Cannot get 5.1 Surround Sound Working on 2021 MacBook Pro

[Luna Murasaki]

I have a 43-inch television sitting on my computer desk that is connected to a 5.1 surround system via an audio cable so that the television is using that for its audio. I only use one input on the TV, which is for a KVM switch. Connected to the KVM switch are many devices including my Xbox Series X, Apple TV, and M1 Max MacBook Pro.

I'm able to get 5.1 surround to work with my Xbox by selecting "Dolby Surround" in the Xbox's audio properties. I am also able to get 5.1 surround to work properly on my Apple TV by forcing the audio format to Dolby Digital 5.1 (which it warns will degrade audio quality, though I don't notice anything).

I don't know a way to accomplish the same thing on the MacBook Pro however. When I go to the Audio MIDI Setup utility, I can certainly select 6 channels, can go to configure speakers, and set it to 5.1 surround. However, when testing things on that same screen, trying to get audio to play out of the left rear speaker (channel 5) just causes it to play out of the left front speaker instead, and trying to get audio to play out of the right rear speaker (channel 6) just causes it of play out of the right front speaker instead. I also notice that the subwoofer channel (channel 3) outputs no sound at all when I test it.

I notice that if I select "5.1 Uncompressed" instead of "Dolby Surround" on my Xbox, I experience the exact same symptoms as on my Macbook, where audio meant to play through the rear speakers is coming out through the equivalent front speakers and the subwoofer is silent. But I can solve this problem by selecting "Dolby Surround" on the Xbox.

Anyone know what I'm doing wrong or if there is anything I can do to give my Macbook the same surround sound my other devices have with this setup?

 

[StuAff]

Ignore Audio MIDI Setup. It makes no difference whatsoever to playing encoded Dolby Digital or DTS content, it's for multichannel setups when recording and mixing that content. Haven't even opened it on this MBP.

Can your KVM actually passthrough surround formats? Is the MBP connected via HDMI? If the answer to both those questions is yes, than it's got to be a software issue. In iTunes/TV app, you need the 'select AC3 passthrough' option selected (NB: I can only assume this works via HDMI, my Logitech Z906s are connected via a USB to optical audio out adaptor & AC3 passthrough won't work). In VLC you need 'Encoded Output'.

 

[Luna Murasaki]

Ignore Audio MIDI Setup. It makes no difference whatsoever to playing encoded Dolby Digital or DTS content, it's for multichannel setups when recording and mixing that content. Haven't even opened it on this MBP.

Can your KVM actually passthrough surround formats? Is the MBP connected via HDMI? If the answer to both those questions is yes, than it's got to be a software issue. In iTunes/TV app, you need the 'select AC3 passthrough' option selected (NB: I can only assume this works via HDMI, my Logitech Z906s are connected via a USB to optical audio out adaptor & AC3 passthrough won't work). In VLC you need 'Encoded Output'.

As I said, I am able to get surround sound working correctly on both my Apple TV and my Xbox Series X, and these are both connected to the same KVM switch and setup. I mentioned that to eliminate the possibility that the switch, speaker system, TV, etc, are not hooked up/configured correctly or don't support it. The problem is specific to the MacBook. It happens regardless of whether or not I connect the HDMI cable to the port directly on the machine or via the USB-C Digital AV multiport adapter.

It looks like I can indeed get surround to play correctly on VLC by selecting the option you mentioned. So it looks like things are as good as they are going to get. It's a real shame there is not some universal switch for this built into the OS because it of course means the vast majority of programs are not going to do surround without some specific option to enable it, especially computer games where I miss it the most, but it is what it is I guess.

I have things set up the way they are because my receiver is dated and cannot do 4K passthrough without downgrading the refresh rate to 30Hz. I've considered replacing it in order to run everything through the receiver but it would be painfully expensive and it doesn't sound like it would improve the situation, though please correct me if I am wrong.

Thank you very much for taking the time to help me and at least now if I am watching something in TV or VLC I will be able to enjoy the surround. 🙂

 

[StuAff]

As I said, I am able to get surround sound working correctly on both my Apple TV and my Xbox Series X, and these are both connected to the same KVM switch and setup. I mentioned that to eliminate the possibility that the switch, speaker system, TV, etc, are not hooked up/configured correctly or don't support it. The problem is specific to the MacBook. It happens regardless of whether or not I connect the HDMI cable to the port directly on the machine or via the USB-C Digital AV multiport adapter.

It looks like I can indeed get surround to play correctly on VLC by selecting the option you mentioned. So it looks like things are as good as they are going to get. It's a real shame there is not some universal switch for this built into the OS because it of course means the vast majority of programs are not going to do surround without some specific option to enable it, especially computer games where I miss it the most, but it is what it is I guess.

I have things set up the way they are because my receiver is dated and cannot do 4K passthrough without downgrading the refresh rate to 30Hz. I've considered replacing it in order to run everything through the receiver but it would be painfully expensive and it doesn't sound like it would improve the situation, though please correct me if I am wrong.

Thank you very much for taking the time to help me and at least now if I am watching something in TV or VLC I will be able to enjoy the surround. 🙂

Yup, this stuff is weird. The onboard optical port connected to Z906 on my Mac Pro 5,1 just works. If I use the USB interface box on the 5,1, AC3 passthrough in iTunes does not work, even though it's the same hardware and software otherwise. VLC and Macgo Blu Ray Player both have no issues outputting 5.1 either way.

 

[eddie78]

it seems that the issue lies in the compatibility between the audio format selected on the Macbook and the 5.1 surround system. It seems that when "Dolby Surround" is selected on the Xbox, the audio output is properly directed to the 5.1 surround system.

To resolve the issue on the Macbook, you can try the following steps:

1. Check the audio format support of the 5.1 surround system.
2. Make sure the audio format selected on the Macbook matches the supported format of the 5.1 surround system.
3. If necessary, change the audio format on the Macbook to the format that is supported by the 5.1 surround system.

I would recommend checking this link for more information on the topic: https://hifiaudios.com/home-theater/dolby-digital-vs-dolby-atmos/