Film-Tech Forum ARCHIVE: DTS-6 Player - Do I need a new board?

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Posted by Manny Knowles (Member # 1171) on 05-18-2002, 12:33 PM:

I have a DTS-6 player and it seems to be working just fine except that I can't tweak my subwoofer levels with great accuracy.

I can go from 81dB to 84dB, but nothing in between. The other player like this one gave me a smooth increase/decrease in all levels.

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~Manny.

Now...where was I ?
Leonard Shelby, MEMENTO.

Posted by Steve Guttag (Member # 268) on 05-18-2002, 12:45 PM:

That all depends...are you using an SPL meter? If so, you don't know what you are reading...if you are using an analyzer, that might be something different.

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"Old projectionists never die, they just changeover!"

Posted by Brad Miller (Member # 2) on 05-18-2002, 12:54 PM:

Just a quick question, but does the other dts player when used in this auditorium have the same problem? I'm wondering if it is something simple such as the digital sub input on your processor is at one of it's extremes, making the output pot of the dts overly sensitive. What kind of processor is it? Please provide as much info as you can.

Posted by Manny Knowles (Member # 1171) on 05-18-2002, 12:57 PM:

Sorry, Brad. I should've stated I'm going through a Dolby CP-45 processor. Amplifier gain is at maximum, I'll have to verify the where the pot is for the sub output (on the CP-45) before saying whether it is/isn't at an extreme.

Clarification: The other DTS-6 unit in this theatre is installed in a different auditorium.

Steve: I was indeed trying to check the level with an SPL meter to do a quick check of the levels. Curious as to why it doesn't work..?

I have an RTA on order, but it has not arrived from Miami yet, so I guess I'll just have to wait until then.

This player was installed about two years ago and as far as I can tell (just by asking around) they haven't used it. As it turns out, this system needs a new timecode reader. It's been turned on everyday for the past two years or so, even though wasn't being used. I guess they killed the LED?

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~Manny.

Now...where was I ?
Leonard Shelby, MEMENTO.

Posted by Antonio Marcheselli (Member # 373) on 05-18-2002, 02:05 PM:

manny,

Did you try a dry contact cleaner on the pot? I had to clean my offset switch and now they work perfectly.

Bye
Antonio

Posted by Gordon McLeod (Member # 33) on 05-18-2002, 04:32 PM:

I use the DTS breakout board and the new DTS setup disk with track two cntaining tone just dial up 300mv on each and you are done

Posted by Steve Guttag (Member # 268) on 05-19-2002, 08:12 PM:

Why it wont work using an SPL meter for subwoofer....

For SPL to have any meaning, one has to know over what range the frequency is being measured. That is why there are weightings and specified range. It works for setting the stage channels since they are wide band, we limit the SPL meter's response to the "C" weighting and we have a very uniform criteria for setting frequencies over the operating range (the ISO 2969 curve). The wild card in this is the typical inaccurate Radio Shack meter that most seem to use. The microphone in it is notoriously not flat and different readings can be had based on how it is aimed, and just which frequencies it thinks deserve emphasis.

But with a subwoofer, we have an inherently band limited frequency range. Particularly for DTS where the subwoofer rolls in at 80 Hz. With bass frequencies, you often can get resonances that can exaggerate particular frequences in a non linear fashion. So say you have a resonance situation, turning up the sub level a small amount might have a big affect on one frequency and show up on the SPL meter but it isn't representitive of the whole subwoofer spectrum.

Steve

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"Old projectionists never die, they just changeover!"

Posted by Dave Williams (Member # 299) on 05-19-2002, 08:14 PM:

I had this same problem with a DTS 6-D unit. It would either sit at full or on minimum. This was the adjustment on the DTS unit outputs, and not the processor outputs.

If you are having this same problem, then it is the pot for the subwoofer adjustment. Cleaning the pot did nothing, so in our case either the pot or the entire board was bad. I didn't stick around long enough to find out.

Dave

Posted by Steve Guttag (Member # 268) on 05-19-2002, 10:10 PM:

To check for a bad pot, do as Gordon says...use either the REV "C" or the current (DS3?) test disc and play the constant 30Hz tone and measure the output...if the pot (or possibly other bad part) causes the signal to vary greatly then you will know.

