IMAX Laser vs Dolby Cinema

[Aron Toplitsky]

I have to admit, up until lately I have been all about Dolby Cinema at my local AMC, which is the AMC Del Amo 18 in Torrance CA. I recently re-watched Dune Part One and was just blown away by the IMAX Laser upgrade. This theater upgraded a few years back, but for some reason it sounds even better these days. When compared to ATMOS, it seems like IMAX cranks it louder and creates a more powerful and thunderous experience. I just LOVE how the low-end sounds at this theater and really shines when a 12-channel mixed film is showing, which I believe is how Dune Part One was mixed.

So, I have a few questions which I'm sure has probably been discussed before...

1. Do most of you prefer an IMAX 12 channel mix, or an ATMOS mix?

2. Are ATMOS surround speakers full range?

3. I know the rear IMAX speakers are full range, but are the additional side and overhead IMAX speakers full range as well?

4. While on the IMAX topic, has anyone been to the TCL Chinese IMAX in Hollywood? They claim to have true 15/70 capability, but I just don't see how. Their screen dimensions don't appear to have the height capability. I also swore not to go back after seeing two films there and the low end seemed dead. And that was after they did a laser upgrade. Anyone notice that sound issues there?

[Marco Giustini]

On the Atmos side, surrounds can have bass management. That is, the surrounds are driven independently and then you can have a number of LF enclosures (placed around the auditorium but can also be placed behind the screen) to extend the low frequency end of the surrounds. If you end up having two bass management cabinets for example and they are installed on the back Left/Right of the room, you'd typically end up with the surround speakers on the left side of the room using the left cabinet and the surround speakers on the right side of the room using the right cabinet.

It's all down to budget really. I believe Atmos Designer supports up to 12 bass management cabinets, then it's really up to the owner of the room and how deep their pocket is. That is, you can have Atmos and choose to just re-direct the surround bass management to the main subwoofer!

[Allan Young]

While on the IMAX topic, has anyone been to the TCL Chinese IMAX in Hollywood? They claim to have true 15/70 capability, but I just don't see how. Their screen dimensions don't appear to have the height capability.

I haven't been, but apparently they built a temporary wooden booth for Oppenheimer, which must still be in place as they're screening Dune: Part Two in 15/70 too. The screen is 1.90:1 and the 1.43:1 15/70 image only uses the central portion of the screen. Dunno whether they use actual masking for this or not.

[Steve Guttag]

Technically, all of ATMOS' surrounds are "full-range" as each speaker is required to have, more or less, the same frequency response as the screen channels. This can be done using actual speakers that can play that low (bass is the difficult part as it requires size and power handling) or via subwoofers as an LFE channel. The surround speakers we've used have, typically gone down to 80Hz (give or take) and the rest is augmented with LFE speakers. Thus far, we've used four LFE speakers (two on each side) to zone off the LFE so it is closer to the speakers it is augmenting. At present, Dolby allows up to 8 Surround LFE "channels". These can be on the side walls, back wall or even behind the screen, if you are just using two. Depending on the room, the majority of ours have been on the side walls. I've toyed with going to 6 surround LFEs or using the main subs to augment the "Wide" channels as they are close to the screen and normally help a sound leave the screen just outside of the image. Due to their distance to the CLA, they are normally larger speakers too (the QSC SR-1590 is our definite "go-to" for that role.

As to why IMAX may sound boomyer or louder...that is going to be more a function of how the system was tuned and how loud the volume was turned up. Without a doubt, an Atmos system can out perform an IMAX. But here is the difference...IMAX is a 1-stop shop. They get to set the terms on the system, check its calibration daily and use what equipment IT wants. On a Dolby Atmos system, that is up to the theatre owner to decide how much they are going to put into it. Dolby has a very wide range of "acceptable" systems. Their parameters relate to overall frequency response and they adapt the system to the room shape/size. IMAX rooms do not vary that much. I have Atmos rooms that are over 100-feet long and under 60-feet. That is a pretty large spread and the speaker layouts reflect that.

Atmos rooms will have their volume levels set by the theatre...just like all of their other theatres. IMAX will lock it in at reference...so that is bound to get you a louder room. Atmos also allows for low-balling the system by "pairing" surrounds (use two adjacent surrounds a one larger channel. They also allow "culling" (combining two Top Surrounds into a single surround)...this reduces amplifier channel count as well as fewer speakers to buy, rig and wire. The problem is, it also makes the system closer to a 7.1 system while still costing significantly more. None of our systems have paired/culled surrounds...they all have 5-screen channels and rarely, if ever have used the "minimum" number of speakers/channels to just get by. The goal for an Atmos room should be to distinguish itself, acoustically (including getting the acoustics of the room correct) so that you do get that WOW factor...not by seeing the speakers but by hearing whatever was mixed on the track.

Like fake-3D, there are definitely some phoned-in Atmos tracks out there. You can tell them while looking at the signal. Essentially, no "objects" but the occasional array fill of Top Surrounds for ambiance. I don't know if IMAX does that sort of thing on their side.

Here is what a full-blown Atmos system could look like (it is my template for setting up an Atmos room...I just remove the speakers/channels that are going to be used in a particular place and move the subwoofers to represent where they actually will go...not necessarily just the side-wall.

FullAtmos.png

[Mark Gulbrandsen]

Speaking of laser projection many technical awards are being handed out this year for the development of the different systems, and the laser diodes used to pull it off... FWIW, here is the article...

