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Author Topic: SPL levels for different surround groups in an EX configuration Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 04-19-2005 08:17 AM                     Mark 3GHz cable is the standard for HD-SDI and is generally good, if the signal conforms to ANSI/SMPTE 292 for up to about 300-feet. The reference standard cable is Belden 1694A (1695A for plenum) It is certainly not "no-loss", hence the maximum length before a repeater for the signal. When one is running these signals...you do have to consider things like "bend-radius" and anything that is going to compromise the cable's capacitance properties...think making a really neat rack with the cable formed just perfectly? Think again...keep the bends to a minimum and gradual when they are needed. Robbie...clearly you've had bad experiences with some cheap Dsub crimps...I've NEVER (and I do a whole lot of cable manufacturing) had one of my crimp pins push out...again, I use AMP brand crimps, shells and hoods exclusively as well as AMP brand crimper. I'll put my connectors up to frequent use as much as I've seen other people's solder. I absolutely agree with you that on both, technique is key...either style can have excellent results or desastorous. One thing I will give the typical solder connector is that all pins are present...which makes for a more secure connection. The least reliable Dsub connector I've come across is the IDC ribbon cable connectors. Dolby was issuing some with their SA-10s that were just dreadful. I do use IDC type ribbons when needed but they cost a fortune to get quality ones. And Mark G's trusty Arbor press does a fine job of assmebling them. I've found that cheap equipment and components normally are just not cheap in the end...in any one given year we must make thousands upon thousands of connections...how can you have any measurable percentage of them be questionable? Hey Michael...I happened across a CP650 manual (issue 2 in this case)...page 4-13, section 4.7 clearly states that when setting up a CP650 for EX...set ALL surround channels to 82dB. [edited to add Surround EX level information] [ 04-19-2005, 09:52 AM: Message edited by: Steve Guttag ]  |  IP: Logged Darren Briggs Master Film Handler Posts: 371 From: York, UK Registered: Dec 2001 posted 04-19-2005 03:55 PM                        There are lots of references to EX on this website, and opinons differ alot. I think that if the film is made in EX it can sound very impresive, but yes not all films are in ex and EX if left on can spoil the surround sound field. Back to the topic though, i find the SA10 manual very good and tells you everything you need to know to get all levels correct.  |  IP: Logged Robbie Hidalgo Film Handler Posts: 47 From: Los Angeles, CA USA Registered: Dec 2003 posted 04-20-2005 01:29 AM                     Steve, agreed, agreed, and agreed. Ultimately, either method can shine or stink indeed... As for those IDC connectors, you almost NEED Mark's arbor press to press those things together reliably! Booooo. On the other hand, what really winds me up is racks full of ribbon (or other pre-fab computer) cables with audio running through them! Aarrgh. And lastly, just for the thread's sake: quote: Hey Michael...I happened across a CP650 manual (issue 2 in this case)...page 4-13, section 4.7 clearly states that when setting up a CP650 for EX...set ALL surround channels to 82dB. Just wanted to highlight that info from the rest of the chatter since it's dead-on topic, and extremely useful information. Time to get Issue 2 of the CP650 manual...!  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 04-20-2005 06:37 AM                        Roberta: thanks for highlighting that. I can never read Steve's posts - he always types so small. Normally I have to get somebody to read them to me. But thanks to you, I was actually able to read these lines without help! Actually, the manual versions higher than 1a (which I looked up here on this website when I wrote the post because I was too lazy to get up and get the latest CD) contain that info. 1a doesn't. Neither does the EX upgrade kit manual. I am still not completely satisfied with the information provided there. If you set all channels to 82dB, then you - theoretically - end up with 85dB or so blasting from the back when the back wall channels are active together. It also seems like a good idea to blow up speakers. Often, you only have 2 or 3 speakers in each group which would have to provide just as much air movement as 4, 5 or 6. Also, it seems to be a contradiction to the procedure described in the SA10 manual where you set the side wall to 80dB and then bring the corresponding back section up to an overall 82dB. Maybe it is one of those things that become obvious once you do it and carefully work your way to a good balanced setting.