Film-Tech Forum ARCHIVE: Re-routing the Center to the L & R on CP500

This is topic Re-routing the Center to the L & R on CP500 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mike Olpin (Member # 1115) on 12-13-2003, 06:10 PM:

Last night, while troubleshooting what I thought was a blown center channel, I came across this thought:

Is it possible to build a custom format which uses the 5.1 stream from the reader, but downmixes the center/left/right information to only the left and right channels? (Think home theatre "phantom" mode) I created a custom format, copying the settings for Dolby Digital (10), but when i tried to re-assign the center channel, it gave me a "Not Legal" prompt. It seems like a high end processor like this one should be able to downmix two channels.

Anyway, after I rebooted the cp500, and power-cycled the amps, it sounded great (obviously not a blown speaker), but nevertheless, I'm still curious about whether this is possible.

Posted by Gordon McLeod (Member # 33) on 12-13-2003, 06:23 PM:

You can assign channel in the pin patch matrix but it sort of defeats the purepose I don't think you can sum though in there
If you a problem that is what bypass is for

Posted by Mike Olpin (Member # 1115) on 12-13-2003, 06:37 PM:

We used bypass yesterday to run the show after we discovered the problem. I was wondering about this because we have a near-sold-out LOTR midnight show in that auditorium a few days from now, and I'd hate to have to run that in bypass.

Again though, it's no longer a problem, after everything booted back up, regular Dolby Digital sounds fine.

I made this post to just out of curiosity to see if such a format could be built.

Posted by Michael Schaffer (Member # 1204) on 12-13-2003, 06:54 PM:

Like Gordon said, in case of E, there is always bypass. If you absolutely want L + R only, make a custom analog format and play the Lt + Rt channels direct.
If you think a front channel might be damaged, use the wonderful internal test tone generator the CP500 has. You can play pink noise through all channels, or send test tones through the system. The swept sine tone is particularly practical, also for detecting rattles like loose lamps in the auditorium.

Posted by Scott Norwood (Member # 30) on 12-13-2003, 09:08 PM:

I'd take Michael's suggestion in this case--custom format with SR (or A or mono, depending on print) and no matrix decoding.

Posted by Michael Schaffer (Member # 1204) on 12-14-2003, 04:42 AM:

If you build a custom format based on format 10, the ProLogic decoder options are all available. However, it has been a while since I played with it. So I don`t remember if the options are simply there because the custom format screens are all the same for all formats, or whether selecting L+R actually has an effect on digital playback also. I tried it a long time ago, and I think it does not work (doesn`t it explicitly say "optical decoder config"), but I may not remember that correctly, so you should give that a try.

Posted by Steve Kraus (Member # 476) on 12-14-2003, 10:40 AM:

According to the signal block diagram in the CP500D manual the DA20 subsystem (SR•D playback) routes its signal to the 2nd Cat.675A DSP card. This is the card running the house EQ program. Therefore it does not seem likely that you'd experience a difference as a result of changing what the 1st Cat.675A DSP card (the one running the matrix decoder program) is doing.

If the point of this is the best possible work-around of a blown center channel, better than by-pass, you'd go with a custom format, based on Dolby SR analog, but with the matrix set for Non-Sync. This gives you (1) SR decoding, (2) Surround, (3) L/R direct on the screen channels (avoiding C), (4) House EQ and I think you can arrange that the sub is still fed. That's the best quality sound and naturally the sound intended for C will be spread equally on L and R. People sitting in the middle may not even notice the difference. No split surrounds but, hey, these are desperate times.

Posted by Jean-Michel Grin (Member # 1360) on 12-14-2003, 03:20 PM:

One day in our "open air cinema" we had to play a film in 01 (mono) format. to ensure a fine result for the entire audiance, we made a custom format. the mono signal was directed to the L,C.R channel.
With this configuration, the audio signal coverage was ensured for the all audience enven in case of strong wind,

Posted by Steve Kraus (Member # 476) on 12-14-2003, 04:15 PM:

Yes you can route one signal to multiple outputs or reroute them but AFAIK you cannot sum more than one signal into an output channel.