[Stefan Scholz]

Surrounds needed to full range since the introduction of digital soundtracks on film, even though many were not. The use of bass management speakers was always possible, but before
DSP based digital speaker management became norm, the setup and alignment was pretty difficult and time consuming. Standard theatre sound processors did not allow for extra Bass
handling in surrounds.
In the mid 1990s a good rule for surround speakers was "anything smaller than 12" bass drivers" is not suitable for the job. Another design goal has always been, that the timbre matches
the front speakers, meaning similar MF and HF drivers in front and surround cabinets.
In reality way too small speakers were used. Instead of horn and identical drivers, eventually direct radiators and dome style tweeters were used. This is the reason, why many surround systems lacked punch and impressive sound. The mid 90s soundtracks definitively played with dynamics and did require powerful speaker setups.
Today the management option enables to use smaller cabinets, and use bass management.
Atmos, or any other immersive sound system does not necessarily give a warranty, that the planned layout of the auditorium is done with the slider to "recommended configuration. Mainly,
theatres are looking for the legal use of the trade name allowance, and so many "minimum configurations" exist. This is to be supported by Dolby, DTS, etc, as otherwise sales of licenses would be minimal.

I have also seen Imax halls during construction, and the installed components were not to my liking in respect to size and quantity compared to the room size. There was no real impressive immersion during a show. My gutt feeling, they do a similar budget depending planning stage.

Many folks know my words, "brewed with love, spoiled by the bar tender" also applies to the movie industry. There are outstanding soundtracks made, which are rarely heard the way they were meant to be reproduced. Looking on Steve's image, it shows quite well, how complex a mid sized sound system can get. I would also add a 2 way LFE channel divided into Kick-Woof and Infra-Woof which is even more
impressive than just a cluster of LFE cabinets in a single group. And, as I learnt from my neighbors 1000 ft away, can be felt in their bed at night.

[Marco Giustini]

Wasn't the CP500 which had the ability to send the filtered LF of the surrounds to a dedicated output - when the crossover card was being used? I know at least one auditorium which used to have bass management for the surrounds in 5.1.
Though back then it might have not been the best idea as I'd imagine mixing rooms were using a normal setup - so what ended up on a surround bass management might have been unpredictable!

[Marcel Birgelen]

Getting back to the IMAX with Laser and Dolby Cinema discussion:

- The Dolby Cinema setup is by far the better picture. Deeper blacks, better color gamut and a WHITE screen, so no ugly speckle.
- The Dolby Atmos system is a more sophisticated sound system than the IMAX sound system, no matter it it's the "classic" 5.0 system or the upgraded 12-channel system.

Then again, true 15/70 is still a league of its own, if done right. So, if you can watch it in true 15/70, then I guess that should be the first choice, even if I doubt the 15/70 system was ever updated to support the 12-channel sound system.

[Scotty Wright]

I haven't been, but apparently they built a temporary wooden booth for Oppenheimer, which must still be in place as they're screening Dune: Part Two in 15/70 too. The screen is 1.90:1 and the 1.43:1 15/70 image only uses the central portion of the screen. Dunno whether they use actual masking for this or not.

they are using masking and the curtain to frame for 1.43 in the center of their screen.

[Scotty Wright]

even if I doubt the 15/70 system was ever updated to support the 12-channel sound system.

It was not. I’ve been told that by a couple imax folks. It’s a legacy system and there’s seemingly no way to simply update the sync system to support the additional channels without redesigning it.

[Gordon McLeod]

Getting back to the IMAX with Laser and Dolby Cinema discussion:

- The Dolby Cinema setup is by far the better picture. Deeper blacks, better color gamut and a WHITE screen, so no ugly speckle.
- The Dolby Atmos system is a more sophisticated sound system than the IMAX sound system, no matter it it's the "classic" 5.0 system or the upgraded 12-channel system.

Then again, true 15/70 is still a league of its own, if done right. So, if you can watch it in true 15/70, then I guess that should be the first choice, even if I doubt the 15/70 system was ever updated to support the 12-channel sound system.

Since the 1570 projectors use a shaft encoder tach to send 96hzpulse in quadrature to either a timecode generator for syncing to a digital player or directly to a dubber. So the only issue would be the playback player

[Aron Toplitsky]

Thank you all for responding. Forgive me if I missed the answer, but as for IMAX surrounds in the 12-channel configuration, specifically the overheads and additional sides, how is bass management handled with those?

As for the IMAX mix, I understand that is handled in Canada, now is that by a different crew of mixers? If so, is the director or sound supervisors present to guide the mix?

When they do a final mix for whether it be Object Based, 7.1 or 5.1 etc, are the mixers recording a full pass for each format, or are they created from a down conversion?

[Aron Toplitsky]

Atmos rooms will have their volume levels set by the theatre...just like all of their other theatres. IMAX will lock it in at reference...so that is bound to get you a louder room.


That's a real shame and explains why some ATMOS presentations seem like they could be louder. Of course, that also depends on how the film was mixed.

How practical is it to speak to a supervisor or manager, and request the fader levels be checked or normalized for Dolby Cinema at an AMC?

[Aron Toplitsky]

[QUOTE=Steve Guttag;n36183]
Atmos rooms will have their volume levels set by the theatre...just like all of their other theatres. IMAX will lock it in at reference...so that is bound to get you a louder room.


That's a real shame and explains why some ATMOS presentations seem like they could be louder. Of course, that also depends on how the film was mixed.

How practical is it to speak to a supervisor or manager, and request the fader levels be checked or normalized for Dolby Cinema at an AMC?

[Aron Toplitsky]

Sorry folks, I'm trying to get the quoting right. I seem to have posted the same thing twice.