Opinion: Serious Issues with IMAX Enhanced on AV Receivers

IMAX Enhanced is both a certification program – like THX was in the “good old days” – as well as additional sound processing overlaid over DTS and DTS:X soundtracks. Some of these soundtracks in fact will have a flag that will trip this additional sound processing.

IMAX says that IMAX enhanced content is digitally remastered for optimum picture and sound. So far so good.

Brands such as Denon and Marantz have implemented IMAX Enhanced sound processing modes and its included on their latest models such as AVC-X3700H, AVC-X4700H, AVC-X6700H, AVC-X8500HA, AVC-A110 and their Marantz equivalent line-up.

I don’t have an issue with a certification program – apart from it adding to the cost of equipment – or even have an issue with digitally remastering content. However, I feel their sound processing in the AVR does not seem to be based on sound research and could actually HURT the sound. Let’s have a look why!

IMAX Audio in an IMAX Theatre

IMAX uses full bandwidth channels and speakers across the auditorium. This means that each channel can go down to 20Hz and therefore can play back the full audio spectrum.

This only works optimally for all listeners if the auditorium is designed with this in mind. This is because low-frequency effects are incredibly hard to control from multiple speakers without interference with each other and with the listening space.

I am unsure how well IMAX models their theatres and controls low-frequency effects across the listening space. As far as I understand they do use Audyssey in at least some of their auditoriums to help with this issue. Controlling low-frequency effects from 10+ speakers optimally is highly challenging however and I have my doubts about how well this can be implemented.

THX – after many years of research – arrived at the position that it was near-impossible to get optimal sound quality for all seats even in modern specifically designed multiplexes without re-routing bass under 80Hz to the subwoofers and controlling those frequencies from there by careful positioning and EQ. Has IMAX figured out a way to do this better? Possibly!

IMAX Enhanced Auto-Settings

On IMAX-enhanced receivers such as the Denon line, IMAX Enhanced will be turned to the auto setting by default. What this means is that the receiver will alter the following settings from what has been set for all other sound-formats when an IMAX Enhanced flag is detected on DTS or DTS:X soundtracks:

• When playing back a 5.1 DTS soundtrack, the surround channels will be played back using the Surround Back speakers – your surround speakers will be SILENT. Unfortunately, this will result in steering and sound-field changes that are not according to what the filmmaker intended.
• Bass information from the main speakers may NOT be redirected to the subwoofer, no matter what crossover you have set. IMAX is using a “special algorithm” to try and re-create the bass from the front and centre speakers even if they are set to small. While I understand that they want to perceptually mimic an IMAX theatre, this will trip up Audyssey Dynamic EQ and Volume. Additionally, why would I want some perceptual algorithm trying to mimic bass when I have set up my theatre to do REAL bass evenly across all seats – deep smooth bass at that. When set up correctly, audio under 80Hz cannot be directionally perceived – that is it will blend in with the main speakers. This is why we set the crossover in both a THX theatre and ideally in our home cinemas to 80Hz – speakers and room permitting. IMAX’s full bandwidth channels are a rather questionable choice even in a movie theatre – let alone in the home when we look at evidence based research – not marketing and hype.
• IMAX post-processing seems to include a bit of a bass boost and a volume boost. This again will throw off loudness compensation algorithms such as Dynamic EQ and Dynamic Volume or in fact Yamaha YPAO Volume if Yamaha were to include IMAX Enhanced certification.
• Some lower-end receivers need to turn off Audyssey for IMAX enhanced to be enabled due to lack of processing power. This is again a big no no and will result in a sound quality drop in most cases.

What Should You Do About it?

I would completely disable IMAX Enhanced on your receiver. It is doing things that should NOT BE DONE to a soundtrack. Old THX sound processing modes were based on very sound research and a lot of thought was put into implementing them. IMAX enhanced seems like a desperate attempt by IMAX for a cash grab and an even more desperate attempt for DTS to stay relevant in the new world of object-based positional audio where Dolby Atmos seems to be dominating.

My recommendation is to TURN IT OFF. It is not based on sound research, but hype and ridiculous revisionism.

If you don’t want to turn it off, thankfully with the latest firmware, there is a manual mode for IMAX Enhanced which allows you to set the following:

High-pass filter (crossover): By default this is set to 80Hz. Set this to what you set in your manual speaker setup for speaker crossovers. Unfortunately, only one setting is given which will be applied to ALL SPEAKERS set to small when IMAX Enhanced content is played back. This is not necessarily ideal as sometimes surround or ATMOS speakers need a higher crossover.

Low pass filter for the LFE channel: This is set to 120Hz by default and you should NOT change this. This is actually correct.

Subwoofer mode: set this to ON to redirect bass under the crossover frequency to the subwoofer.

I urge all manufacturers to make these processing modes optional – flag or no flag in the signal.

UPDATE – Dec 2021

Since this article was written, there seems to be a bit of a change in direction. Firstly, IMAX has allowed Trinnov to disable psycho-acoustic bass enhancement as well as use the existing crossovers the room EQ has set up for IMAX Enhanced content. I think this is great. Of course, the obvious question is… what is left beyond these two things in IMAX Enhanced processing and can you just use the regular DTS:X decoder? Since my AVR disables Audyssey Dynamic EQ and Volume on my receiver for IMAX Enhanced, I know which decoder I will choose.

Also, Onkyo has been allowed in their new lines to have an option that uses the same crossovers as set in speaker settings for normal content. I am unsure if bass-enhancement is enabled or disabled in these new AVRs however. It is also worth checking out whether the new Pioneers and Integras – which are based on the same DSP designs as the new Onkyos – also follow suit.

One VERY POSITIVE thing however is that Disney+ will be enabling DTS:X streaming on their platform and will stream IMAX Enhanced DTS:X tracks. These audio streams will have the full theatre mixes and a high dynamic range. This does mean you will need Loudness Compensation and DRC on (such as Audyssey Dynamic EQ & Volume) if listening at lower volume levels, but finally we will have much better audio on Disney+. As I said at the beginning of this article, I fully support and praise this approach. I just don’t care for IMAX Enhanced processing for now.

Related Free Guides

If you are planning to buy or have recently bought a Denon or Marantz receiver, check out the below guides

How to Configure Audyssey – The Right Way

Why Audyssey Sounds Best with Room Treatment

Professional Guide

Secrets of Audyssey is a Professional Guide available for those that want to get the very best out of their Denon or Marantz receivers.