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Author Topic: Dolby CP850 bypass function Kris Verhanneman Expert Film Handler Posts: 182 From: Belgium Registered: Dec 2009 posted 02-13-2016 10:39 AM                     Is there a bypass function on the dolby CP850. They've blown the HF speaker on the centre channel and asked if there is a bypass function like on the CP500 (analogue) or like on the QSC DCP gear? (edit)Someone told me that a reboot could fix this?  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 02-13-2016 12:03 PM                     No there is no bypass, that's simply not possible on a device like CP850. As to a reboot fixing it, if the HF is damaged no amount of rebooting is going to help. But if the CP850 is performing crossover functions I guess it's possible that this isn't working properly and a reboot might resolve it. CP850 has been utterly reliable for us so far.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-13-2016 12:31 PM                    Not a bypass in the traditional sense where the majority of a processor is taken out of service--not possible with an object-oriented track. But is there no way to tell the processor that a given B chain channel is out of service and have it route sound as best as it can around the problem? That would surely seem doable given the capabilities of the processing. I guess if you wanted a real backup you'd need either a 2nd conventional processor (already tuned) for playing a 5.1 or 7.1 track and a quick way to connect to the amps. Or at least a D to A and a note of how the adjust the amp gains.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-13-2016 01:32 PM                     In theory it should be entirely possible to intentionally create a CP850 "design" without a center, forcing equal distribution of that information to the next two closest speakers. This is done on the surround array, so unless there is some hard-coded restriction, it should be able to be done for the center. Granted it's not going to be as simple as pressing a button, but a tech should be able to re-load the alternate config to quickly get back up to save the weekend. It wouldn't surprise me though if Dolby intentionally has blocked such a thing to force people to keep their center channel maintained, as often once something gets put into bypass, the emergency is over and it can get forgotten about if the technical crew is not diligent. Anyone who integrates Q-SYS into their Atmos room (or even a normal room) can easily create quick buttons on the UCI to accomplish this though. Plus the sound is FAR superior to calibrating within the CP850.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 02-13-2016 01:40 PM                     QSYS is incredible. Never though of creating an emergency snapshot. And yes, the same should be doable within the 850. I'd be curious to hear how a phantom centre channel would sound in a 5-stage Atmos theatre.  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 02-13-2016 04:27 PM                     I've met a couple of the people at Dolby who were on the CP850 design team and have whined to them on several occasions about the lack of any type of bypass or the ability to have complete flexibility in re-assigning channels in an emergency, after I had a similar situation last fall when a center channel amp completely failed. They listened politely, and that was that. (And I manage to bring it up again every time I see them) I had a spare 'repeating coil' type transformer (one input, 2 outputs) and was able to run the center channel audio through that and split it to the left & right screen channels. Fortunately, the theater in question had an old, long, narrow, "shooting gallery" type of auditorium, with mediocre acoustics, so unless you were sitting in the front several rows, most people wouldn't notice the lack of center channel. Was it an 'ideal' fix- - no. But it worked well enough to get them through a busy weekend, with no complaints, until a new amp could be installed Monday.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 02-13-2016 05:08 PM                     If Dolby was concerned about people running that way, they could always update the CP850's software so if the unit was put into bypass mode that it would only play the 5.1 track and as such, any Atmos logo would play silent.  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 02-14-2016 04:57 PM                     Isn't the whole idea of those fancy Multi-Dimensional formats that it adapts the soundtrack to your sound system and room conditions? If you have a gazillion of speakers in your room, because you're doing Atmos all the way from the sun to the moon and back again, how big are the chances of one of your speakers or amps crapping out now and then? Dolby should offer an easy maintenance option that allows you to temporarily disable a speaker and the system should compensate for that speaker as good as it can. Heck... the system should run a daily self-diagnostic, where it plays a predefined set of test-loops and it should identify bad channels, mark them, log them, mail them to you and take them temporarily out of service automatically.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 02-15-2016 07:17 PM                     I remember that was a passage in one of the ATMOS whitepapers on fault redundancy and automatic speaker defect masking. Just don't know where that was, and wether it is capable to mask the most important speaker in a cinema system as well. Although a phantom center is perfectly ok as a temporary measure. - Carsten  |  IP: Logged Jay Wyatt Film Handler Posts: 33 From: Los Angeles, CA Registered: Mar 2015 posted 02-16-2016 01:03 PM                    quote: Marcel Birgelen Dolby should offer an easy maintenance option that allows you to temporarily disable a speaker and the system should compensate for that speaker as good as it can. I see it as slippery slope - if you allow users to make a phantom center they'll be less inclined to fix their Center loudspeaker issues. This is far from ideal for cinema playback and its not Dolby's responsibility to create non-ideal features to bail out cinemas - especially if they're trying to promote a brand like ATMOS. At the end of the day it's up the the theater owner to keep his equipment maintained and running. If something vital to the movie-going experience fails (ie Center channel) get it fixed.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-16-2016 01:10 PM                    Oh come on. You could say the same thing about bypass on the older processors. The point is to save shows until the repair is done.  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 02-16-2016 03:43 PM                     The whole purpose is indeed to save shows. Resiliency and redundancy is not an excuse for lack of maintenance, it's merely accepting the reality of failures and incorporating them in your design. Just like RAID is capable to compensate for disk failures, it's no excuse for not replacing broken disks. There's also no excuse not to repair a broken light fixture, but should it be a showstopper? The more technology you put into a theater, the more likely it will be some components will fail. Incorporating failure modes into your design and ways to compensate for them without noticeably impacting quality will only lead to a better product for your paying customers.  |  IP: Logged Jay Wyatt Film Handler Posts: 33 From: Los Angeles, CA Registered: Mar 2015 posted 02-16-2016 04:25 PM                    quote: Marcel Birgelen The more technology you put into a theater, the more likely it will be some components will fail. Incorporating failure modes into your design and ways to compensate for them without noticeably impacting quality will only lead to a better product for your paying customers. I agree with you here, but I'd argue certain failures should be show stoppers. If center channel was gone in a movie I'd want my money back. Also, (unless Lc and Rc exist) no immersive format is going to be able to 'compensate' for a missing Center. Routing dialogue to the surrounds or ceiling speakers would be a poor fix.  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 02-16-2016 05:32 PM                     We smaller cinema operators love the idea of having bypass, fallback, etc, for obvious reasons. But when I think about it, you are right in that ATMOS is such a high-profile system and only used in premium auditoriums. I wouldn't want to pay a surcharge/premium for such a system when it is comstricted by a technical fault. And every cinema with an ATMOS system should have the resources to have these systems properly maintained. If there was an automated masking function, there would only be a red light somewhere, that could be missed or ignored for days, weeks, months... A CP850 should always have an automated email alert sent to Dolby NOC in case of an error, with Dolby mandating a repair within a specified deadline, otherwise Dolby would pull out out the equipment... - Carsten  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 02-16-2016 09:17 PM                        To help you find failed (or stolen) speakers, the USL LSS-100P can send a command to put a CP-850 or QLI-32 into a test mode where pink noise is sent to each speaker in sequence. The LSS then reports any out of tolerance SPLs from each speaker. Harold  |  IP: Logged

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