Steve

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"Old projectionists never die, they just changeover!"

Posted by Karen Hultgren (Member # 395) on 05-20-2002, 01:27 PM:

Manny,

To calibrate the DTS subwoofer, you should use the DS3 setup and set all levels for 300mV RMS using tone. Then, use the RTA to set CP EQ.

If you have only a SPL meter, use a DTS setup disc and play subwoofer pink noise. When that plays, turn off the surround amplifiers and adjust the DTS subwoofer level trimpot until you get about 88dB SPL in the audirorium (subwoofer speaker). That will get you by until you can adjust properly using tone and the RTA / CP.

Karen at DTS
khultgren@dtsonline.com

Posted by Manny Knowles (Member # 1171) on 05-20-2002, 02:01 PM:

Okay, how exactly do I take this measurement?

I'm asking because I'm getting like 0mV using a multimeter, even though I'm hearing the tone nice and loud. Is that the wrong tool for this?

------------------

~Manny.

Now...where was I ?
Leonard Shelby, MEMENTO.

Posted by Antonio Marcheselli (Member # 373) on 05-20-2002, 03:12 PM:

Steve,

I understood that Subwoofer channel is not full-range so that measuring the SW is not the same as measuring a stage channel.

But when you set the SW level with an SPL at the DTS unit the CP is already equalized and so there should be no resonances in the auditorium that can change the SPL meter's read.

I thought that since SW is limited 20-80 (or 20-150 with Dolby) and each subwoofer (despite the EQ) has a different frequency response, SPL is not so accurate.

A quasi-OT question: if I'm setting the SW channels with and SPL (instead with a RTA), DTS SW level is 91, and what about Dolby Level using CP500 built-in generator?

Karen,

88dB? Wasn't it with old setup disk? Is it not 91dB now???

Bye
Antonio

Posted by Gordon McLeod (Member # 33) on 05-20-2002, 06:21 PM:

SPL meters can not be used to set any sub since they are not a narrow band product
DTS makes a nice breakout board for setting the 300mv with prob sockets on it

Posted by Steve Guttag (Member # 268) on 05-20-2002, 08:58 PM:

If you are reading 0mV yet hear the tone...then you are not measuring correctly! Perhaps you have your meter set to DC? It should be reading AC...perferrably a true RMS meter with an appropriate frequency response.

Setting subwoofer level with an SPL meter is just plain wrong; it doesn't work! As Karen said, you can do a quicky level set to get you by but it has no real bearing in real life. If you don't have the proper tools, don't do the job.

Steve

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"Old projectionists never die, they just changeover!"

Posted by Manny Knowles (Member # 1171) on 05-21-2002, 12:41 AM:

Steve is correct. I was set to DC instead of AC. I'll try again in the morning and then I'll post the result when I return.

Thanks to you all for being such a big help.

------------------

~Manny.

Now...where was I ?
Leonard Shelby, MEMENTO.

Posted by Antonio Marcheselli (Member # 373) on 05-21-2002, 04:19 AM:

Steve said:
--
perferrably a true RMS meter with an appropriate frequency response.
--

What do you mean?

Bye
Antonio

Posted by Gordon McLeod (Member # 33) on 05-21-2002, 08:43 AM:

There are different ways that meters read AC voltages and currents
One is the peak voltage ie the maximum of the sine wave
others read the average voltage
the best and most accurate is the RMS (root mean squared) reading type
(they are typically more expensive though wavetek has some good ones now)
The RMS value is .707 of the peak (45 degree angle of the sine wave)
This was based on the equivelent heating effect of D.C.

Posted by John Pytlak (Member # 331) on 05-21-2002, 09:09 AM:

Some links:
http://www.ultracad.com/rms.pdf
http://vanadium.rollins.edu/~griffin/phy121/exp5.pdf
http://www.inter-netco.com/images_and_links/electrowave/power_measurements.htm
http://www.jaycar.com.au/pdfs/ohmpower.pdf

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by Karen Hultgren (Member # 395) on 05-21-2002, 11:56 AM:

Antonio,

As mentioned in my posting, the 88dB SPL is meant to get him in the correct range and to get him by until a subwoofer adjustment with a RTA can be done.

