a higher dynamic range as well as a more natural and more detailed image.
Important: with certain AV receivers, Dolby Surround post-processing technology cannot be applied to incoming DTS signals, but only to PCM or Dolby (Digital, Digital Plus, True HD) signals.
DTS Neural:X, a mono signal for ceiling speakers or upfiring speakers
DTS Neural:X is the equivalent of the new Dolby Surround. Note: for certain receivers, DTS Neural:X post-processing cannot be applied to Dolby sources. Only PCM and DTS signals can benefit from DTS Neural:X remixing. Contrary to Dolby Sound, DTS Neutral:X can process incoming mono signals (1.0) and remix them for 7, 9 or 11 speakers, including ceiling or upfiring speakers. DTS Neural:X replaces DTS Neo and guarantees an audibly wider dynamic range.
To enjoy Dolby Surround and DTS Neural:X post-processing, you?ll need to deactivate the Direct mode on your AV receiver and activate surround sound processing. It?s very simple, since 99% of the time, all you?ll need to do is press the SURROUND button on the receiver?s remote control.