Film-Tech Forum ARCHIVE: non-sync audio bleeding through into feature

This is topic non-sync audio bleeding through into feature in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Steven Stroud (Member # 6775) on 02-21-2012, 01:50 AM:

I am but a humble booth monkey looking for some input on a situation.

I have several auditoriums with older Smart Mod IIB & IIIB processors with the high end of the non-sync audio bleeding though into the feature audio.

None of the houses with the newer processors have this problem.

Our booth tech has, at this point, advised us to turn the preamp trim pots on the DA 226 processor that feeds the individual houses down to their lowest levels. Meanwhile he says that we can turn the individual house non-sync trim pots up a little more to compensate.

If anyone could just point me in the general direction of a fix for this situation, I would be most appreciative.

I don't like that fact that my guests who are there to watch Hugo have to hear the remix of Beauty and the Beast stepping all over the dialogue during the quiet portions...

Posted by Monte L Fullmer (Member # 2797) on 02-21-2012, 02:56 AM:

maybe put a switch on the N/S feed, which comes from the source, so you can physically disconnect the feed from going into the processor...as an easy and cheap fix for now.

Seen a few of those installations mods in older booths from time to time....

Posted by Bernie Anderson Jr (Member # 410) on 02-21-2012, 08:21 AM:

is this both in digital and analog playback or just analog?

Posted by Manny Knowles (Member # 1171) on 02-21-2012, 09:20 AM:

quote: Steven Stroud
Our booth tech has, at this point, advised us to turn the preamp trim pots on the DA 226 processor that feeds the individual houses down to their lowest levels. Meanwhile he says that we can turn the individual house non-sync trim pots up a little more to compensate.

Have you tried this yet?

Posted by David Zylstra (Member # 4230) on 02-21-2012, 09:26 AM:

I had theatres with Smart Mod IV processors (with a Smart DA for non-sync) and the non-sync on those would bleed through as well - once we lowered the gain on the DA and balanced the non-sync it was fine.

Your tech is correct that the gain on the DA226 should be turned down - that was our exact solution 20 years ago.

Posted by Louis Bornwasser (Member # 3063) on 02-21-2012, 06:14 PM:

Don't turn it down "all the way."

btw: isn't this HIS job?? Louis

Posted by Kenneth Wuepper (Member # 1174) on 02-21-2012, 07:39 PM:

Too many Tweakers can lead to Twadgedy!
Courtesy of Elmer F

Posted by John Wilson (Member # 269) on 02-22-2012, 01:01 AM:

I'm hunting wabbits...

Posted by Manny Knowles (Member # 1171) on 02-22-2012, 01:34 AM:

Finally, this thread has real value.

Posted by Steven Stroud (Member # 6775) on 02-22-2012, 04:04 AM:

Thanks, Manny.

Posted by Manny Knowles (Member # 1171) on 02-22-2012, 09:33 AM:

(I was being sarcastic.)

So...? Did you try adjusting your DA output trims (down) and your Non-Sync volume controls (up)? How'd it go?

As I recall the DA-226 has trims on its input - mine were about 3/4 of max.

Next - each output has individual trims for left/right. Turn them down to 1/2 max or perhaps slightly lower.

The trick is keeping the left/right output levels balanced so the music doesn't end up lopsided. To help with this, I burned a disc with a steady 1kHz tone and made it repeat in the CD player so I could take my time and measure all of the outputs (with an AC volt meter) and tweak them to make sure they were all equal.

Finally, play your normal music CD and go to each cinema and use the Non-Sync trimpot in the processor to adjust the playback level for each cinema. (1) Make sure your main cinema volume controls are in their usual position before you adjust the Non-Sync volume. (2) It will be easier if 2 people with walkie-talkies tackled this part - one in the auditorium evaluating the music level, and one in the booth making the adjustments.

Test your work - switch to a film format (like Stereo or SR) with no film playing - do you still hear the music?

