Film-Tech Forum ARCHIVE: CP 650 Too loud to handle at 4.3?!

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Posted by Jason Greek (Member # 3159) on 05-30-2005, 04:48 PM:

Hi everyone,
I've been looking around these forums for some time, and of course, the manuals for our equipment, and it keeps staring me in the face: THE DOLBY CP650 RUNS AT A REFERENCE POINT OF 7.0!!!
The only problem I have with that is, Our large houes can be earsplitting at 4.3, with some prints having to be run as low as 3.5! There can be noticeable sacrifices to surround quality. So, I was just wondering; are there any other adjustments that can be made to fix this, is it supposed to run like this (all theatres in our chain with 650's run around this volume or lower)or is the problem elsewhere?

Posted by Brad Miller (Member # 2) on 05-30-2005, 05:42 PM:

*You have lousy acoustics.
*You have lousy speakers.
*Your tech did a lousy job of B-chaining the CP650.

It's one of the three, or maybe a combination.

Posted by Michael Schaffer (Member # 1204) on 05-30-2005, 06:08 PM:

Or maybe the levels were set properly, but with the trimpots on the amps not all the way up, and then somebody decided to turn them up to "enhance" the sound.
I used to be against setting the trimpots all the way up and lower the channel level in the processor, for noise considerations. But I have changed my mind, mostly because some recent equipment is sufficiently quiet, and yes, I do see now that there is no other way to keep people from playing with the levels.

Posted by Brad Miller (Member # 2) on 05-30-2005, 07:01 PM:

Indeed, Michael's theory is yet another one. To add to it, an amplifier could've died (probably the center) and it was replaced by someone other than the tech with his sound equipment (as such, not being properly calibrated).

At least with the amp gains maxed, a projectionist or manager can change the amp out and be pretty darned close to the level it needs to run at. I however tend to go for other compromises. For example, if I find that after tuning the amps all need to be between 1/2 and 3/4 up, I will set them all to 3/4, then adjust output pots accordingly to keep things "standardized" while still minimizing noise as best as possible. Sometimes I will put a tag on the amps "gain at 9:00" too.

Posted by Jason Greek (Member # 3159) on 05-30-2005, 07:32 PM:

all amps are original. we've only been open for a year and it's always been this way. but i have also noticed that sometimes, and there seems to be no pattern to it, the "diagnostics" section on the monitor shows a "load fault." it doesn't seem to have amy affect, but it does concern us. As well, the head projectionist from another of our theatres, says our centre amp has a few Display LEDs lit up that shouldn't be. our booth was set up in a hurry and some things may have been overlooked, and the sound does seem fine for the most part, but it does concern us a lot! I really don't know how to explain it. I'll get some pictures to help and show you amps are QSC Digital Cinema Amplifiers... That's all i can remember off the top of my head. I'm in tomorrow, I'll get back to you,
and thanks for the suggestions! greatly appreciated, and I'll mail a pic of me tomorrow when i post the pics of the amps [Smile]

Posted by Michael Schaffer (Member # 1204) on 05-30-2005, 07:40 PM:

Those LEDs may be the clipping indicators, if they are on a lot, it certainly may be the case that the output level is set too high on the processor. There is also a level setting in the DCM which may not have been configured properly.
The Load Fault indicator tells you when an amp has no output compared to the input, or when the amp output is open or shorted. If you have these lights come on intermittently, you either have an intermittent problem OR maybe the data cables which go from the DMC to the amps are not plugged in properly.

Posted by Maddison Lake (Member # 2876) on 05-30-2005, 07:43 PM:

I might be wrong, but using the CP650 you should be running the amps wide open and then B-Chain the whole thing. Amps (expecially new ones) need to be ran wide open for digital use. Analog is a different story.

-ML

Posted by Dave Macaulay (Member # 813) on 05-30-2005, 09:51 PM:

Maddison: There is no "digital" reason to run the amps wide open, and there are very good reasons to set them to a lower level. Those reasons have been dealt with in other threads but basically for the lowest noise all system components should operate at their optimum signal level. Setting the amps wide open constrains the processor output level adjustment.
We're saying here that the problem may be that the installer set up the system properly with the amps at a middle gain setting, but somebody has turned them up all the way and thus the CP650 must be run way below the reference 7 level.
Also, the risk of this happening may make setting the amps wide open a good idea even if that doesn't produce the system's optimum gain structure.
More likely in a rushed install: nobody ever did a B chain setup.

