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Author Topic: Room levels Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 09-26-2003 05:39 PM                        I'm a supporter of Dolby's standards. I understand why standards are so important. I usually make picture example. Let's suppose I show a picture of Van Gogh in my house. But the color of the picture are not satisfying me. So I decide to put a green light at the picture to change the colors. No, I'm showing a picture of Van Gogh, and if Van Gogh decided to make a particular balance of colors it's not supposed to change it. But, I can try different white lamp and different lamp orientation to have the BEST picture at human eyes thinking what Van Gogh has intended to show. The same is the sound. Dolby's standards are VERY important. But when DTS and Dolby decided to install an array of surround speakers at their systems it means that the audience should be able to clearly hear them! I can agree with Matt, but the bottom is that ears are the last judge of the quality of the sound in our theaters. I can't believe that some surround sounds are put in the soundtrack so low intentionally. At least not all, of course. I realize that surround has to be VERY balanced with front channels, both in tone and volume. In my opinion, with 82dB surrounds are too low compared with front channels. Bye A  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 09-26-2003 06:28 PM                     quote: But when DTS and Dolby decided to install an array of surround speakers at their systems it means that the audience should be able to clearly hear them! Antonio, I believe that your heart is in the right place and I'm sure that you have the very best of intentions but you're making me nervous. I hear this same logic being expressed whenever I comment on the sound in poorly-balanced home theatres. Occasionally, I have gotten similar feedback from one or two customers who complain that "the surrounds aren't working." I really believe that the advent of home theatre systems is partially responsible for this problem because it created a situation in which many consumers have developed a taste for "surround heavy" balancing. I seriously doubt if customers complained about "surrounds" prior to the introduction of Dolby Surround for the home. Of course, very few of us are actually there to hear what Antonio is hearing (or...not hearing). Really, I should reserve comment because several of my theatres weren't properly constructed and I have been forced to get creative from time to time. Ultimately, you have to be satisfied that you have gotten the best result you can get.  |  IP: Logged Alan Haigh Film Handler Posts: 45 From: Watford, UK Registered: Jul 2003 posted 09-27-2003 03:00 AM                    Hello Antonio So in my view I would be attempting as much as possible to recreate the light the Van Gogh painted it in, irrespective of what I preferred. So if the mixer had surrounds at 82 with the curve, then he was happy with what he put down, and would have changed it if he wasn't. They like to keep your attention on the screen.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 09-27-2003 04:09 AM                        Antonio - you own a Van Gogh? Do you have any idea what that stuff is worth? Actually Van Gogh is not a good example when it comes to audio quality. Remember he cut his ear off.  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 09-27-2003 06:06 AM                        Alan You're right. But what about if YOU are sure that that white light suggested by Van Gogh, for thousand of reasons, is not the right light? You change light always keep in mind what should be the correct result. Manny, I know how poorly balanced Home Theater setups sounds. I can assure you that is not what I'm thinking!!! I'm pretty convinced that surround sound has to be non invasive, that not all movie has to be full of surrounds and that not all scenes are full of surrounds. Surrounds has to be perfectly balanced with front channels, they have to be clearly heard by audience but no more. When sound change from front to rear the sound tone and level MUST be the same. Otherwise it is like a poor balanced Home Theater setup!! Let's suppose that, instead of 82dB, Dolby's manuals says - "Set Surround levels using cat. 888 (!!!) until surround sounds are well balanced with front channels" !!! I'm sure that none will set them at 82dB! I'm questioning this standard because, at my ears, it is not correct! I don't know why, but it is absolutely, at my ears, not the right level. Perhaps it is correct for some theaters, with some type of speakers. Michael! I didn't make personally the EQ in the theater you heard in Florence but I know that surrounds were at 85dB. I can agree with you that perhaps in that case they were a bit too high in level, Perhaps 84dB would be better. How did they sound? Be frankly! Bye!! A  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 09-27-2003 09:44 AM                     A loop of Dolby's surround level test film (Cat. 151B) would probably prove beneficial in this instance. Cat. 151B quickly switches a noise signal back-and-forth between the stage and surround speakers. It makes a "choo-choo" sound. The levels should match -- I do this with a meter in my hand while listening in the theatre. I check this level from the centre-line of the room, which is