Actually, auto-balance correction is built in to many Pro-Logic decoders and is always active in Pro-Logic II Movie mode. The Auto-Azimuth correction actually corrects phase errors between Lt/Rt that can be caused by a misaligned analog master tape, misaligned Dolby A or SR noise reduction decoding, improper EQ and errors in disc mastering, etc... Since phase shifts are actually small time delays between the channels, the Auto-Azimuth looks for sounds that are equal in level between the two channels, like dialog, and then measures their high frequency coherence - because phase errors most often manifest themselves in the high frequencies, causing sibilance and dialog spilling into the surrounds - it then applies small amounts of time delay to bring Left Total and Right Total back I to phase coherence so when they are decoded there are no, or greatly reduced, errors in the decoding. It massively reduces sibilance splatter and dialog leakage into the surrounds. The more channels you have matrixed into the two original channels, the more critical phase and level accuracy becomes. For example, with standard Dolby Pro-Logic decoding the surround channel is just L-R and the Center Front channel is just L+R - since the two are 180 degrees apart on the energy sphere they naturally cancel 100%, as long as the level and phase between Left Total and Right Total is accurate. When stereo surrounds are added though, like Pro-Logic II or DTS:Neo-6, the natural channel separation between Center Front and the left or right surround channels is no longer 180 degrees - its more like 135 degrees which equals only 6db of channel separation without logic enhancement. So not only does the logic enhancement become more critical, but the level and phase accuracy between Lt and Rt becomes more critical as well. That's why Dolby has Auto-Balance always engaged in the PL-II Movie mode (its OFF in music mode since many recordings place performers slightly on either side of center, which the auto-balance would see as an error and correct, causing incorrect performance).

I know a guy who worked for Shure's HTS division and has a whole Shure Stereosurround encoding and decoding system, including the phase corrector, but he prizes them and won't sell any of it - so, I have an eBay AutoSearch set up for the Shure HTS300SDC Interchannel Delay Corrector as well as the HTS100SE Stereosurround Encoder - the encoder uses high precision 16-Pole Quadrature Phase Shift Networks to produce the highest quality surround sound encoded master - its surround channel encoding is wideband, unlike Dolby's standard Dolby Surround encoder - without the standard 100 Hz low frequency and 7 kHz high frequency roll off (which Dolby implemented to reduce dialog leakage into the surrounds due to the poor phase response of 35mm optical stereo sound and the small surround speakers inability to handle low bass). So Shure Stereosurround encoded recordings will have full 20-20KHz response surround channels when decoded with PL-II, Neo-6 or Circle Surround decoders which all have full bandwidth surround channels.

If I had a surround encoder I'd make remixed soundtracks for the Sensurround films that duplicated both the rumble and surround effects as closely as possible. Since, except for Rollercoaster, various home video releases have the control tones - and I have articles which explanation the effect each control tone triggers, looking at the presence and level of the control tones with a spectrum analyzer should tell me where and when to activate the effects, plus their level and if they are front-only, surround-only or both front and surround. I have a 18-bit, lossless 2 minute sample taken directly from a Sensurround rumble generator card so the rumble would be exactly the same as that used for the theatrical showings. I just need to find a surround encoder and one of those low-cost Radio Shack mixers - a 3 or 4 channel one would be good enough since, except for Earthquake, all the Sensurround films were in mono and the Sensurround mixes were done AFTER the full mono mix was done - which means, except for the surround encoder, if I had the mixer I would have everything needed to create Sensurround mixes for the home video versions.

Andrew, what did you mean by?

Unless I'm misunderstanding, why would two be needed?

I know a guy, a one-time cinema projectionist, who has a Perspecta decoder. There's a system which hasn't been treated well in home-video releases!


I don't think he's ever heard of "everything in moderation"!

No, even Criterion botched their one release where they tried to use Perspecta decoding for the DVD. I do not understand why Perspecta integrators are not used when transferring Perspecta films to home video - with the discrete channels we have now its easier than ever. The Spanish - or is it French? I forget - anyway, the non-English mono soundtrack on the DVD of Forbidden Planet has the Perspecta control tones on it. I'd love to be able to hear the Perspecta version of Gone With The Wind - David O Selznick had a hand in its remixing for Perspecta and Chase Audio used its directional cues when they did the stereo remix for the 1989 theatrical re-release - it had full directional dialog and was quite wonderful - but all the home video releases since have been mono or Chase's 1998 5.1 mix, which isn't all that impressive and has no directional dialog.

For some reason people think Perspecta was just a crude switching system when, in reality, it produces smooth pans between the front 3 speakers and could raise and lower any or all channels levels by 10db, which allowed it to be used as a form of dynamic range expander and noise reduction system too - sadly, the modern Perspecta systems designed to fit into Dolby processors don't utilize the ability to increase dynamic range or act as NR. They are the crude switching that everyone thinks Perspecta is.

The Todd-AO Cinestage theatrical release of Around The World In 80 Days used Perspecta on the surrounds to create 3 surround channels and, happily, the sound mixers duplicated the effect on the DVD with Dolby Surround EX so you can not only experience the film in its true 30fps form but hear the 3 surround channels as they were meant to be heard during its roadshow engagements. I got an email from one of the sound mixers and he said the technical documents on ...80 Days showings that are available online from the Widescreen Museum were a great help to them getting it mixed correctly for DVD.

Buy a few or all of them at that low price ware years ago would have cost thousands for a single CP1 2 or 3.

What I mean is the signal sounds like it has one side that is reversed and is throwing all the sound all over the place.

I might try and idea later if I can be asked and see what happens?