Dolby Pro Logic IIz is an audio processing enhancement implemented in some home theater receivers that extends surround sound vertically, filling the space above and in front of the listener. This adds an overhead sound field that is great for weather, helicopter, and plane flyover effects.

What Is Dolby Pro Logic IIz?

Dolby Prologic IIz can be added to a 5.1/5.2 or 7.1/7.2 channel setup by connecting two front speakers above the left and right main speakers. Dolby ProLogic IIz is also compatible with two-channel and multi-channel surround sound sources, including Dolby TrueHD and DTS-HD Master Audio.

You have both surround back and front height speakers when Dolby Prologic IIz is added to a 7.1 or 7.2 channel setup (nine channels total). However, you need amplification for all nine channels. Since most home theater 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.

Dolby Pro Logic IIz Speaker Location

The front height speakers should be mounted approximately three feet directly above the front left and right main speakers. The speaker level settings for the height channels should be set slightly lower than the main left and right front speakers if you want to retain the character of the original surround sound mix.

The Motivation Behind Dolby Pro Logic IIz

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.

In most cases, a 5.1 channel surround setup provides enough rear audio information for the listener. 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. In smaller rooms, adding one or two surround back channels can be physically impractical.

Although the familiar Dolby brand name draws attention to Dolby Pro Logic IIz, other formats from Dolby and other companies provide a similar listening experience:

  • Audyssey DSX adds front-vertical height speakers, but it also provides for left/right wide speakers positioned between the front left/right and surround left/right speakers.
  • DTS Neo:X is an 11.1 channel surround sound format designed to look for cues present in stereo, 5.1, or 7.1 channel soundtracks. It places those cues within the front-height and wide channels and distributes them to front-height and rear-height speakers, creating a more enveloping sound environment.
  • Dolby Atmos is an encoding/decoding system that 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 is an immersive, object-based surround sound format that is a competitor to Dolby Atmos.
  • DTS Virtual:X is a surround sound processing format that projects a height/overhead sound field without adding extra speakers. Using complex algorithms fools your ears into hearing height, overhead, and rear surround sound depending on how it is implemented.
  • Auro 3D is a channel-based surround sound system in which sound can be recorded, mixed, and reproduced in three layers. There is a traditional 5.1 channel layer, a 5 channel height layer (placed slightly above the listening position), and a single top layer. This system can be adapted for headphones or in-car use.

Do You Need to Upgrade?

Don’t replace a home theater receiver just to add two more front or side speakers. If you have a 5.1 channel system, good speakers and appropriate speaker placement go a long way in providing an optimal home theater surround sound experience. If you are looking for a new receiver with Dolby Pro Logic IIz or any of the other technologies mentioned above, consider the added speaker layout requirements.

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