where I balance and EQ the surround channels (relative to each other). If the levels do not match then you might want to re-check the A-chain before raising output levels. By the way...Can anybody tell me whether the noise in Cat. 151B is centre-surround or LCR-surround. I really don't know. I suppose I could go run a loop and watch the response lights but this is so much easier. If I were going to guess I would say it was centre-surround otherwise the SPL of the stage would overpower that of the surround array. And besides, it's called "151" which probably is derived from the mono-surround-mono nature of the track. Dolby is a little playful when it comes to numbering their products. But what about the "B"? What's going on there??? Was there ever a Cat. 151A or did they go to 151B directly after the original 151? What's the difference? And why doesn't this test film have an SRD track? Maybe I just have an old batch of the test film. Maybe they're on "151C" already and I missed it!? (Heavens, no!) Or is this strictly intended as a way to double-check the azimuth alignment of an analog head? Gosh! I never realized I had so many unanswered questions about this test film. Here comes one more! Is that pink noise on the 151B track or does it just sound a little bit like pink noise? [ 09-27-2003, 12:20 PM: Message edited by: Manny Knowles ]  |  IP: Logged Christos Mitsakis Expert Film Handler Posts: 242 From: Ag.Paraskevi, ATHENS, GREECE Registered: Sep 1999 posted 09-27-2003 02:28 PM                     Manny, You already gave the answer. Cat151 is purposed to balance the level of surround in relation to center channel. It uses pink noise constantly changing from in phase mono (center) to out of phase mono (surround). It is used after the level set stage to subjectively evaluate (so the literature says) the level of the surrounds so it would not be louder than the screen channels. However I do take reading with an SPL of the general volume of the auditorium during this process. 151B uses band filtered pink noise (attenuated lows and very highs) so that judgement by ear is made easier. Christos.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-27-2003 04:05 PM                     151 is to set the optical surround level only Because of the effects of time lag in the matrix circuits it was originally felt that the optical surround level be set with a rapidly changing phase angled test loop The specs originally called for the time delay to be dialed out the sub and left /right screen speakers off This was to balance the matrix action effects between the centre and surround channels in optical and in fact many of the processors had a optical surround gain adjustment All that said it often worked out that 87db on the surrounds was about the same thing for optical At the same time it was noted in the notes that came with the film was that many directors were upset with the excessive levels many theatres boosted there surround levels too and were scaling back the use of the track  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 09-27-2003 04:22 PM                     quote: All that said it often worked out that 87db on the surrounds was about the same thing for optical What exactly are you saying here? Do you set surrounds for 87db? Are you referring to optical or digital?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-27-2003 04:32 PM                     The optical surround when a steady out of phase Pinknoise was injected was about 87dbc  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 09-27-2003 04:55 PM                     What I mean is: How do you personally go about setting levels in the B-chain process? Do you use normal pink noise to set the levels? What SPL (per channel) do you personally aim for when setting the surround levels? What role does 151B play in the process? I'm trying to be clear on your stance on the surround level issue that started this thread.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-27-2003 05:48 PM                     I follow the textbook lcr at 85dbc the optical sub to provide boost of 3db in the overlapping regions and the P and Q are set for 82.3 each (one .2 higher because the #1 mic is slightly closer to one side) Then I run the 151 and if the processor has the adjustment adjust the "optical surround trim" to match the stage channel  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 09-27-2003 06:46 PM                     I find the "choo-choo" moves around too quickly to take individual readings with both channels active so I usually turn on only one amplifier channel at a time. First the centre channel amplifier and then the surround amplifier(s) to take a reading. Just wondering if anyone else does it this way. I never got instructions with 151B. Hmmm...Now why don't we have them in the Manuals section??? As for microphone placement: I like to reposition the mic to the centreline when equalizing and setting levels of the surround channels to ensure they are indeed equal.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-27-2003 07:02 PM                     Read the CP50 Cp100 and especially the CP200 manual  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 09-27-2003 07:36 PM                     Well, well, well... Here it is in my CP50 manual! Thanks for pointing me to it, Gord.  |  IP: Logged

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