Posted by Paer Hoegberg (Member # 3133) on 05-31-2005, 12:02 AM:

Exactly the same at our setups, Normal level is 4.0 (somtimes lower).
I tried to go up a bit on Star Wars III, but 4.6 seems to be the absolut limit the audience can cope with.

Our Cimena opened February 2004, with CP650 on 3 screns and CP500 on 1 screen, The same levels on all four screens. The CP650 are new, the CP500 are 5-6 Years old. New speakers (KCS) and new amps (Lab).

[ 06-01-2005, 05:08 PM: Message edited by: Paer Hoegberg ]

Posted by Carl Martin (Member # 1146) on 05-31-2005, 02:49 AM:

our normal levels are in the 5-5.5 range. this is fine on our cp65 but on our two cp45's, if we play something in mono we have to crank it to 7. would i be right in assuming that if 7 was the normal level for the other formats then it would still be correct for mono? (i'm told there is no mono level adjustment on the cp45.)

yes, it's pretty rare that we see something in mono these days, but a nearby theater has a cp45 and has a regular midnight series. they have to ride the volume as sound formats change and the results are less than satisfactory.

carl

Posted by Michael Schaffer (Member # 1204) on 05-31-2005, 03:06 AM:

quote: Paer Hoegberg
New speakers (KFC)

KFC now make speakers? Do they come with 2 sides?

There is no real standard for mono, one of the reasons Dolby left about 10dB (7-10) headroom on the fader when they introduced their system in the 70s. There may have been a standard for Academy Mono that I am not aware of, but even then there was such a variety of mono formats over the decades that you can not say this or that is the correct level.

Posted by Scott Norwood (Member # 30) on 05-31-2005, 07:27 AM:

Interestingly, the CP65 manual says to set the mono trim to 79dB (not 85), while at least one other Dolby manual (CP50, I think) says to set mono to 85dB.

If you set the CP65 mono trim to 85dB (which I did by mistake once), the sound is way too loud with mono prints (a fader setting of about 5.5-6 is about right for those), though the sound will drop if you switch back and forth between A/SR and mono with an SR print. Thus, 79dB is probably about right for the CP65 mono trim.

Also, if you reset the levels at any time, be sure to reset the bypass levels as well; otherwise, you may have a big surprise (very low sound or blown speakers/eardrums) if something fails and you have to run in bypass.

Posted by Jason Greek (Member # 3159) on 05-31-2005, 08:38 AM:

as far as the "load fault" goes, I noticed Star wars is registering one every show.

quote: Michael Schaffer
The Load Fault indicator tells you when an amp has no output compared to the input, or when the amp output is open or shorted. If you have these lights come on intermittently, you either have an intermittent problem OR maybe the data cables which go from the DMC to the amps are not plugged in properly.

Star wars was really the main reason I started this whole thing up; we recieved a notice, all you guy/gals may have too, that told us not to run ep III below 7.0, so we have been, but we've been getting complaints. we have managed to sneek it down to about 5.5-6 without management noticing, but like i said, that house usually runs at about 4.3

Posted by Steve Guttag (Member # 268) on 05-31-2005, 11:45 AM:

Note, the Load Fault only works properly if the installer sets up the loads properly in the software (notes the impedance of the speakers and how may are series and parallel.

Posted by Brad Miller (Member # 2) on 05-31-2005, 05:07 PM:

Ignore those notices in the cans. It's absurd to expect that every sound system is calibrated properly. As it is, if you are making your customer's ears bleed and inducing headaches, you are distracting from their enjoyment of the movie.

(We are running every show of Episode III at 8.)

Posted by Monte L Fullmer (Member # 2797) on 06-01-2005, 02:18 AM:

..true, you have to adjust the sound level for your customers-which should be the first priority of any theatre business.

True, running SW:Ep-III at 8.0 sounds GREAT, but...the majority of the folks likes to keep their brains from being rattled around in the noggins, and not having bleeding, ruptured eardrums from too much volume of sound when they exit the theatre. .. and they'll remember this the next time they think of going to that certain theatre.

