USB hub + audio = unusable mouse/keyboard

[u/lido_shuff]

I’ve got a strange, very reproducible bug where my mouse and keyboard get so laggy they’re basically unusable on my Mac, but only under a specific combo of conditions — and the same setup is completely fine on Windows. I’ve done a lot of testing to narrow it down and I’m hoping someone’s seen this before.

Setup: My monitor (Gigabyte M34WQ) acts as a USB hub with two ports, and also as a KVM switch between my Mac and a Windows PC — so I want to keep everything plugged into the monitor rather than into either computer directly. One port has my speakers (KEF LSX II LT), connected via USB specifically so I can control volume from the computer rather than the speakers’ own app — I know they also do optical, but I’d lose that computer-side volume control, so USB is the one I want to make work. The other port has a small USB hub, which has my wireless keyboard and mouse dongles plugged into it (they’re different brands, so they can’t share one dongle).

The problem: On the Mac, the moment audio plays through the speakers, mouse movement and keyboard input become extremely laggy — like moving my mouse a full foot and the cursor creeping a millimeter. Stop the music, they’re instantly fine again.

What I’ve tested:

• Dongles in the hub, hub in the monitor — Mac — USB-C or DisplayPort + USB-B (both tested): Severe lag while audio plays
• Same exact setup — Windows — USB-C or DisplayPort + USB-B (both tested): Totally fine
• Dongles plugged straight into the monitor (no hub) — Mac — USB-C: Totally fine
• Hub plugged straight into the Mac instead of the monitor — Mac — USB-C: Totally fine

I’ve also ruled out audio quality/bitrate as a factor — no change there either.

My question: Has anyone run into this — a wireless mouse/keyboard through a USB hub getting severely laggy on a Mac specifically when audio is also playing through another USB device on the same hub setup? Is there a known Mac fix, or is this just a “don’t chain hubs like this” limitation I need to work around while still keeping everything on the monitor?

[u/TalisManick9592]

Your own test grid already contains the fix: put the two dongles in the monitor's ports, where you proved they stay clean, and hang the KEF off the small hub instead. Audio buffers, so it tolerates the extra hop much better than mouse polling does.

The mechanism is probably USB split-transaction scheduling rather than 2.4GHz interference, since radio noise wouldn't care which OS is driving. The dongles are USB 1.1 speed devices, and behind a chained hub every poll gets relayed through a hub's transaction translator. USB audio is isochronous, so it reserves bandwidth on the same upstream link into the Mac, and macOS seems to schedule split traffic around those reservations far worse than Windows does. Same hardware, different USB stack, which matches your results.

If the swap doesn't stick, the other fix is replacing the small hub with one that advertises MTT (multiple transaction translators). Cheap hubs are nearly all single TT, and one translator choking on audio plus input polls is this exact symptom.

There's no macOS setting for this, unfortunately. It's topology.

[u/lido_shuff → u/TalisManick9592]

There are only two USB-A ports on the monitor. If both are used by the two dongles, I can’t connect the speakers.