Posted by Dominic Espinosa (Member # 2122) on 02-22-2012, 01:39 PM:

This is pseudo related being a nonsync question so please forgive me for butting in.

Do you guys set your ns volume to a specific level in db?

I personally like to have everything that is required to be adjusted for each house to be identical. Most techs I've noticed whether admitting so or not don't seem to have much thought toward nonsync as long as its playing and not overly loud or overly quiet. Some major chain techs also seem to think it should be as loud as the feature too apparently.
But I digress.

Seems to me Id burn something like pink noise and set it just like the film sound but at a lower volume. Is this excessive?

Posted by Manny Knowles (Member # 1171) on 02-22-2012, 02:02 PM:

I used to do that when I worked in multiplexes. I'd get the DA set up and then play some music and let the manager (or owner) tell me what level they liked.

Next, I'd switch to a CD with a pink noise track to quantify that level, and use that SPL value as my guide for setting level on the remaining screens (using pink noise).

However, if you have significant variation in house sizes, you'll find it necessary to increase SPL in the larger houses and decrease SPL in the smaller ones. But I think it's good to have a known reference point.

Posted by Dominic Espinosa (Member # 2122) on 02-22-2012, 11:50 PM:

Sweet.
Thanks, Manny!

Posted by Steven Stroud (Member # 6775) on 02-23-2012, 02:20 AM:

No worries, Manny. I have a sense of humor.

The problem was most evident on the house with the Mod IIB processor while it was in surround. It was significantly less obtrusive when switched to stereo. The Mod IIIB houses weren't as noticeable, but it's still too obtrusive for my personal tastes.

We did as our tech instructed and lowered the preamp trimpots, and it's certainly helped, but I can still hear the disturbance.

The entire pre-show setup is run by a third party who send their own techs out on regular visits. They insist that the audio levels on the pre-shows be set to absurd levels... which we always end up decreasing after the old people complain about it being too loud. It occurs to me that we are about due for another visit, so I'll bring this whole ordeal up with them. Hopefully they will be able to get this ironed out once and for all... or at least until our landlord agrees to convert us to digital.

Posted by Manny Knowles (Member # 1171) on 02-23-2012, 11:12 AM:

Maybe you want to verify with the incoming techs that they are setting playback levels at the processors, not the DA.

Posted by David Zylstra (Member # 4230) on 02-23-2012, 01:52 PM:

what Manny said . . . . . as I recall more bits and peices about the Smart equipment I worked with years ago - in our case there were 3 adjustments to tweak: 1) L/R output of the DA, 2) L/R input on the Smart, and 3) the overall non-sync volume. Note that I do not recall if the IIB and IIIB have the same input controls as the IV I worked with. Our bleed through "fix" was to find the happy medium (AKA no bleeding) between the output level from the DA and the input level at the Smart, then the overall non-sync volume knob could be used to adjust the sound level without much worry about bleed through.

Posted by Manny Knowles (Member # 1171) on 02-23-2012, 05:41 PM:

Yes, I think David is correct. (It's been over 10 years since I worked with the IIB, so it's taking a while to come back to me also.)

Anyway...

Look on the Output/Music card for a pair of "Music L/R" trimpots -- As I recall, having THOSE set too high is what causes the crosstalk.

Since this is affecting your shows now, why not try this:

With no movie playing...Put your system into "surround" mode (since that's where you get the most crosstalk) and leave the main fader where you normally have it for movie sound.

(Make sure that the music is playing.)

Turn down both L/R Music levels using the trims on the Output/Music card. Try to make equal adjustments to maintain L/R balance. Stop when the crosstalk is gone.

Switch to your Non-Sync format.

Trim the overall music level (up) so that you're back to the desired NS level. (The overall trim is a little pot hiding next to the main fader. It gets hidden when the front cover is in place.)

This should resolve the issue well enough for the time-being. Your tech can fine-tune things later.