Crackling sound in rear speakers using Dolby surround

[Shotgun Rico]

So I have my new Ultra setup with my main speakers utilizing the sub out with bass management. My amp is powering my rear surround speakers. Everything seems to work but when I set the Group Audio Delay to 70ms there is a very noticeable crackling sound in them. When I set the delay to 150ms it’s no longer noticeable but the lip sync is slightly off. At 70ms the sync is fine but the crackling sound is too loud. Has anyone ran into this issue? Any suggestions? I’ve submitted a feedback/ticket to support. They’ve gotten back to me and have submitted my info to the engineers so hopefully something will come of it. Thanks

 

[Shotgun Rico]

Anyone? Bueller? Am I the only one with issue? Nobody experiences this at 70ms?

 

[BMeek]

I experienced audio issues when I experimentally tried to set a low latency group delay with the Ultra's HDMI ARC source. Although I've got my ultra connected to a Dolby 5.1-capable Apple TV 4K, it's essentially a music-only 2.1 system with a nearby WiiM Pro driving another set of 2-channel stereo speakers that must be in very close time sync with the Ultra's (due to their overlapping sound zones). Lip sync with a TV at the source is not my current goal.

I've played with the low latency mode in this setup enough to understand that dropping the HDMI [or WiFi] group delay to 70ms or even 150 would soon or eventually cause various types of burps in the sound. I also found jarring volume fluctuations and other audible burps through the Ultra when I allowed my ATV4K to 'auto' switch to Dolby AC3 instead of forcing it to a steady Stereo LPCM output. For example, Atmos-encoded Apple Music tracks would seemingly add latency to the Ultra's to-do list and cause... interruptions. I'm stable now back on the default 800ms HDMI Group Delay and satisfied with the Speaker Group time alignment.

WiFi surround sound is still really hard to do well on most people's home networks. I've got a quality home network with the Ultra on WiFi-6 and the Pro connected via wired Ethernet, but with just the two of them and the streaming media source traffic active I heard too may low-latency glitches to consider a Surround system around this stuff. OTOH, the surround networking code may be completely unrelated to my group delay observations.

 

[Shotgun Rico]

Well at least I know now that something is going on with the lower latency setting and it’s just not me I realize their Dolby Digital is in beta so I’m hoping they can get the lip sync to match up better in the future.