Onkyo today introduced three new home theater receivers, including world’s first to offer Dolby’s new ProLogic IIz processing. All three receivers include an array of advanced HD audio and video technologies from Onkyo, Dolby, DTS, Audyssey, Faroudja and others, but it is the TX-SR607 receiver that is the most interesting as it features Dolby ProLogic IIz.

So what is Dolby ProLogic IIz? Well it is a new format from Dolby that adds surround speakers in the front of the room, three or four feet above the left and right main speakers. Dolby calls it height channels and it is designed to provide a greater sense of envelopment that wasn’t present in previous generations of Dolby or DTS surround sound systems. So now the surround sound system requires five front speakers and four rear speakers along with subwoofer bringing the total to 9.1 surround sound.

“Expanding on established Dolby Pro Logic II matrix decoding innovations, Dolby Pro Logic IIz identifies and decodes spatial cues that occur naturally in all content-stereo and 5.1 broadcast, music CDs, DVDs, 5.1 and 7.1 Blu-ray Discs, and video games,” explains Dolby’s website. “Dolby ProLogic IIz processes low-level, uncorrelated information – such as ambiance and some amorphous effects like rain or wind – and directs it to the front height speakers.”

Now back to Onkyo’s new receivers, the top-of-the-line TX-SR607 features six HDMI inputs and is the first AV receiver with a front panel HDMI input for use with cameras or portable devices with HDMI output. It also supports Dolby True HD, DTS_HD Master Audio, 1080p, Deep Color, x.v.Color and Onkyo’s new proprietary rear-panel universal port, which simplifies the connection for Onkyo’s forthcoming HD Radio tuner and iPod Dock.

The second AV receiver TX-SR507 is almost similar to TX-SR607, except it doesn’t support Dolby ProLogic IIz format. The entry level TX-SR307 has HDMI pass-though switching on three inputs, while it also support HD audio and video along with 1080p, Deep Color and x.v. Color.

The Onkyo TX-SR307 and TX-SR507 will be available in March, and the TX-SR607 in April with suggested retail prices of $299, $399, and $599 respectively.