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» Film-Tech Forum   » Operations   » Large Format Forum   » Difference between IMAX D and IMAX film for sound (Page 1)

 
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Author Topic: Difference between IMAX D and IMAX film for sound
Terry Lynn-Stevens
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 - posted 08-23-2013 08:55 PM      Profile for Terry Lynn-Stevens   Email Terry Lynn-Stevens   Send New Private Message       Edit/Delete Post 
Can anyone quickly tell what are the differences between 15/70 and IMAX Digital when it comes to sound?

Say I watch Star Trek Into Darkness in 15/70, will the sound be different than Star Trek Into Darkness in Digital IMAX? Can someone also comment on the equipment?

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Edward Havens
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 - posted 08-25-2013 11:57 AM      Profile for Edward Havens   Email Edward Havens   Send New Private Message       Edit/Delete Post 
My understanding is that 15/70 prints before the early 1990s used a type of interlocking 35mm magnetic film soundtrack not unlike the one used for Cinerama in the 1950s. With the advent of digital sound, IMAX 15/70 prints moved to a CD-ROM (then DVD-ROM) based time-coded soundtrack not unlike DTS. IMAX digital uses the same kind of digital sound DLP projection uses.

Since a movie like ST: ID would have a digital soundtrack regardless of whether the film was presented digitally or on 15/70 film, I would assume the soundtrack would be the same.

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Terry Lynn-Stevens
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 - posted 08-25-2013 01:29 PM      Profile for Terry Lynn-Stevens   Email Terry Lynn-Stevens   Send New Private Message       Edit/Delete Post 
Edward, I understand what you are saying. But would the speaker lay out and equipment in a digital IMAX be the same in a 15/70 cinema?

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Marcel Birgelen
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 - posted 08-25-2013 11:11 PM      Profile for Marcel Birgelen   Email Marcel Birgelen   Send New Private Message       Edit/Delete Post 
The Digital IMAX locations that have been converted from "ordinary" theaters usually don't have a height channel deployed. The rest of the channels seem to be the same.

Regarding speakers: According to IMAX, all speakers are designed and manufactured specifically for that auditorium. I cannot say if that is true in any way, but the speaker cabinets themselves for the D-IMAX locations that I've seen them, all look exactly the same. Please note that I didn't have the possibility to look inside of them and I might also be misjudging sizes from memory.

What I also do know from my own perception is that the average converted D-IMAX theater usually plays movies much louder than the regular 15/70 IMAX venue. I cannot say if that's due to the fact that the larger venues just cannot create the same wall of sound or just the 15/70 exhibitors being more reasonable.

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Ron Lacheur
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 - posted 08-26-2013 02:26 PM      Profile for Ron Lacheur   Email Ron Lacheur   Send New Private Message       Edit/Delete Post 
Most multiplex IMAX locations are eliminating the top-center channel. Other than that, it's pretty much the same. The big disappointment with the local Cineplex IMAX,was they "upgraded" the two way coaxial system with the three-way "tower of tinnitus " speakers as I like to call them. These shriek so bad, I won't be coming back.

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Ivan Plamondon
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 - posted 08-29-2013 06:16 PM      Profile for Ivan Plamondon   Email Ivan Plamondon   Send New Private Message       Edit/Delete Post 
Sound levels and quality certainly play a big part on whether the whole experience will be pleasurable or not.We still have the old style speakers at IMAX Niagara with digital eq's to process them. Features tend to venture into the 100 dB zone at times, but overall the sound system is great for full length films

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Marco Giustini
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 - posted 09-07-2013 02:48 PM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
In a Dolby calibrated room when a movie is run at 7.0 a single stage speaker will be capable of 105dB, a single surround channel will play up to 102dB and the subs will be capable of 115dB.

Considering you are playing these channels together, I would expect more than 100dB in the loudest peaks.

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Claude S. Ayakawa
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 - posted 09-07-2013 05:27 PM      Profile for Claude S. Ayakawa   Author's Homepage   Email Claude S. Ayakawa   Send New Private Message       Edit/Delete Post 
Just being a patron and not a film theatre technician like most of you here, I have found the sound system of 15-70 and digital IMAX sound just about the same-Superb!