Karen at DTS

Posted by Gordon McLeod (Member # 33) on 05-21-2002, 12:08 PM:

Steve said" If you don't have the proper tools, don't do the job."
I agree 100%

Posted by Antonio Marcheselli (Member # 373) on 05-22-2002, 05:19 AM:

Karen,

Ok, thanks. I didn't caught the meaning of 88!!

Gordon,

Very clear. How can I know how my meter measure the current? My DTS6 come back from DTS UK few months ago and my meter read exactly "300mV" on the outputs. Can I assume that it reads RMS correctly?

John,

Very interesting links, I'll study them deeply.

Thanks to all.
Antonio

Posted by Gordon McLeod (Member # 33) on 05-22-2002, 10:38 AM:

Probably it is correct.
Measure it on a wall outlet and it should measure what the local mains are which I think is 240 volts in Italy
If it reads the mains correctly then it is reading the RMS as that is published value of the mains

Posted by Antonio Marcheselli (Member # 373) on 05-22-2002, 05:34 PM:

Gordon, Karen,

A tech told me that he is not convinced bout the 300mV procedure because the meters are set to read 50Hz tension while the DTS test tones are at 1000Hz or 30Hz.

How can I reply?

Karen,

Just a curiosity: why on older empirical test list I read "1 Khz at reference level (250mV)"?

Bye
Antonio

Posted by Gordon McLeod (Member # 33) on 05-23-2002, 07:44 AM:

The newest disk had the reference tones at dolbys stantard of 30mv
Most analogue meters and most good digital meters do not have much of a problem until you get into very high frequencies

Posted by Antonio Marcheselli (Member # 373) on 05-23-2002, 08:00 AM:

Gordon,

I just tried with my meter. I've connected the meter to my SB live! output and I generated a 1000Hz tone. I've set the volume so the meter was at 300mV.

I switch to 30Hz tone, same level. Meter says 650mV.

I'm going to check our DTS6D with the "tone way". Are you sure that it is a correct procedure?

Bye
Antonio

Posted by Karen Hultgren (Member # 395) on 05-23-2002, 11:44 AM:

Antonio,

All DTS output levels should be adjusted to 300mV RMS. With the DS3 disc, use the tones: 1kHz for screen and surround channels, and 30/40Hz for the subwoofer.

Karen at DTS

Posted by Antonio Marcheselli (Member # 373) on 05-23-2002, 01:41 PM:

Karen,

Thanks for your reply. You already explained the procedure to me. I just want to know how to reply to our tech.

I've already shown your e.mail to him, he is collecting information about this because he really was not informed about the 10dB in-band gain of the subwoofer via RTA and the 1kHz/40Hz tone for DTS.

Bye
Antonio

Posted by Karen Hultgren (Member # 395) on 05-24-2002, 12:02 PM:

Antonio,

The old level setting of 250mV was chosen at the time as a preliminary setting so that when the unit was installed and a setup disc played, sound would be heard. As mentioned in the manual, that level would not over drive speakers and we asked people to complete the level adjustments using a setup disc and SPL meter.

Things have changed and we now ask theaters to setup our players to the cinema processor line level which in most cases is 300mV. This will ensure equal SPL playback in digital and analog.

Karen at DTS
khultgren@dtsonline.com

Posted by Manny Knowles (Member # 1171) on 05-30-2002, 08:59 PM:

Thanks very much to all of you...

Here's an update:

Both DTS-6 players are working fine; there's nothing wrong with any of the boards (although they probably don't have the latest firmware).

I now have much more satisfying levels after "dialing up" 300mV by using the DS3 disk and the JM21 breakout board, as described in previous posts.

Karen's notes were helpful in determining once-and-for-all that a reader had faded.

Once again, my thanks to all.

"I love it when a plan comes together."

~Manny.

Posted by Karen Hultgren (Member # 395) on 05-31-2002, 11:54 AM:

Manny,

Glad to hear things worked out for you! Please do not besitate to contact me at any time when you have a DTS question.

Karen at DTS
khultgren@dtsonline.com