Film-Tech Forum ARCHIVE: Sound Levels on a Ultra Stereo/DTS system

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Topic: Sound Levels on a Ultra Stereo/DTS system

Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 06-05-2001 06:31 PM

I'm having some trouble setting the levels on an older Ultra Stereo processor (the model number escapes me at the moment). I posted a problem with the DTS unit a few months ago and finally got around to swaping the unit out with another. While testing i went in front of the screen and noticed no sound coming from the left channel... great. Well, one of the managers and I swaped out the left channel card from a spare. We are trying to set the correct sound levels but i think we don't have the right equipment to do so. What all do you need? An spl meter? which sound loop should you use? Do i need the DTS setup disk? While we were messing around with the sound levels we noticed that there is no right surround. I suspect that since this is unit was upgraded to DTS sime time ago the installers didn't feel the need to seperate the mono surround and just fed the left surround to all surround speakers. Its very strange because we have two large 7500 BGW two channel amps that are hooked to left, right, center, and surround. There is a smaller two channel amp in which only one channel is used thats hooked to the dual 18 inch subs. If memory serves me correctly DTS does have left and right suround, right? Also, wouldn't it make more sense to run the sub from the larger amp and use the smaller two channel amp to drive the surrounds? Right now it doesn't sound too bad, but i would like to set the levels correctly. Any help would be greatly appreciated. Thanks.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 06-05-2001 06:41 PM

1st you need a pink noise generator card for the UltraStereo processor
2 you need a RTA since you swapped an eq card it has to be eq for the room + the sub level has to be set with a RTA not a spl meter.
3 DTS is normally split surrounds but was the processor upgraded for that? You have to configure the DTS to match the processor config
4 DTS setup disk

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Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 06-05-2001 06:58 PM

Hmm, i guess its a bit more involved then I thought. What is an "RTA"? As for the EQ settings i could just copy them from the old card. What do you think it would cost for a pink noise generator and an RTA?

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 06-05-2001 07:10 PM

I haven't had to price the p/n cards in awhile. Something like $400 if memory serves (which it probably doesn't). I doubt you'll find a really good RTA for under $1000.

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Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 06-05-2001 07:24 PM

It would be nice if we had a real tech with the right equipment. I guess we will have to go through our supply co. Its too bad that most of this equipment requires professionally priced gadgets to set them properly. You'd think that software could be written to run on a laptop to produce the same results. Our adjustments are going to have to do for now since we don't have that kind of money. At least it sounds alot better now. Thanks.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 06-05-2001 07:31 PM

There are good RTAs that can run off of a laptop. Only problem...you'll still pay about a thousand bucks for it!

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Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!

Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999

posted 06-05-2001 07:49 PM

RTA=Real Time Analyzer (also known as a 'spectrum analyzer')

The Holy Grail of RTA's for cinema use would be the Lucasfilm THX R2 unit. Other hardware RTA's will set you back close to $1000 minimum.

I use a software-based RTA called Spectra Plus, that has given me great results, but a word of caution: the sound hardware in your laptop (or desktop machine if you decide to go that route) must be QUIET. I have a laptop right now that is useless to me as an RTA system because its sound hardware is VERY noisy However On another machine its very quiet...

You can get a 30 day trialware version of Spectra Plus at http://spectraplus.com . It costs $199 to register the basic mono RTA functions, as for cinema use you really don;t need all the other bells and whistles that the software offers (plus they cost more to register).

You will also need a USL Pink noise generator, the model number is JPN-10, its a little pink colored slide-in box with switches on the front panel to select the channel(s) to send pink noise to.

Most importantly, to get it equalized properly, you will need a precision microphone setup, USL sells a nice microphone multiplexer kit which includes 4 Countryman mikes (the same type that THX and Dolby use) and the multiplexer box model MMP-10

For further info on the Ultra-Stereo alignment products visit http://uslinc.com .

For setting the sound pressure levels, you can use the RTA, or a handheld SPL meter set for C weighting and slow response.

Re: DTS and Split Surrounds- Your USL processor may not have split surround capability, that is why the DTS was set up for left surround output only. You will need to upgrade to a split-surround card, if it is possible (JS-200/1000 series only, IIRC) and you will have to set up the DTS for split-surround operation by changing DIP switches (or jumpers on some very old DTS units) inside the DTS unit. Then you will need the 6-channel DTS setup disc (its self-starting and does not require timecode to run) to set the DTS sound pressure levels.

Good Luck!

Aaron

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Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 06-06-2001 04:11 AM

Okay, I probably don't understand the whole process but here's something I thought of. How about i use the software RTA, take my laptop, plop it in the center of the auditorium with a mic. Run upstairs, throw in the DTS setupdisk. Run it through and match the levels which DTS reccomends on their website (what is it 85 Db for left, center, and right?). Yeah so that wouldn't be doing it properly... id say that wouldn't be bad for doing it for free. I just want to get the channels at the correct volume in respect to one another. Anyone think this will work?

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 06-06-2001 04:22 AM

You cannot just grab any old mic and be able to use it with an RTA for proper results. However, if all you are trying to do is balance the levels and not correct the EQ (which is now off since the cards were swapped), you can do it with a decent degree of accuracy purely on using an SPL meter and the dts pink noise disc. It leaves out a lot of various factors that should be addressed, but it would probably be better than nothing if your current sound is audibly off balance.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 06-06-2001 10:16 AM

I would recomend calling in your service engineer as that is what they do for a living and they have the correct tools and instruments to do the job right
Do it wrong and you will probably blow a driver or amp or just have bad sound

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Karen Hultgren
Master Film Handler

Posts: 492
From: Agoura Hills, CA, USA
Registered: Mar 2000

posted 06-07-2001 01:52 PM

Hi Tom,

If you need a DTS setup disc, please let me know. Please send me an email if you'd like one. (You will need to get a SPL meter, Radio Shack has them for around $45). The disc is to be used to check DTS only, it is not meant to set levels or adjust EQ on a Cinema Processor.

To set "B" chain CP levels and EQ, you should get a pink noise module. Component Engineering makes a nice one for Dolby CPs and UltraStereo makes one for their CPs. Your service tech should have these on-hand and should be called to check out the problem.

Note: For EQ, you also need a RTA and calibrated mics, and they can be costly.

Karen at DTS
khultgren@dtsonline.com

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Karen Hultgren
Master Film Handler

Posts: 492
From: Agoura Hills, CA, USA
Registered: Mar 2000

posted 06-07-2001 02:00 PM

Oh, and I forgot to mention, you need to be trained on how to perform an EQ adjustment. You may want to consider taking a course from THX. They offer classes several times a year and cost around $1000.00. It's well worth getting certified if you plan on expanding your career in sound playback.

Karen at DTS

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 06-07-2001 06:03 PM

Karen even with the setup disk and spl meter he still needs a rta to set the sub level.
THe use of a SPL meters on low band is not accurate because of the weighting.
The level must be set with band filtering that most cheap spl meters can't do

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Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 06-09-2001 02:25 AM

Thanks to everyone for their help. I found out the other night that the center EQ card is going out also. I switched it with the left so now if it goes in and out its not as noticable. When we get a replacement card i'll have to recommend that our supplier (tech?) comes in and does the proper adjustments. I just hope we don't have any more trouble with this processor. I'm willing to bet this all started when its power supply went bad a year or so ago.

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