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Posted by Antonio Marcheselli (Member # 373) on 09-24-2003, 12:31 PM:
 
Hi everyone.

I have a question that it's a long time I would like to share with you.

Dolby and all sound manufacturer says that channel's level in the theater has to be

LCR: 85dB
Surrounds: 82dB
Subwoofer: 91dB or +10dB in band gain.

I'm talking of digital formats of course.

However all equalization I've heard following these standards had a very lack in surround sound.

In my experience the "correct" level for surrounds speakers is 85dB or, better, the same level of front channels.

With this setting surround sound is clear, not too high, clear enough to be clearly heard in all situations. If I set my surrounds at 82dB usually during louder scenes surrounds die and cannot be heard.

I remember a post where Brad says that to have good surrounds they have to be set 1,5dB higher than specs. So 83.5

What is your opinions?

Bye
A
 

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Posted by Brad Miller (Member # 2) on 09-24-2003, 01:46 PM:
 
I will frequently do 82.5, as that sums more accurately to 85db, but it would be a rare case when the surrounds would need to be raised to 83.5. I don't remember ever recommending that. If I did, it was quite possibly a typo. If you are having to set each surround zone at 85db, something is wrong.
 

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Posted by Larry Zuverink (Member # 1483) on 09-24-2003, 01:54 PM:
 
I disagree. I have heard surrounds set to 85 and find it very annoying. Now maybe that is just our set up. Depending on distance between surround, type of speakers, and power handling head room might make a difference.
 

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Posted by Antonio Marcheselli (Member # 373) on 09-24-2003, 01:58 PM:
 
Brad,

I saw surrounds set at 82 and 85dB in many theaters. Both with ARTA 80 and THX R2. 82dB is, at my ears, not enough. You can see surrounds only in quite scenes or only surrounds that are very very loud.
I believe in dolby standards but in this case I cannot understand how a theater can be set at 82dB.

82.5, you're right, it was my memory, you said 1/2 db and not 1.5 dB!

I cannot understand. It's not a single theater, it is all theater I worked for!!

Michael, do you remember Supercinema in florence? That had the surrounds at 85dB. You told me that surround was very good..
(just FYI, Supercinema is closed now... )

Bye
A
 

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Posted by Manny Knowles (Member # 1171) on 09-24-2003, 03:17 PM:
 
I usually go to 82.5 or 83db. Whatever it takes to get me to a sum of 85db. I've never had to go higher than 83db per channel.

I remember when I was first starting out; I misunderstood the spec's and went for 85db per channel and I could tell immediately that I had made a terrible mistake because the screen channels became hard to understand. It was a mess.

Look at what you wrote...

quote:

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I saw surrounds set at 82 and 85dB in many theaters. Both with ARTA 80 and THX R2. 82dB is, at my ears, not enough.

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...and consider the possibility that your personal taste disagrees with the standard. I thought my theatres sounded just wonderful until I visited a cinema in South Florida with very good sound. Rather than get depressed about my ignorance, I became very excited about starting from scratch in hopes of obtaining similar results.

I think it is possible to continually improve at this so long as we resist the temptation to become too opinionated as to how a room should sound.

Someone on this forum once noted that although our ears play an important role in setting up and evaluating our sound systems, we have to take care that they are "calibrated" just like the rest of our equipment. In other words, we need to keep ourselves reminded of what a theater is really supposed to sound like. Otherwise, we are just guessing.

I don't know the theatre to which you refer -- the one with the surrounds at 85db each -- but even if that is true, there may be peculiar factors in the design of the space that impacted the decision to set the system up in that manner. Then again, maybe not. It may have been a bad setup that you got used to hearing.
 

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Posted by Antonio Marcheselli (Member # 373) on 09-24-2003, 03:42 PM:
 
manny

I fully agree with you!! That's why I said "at my ears". I'm not saying that 82dB is wrong, just that I've had the chance to hear different setup of equalization and I found that, for my personal taste, 85dB of surrounds is better.

Of course too many surrounds are not a good idea, front channels has always to be clear.
However I put myself in customer's head. Customers are not so used to surround sound (they don't work in a theater!) so, like myself first time in theaters, they note surround sound less than me that I'm able to concentrate on both side of a movie: sound (front and rear) and image (first movie, years ago, I had to close my eyes and concentrate on surround sound to clearly hear them!!).
So, I wonder, What is the audience hear if I can barely hear surround sound?

I realize that we should hear a movie in the same theater to understand our personal taste, but I can assure that i DON'T like too high surround, when majority of sound come from rear instead of front. I like perfectly balanced surrounds, where you can clearly hear surround from rear but when they don't cover the stage channels.