I have seen IMAX 15-70 films at the Kennedy Space Centre IMAX, Lincoln Centre IMAX IN NYC, Niagara Falls IMAX, Polynesian Centre IMAX , Waikiki IMAX and the Dole Cannery 18-IMAX -RPX here in Honolulu in Digital IMAX.

-Claude

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Jonathan Goeldner
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 - posted 10-19-2013 08:19 PM      Profile for Jonathan Goeldner   Email Jonathan Goeldner   Send New Private Message       Edit/Delete Post 
quote: Ron Lacheur
Most multiplex IMAX locations are eliminating the top-center channel. Other than that, it's pretty much the same. The big disappointment with the local Cineplex IMAX,was they "upgraded" the two way coaxial system with the three-way "tower of tinnitus " speakers as I like to call them. These shriek so bad, I won't be coming back.
I'd find that counterintuitive to eliminate the top center when the new systems like Auro and Atmos pride themselves with height channels - personally I'm finding IMAX's 5.0 setup antiquated compared to other system setups.

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Marcel Birgelen
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 - posted 10-20-2013 06:46 PM      Profile for Marcel Birgelen   Email Marcel Birgelen   Send New Private Message       Edit/Delete Post 
From IMAX's point of view, the elimination of this speaker makes perfect sense...

Those Digital IMAX screens usually are just 1:1.77, so the height channel doesn't add very much. Since Digital IMAX venues almost never play original IMAX content, they're stuck with content that was originally mixed in 5.1 or 7.1.

But yes, Digital IMAX's current sound system is nothing more than some glorified 5.1 system. Although with very powerful surround speakers [Wink] .

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Gordon McLeod
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 - posted 10-20-2013 09:22 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
historically Imax used bass management and the stage channels had a fairly steep cut off and summed to a large sub array
when connecting a 35-70 processor to it one had to insert the sub signal back into the the three stage channels and let the imax filters do their job

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Terry Lynn-Stevens
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 - posted 10-26-2013 12:03 PM      Profile for Terry Lynn-Stevens   Email Terry Lynn-Stevens   Send New Private Message       Edit/Delete Post 
quote:

But yes, Digital IMAX's current sound system is nothing more than some glorified 5.1 system. Although with very powerful surround speakers [Wink]

Marcel. I am under the impression that IMAX modifies the sound similar to what they do with the DMR process for the image. In other words, the IMAX mix is slightly different than the studio original. Do you have any info on this?

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Marcel Birgelen
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 - posted 10-26-2013 05:05 PM      Profile for Marcel Birgelen   Email Marcel Birgelen   Send New Private Message       Edit/Delete Post 
The soundmix in IMAX DCPs is different. How different is IMAX's secret sauce. But they actually rather open to the fact that their DRM process also involves "remixing" the sound.

As Gordon already stated, the IMAX sound system uses bass management exclusively for the subs, so there is no LFE channel in the mix. Essentially it's a 6.0 system (and not really a 5.1 system) with a rather large subwoofer array. In most modern systems, it's a 5.0 system, because of the missing height speaker.

The bass management approach of IMAX is actually not all that bad if you ask me. I don't understand why modern, post SRD/DTS sound formats still retain a separate LFE channel.

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Jonathan Goeldner
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quote: Marcel Birgelen
I don't understand why modern, post SRD/DTS sound formats still retain a separate LFE channel.
isn't the reason that unlike IMAX speakers which are larger and can produce bass in all the channels - typical 'standard' theatrical speakers can't reproduce low levels due to their size and the number that are arrayed in an auditorium would be a tad excessive. Since bass is omni-directional, one or two bass speakers behind the screen is more than adequate.

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Marcel Birgelen
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 - posted 10-27-2013 03:09 AM      Profile for Marcel Birgelen   Email Marcel Birgelen   Send New Private Message       Edit/Delete Post 
Yeah, but any modern cinema sound system already uses bass management. The frequencies the main and surround speakers cannot handle, should already be redirected to the sub.

The separate LFE channel was useful in 6-track magnetic soundtracks, as to avoid distortion of the other channels. SRD and DTS might have kept it for backward compatibility reasons.

But in modern installs, the LFE channel should be totally obsolete.

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