SR separation

[Frank Raia]

When format 05 SR is selected on the CP500, is there little separation between all channels? Is discrete only in SRD? I ask because I do NOT have any test film to align the red light reader and must do it by ear the best I can. I have simplex 5 star sound head with a BASD reader and the CP 500. I know the reels I run have SR because the heads say so and so does the internet, so it must be true. I have fused around with alignment with the same results. I do notice the left channel is always influenced by the center more than the right. I have moved all adjustments and not any dramatic changes. Again, I do not have any test film and would like to get your thoughts on doing this without them. Thanks everyone IMG_20250626_195036.jpg IMG_20250626_194844.jpg

[Tony Bandiera Jr]

It is IMPOSSIBLE to get a proper optical alignment without test films, an oscilloscope and an RTA.

Edited to add: ALL of this applies to the SR-D digital track as well, focus, azimuth and lateral MUST be within a tolerance that is very slightly more forgiving than analog optical. You will need a computer and the Dolby DRAS Software (or a very good oscilloscope) as well as test film. (IF you are running a DOLBY digital 700 or 701 or BACP penthouse reader.)

Focus, azimuth, lateral position and even illumination is a MUST for ANY stereo optical track to work correctly. Now if you were only running mono sound, you CAN get an acceptable result tweaking by ear...if your ears (and booth monitor) are good enough.

For Dolby to decode accurately and without unpleasant artifacts (in parentheses), the azimuth must be spot on. (Surround bleedthrough, NR mistracking, phase errors) The frequency response MUST be as flat as possible (NR "pumping", muffled sound and improper signal levels). The "slit" illumination MUST be perfectly uniform for the full width of the two tracks (Surround bleedover, matrix decoding errors, NR decoding errors, compression/clipping which can damage speakers,). The L/R levels MUST be perfectly matched and at the proper reference values (Dolby NR mistracking/"pumping", Clipping and/or distortion, matrix decoding errors). And finally, lateral position to avoid scanning frame lines or the dead space outside the optical tracks (Buzzing, motorboating, severe clipping, severe NR and matrix mistracking.)

Bottom line is this: you MUST get the proper test films and equipment to do a proper 'A" chain alignment, or hire a local tech to come in and do it for you. It is NOT something that can be done by ear and eyeballing the optics. (That said, after many years I can get a very rough setting that saves some time with the test films by eye and ear, but that took hundreds of "A" chains and a lot of practice to do. AND even then, the films and instruments showed I was still way off.)

You other option to halfway decent sound is run only mono films or all stereo films in mono only (but be aware that azimuth and lateral errors will still cause bad sound in mono.)

Remember what you are trying to do when reading an optical track.. you are trying to read a very tiny slit image of the track (5mils or less) in perfect positioning (azimuth has less than a few mils of tolerance) on a piece of moving film. The digital SR-D data blocks are read differently, but the accuracy is still measured in tiny numbers.

I'm not trying to discourage you or anyone else who wants to set up thier own film projection, but all of what I said is the reality if you want to do it. The laws of optics and physics cannot be cheated.

[Frank Raia]

Tony, thank you for your response. I do realize that I can not achieve optimal alignment without test film, but this is not in a theater this is in my basement. I do have decent sound at the moment but I notice that it is not very discrete. I am looking for advice on how to make it better with what I have. If I can't than it is what it is, but I have the luxury of playing with it over and over. I guess the next time I go to the last mom and pop theater that is open in my area I could find out who their tech is.

[Frank Raia]

Any suggestions on where I might be able to get test film without it costing an arm and a leg? I don't think I can thread the projector with one arm

[Mark Gulbrandsen]

Place a "Wanted Test Films" add on this site and you may actually get a response or two...

[Ryan Gallagher]

Any suggestions on where I might be able to get test film without it costing an arm and a leg? I don't think I can thread the projector with one arm

I scored some of mine on eBay, and you can post here in Wanted too. Let me know which one you are after…. If I have more than one loop I could maybe send you a loaner.

[Ryan Gallagher]

Note to do it by the manual involves the following, maybe edit your wanted ad to list them:

Dolby Tone 69T
Cell Alignment Film Cat No. 97
SMPTE Buzz track P35-BT
Dolby Pink 69P

You’ll want to eventually own a tone and pink loop for sure, the other two you could borrow in for calibrations.

[Frank Raia]

Ryan, eBay is dry. I did find some in Europe but ridiculous prices. I might have found a source and I did post in wanted on this site. I appreciate your offer for a loaner, that is awesome that you would do that. My luck something would happen to it and not be able to replace. I am just going to keep fiddle around with it. I just wish someone would answer the question of is there discrete or not in SR

[Frank Raia]

Thanks Ryan. Again thank you for the loaner offer

[Josh Jones]

I am looking for some illumination uniformity loop if anyone has some to spare. I have all the rest.

Optical alignment isn't all that easy or intuitive, as many of the adjustments interact. Every time I align a machine, it seems I have to relearn how to do it.

[Ryan Gallagher]

Ryan, eBay is dry. I did find some in Europe but ridiculous prices. I might have found a source and I did post in wanted on this site. I appreciate your offer for a loaner, that is awesome that you would do that. My luck something would happen to it and not be able to replace. I am just going to keep fiddle around with it. I just wish someone would answer the question of is there discrete or not in SR

For sure, Ebay is best used when you know what you want and save a search for it with notifications. I've gotten quite a few film things that way that otherwise are non-existent when searching in the moment.

Works best when are not in a rush for something.

[Josh Jones]

I just wish someone would answer the question of is there discrete or not in SR

Google is your friend https://en.wikipedia.org/wiki/Matrix...(matrix)_4:2:4
The matrix forwards hard left/right information to the appropriate channels. Center and surround are encoded using phasing and amplitude differences of the left total and right total channels of the SVA track, post NR that is.

Josh