Hwo do you equalize surround speakers? Same X-curve of the stage channels?

Bye!
A
 

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Posted by Rick Long Jr (Member # 541) on 09-24-2003, 08:07 PM:
 
As far as Dolby goes, 82 db is correct for all processors except the CP 65, which has them at 85 db each and 88 db summed. (due to the cat 441 card). If set to 82, the surrounds become practically inaudible.
 

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Posted by Martin Brooks (Member # 1269) on 09-25-2003, 08:47 PM:
 
In most NYC theaters I attend, I never think I'm perceiving the surrounds. I always think they're set too low. Now sometimes, the end-credit music is mixed only to the front and then I'll hear the difference.

There's a local theater near me in which I saw American Splendor. It's a relatively small theater and there I heard the surrounds quite clearly.

When I've been on the left coast (which hasn't been for some time), I've always felt that the surround levels were higher and sounded better.
 

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Posted by Matt Zeiner (Member # 1914) on 09-26-2003, 09:06 AM:
 
Hey folks - new guy chiming in... for what its worth, I approach the surround array as a near-field system and the screen speakers as a mid/far field system - totally separate. As such, I generally treat each differently. I will apply the X-curve to the screen channels as room reflections (or lack thereof at certain frequencies) will color the sound. The listener perceives predominantly direct sound from the surrounds and as such, I tend to leave them flat - 82 - 82.5 DBc works fine as long as you don't go rolling off the high end...
 

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Posted by Manny Knowles (Member # 1171) on 09-26-2003, 09:14 AM:
 
Hi Matt. Welcome!

You're a controversial fella, aren't you?
 

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Posted by Matt Zeiner (Member # 1914) on 09-26-2003, 09:20 AM:
 
Yeah, maybe... doesn't it kinda make sense, though?
 

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Posted by Antonio Marcheselli (Member # 373) on 09-26-2003, 12:52 PM:
 
I know someone that set surrounds flat. Surrounds are brighter and more... funny but they're not balanced with front channels, IMHO.

However my thought is: if at 85dB you can hear sounds that at 82dB you cannot hear... How can the mixer put this sound if it shouldn't be heard?

Bye
A
 

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Posted by Matt Zeiner (Member # 1914) on 09-26-2003, 01:04 PM:
 

quote:

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I know someone that set surrounds flat. Surrounds are brighter and more...

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I think the word you are looking for after your periods is "present." the ear is much better at discriminating sounds above 2k than it is at 200hz. This is why I beleive it is appropriate to set them flat - it seems to me that if you roll off the surrounds above 2k per the x-curve, you are actually not compensating for an acoustical coloration because the ear is latching on to more of the direct sound than the reflections, and as such, you are causing the perceived sound from the surrounds to be predominantly midrange-heavy. In order to make them more clear and distinct to the listener, one would have to set them to a higher average SPL than the spec demands - hence the reason that most techs find the need to boost surround levels above 82 DBc. IMHO, of course.
 

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Posted by Alan Haigh (Member # 1781) on 09-26-2003, 03:21 PM:
 
I think Antonio has hinted at the key to this one, and it applies equally to high end hi-fi.

Should a playback system be set to reproduce the master tape as accurately as possible, or should it be "tuned" to personal taste?

For myself, I'm with the former option. So surrounds at 82, with the curve, just like in the dubbing theatre (also level on "7"!). This is what you are matching. Maybe the mixer wanted the surrounds to be unobtrusive, to "fill" the stereo image. You can't really hear them, but it would sound worse without them. Or perhaps they are only really audible at reference level. If you deviate from the curve or other settings, it must be for size of room/ acoustical factors (see other thread) and not for personal taste. Mind you, having said all that, the audience chooses to pay your wages (by choosing your cinema), not the director. But surely if you set the surrounds loud, then eventially there will come a film with REALLY loud surrounds...
 

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Posted by Matt Zeiner (Member # 1914) on 09-26-2003, 03:51 PM:
 

quote:

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If you deviate from the curve or other settings, it must be for size of room/ acoustical factors

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quote:

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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!

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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.
 

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Posted by Alan Haigh (Member # 1781) on 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.
 

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Posted by Michael Schaffer (Member # 1204) on 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.
 

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Posted by Antonio Marcheselli (Member # 373) on 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
 

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Posted by Manny Knowles (Member # 1171) on 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 ]
 

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Posted by Christos Mitsakis (Member # 143) on 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.
 

