Dolby Pro Logic IIz – What You Need to Know

Add Height to Your Surround Sound Experience

Ever since Thomas Edison invented the phonograph in 1877, the quest has been to make the reproduction of sound as real as possible. Today's surround sound technologies are a continuation of this quest.

Dolby Pro Logic IIz: Surround Sound Goes Vertical

Dolby Pro Logic IIz is a processing enhancement implemented in some home theater receivers that extend surround sound vertically, filling the space above and in front of the listener.

Dolby Prologic IIz requires adding two front speakers above the left and right main speakers. This adds a "vertical" or overhead surround sound field (great for rain, helicopter, plane flyover effects). Dolby Prologic IIz can be added to a 5.1/5.2 or 7.1/7.2 channel setup.

Dolby Prologic IIz Example

Dolby ProLogic IIz is also compatible with two-channel and multi-channel surround sound sources, including, if applied correctly, Dolby TrueHD and DTS-HD Master Audio.

When added on to a 7.1 or 7.2 channel setup (9 channels total), you have both surround back and front height speakers. However, you need amplification for all 9 channels. Since most receivers provide amplification for 7.1/7.2 channels, you must forgo the surround back channels when using Pro Logic IIz. This means you end up using a 5.1/5.2 channel setup and adding the Dolby Pro Logic IIz height channels to obtain a 7.1/7.2 channel setup.

The front height speakers should be mounted approximately 3ft directly above the front left and right main speakers. To retain the character of the original surround sound mix, the speaker level settings for the height channels should be set slightly lower than the main left and right front speakers.

The Motivation Behind Dolby Pro Logic IIz

The motivation that guided the development of Dolby Pro Logic IIz is the observation that humans hear more from the front, above, and sides than from the rear. This means it's more advantageous to emphasize sound coming from the front, sides, and above the listener than to add sound coming from the back.

In most cases, a 5.1 channel surround setup provides enough rear audio information for the listener, and adding one or two more surround back channels, as is promoted with 7.1 channel home theater receivers, doesn't always give the listener that much more of a surround sound experience. Also, in smaller rooms, adding one or two surround back channels is physically impractical.

Pronunciation: Dolby Pro Logic Two Zee

Also Known As: Dolby Pro Logic IIz

Alternate Spellings: Dolby Prologic IIz, Dolby Pro-logic IIz

Related Technologies to Dolby Pro Logic IIz

Although the familiar Dolby brand name draws attention to Dolby Pro Logic IIz, there are other formats from Dolby and other companies that provide a similar listening experience or build on it.

  • Yamaha Presence: Yamaha offers a similar technology on some of its home theater receivers called Presence which requires the addition of two front height speakers for a full surround experience from the front and above the listening position.
  • Audyssey DSX: Audyssey, a company well-known for speaker setup, room correction, and sound processing software, offers DSX (Dynamic Surround Expansion). Like Dolby Pro Logic IIz and Yamaha Presence, DSX adds front vertical-height speakers, but it also provides for left/right wide speakers positioned between the front left and right and surrounds left and right speakers.
  • DTS Neo:X: DTS offers an 11.1 channel surround sound format that they have labeled DTS Neo:X. DTS Neo:X is designed to look for cues already present in stereo, 5.1 or 7.1 channel soundtracks and places those cues within the front height and wide channels that are distributed to added front height and rear height speakers, enabling a more enveloping "3D" sound listening environment.
  • Dolby Atmos: Where Dolby Pro-Logic IIz adds vertical height to existing 5.1 or 7.1 channel content (and only to the front sound field), Dolby Atmos is an encoding/decoding system at allows vertical height sound components to be placed in multiple locations within a soundtrack during the recording and mixing process making it more precise.
  • DTS:X: DTS:X has also come up with an immersive, object-based surround sound format that is a competitor to Dolby Atmos.
  • DTS Virtual:X: DTS Virtual:X is a surround sound processing format that projects a height/overhead soundfield without adding extra speakers. Using complex algorithms, it fools your ears into hearing height, overhead, and even rear surround sound depending on how it is implemented in a sound bar or home theater receiver.
  • AURO 3D Audio: Auro 3D is a channel-based surround sound system in which sound can be recorded, mixed, and reproduced in three layers. First, there is a traditional 5.1 channel layer, Next, a 5 channel height layer (placed slightly above the listening position) is added, and finally, there is a single top-layer (referred to as VOG or the "Voice of God"). In addition to home theater, this system can be adapted for headphones or in-car use (without all the speakers!).

Do You Need to Upgrade?

You are probably asking yourself, "Is my current home theater receiver obsolete if it doesn't offer any of these technologies?". The short answer is "NO". If you have a 5.1 channel system, good speakers and good speaker placement go a long way to providing a good surround sound experience.

Don't replace a home theater receiver just to add two more front or side speakers. Other things, such as the ability to perform Dolby TrueHD/DTS-HD Master Audio decoding and HDMI connectivity are a more logical reason to upgrade. However, if the receiver you are considering also has Dolby Pro Logic IIz or any of the other technologies mentioned above, that is an added bonus, provided you commit to added speaker layout requirements.