It's amazing how much those notices in the cans are ignored..

..but a CP-650 being too loud a 4.3, is definitely a "B" chain problem.

-Monte

Posted by Brad Miller (Member # 2) on 06-01-2005, 02:41 AM:

Nope Monte...not ONE SINGLE COMPLAINT. We have received some "turn it up more" requests though. Remember, no two sound systems will sound the same. Something at 4 on one system will make someone's ears bleed, but may be able to be played at 7 on another without being uncomfortable to listen to. Most of this is due to calibration, as a shitty EQ job will be painful to listen to at even a moderate volume.

I have also found since I got the D2 analyzer that I end up playing movies at about 8 on the fader. As such I've been setting the reference point of 7 = 88db to compensate.

Posted by Monte L Fullmer (Member # 2797) on 06-01-2005, 04:29 AM:

Whoops, sorry Brad. I didn't mean your operations at your theatre. For you mentioned that 8.0 level was being used, which makes the audience LOVING it being that loud.

Just that some theatres planning on running 8.0 better plan on getting a bunch of complaints from the patrons-especially the theatres that are used in showing "quiet" movies.

Shoot, when I ran EP-I back in '99 in a 400 seat house using CP-500's, I had that thing cranked wide open ...10.0 ... and they wanted MORE...and my QSC's were wide open as well!!! .. as they wanted from you with EP-III.

-Monte

Posted by Michael Schaffer (Member # 1204) on 06-01-2005, 05:06 AM:

quote: Brad Miller
I have also found since I got the D2 analyzer that I end up playing movies at about 8 on the fader. As such I've been setting the reference point of 7 = 88db to compensate.

That is very interesting. Apparently the R2 was offset by about 3dB in the other direction, a lot of THX certified installations I found about 3dB too loud when measuring the SPL with other analyzers (such as the IE-30A). Although in our most recent installation, a friend of mine came in with his D2 and tuned the rooms, looking at the levels later with my IE-33, I found the levels to be very close.
Of course, with Brad being located in Texas, things are different anyway...TX law allows the technician to shoot any member of the audience who complains about loudness [Big Grin]

More seriously, I also found that with the mix on "Epsidoe III", reference level (whatever that means in real life), worked very nicely. It really comes down to how the movie is mixed and how the playback systems handle it. With our new all-QSC playback chain (DCM-1, DCA series amps, and SC-423 3-way speakers), I found the soundtrack on that movie engulfing and pleasant at the same time.

Posted by Jason Greek (Member # 3159) on 06-01-2005, 07:18 AM:

quote: Brad Miller
Ignore those notices in the cans...

Now that the theatre isn't filling up every night, we've managed to talk the managers into turning it down to 5-5.5. The notice that came with that lovely star wars "box" was just stuck on it, so our managers saw it right away and made us obey it faithfully as if our lives depended on it. I hated runing it that loud.you could hear it down a hallway, around a corner, down another hallway, through a soundproof door, and then 2 theatres down the hall! I don't know why the people in the next theatre didn't complain, they must have heard it...

[edit June 1st, 9:33pm, atlantic standard time]
AHA! I found them! How stupid of me!! all along I had suspicion the problem was with the amps... you guys confirmed it for me! and I finally found the manuals for the amps! so the gains are cleverly hidden by a nondiscreet panel! and they are all cranked up! I'm soooooooo DENSE! So now all I need to know is exactly how do you folks prefer to go about setting these to a comfortable level? would I be right in guessing running a B-Chain and doing it by personal preference? that sounds kind of rough around the edges to me...

[ 06-01-2005, 07:36 PM: Message edited by: Jason Greek ]

Posted by Brad Miller (Member # 2) on 06-01-2005, 09:08 PM:

Jason, not trying to be rude, but clearly you are not trained in what you are jacking around with. At this point you need to call your technician in and have him fix the system properly. Until he can get there, you should leave things alone and continue to run at 4 if needed. You stand a greater chance of damaging your sound system if you start tinkering with the level of knowledge that you have at this point.

For the sake of your company's equipment (and the future of your job), I am closing this thread.