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Posted by Gordon McLeod (Member # 33) on 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
 

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Posted by Manny Knowles (Member # 1171) on 09-27-2003, 04:22 PM:
 

quote:

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All that said it often worked out that 87db on the surrounds was about the same thing for optical

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What exactly are you saying here? Do you set surrounds for 87db? Are you referring to optical or digital?
 

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Posted by Gordon McLeod (Member # 33) on 09-27-2003, 04:32 PM:
 
The optical surround when a steady out of phase Pinknoise was injected was about 87dbc
 

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Posted by Manny Knowles (Member # 1171) on 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.
 

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Posted by Gordon McLeod (Member # 33) on 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
 

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Posted by Manny Knowles (Member # 1171) on 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.
 

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Posted by Gordon McLeod (Member # 33) on 09-27-2003, 07:02 PM:
 
Read the CP50 Cp100 and especially the CP200 manual
 

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Posted by Manny Knowles (Member # 1171) on 09-27-2003, 07:36 PM:
 
Well, well, well...

Here it is in my CP50 manual!

Thanks for pointing me to it, Gord.
 

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Posted by Brad Allen (Member # 470) on 09-12-2004, 02:31 PM:
 
Ok, I've read thru numerous post's, but my dense brain is still confused on the proper level for split surrounds.

Should each "channel" of surround be set separately for 83.5db? (Brad's favorite level )

Or should the left and right surround channel be set as a combined total to 83.5db?

Processor is a Cp-45 with the split surround option installed.

As you know, during setup this processor puts out a summed pink noise to both surround channels. If I set it by this method, the surrounds are only audible at rare instances during a film.

So, should I be disconnecting one channel of surround at a time, and setting them individually to 83.5db?

Please explain to a confused old dude!

Thank you in advance!
 

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Posted by Brad Miller (Member # 2) on 09-12-2004, 02:41 PM:
 
No, no, no. I did not say 83.5db Sheeesch! Check page 1.
 

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Posted by Steve Guttag (Member # 268) on 09-12-2004, 03:05 PM:
 
I have found that surround density and position tends to affect the need for louder surrounds for a perceived level.

We have one theatre that had their surround array designed by a "legend" and if set to anything less than 85dB a side you might as well turn them off. They are about 20-feet in the air.

Now with a denser coverage (read more speakers) I find that 82/side does just fine...as the coverage goes down (read fewer speakers) then how they sound will vary greatly on room acoustics and where you are sitting.

My favorite is when a studio will tell me to raise the surround level by 2dB or so when tuning up for a screening....all I can think is...."couldn't you've done that when mixing the darn thing?"

Steve
 

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Posted by Brad Allen (Member # 470) on 09-12-2004, 03:37 PM:
 
I was joshing with you Brad.

So, do I understand right that I should turn one channel of surround OFF, while setting the level for the other channel at approx 82db+/-?
Then do the same for the other channel?
Sorry for being so dense.
Thanks!
 

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Posted by Gordon McLeod (Member # 33) on 09-12-2004, 05:58 PM:
 
Yes do each surround channel individually then turn them both on and it whould be 85 then
 

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Posted by Brian Guckian (Member # 1678) on 09-13-2004, 08:05 PM:
 
I agree with Mr. Guttag - correct layout and positioning of the surround speaker array is essential to achieve the proper summed 85dB level.

I once worked in a theatre where at the install we were told to fix the surrounds (JBL 8330) "straight to the wall". I was innocent then and knew nothing of angled brackets, etc. Needless to say the aiming was off (although not by much) and it was always a struggle to get perfect results. The theatre wouldn't buy the brackets either.

I personally think that though there is some room for personal taste in the setup, always the film director / sound re-recording mixer's intentions should be honoured, and hence the standards should be followed. AND the surrounds should not be noticeable as such - in the really great theatres you simply feel immersed in a spacious, balanced sound field. It goes back to having a really good room design, something that comes up time and again in this forum.

WHY are theatres so often so badly designed? Is it really that hard to get it right? THX are there to help the theatre owner do just that, yet are often dismissed as a "gimmick".

BTW thanks Rick Long for pointing out the level difference in the CP65 because of the 441 card
 

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Posted by Brad Allen (Member # 470) on 09-14-2004, 09:08 PM:
 
Thanks all for the replies. I also have 8330's, with brackets, they are installed as per JBL's guidelines. Thanks again.
 

