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Author Topic: Cinema Sub Limiter?  (Read 592 times)

Peter Kowalczyk

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Cinema Sub Limiter?
« on: April 12, 2018, 05:11:34 pm »

A cinema client burned up the driver in his subwoofer.  I'm exploring options to address the issue.  One is a bigger box that can handle more power and generate more output (enough rig!).  Another is to repair the driver and add a limiter to the system to protect it from future damage. 

So, I'm looking for a simple average-power limiter to place before the subwoofer amp.  Preference for something with phoenix or screw-terminal connections (this will live permanently in their equipment rack) and a small form factor (1RU or even smaller 'black box').  dbx 160A seems to be an option, but there's no control of time constant and I'd love to not have to solder XLRs to connect it;  RDL's ST-CL2 looks like a handy and cost-effective option, but I'm wary of its 'fully automatic operation' and absence of typical control parameters.

What would you use?
Thanks!
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John L Nobile

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Re: Cinema Sub Limiter?
« Reply #1 on: April 12, 2018, 06:13:54 pm »

I have to ask...was there a HiPass filter on the sub?
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Mike Caldwell

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Re: Cinema Sub Limiter?
« Reply #2 on: April 12, 2018, 06:20:53 pm »

Is this in a professional movie theater or a home theater/cinema.

Tim McCulloch

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Re: Cinema Sub Limiter?
« Reply #3 on: April 12, 2018, 06:21:46 pm »

A cinema client burned up the driver in his subwoofer.  I'm exploring options to address the issue.  One is a bigger box that can handle more power and generate more output (enough rig!).  Another is to repair the driver and add a limiter to the system to protect it from future damage. 

So, I'm looking for a simple average-power limiter to place before the subwoofer amp.  Preference for something with phoenix or screw-terminal connections (this will live permanently in their equipment rack) and a small form factor (1RU or even smaller 'black box').  dbx 160A seems to be an option, but there's no control of time constant and I'd love to not have to solder XLRs to connect it;  RDL's ST-CL2 looks like a handy and cost-effective option, but I'm wary of its 'fully automatic operation' and absence of typical control parameters.

What would you use?
Thanks!

Is there an applicable Dolby® or other standard that is being met?

Is this in a professional movie theater or a home theater/cinema.

That's where I was headed with this...
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Caleb Dueck

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Re: Cinema Sub Limiter?
« Reply #4 on: April 12, 2018, 06:29:40 pm »

A cinema client burned up the driver in his subwoofer.  I'm exploring options to address the issue.  One is a bigger box that can handle more power and generate more output (enough rig!).  Another is to repair the driver and add a limiter to the system to protect it from future damage. 

So, I'm looking for a simple average-power limiter to place before the subwoofer amp.  Preference for something with phoenix or screw-terminal connections (this will live permanently in their equipment rack) and a small form factor (1RU or even smaller 'black box').  dbx 160A seems to be an option, but there's no control of time constant and I'd love to not have to solder XLRs to connect it;  RDL's ST-CL2 looks like a handy and cost-effective option, but I'm wary of its 'fully automatic operation' and absence of typical control parameters.

What would you use?
Thanks!
If the issue was improper HPF or not enough Rig for the Gig - a limiter isn't the answer.  Like everyone so far - I'd explore more details first before talking about which limiter.

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Stephen Kirby

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Re: Cinema Sub Limiter?
« Reply #5 on: April 12, 2018, 07:04:30 pm »

Not sure about modern 4K projection systems but back in the days when things had to be able to revert to optical, the mixes were pretty brick walled.  The calibrated levels were with the CP500 or whatever at "fader 7" but that would chase most audiences out so most theaters would turn it down 6-10dB just to keep Michael Bay's explosions reasonable.

I recently went to a movie though and was stunned at how loud it was.  Seemed like they were turning things back up.  Might be related to the new LuFS thing which keeps average levels down and things sound more dynamic than the smashed old days.  Should be easier on the sound system compared to what we had running a smashed action flick at cal'd levels.
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Scott Holtzman

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Re: Cinema Sub Limiter?
« Reply #6 on: April 12, 2018, 07:17:32 pm »

Not sure about modern 4K projection systems but back in the days when things had to be able to revert to optical, the mixes were pretty brick walled.  The calibrated levels were with the CP500 or whatever at "fader 7" but that would chase most audiences out so most theaters would turn it down 6-10dB just to keep Michael Bay's explosions reasonable.

I recently went to a movie though and was stunned at how loud it was.  Seemed like they were turning things back up.  Might be related to the new LuFS thing which keeps average levels down and things sound more dynamic than the smashed old days.  Should be easier on the sound system compared to what we had running a smashed action flick at cal'd levels.

We saw a movie in Imax last year (the watered down theater iMax).  They had all the amps and processors racked up in IT style cabinets behind a glass window so you could see the blinky lights.  It was all QSC amps.

It was nuts loud.  Average LF extension. Everything in the room was rattling too.   

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Peter Kowalczyk

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Re: Cinema Sub Limiter?
« Reply #7 on: April 12, 2018, 08:00:20 pm »

This is a professional theater that sells tickets to paying customers.  The audio stream is managed by a Dolby branded processor, but given the age of the speakers themselves and the relative hodgepodge of other components, I'd be surprised if this was calibrated to meet any particular standard.  Will have to ask the owner.

I'll have to double check the HPF setting.  Good call, and my oversight for not verifying this parameter.  If engaged, it'd be through the QSC Amp's DIP switch settings, or possibly in the Dolby Audio Processor that drives the system.

As usual, more digging required.  Thanks all for asking the right questions....





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Corey Scogin

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Re: Cinema Sub Limiter?
« Reply #8 on: April 13, 2018, 12:02:53 am »

We saw a movie in Imax last year (the watered down theater iMax).  They had all the amps and processors racked up in IT style cabinets behind a glass window so you could see the blinky lights.  It was all QSC amps.

It was nuts loud.  Average LF extension. Everything in the room was rattling too.

The one IMAX room near me is consistently excellent. It's the only theater I'll pay to see a movie in because the others suck and/or are often broken.
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Stephen Kirby

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Re: Cinema Sub Limiter?
« Reply #9 on: April 13, 2018, 08:39:38 pm »

Peter, I think you should reach out to Dolby.  They may have gone public since I worked there, but I'll bet the culture of helping get things right is still there.
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