Welcome to part 8 of WLPR’s ongoing series all about Atmos and Spatial Mixing in Logic Pro. Throughout this series I’m sharing what I learn to help you grow into this new world of audio. 🔊
Also – this series is sponsored by IK Multimedia! IK was kind enough to loan me the awesome iLoud MTM Immersive bundle for this series.
The iLoud Immersive bundle is a bundle of 11 iLoud MTM speakers for immersive mixing, production & playback. And this bundle rocks!
If you’re interested in setting up a system for Spatial Mixing, you should definitely click here to learn more about the iLoud MTM Immersive bundle.
In part 8, let’s figure out what the heck the LFE is actually for. Plus, I’ll show you how to route audio to the LFE with the various channel strip and panner types, and more.
Check out the video above in today’s post for more 👍
If you read the Dolby documentation it is recommended that the LFE channel only has audio that is not present in any other channel. This is because the stereo downmix will have phasing problems. The LFE is a stand alone channel and has no correlation with the other audio channels. This is a much misunderstood area with respect to immersive audio from 5.1 onwards
Hi Ian, thanks so much for pointing that out! Is there a link you can point myself and others to check out? That would be a huge help.
I will look up the relevant manual concerning 5.1 and down mixing with respect to LFE tomorrow. There is an awful lot of misconception regarding sub woofers and bass management and the LFE channel. As originally envisaged the LFE is a stand alone FX channel that only has its own unique audio routed to it. Left & right in the surround system are full range channels and don’t require any use of the LFE channel to enhance their frequency response.
Also as an audio quality control supervisor on world events I always liked to be able to switch the monitoring speakers between bass management and raw 5.1 so I could then hear what was uniquely routed to the LFE
Hi Ian, I appreciate your follow up comments and look forward to the documentation regarding the LFE.
I do wonder if the same can be said regarding Atmos? Taking a look at the Logic Pro Atmos demo projects, the LFE is employed for a variety of tracks not dedicated strictly to the LFE channel. For example, the kick drum in the Lil Nas X project and many of the channel strips in the Spatial Audio Starter Grid are sent to the LFE in varying degrees while still occupying the main surround bed outputs.
Also, I took time with a bass Apple Loop switching the monitoring format of the Atmos plug-in from the Dolby Renderer to 2.0. According to the Logic Pro manual, the 2.0 version approximates how an Atmos mix will playback on stereo speakers and headphones. As far as I can tell with the LFE level set to 0 dB, the LFE level appeared to not be included in the 2.0 version.
By no means do I doubt the possibility that the LFE can prove more trouble than its worth. I spent a considerable amount of time looking up articles and getting to know the LFE channel in Atmos. But as far as I understand the benefits of Atmos over previous surround formats is the encoding and decoding of Atmos mixes to conform and adapt appropriately for different speaker arrangements. All that to say, I assume this to include the LFE output as well.
But I’m certainly open to needing more understanding in this area! Please feel free to follow up and correct me where necessary 🙂
Morning!
I’ll dig out the relevant manual later I promise, in the meantime a 2.0 downmix is defined by the metadata associated with the Dolby E stream. There is the option of including the LFE or not. Due to the nature of this signal, extremely low and loud, it is assumed that it might not be handled by a small domestic pair of speakers, hence the option.
As a broadcaster (retired!) Dolby E streams and delivery processes and formats played a large part in my life! I’ve gone from mono radio to Atmos TV in that time!!!!
The Logic Pro Atmos I presume as I’m only stereo with Logic is a descrete system and hasn’t any bearing on its distribution path, obviously for broadcast it’s squeezed into two Dolby E streams and the subsequent limitations thereof.
There’s also the digital delivery system to the consumer to take into account after us pros have been banging the stuff around, with faster and more audio channels being available it’s very easy remaining in the discrete world until that crashes against getting it to the public😊😊😊
And of course Dolby isn’t the only immersive format😱
Regards Ian
I’ve just read the SoundCode Stereo LtRt plug-In users guide.
Interesting in that making a discrete stereo downmix it allows levels on all 5.1 channels to be from -INF to +3 dB, something a Dolby device won’t do!
Hi, I’m back again!
In all my Dolby literature I can’t find their original note regarding the use of LFE and not having a signal in other channels as well🤬
Their latest sheet
https://www.dolby.com/uploadedFiles/Assets/US/Doc/Professional/38_LFE.pdf
Is technically vague in my opinion.
Hugh Robjohns’ article is better.
https://www.soundonsound.com/techniques/surround-sound-explained-part-4
But it would be interesting to hear what Tim Carroll would have to say.
I read an article many moons ago by two Japanese researchers regarding the phase relationship between the 5 and the .1 and I’m sure that they came up with a figure around 20 degrees.
As I have always explained to mixers, understand the delivery format, it ultimately dictates what happens to your art, no such thing as a “transparent” pipe. This applies even more so now with today’s multi-platform, multi-standard, multi-format world!
Good to share this discussion with you. Best regards, Ian
Hi Ian, thanks so much again for your follow up and links. Both articles look familiar from my own research. But I’ll be sure to read through them again more thoroughly.
I’ve found a surprising amount of vague details in Apple and Dolby’s own documentation regarding the specifics of Atmos. So I’ve had to spend a good amount of time on my own testing my interpretation of how these things work. Definitely not for the faint of heart!
As my understanding improves I’ll be sure to update this post and video 👍