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Posted by Frank Angel (Member # 248) on 09-17-2004, 04:27 AM:
 
Years ago when THX was first coming on the scene, I read somewhere, most probably in an SMPTE article or a white paper at one of the conventions, that THX's first preference for split surrounds was with a point-of-source configuration -- single, albeit hefty, speaker systems positioned in rear corners of the room. Multiple, smaller side speakers were THX's second choice for the surround source. Any one ever hear that? Unfortunately I can neither find any reference to that anywhere, or know of anyone who espouses that configuration. I know I read it because it was based on that concept that I put two JBL double bins with their 90* constant Q horns hanging in each corner of our big theatre, about 20ft from the floor and abandoning the smaller column arrays that were in the traditional "along the wall" configuration. I must say, the corner setup delivered a much greater sense of "surround," with localization coming from behind you rather than from the side of you. And of course with such big mutha bins, there was never any problem getting really deep, vibrate-your-gonads sound from the surround tracks, even with analog.

I also read an article, again, more than likely in one of the white papers that Dolby first submitted to the SMPTE in the very first days of their introduction of stereo optical, that "ceiling surrounds" were an acceptable surround channel configuration. The Brooklyn Museum has that setup, not by design, but by the fact that their PA uses ceiling speakers, elaborately delayed, for their non-film sound system. For film, there was no surrounds at all. I figured, cieling speakers were better than no surround at all, so I hijacked the PA to reproduce the surround channel when we played film. And of course it brought to mind that I recall Dolby saying it's OK. But again, I can't verify where that was ever stated. Anyone ever hear that? Now I am not talking about that recent idea of an overhead channel (for that ear in the top of your head). This goes back to the mid-70s when Dolby first talked about their new system.
 

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Posted by Steve Guttag (Member # 268) on 09-17-2004, 08:10 AM:
 
Frank, I think your memory is playing tricks on you. Ceiling speakers never were regarded as an acceptable surroud channel due to beaming effects resulting from how a ceiling speaker projects. This is not to say that ceiling speakers were not used...but they were never recommended by Dolby or THX and I doubt you will ever be able to find any literature that states otherwise. You may wish to consult our search master, John P.

In Dolby's "Technical Guidelines for Dolby Stereo theatres" circa 1994...on page 20 section 2.3.2 paragraph 2, it states:

"Selection of a suitable type of loudspeaker, thought, demands of assessment of more than just power handling capability. Diffusion is a major requirement of surround channels, meaning that surround signals should never appear to come from a point source. This means that a large number of loudspeakers are always preferable to a few, regardless of power handling."

THX has never, for theatres, allowed a point source system and I doubt you will find any THX certified theatres that have just a pair of surround speakers in the rear. In fact, they tend to go to the extreme with speakers spaced about every 4-6 feet.

For the home, THX has traditionally proclaimed to use dipole speakers mounted on the sides of the room. The dipoles are aimed to point kinda forward and behind to create a diffuse surround field with just two units...however they do not resemble a point source either.

Steve
 

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Posted by Brad Allen (Member # 470) on 09-18-2004, 01:25 PM:
 
Holy Cow! Does everyone really run the fader at 7?
I've adjusted my cp45 to a level of 85db as per instructions.
But when running a film.......say Resident Evil....with the fader at 7, it is simply ear splitting at times. Now I'm not a loud movie prude by any means, but when passages make your ears have that rattle sound, it's too loud. I don't want to be sued by ear bleeding customers. This is when using both DTSXD10 or SR for playback. What DB should a movies level peak at? Is this really what a director intends? The fader set @ 5.5 was still very impressive sound wise and more than adequate.
Yep, I've went back and rechecked all levels. Everything seems to be set where it is suppose to be.
 

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Posted by Frank Angel (Member # 248) on 09-19-2004, 12:14 PM:
 
Brad, seems like yours is a VERY common complaint and has been discussed here before....you might want to do a search to see if it comes up and what the consensus was -- I can't remember exactly. Me, I don't worry about that magic Number Seven. To me, it's all relative with the room playing a BIG role in the perceived loudness, as does the soundtrack mix itself, as does even the age of the audience. That's why they put a fader there and didn't lock it down at a prefixed 85dB level. I guess in theory, there should be no need for a volume control -- just like in theory, there shouldn't be any need for a Framing Knob on the projector as some techies here espouse. But we live in an imperfect world. Forget about the #7. If you aligned your system correctly and it's too loud at that setting, don't fret (everything else being equal -- like clean sound without distortion)....just turn it down. In the end, it's the customers who paid for the tickets, not Ray Dolby (although he sure does get his cut indirectly, eh?). If you want the paying public to come BACK to buy more tickets, then the final issue is that it has to sound good to them, not meet some arbitrary technical benchmark. Of course that is technical heresy, and a techie will pull his hair out and go gray in order to figure out why he's getting sound that is too loud at what the manual says is the "correct" setting, but not to worry about him....that's his job -- it's what make him a techie. You just relax and set it where it makes your audience happy.

