i came up with surround EX that " i " original called CBS centre back surround . idea came to mind while i was young projectionist working for CIC UCI cinemas 1989 1990 , tower park 10 plex site , poole , uk 7 miles away from me . split stereo surrounds bothered me at other cinemas in 70mm which was at time only best sound format . while in projection i often look at the movie though port window while listen to how the sound , sounded with Dolby Stereo matrix , on the ( booth monitor ) listening to the mono matrix surround at how it worked or sounded or reduced crosstalk of centre and often some L R depending on how well the movie encoding mix ? i shared the idea in 1998 when i had my idea up and running way ahead of Dolby labs . i could have done this around 1995 but Dolby AC-3 laserdisc was too expensive even players modified . 1997 i saw dts millennium decoder price drop . i didn't get the dts till 1998 . I used yamaha DSR70pro connected to the dts stereo surrounds L R outputs did the simple connecting to amplifiers , run pink noise and dts test disc CD as well to align the channels/speakers . i had JBL control 5 LCR , JBL home made clone ( made in 1997 ) 4645 18" sub , looked like the real thing still use it today with JBL 4645C . i used x9 speakers for surround and this was 1998 . no one at that time knew " star wars 1 , the jar jar story " was going to have new sound format for it ? it wasn't public yet . but everyone knew there was new star wars coming due 1999 . i used x9 surrounds speakers pa small from closed down shopping centre . i placed x2 per each sidewall and x5 on the back wall for centre back surround " CBS " . i tested goldeneye dts THX laserdisc . wow it actually works . wow it removed the centre phantom as i predicted it would in 1989 . i was excited and shared the idea ( thou i now regret sharing with Dolby labs ) Dolby labs new york , offices as uk offices was closed at the time of 6pm so i waited few hours , till 9pm phoned , Dolby labs new york . i was talking with , eric kristofferson . he seemed very interested in my idea . too interested as matter of fact . the telephone call lasted for 30 mins . 9pm to 9:30pm uk time to new york . i been saying this story now for years . so Dolby labs taken my idea which is so simple . taken my idea without giving me any credit for the idea or discovery of the idea . taken my idea and stabbed me in the back . i don't care which , or who you believe ? so Dolby labs they take one of there cheap CP45 and modify it , which became Dolby SA10 , Dolby digital surround EX . which uses same pro-logic chip uses 4 output channels . (where consumer used only 3 output channels ) now then ! i use SA10 today as they was cheap as fish and chips few years ago around £20 each on ebay ! i knew they where an okay processor . also i got cheap CP45 around £50 each . its ether that or the skip . cinemas was throwing it all out , in favour of the rubbish 4k digital cinema , that can't cater movies now stuck with digital as not all movies are on digital format . oh but they can play a laserdisc or dvd blu , sigh that ain't cinema when most of the sound mixes are , near field remixed . sigh , cinema has really gone down hill since 1999 when DLP was introduced to cinema . i last worked for warner bros 1998 and after that had no more interest in working for the movie/cinema industry . so there it is . i came up with what most commonly may still have . Dolby labs will go to any length to lie tell lots of lies to support their own . wow . a company that i once respected ? well it is true others have claimed Dolby lavs stealing this or that and there have been law suits . as well as Dolby labs claiming and suing others . so that's the movie industry it ain't all a cheery with whipped cream on top . it is a dodgy industry . oh and you think Dolby dsu makes all speakers active with overhead ? heights 1 2 3 . it sends same signal to all speakers . it doesn't allow the sound to pan down the speakers from back to middle to front . it only does stereo from left to right so your hearing duplicated stereo . possible PLIIx that is taking the signal from the side-surround output of modified PLIIx chip ? i gather you clearly haven't listened to the overhead ( with all other speakers switched off ! ) clearly you can hear the L R common crosstalk but you need to know . " what to look for , what to listen for and what to feel for ". go and get avr with PLIIx or even PLIIz and do close listening comparing the surround outputs of each avr with current avr that has Dolby dsu .