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Author Topic: Cinema sound Calibration system
Tacky Ting
Film Handler

Posts: 13
From: Hong Kong / China
Registered: Jan 2015


 - posted 01-18-2019 03:49 AM      Profile for Tacky Ting   Author's Homepage   Email Tacky Ting   Send New Private Message       Edit/Delete Post 
Excuse me, everyone is using the Acoustical Measurement System.
I am using AcoustX D2. https://www.acoustx.us/D2_Acoustical_Measurement_System.html
NTi audio XL2 Cinema Meter, have you used it? Is it simple to use? How effective? https://www.nti-audio.com/en/applications/electroacoustic-installations/cinema

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Dave Macaulay
Film God

Posts: 2168
From: Toronto, Canada
Registered: Apr 2001


 - posted 01-18-2019 08:31 AM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
The D2 is relatively easy to use, Several microphones are set up and combined in the device so adjustments are "real time" - you look at the response graph and make live EQ changes.
The NTi unit uses one mic, up to 8 positions can be combined after moving the mic around and taking repeated readings. Whether you use one or several positions, you get a guide to correcting the EQ, make adjustments, and take another set of tests to check if more is needed. That takes MUCH more time for pretty much the same outcome.
There are other approaches, Dolby uses Smaart with multiple mics and real time averaging for ATMOS, Imax uses Smaart with temporal averaging while one mic is moved around. The sound processors used are designed with their techniques in mind.
Believers will argue for hours about what approach is best.
I prefer the multiple mic and multiplexer or combiner averaging: working with many sound processors with different adjustment modes, doing recursive EQ just gets too tedious for me.. and owners rarely want to pay for the hours it takes to EQ one room that way.

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Sean McKinnon
Phenomenal Film Handler

Posts: 1604
From: Peabody Massachusetts
Registered: Sep 2000


 - posted 01-18-2019 08:54 AM      Profile for Sean McKinnon   Author's Homepage   Email Sean McKinnon   Send New Private Message       Edit/Delete Post 
I have used the D2 and really like it (especially for A-Chains on film projectors) in fact I still have a D2 setup. Now I am using SMAART from Rational Acoustics an a Roland Octacapture with 8 (I tend to do a lot of large houses with balcony's so the extra mics cut down on my time running up and down stairs with Mic's) Beyer Mic's. I really like the Beyer Mic's and I really like the Octacapture. One Caveat is that if you get Beyer Mic's you will have to send them out to have the calibration files made. There is a place here in Mass that does them. If you go with Earthworks they give you the files but they are more expensive.

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Tacky Ting
Film Handler

Posts: 13
From: Hong Kong / China
Registered: Jan 2015


 - posted 01-18-2019 09:30 AM      Profile for Tacky Ting   Author's Homepage   Email Tacky Ting   Send New Private Message       Edit/Delete Post 
Dolby Smaart v8 for CP750 & CP850 , Is it easy to use?

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Sean McKinnon
Phenomenal Film Handler

Posts: 1604
From: Peabody Massachusetts
Registered: Sep 2000


 - posted 01-18-2019 09:40 AM      Profile for Sean McKinnon   Author's Homepage   Email Sean McKinnon   Send New Private Message       Edit/Delete Post 
SMAART is made by rational acoustics not Dolby. I was able to pick it up without going to any of the trainings they offer but I was able to watch and work with other tech's who knew how to use it. It is very powerful and has a lot of features so there is a learning curve if you've never used it before.

From my experience SMAART seems to be the industry standard when it comes to live events and music.

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Christian Lerch
Film Handler

Posts: 3
From: Potsdam, Brandenburg, Germany
Registered: Jan 2014


 - posted 01-18-2019 09:44 AM      Profile for Christian Lerch   Email Christian Lerch   Send New Private Message       Edit/Delete Post 
You can request MM1 calibration files from Beyerdynamic by sending the serial numbers of your microphones. The corresponding email address can be found on the website.

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Gunter Oehme
Film Handler

Posts: 17
From: Frankfurt, Germany
Registered: Jun 2000


 - posted 01-18-2019 10:34 AM      Profile for Gunter Oehme   Email Gunter Oehme   Send New Private Message       Edit/Delete Post 
You should send the email to request the individual MM1 calibration files for your serial numbers to AudioSystems@beyerdynamic.de.

Beyerdynamic is able to provide the calibration files for microphones manufactured since about 2007.
So you can get the calibration files for rather old MM1s as well.

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Sean McKinnon
Phenomenal Film Handler

Posts: 1604
From: Peabody Massachusetts
Registered: Sep 2000


 - posted 01-18-2019 11:36 AM      Profile for Sean McKinnon   Author's Homepage   Email Sean McKinnon   Send New Private Message       Edit/Delete Post 
That's good to know. Thank you!

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12294
From: Annapolis, MD
Registered: Dec 1999


 - posted 01-18-2019 03:01 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
What I like about the D2 over others is that, aside from it all being calibrated right out of the box, you don't have to find an outlet in the theatre (Octacapture needs an outlet). The D2 self-normalizes to Mic 1 (the reference position) so if your mic 3, lets say, is nearest the screen, it will artificially contribute more to the average than the mics further away, despite the seats being further away more likely to have people watching the movie.