And Steve, thanks for the info. But I question the Dolby position circa 1994 -- obviously they did published that, but my recollection is from much earlier with the very first white papers that came out around 1975-76 when they first described the stereo optical system. They very well may have changed that concept down the line, but I do believe they mentioned ceiling configuration as an acceptable, although perhaps not their first choice, way of dealing with the surround channel. Just like in those first descriptions unveiling of the system, the paper said that the matrix they used was the Sansui Vario Matrix chip; after those initial papers, obviously that changed and you never heard them mention Sansui -- after that it was they who invented phase dependent matrixing. And I agree that the problem with ceiling speakers not giving adaquate coverage might be valid in 99% or the cases, but in this particular room, the PA was computer designed so that each speaker's optimum "cone" of coverage overlaps the next with mulitple delay zones so that each seat has uniform coverage. It's main fault is that I can't get them up to 85db without stressing them, so threshold compression keeps them from cracking at the loudest portions of the soundtrack whilst at normal levels the effect is every effective. It's either this or no surround at all, which is the way the installer left it when the museum said, no speakers on the walls (museums are notorious for that kind of "artistic" snobbery).

As for the point source configuration; I won't press that until I can find where I read it, but I know it was published because the system that we set up in the large theatre was based on that recommendation and second by the acoustical engineer firm of no less pedigree than Klepper & Klepper (redesigned Alice Tully Hall at Lincoln Center) installed it. Whether or not that early on (our system was installed in the early 80s) the discussion of point source was preliminary and THX may have subsequently modified or completely revamped its recommendations in favor of multiple sides, I will not dispute. In fact, I will even give you that point source might have been discussed in an SMPTE Journal article as an alternative to side surrounds with THX mentioned and I am linking the two, and I will agree that to that extent my memory may be playing tricks on me, but there is no doubt that there was such a discussion.

In any event, the corner surround have worked exceptionally well in our theatre, easily matching the SPL and characteristics of the screen channels and localizing surround from behind the audience when it needed to be dominant as in a plane fly-by; yet when the mix was intended to be difuse ambience and it was mixed subtily, the corner surrounds presented that effect quite nicely too. It especially became apparent how well corner surrounds recreate rear stereo with digital tracks. When a plane flies from the right side of the screen to BEHIND the audience left, it sounds exactly like that -- like it has flown behind them, rather than vaguely to the left SIDE of them. Localization is in the back.

We also extended the corner surrounds to the back wall with two speaker clusters (six custom boxes each with URIE drivers) directly behind the audience. That insures that the center rows get enough surround to localize it -- again, from BEHIND them and not from the side of them. We will be able to use these center clusters for the EX surround channel, should we ever get the decoding hardware -- although my gut tells me that an extra outboard CAT150 should be able to decode center surround easily enuf.
 

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Posted by Brad Allen (Member # 470) on 09-19-2004, 12:35 PM:
 
Thanks Frank, that makes total sense and what I had finally decided.
 

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Posted by Gordon McLeod (Member # 33) on 09-19-2004, 03:43 PM:
 
In Phillips book desinging the cinema it recomends ceiling mounted surround speakers
 

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Posted by Frank Angel (Member # 248) on 09-20-2004, 03:30 AM:
 
ah-HA!
 

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Posted by Brian Guckian (Member # 1678) on 09-20-2004, 06:40 AM:
 
Great! Now we'll have to revise all the standards!

There's also Tomlinson Holman's 10.2 channel configuration (Search previous posts...)

Brad, re. your comment on the fader level, as Frank mentions there's some really great discussions and info going back over the last few years here. The most common theme is the perceived disjunction between the engineering standards and the actual soundtrack level - but here's nothing wrong with the reference levels! (Stage and surround speakers both).

If anyone follows post-production sound issues, they will see the debate re. "artistic" degrees of loudness - and also...hearing loss among members of the re-recording mixer community through prolonged exposure to such high programme levels.

Dolby's Cat. 767 loudness meter (geddit?) has helped enormously - especially in the trailer / ad area where the problem was getting way out of hand a couple of years back.

(BTW I always recommend fellow Projectionists to visit a Dubbing Theatre...the techs are almost always very friendly and approachable, and delighted that people from exhibition are taking an interest. It's a marvellous way of learning more about the "nuts and bolts" of cinema sound)
 

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