Dolby Pro Logic II

**Dolby Pro Logic II** is the successor to the original **Dolby Pro Logic** system, introduced on June 20, 2000. Created by former Harman engineer Jim Fosgate (1937-2022) as a means to combat the limitations of the original Dolby Pro Logic under the name **6-Axis** before Fosgate and his patents were transferred to Dolby, it marked a major improvement in terms of directionality, time of calculation of dominant and non-dominant sounds, fidelity, rear-channel range, and freedom from artifacts in the decoding process; as well as serving as a good means of converting the then-emerging **Dolby Digital** technology soundtracks into the analog realm.

In the wake of consumer electronic manufacturers replacing traditional Dolby Pro Logic processing circuitry with their own, DPL II instead eliminates it altogether, with servos containing negative feedback circuits instead being used to derive five channels (one extra channel from the original DPL). How extra channels are determined come from determining differences between the left and right audio channels in stereo mode, or mapping Dolby Digital's 5.1 audio channels to each speakers - now in full-range compared to the original somewhat limited range that the surround channel had in the original DPL.

Three different modes were implemented - "Movie" mode, which was the default behavior of the decoder, "Music" mode which optimizes channel delays and allows for sound stage width tuning with user controls of the various channels, and "Game" mode, which adds some extra bass to an assigned LFE channel.

The **Dolby Pro Logic II** family received numerous extensions as detailed below, and would eventually be succeeded by the 2014 incarnation of **Dolby Surround** for upmixing tracks to Dolby Atmos standards.

## Extensions

On September 2, 2003 at the CEDIA 2003 conference, the system was extended to add 6.1 or 7.1 surround capabilities to a stereo, Dolby Surround, or a Dolby Digital stream by matrixing additional channels. This system would be known as **Dolby Pro Logic IIx**. For Dolby Digital Surround EX soundtracks, this proved to be a decent way to make use of a seventh speaker with its matrixing capabilities, as this system was meant as a way to accomodate for those soundtracks. (a similar system optimized for EX would exist by the name of *Dolby Digital EX*) However, this did not mean the audio track was now natively 6/7.1, just it is now matrixed instead.

Dolby Pro Logic II would be further extended in January 2009 at the 2009 CES with **Dolby Pro Logic IIz**, adding height channels above the traditional left/right speakers in the process up to a 9.1 system. Making use of spacial cues with low-level information, height is determined in the process (namely with ambiant sounds such as wind or rain). It marked an early appearance of the usage of spacial audio with height, which would come in a full discrete audio system three years later in the form of Dolby Atmos, though obviously it was much more crude than the latter system.

## Trivia

* Fosgate's system was not the original system intended for Pro Logic II. Instead, a competing system known as **Logic 7** was invented by Harmon which upmixed into 7.1, although far more crudely than Fosgate's system. After Fosgate was terminated from Harmon, he then went to Dolby employees to explain the drawbacks of Logic 7, and with both their approval and Ray Dolby himself ensuring its success, Fosgate's 6-Axis system would be formed into the basis for Dolby Pro Logic II.
* Receivers would start receiving support for Dolby Pro Logic II around December 2000.
* This format was sometimes labeled as **Dolby Surround Pro Logic II** (or in rare cases, **Dolby Digital Pro Logic II** for PS2 games that employed both) in its earlier years.
* The very first game to make use of a DPL II soundtrack would be Square's *Final Fantasy X* for the PlayStation 2, released on July 19, 2001 in Japan (a Dolby Digital Surround EX soundtrack was also supported for cutscenes only).
* Games would make use of Dolby Pro Logic II soundtracks for a large part of the GameCube, Wii, and PlayStation 2 libraries when it was available. Additionally, a small amount of PC, PlayStation 3, and even PlayStation 4 games would make use of Pro Logic II tracks when Dolby Digital was not available. The Xbox and Xbox 360 also made use of Dolby Pro Logic II, but was only available as an analog fallback from Dolby Digital audio.
* The Pro Logic II family marked the final venture of Dolby into the analog domain, as after this Dolby elected to focus exclusively on digital sound from then on.