Note, for Atmos, you don't need SMART...the CP850/IMS3000 don't use SMAART, they use the Octacapture (or other ASIO based mic plexer). SMAART is just for you to see what it did once it was done with the auto-tune.

As Sean indicated, the SMAART analyzer can do a bunch of stuff that the D2 can (for B-Chains), like a Transfer Function, which can greatly aid in setting the proper delays/getting phase right. Then again, if you know what you are doing you can surmise some of that without it and if you have a tone generator and are setting delays at crossover, if you peak the response, you'll get the delay right.

Another issue with SMAART (for me) is it is that it is licensed to the computer, not the person so if you change computers, the software doesn't necessarily come with you (perhaps there is a transfer procedure). Since the D2 is hardware related, where ever the equipment goes so can the software that drives it. The current version of D2 can work with AZIO (started with version 2.1) so it is viable for an Atmos calibration.

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John Thomas
Film Handler

Posts: 61
From: Northville, MI, USA
Registered: Sep 2011


 - posted 01-18-2019 05:16 PM      Profile for John Thomas   Email John Thomas   Send New Private Message       Edit/Delete Post 
Not thrilled with the OctaCapture. Feels flimsy. Calibrating SPL I find inputs 5-8 reading a dB or two lower than 1-4 which leads me to suspect they are using substandard components for the inputs most users don't touch. Not a problem after calibration, but it's the principle.

I've been interested in the MOTU 8pre as a replacement interface. MOTU's interfaces are extremely well regarded, it takes a "kettle" type plug instead of an external AC adapter, and the chassis seems very road-worthy. Unless something has changed though I believe the OctaCapture is the only "approved" interface for an ATMOS kit.

I have been happy with SMAART and MM1's. If you buy your MM1's from Trinnov you get the calibration files for tuning Ovation processors, and after an email to BeyerDynamic you have one kit fit for most jobs.

The iSEMcon EMX-7150 is supposed to be a good mic as well, but pricey.

Steve's qualms with SMAART are valid. Managing multiple licenses while people are reformatting and trading computers can be a chore.

My coworkers who use the D2 can move house-to-house much faster than me in a multiplex and their kits are much lighter. Those mic stands though... no thanks.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16269
From: Bountiful, Utah
Registered: Jun 99


 - posted 01-21-2019 11:53 AM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
quote: Christian Lerch
You can request MM1 calibration files from Beyerdynamic by sending the serial numbers of your microphones. The corresponding email address can be found on the website.
It is wise to send mics in every year as the glass diaphragms in those and the D-2 mics are thinner than a human hair and even just a light coating of dust will change the response of the mic. Theatres for the most part are actually filthy places, even though a room may appear clean. New builds are the dirtiest! Some manufacturers have a way to clean them and run a new calibration curve to make sure the mic is still within spec. In extreme cases the condenser unit will have to be replaced, or in the case of the D-2 possibly the entire set of Mics.

Mark

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Sean McKinnon
Phenomenal Film Handler

Posts: 1604
From: Peabody Massachusetts
Registered: Sep 2000


 - posted 01-22-2019 01:39 PM      Profile for Sean McKinnon   Author's Homepage   Email Sean McKinnon   Send New Private Message       Edit/Delete Post 
Everything Steve said is pretty spot on. In my case I am not doing a lot of multi-plex's I am doing very large rooms sometimes with non traditional or custom configured speaker systems so for me the transfer function is handy and I am not worried about moving from room to room as much as I am about "moving" mics in the room.

I have found that the Octa Capture is very good at keeping its settings. I have labeled everything so the same mic gets the same cable and plugs into the same input and so far I have not had to re-calibrate yet. I put the Mic calibrator on and it reads 94 every time. I like that! It is funny though one of my mics does require more gain than the others but if I compare them side by side they show identical results.

The cost to get the MM1 calibration files made is pretty reasonable and my intention is to do it regularly. The place we use is quick and seems to do a very good job http://www.cross-spectrum.com/ http://www.cross-spectrum.com/

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12294
From: Annapolis, MD
Registered: Dec 1999


 - posted 01-22-2019 04:11 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
After re-reading my post...I made some can for can't mistakes. the D2 does NOT do transfer functions whereas SMAART does.

A feature of the D2 that I gave a poor example for was how it normalizes to mic 1. That is, if you are running the unit in plex mode, the D2 will normalize all mics to mic 1's level so the display does not bounce around in level. Thus, all microphones will equally contribute to your result regardless of their location relative to the sound source.

I think this adds into (in addition to calibrated mics) the fact that I've noted if someone else has tuned a room on an R2 or D2, when I go in behind them (next time the room is to be tuned), The results are the same despite the mics not being in the same place. It sort of proves that the D2 system gets uniform results, regardless of method (when it comes to response).

As any experienced technician should know, however, merely getting a display to show a response does not show the method of achieving it. So one may badly tune a room using alternate EQ controls and show a proper response while another tech may get an equivalent response with minimal tuning and it is the latter one that will sound best.

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