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Author Topic: Why Dolby EX seems to be going nowhere Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 04-11-2007 06:52 AM                     That does make sense. I know that's not exactly how it's set up at this theater. They are using the optical input. Should this system be engaged (so that it's playing in "EX") all the time, or only for films recorded in EX? If you're not using EX, then I still don't understand how you would get the LSback to become part of the LS and the RSback to become part of the RS. Isn't that what an SA10 does when you turn EX off? Should the EQ on the center channel in the CP50/whatever be flat, since you are EQing in the original processor? All that being said, is this really worth it? What if the CP50 fails? Can you even get parts for it any more?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 04-11-2007 01:24 PM                     It should only be engaged when playing an EX film. The secondary processor needs to be modified to let a L+R sum pass through the C channel for non-EX films. This is why the CP200 is the easiest processor to make an EX box out of. The main processor should not have any EQ on the surrounds and all of the EQing should be done on your CP50 or whatever you are using for EX via the LCR cat64 cards. I would say a CP50 has about the same chance of dying as an SA10. There are plenty of used cards on the market. Ideally, just get a friggin' CP650.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 04-11-2007 01:49 PM                        Brad is right about the eq. Any eq or for that matter anything that affects phase or level that occurs before the matrix will cause falses; bad steering. After the matrix you can do anything or nothing. Louis  |  IP: Logged Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 04-11-2007 04:44 PM                     After reading your posts over a couple times, I have to say your method makes sense. I know that's not exactly the way it's set up at my theater. They are using the optical inputs and the CP50's only have one EQ card in them. Next time I'm there I'll try to take some good notes on how it's wired and see if I can understand it a little better. I still have a few questions. quote: Brad Miller Don't use the optical inputs on a CP50/55/etc. Use some form of auxiliary input that will not alter the frequency response like the optical preamp card will. If you have slit loss EQ turned all the way down, why would the optical input alter the frequency response in any way? On a CP50 or CP55, I thought the only format that uses the matrix is optical, and that the auxillary input is discreet. Which input should I use? quote: Brad Miller It should only be engaged when playing an EX film. So how do you engage and disengage it? The way it's set up right now with the optical inputs, Format 04 is "EX On." How would I turn it off? quote: Brad Miller The secondary processor needs to be modified to let a L+R sum pass through the C channel for non-EX films. Am I to understand this to say that when not playing EX, the rear wall surrounds will ALL produce the LEFT surround AND the RIGHT surround information? Brad, do you think you could come up with a block diagram and some simple instructions on this?  |  IP: Logged Demetris Thoupis Phenomenal Film Handler Posts: 1240 From: Aradippou, Larnaca, Cyprus Registered: Apr 2001 posted 04-13-2007 02:11 AM                     From what I understand and correct me if I am wrong: 1. Take the LS and RS output from your CP200 or whatever and rout it in the CP50 L/R Auxiliary or Music Input 2. Route the Front Left, Front Center, Front Right of the CP50 to the amplifiers for Surrounds 3. Do not EQ the surrounds on the CP200 but EQ them on the CP50 as "front screen channels". Hopefully it will work!  |  IP: Logged Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 04-13-2007 09:15 AM                     It seems that my understanding agrees with your understanding. But I am still waiting for someone to tackle my unanswered questions from my last post. Any takers? Brad?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 04-13-2007 12:36 PM                     Demetris is basically correct. To answer your other questions, you have to solder in some diodes to make custom formats on a CP55/200. I haven't done this on a 50, but I'm sure it can be done. Unfortunately you are asking me to remember something I did years ago and I don't know where my notes are.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 04-13-2007 03:41 PM                        On the CP-50, remove the first 4 cards. Solder directly to the cat 150 stereo input. Observe the 500 mv level and you're finished! You will need eq cards in L-C-R channels. Louis  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 04-13-2007 07:10 PM                     And then Louis remembers that the Cat 22s contain the line amps for the Left and Right channels.... There is more to it if you want to do it right so that you can switch between 5.1 and EX with all of the channels going in the right place and also match levels. Steve  |  IP: Logged Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 04-13-2007 09:16 PM                     quote: Steve Guttag There is more to it if you want to do it right so that you can switch between 5.1 and EX with all of the channels going in the right place and also match levels That's what I figured. That's the part I'm having a tough time understanding.  |  IP: Logged Demetris Thoupis Phenomenal Film Handler Posts: 1240 From: Aradippou, Larnaca, Cyprus Registered: Apr 2001 posted 04-14-2007 10:15 AM                     I guess you will be needing an isolated relay switching module where you will be able to route LS and RS to the BS channels! I would recommend tying on 2 three contact relays the following: Relay 1 Common: To BS Left Amplifier Relay 1 Normally Closed: From CP50 Front Left (Left Surround) channel Relay 1 Normally Open: From CP50 Front Centre (Centre Surround) channel Relay 2 Common: To BS Right Amplifier Relay 2 Normally Closed: From CP50 Front Right (Right Surround) channel Relay 2 Normally Open: From CP50 Front Centre (Centre Surround) channel. The relay can be activated by a 12V DC Power Supply in order to do the switching and I am sure you can figure out a way of hooking up a switch to it! The basic concept is that when no 12V DC power is applied on the coil of the relay it will be Normally Closed thus the standard Left Surround and Right Surround will pass to the Back Surround Channels. When 12V DC power is applied on the coil of the relay then the back surrounds will operate as Back Surrounds. The only real issue you need to worry is that the relays are trully ISOLATED from the Coil otherwise humming bzzz e.t.c Demetris  |  IP: Logged

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