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 04-20-2005 08:11 AM                     Michael, You read too much into the CP650 setting...who says that it is in EX mode when you set levels? If I were designing the processor...I would have everyone set the levels even more uniform...that is, 85dB per channel so only one number need be memorized and so that the room is properly excited while EQing. Then when the processor is acutally playing the film, it would adjust the surround levels appropriately. That kinda what Dolby is doing...though they chose 82dBc which is more the surround standard level. The SA-TEN can't do that since it is working with a processed signal. You are sending your pink noise from your host processor and having it go through the SA-TEN as if it were the actual film. Note too the other limitations of the SA-10...you only have 3-EQ channels and three output level controls for 4-channels. As such, you have to set the levels between the four channels. With the CP650, you don't have any of these restrictions, you have four independant EQs and four level controls so each of the four surround channels are treated on their own...then the CP650 can set the balance of the four channels as appropriate for the two modes. As to blowing up speakers...that only happens in poorly designed systems. Surround-EX puts much greater demands (particulalry on the rear-wall) surround speakers. Each of the three sides needs to be able to handle what the entire system could handle before (level). Note too, that the rear wall often needs to be able to reach further since most auditoria are longer than they are wide (though that is certainly not always the case). When choosing surround speakers (or any speaker for that matter) you need to not only consider coverage but power handling. If you don't have the power handling with just 4 speakers on the back wall, then you must go to six and space them tighter...it is just that simple. Often a better choice is to use a more efficient, though often a more expensive, speaker to deal with the power. There is a reason companies like JBL have speakers like the 8340A in addition to the 8330A...you go from 91dB @ 1W/1m to 96dB @ 1W/1m...that is a huge increase in sensitivity. In terms of wattage...that would take you from say 600-watts per surround side to say 190-watts.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 04-20-2005 11:56 AM                        quote: You read too much into the CP650 setting...who says that it is in EX mode when you set levels? ... With the CP650, you don't have any of these restrictions, you have four independant EQs and four level controls so each of the four surround channels are treated on their own...then the CP650 can set the balance of the four channels as appropriate for the two modes. That is probably what I missed - that the CP650 actually "knows" what mode it is in and that it can (and hopefully does) adjust the outputs accordingly. Thanks for pointing that out.  |  IP: Logged Robbie Hidalgo Film Handler Posts: 47 From: Los Angeles, CA USA Registered: Dec 2003 posted 04-20-2005 05:59 PM                     Herr Shaffer, I knew you would appreciate it. I know your vision tends to get a little blurry from time to time...  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 04-21-2005 06:00 AM                        About EX levels... I've checked the CP650 manual (the last online) and, really, there are no indications on how set the Back surround levels. The SA10 does not consider the surround in quadrant so the level, I think, would be different than a CP650. On DTS-ES the Surround are set 82dB LS and RS, 80dB BRS and BLR, so that Back Surround give 82dB. Has more sense to me. Does CP650 with integrated EX card do the same? Is something official wrote from dolby? Bye A  |  IP: Logged Christos Mitsakis Expert Film Handler Posts: 242 From: Ag.Paraskevi, ATHENS, GREECE Registered: Sep 1999 posted 04-23-2005 01:14 PM                     Antonio, CP650s current manual, I think, is issue 4. Quoting from it (Chapter 4, B-Chain Alignement, page 4-7) "..setting the Ls and Rs channels (Ls, Bsl, Bsr, and Rs channels if your unit is equipped with Dolby Digital Surround EX) to 82 dB. Ls and Rs = 82 dB or Ls, Bsl, Bsr, Rs = 82 dB" So what Steve wrote in his post above is correct. Christos.  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 04-23-2005 01:34 PM                        Christos Thank you! Seems that I have only Issue 1A (the one that is available on MANUALS - Is there a way to download an updated one?) AND, much important - Brad will punish me -, I didn't read carefully Steve's post, otherwise I didn't had made the question... THANKS! Bye A  |  IP: Logged Christos Mitsakis Expert Film Handler Posts: 242 From: Ag.Paraskevi, ATHENS, GREECE Registered: Sep 1999 posted 04-24-2005 02:47 AM                     Antonio you may try to download a manual here: http://www.iceco.com/Technical.htm There is a CP650 installation manual, unfortunatelly no time to dowload and see. I hope it is an updated edition. C.  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 04-24-2005 01:21 PM                        Thank you Christos, It is Issue 2. Bye A  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 05-01-2005 12:08 PM                        I made a search and I have a curiosity. During EX playback does the Back Surround channel have a higher level? I understood that with Digital processor like CP650 you set all surround channels to 82dB. But what happen when EX is working with a film? Does the Back Surround operate at higher level? In other words, if I cycle the same pink noise on LR, BS, RS (while the processor in EX mode) should I measure an higher SPL from the Back Surround? I searched on Dolby.com but I found nothing. Thank you! Bye Antonio  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 05-01-2005 01:08 PM                        I asked the same question, and Steve already answered it (see 6 or 7 posts above).  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 05-01-2005 01:40 PM                        I understand that, so the "processed" Back Surround level is 3dB higher than Left and Right Surround? While in EX the surround levels are Ls:82 Bs:85 and Rs:82 and While NOT in EX Ls:82 and Rs:82? Bye Antonio  |  IP: Logged

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