Dolby CP750 Sound Level Display

[Paul Finn]

I'm perplexed about why the CP750 channel level displays indicate only the sound channel input levels? It's nice to see there is audio there, but worthless to adjust theater sound levels for uniformity between different program sources (digital, various film, multi-channel analog, etc.) in the same program. Other processors I've worked with have a display that can indicate the output audio level to the power amplifiers and thus the relevant theater sound level. Is there an explanation?

Thank you, Paul Finn

[Dave Macaulay]

How could it know? The fader number tells you the auditorium level if anyone calibrated the room to reference level.

[Ryan Gallagher]

I'm perplexed about why the CP750 channel level displays indicate only the sound channel input levels? It's nice to see there is audio there, but worthless to adjust theater sound levels for uniformity between different program sources (digital, various film, multi-channel analog, etc.) in the same program. Other processors I've worked with have a display that can indicate the output audio level to the power amplifiers and thus the relevant theater sound level. Is there an explanation?

Thank you, Paul Finn

What other processors are you remembering this feature on? I know our AP20 also only showed the input signals on the LCD meters.

I think you are asking for front panel meters that follow the fader level attenuation. Not unreasonable, but definitely a different function than analyzing the source signals.

[Marco Giustini]

The 750 shows the levels BEFORE the fader. And really it's just an indication for the operator to ascertain whether "there is" or "there isn't" sound. For your purpose you'd probably need something with a range between -30 to 0dBFS - I believe the 750 is more like -60dB to 0dBFS and it might not be linear.

I never considered that with a more meaningful meter you could have an idea of what the level in the auditorium is. But with the high dynamics of cinema soundtracks, it might not be as useful. But yes, during some dialogues, you could have an idea of the level by looking at a proper meter.

[Steve Guttag]

1) This is the FHF and the CP750 is a DCinema processor only (no film) aside from its multichannel input.
2) I am not aware of many processors that will show post fader/post EQ/level set. You'd be into the DSP based units and with particular features.

Now, there were booth monitors that allowed for level/meter set on both processor and amplifier. Probably the most complete was the Panastero CX-230 (EX). It had separate trimmers, for each channel, including HF/LF for stage channels, and a sensitive meter. You could tune you system...then calibrate the meter on both processor and amplifier and get a sense for how loud it was in the theatre.

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The QSC DCM series did have some degree of level setting, as I recall, but no meter. The QSC DCP series of processors had a degree of level setting and did have meters, post fader and right up to the amplifier.

[Ryan Gallagher]

Yeah, I think for a long time much of our industry dedicated that function to a separate device in “booth monitor” function.

Our booth had always contained a cheap little 8 band RTA sitting on a top shelf with a capsule mic hung outside of one of the ports for this sort of “eyeballing/confirmation” function. Dates well back into our film only era, but still worked.