A Multi-Output Device has to keep every member speaker locked to the same clock, because they are all playing the exact same stream. When the devices don't share a native sample rate, or one device's clock drifts against the others, macOS has to correct for it as it plays, and that correction is the stutter or glitch you hear.
This is not a fault in your speakers, your Mac, or the app that is playing. It is a direct consequence of how a Multi-Output Device works: several independent devices, each with its own clock, being asked to output one identical stream in step with each other. Below is what causes the mismatch, the checks worth running in Audio MIDI Setup, and where Chorus can and cannot help.
Why does a Multi-Output Device need every speaker on the same clock?
Every audio device, wired or wireless, runs on its own internal clock that ticks at a fixed number of samples per second. When macOS builds a Multi-Output Device, it does not merge those clocks into one; it picks one device as the group's primary time source and has to keep nudging every other member back into step with it. If the devices agree closely enough, that nudging is inaudible. If they don't, the correction becomes a periodic stutter, glitch, or brief dropout, worse the further the clocks or sample rates are apart.
Mismatched sample rates are the most common cause
Check this first. Every device in the group has its own native sample rate, and macOS defaults each one to whatever it reports as its preferred rate rather than a rate shared across the group. A Mac's built-in speaker commonly defaults to 44.1kHz, while a USB audio interface or a display's built-in speakers may default to 48kHz. Leave a Multi-Output Device running with members at two different rates, and macOS has to resample one stream to match the other continuously, which is the single most avoidable cause of audible stutter.
Open Audio MIDI Setup (Applications > Utilities), select the Multi-Output Device in the left-hand list, then click through to each member device inside it and check its Format dropdown. Set every member to the same value, either 44.1kHz or 48kHz, rather than leaving each on its own default. This alone resolves stutter caused by a straightforward rate mismatch, and it takes under a minute to check.
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Download for MacDoes mixing Bluetooth and wired speakers cause stuttering?
Often, yes. A wired output, whether built-in, USB or HDMI, holds a fairly precise clock and a small, predictable buffer. Bluetooth output does neither: it buffers audio in larger, more variable chunks to absorb radio interference and connection quality, and its clock precision is coarser to begin with. Put a Bluetooth speaker or headphones in the same group as a wired device, and it is usually the Bluetooth side that drifts first and needs the most frequent correction, which is what you hear as the stutter. Two wired devices set to the same sample rate are the most stable combination a Multi-Output Device can have; a wired-plus-Bluetooth group is the least.
Turn on drift correction for the non-primary devices
Matching sample rates stops the most obvious mismatch, but clocks can still drift slightly even when both devices report the same rate, since no two pieces of hardware run at exactly the same real-world speed. Audio MIDI Setup has a setting for this: inside the Multi-Output Device, one member is set as the primary, the clock the rest follow, and every other member has a Drift Correction checkbox next to it. Ticking Drift Correction on the non-primary devices tells macOS to keep actively resyncing them against the primary's clock, instead of letting the gap grow until it needs a larger, more audible correction.
Should the built-in Mac speaker stay in the group?
Only if you actually want sound coming out of it. The built-in speaker has its own native sample rate, and if it doesn't match the external gear you have grouped with it, it adds one more device macOS has to resample on the fly, and one more source of drift to correct for. If the built-in speaker isn't doing useful work in that group, untick it in Audio MIDI Setup. Fewer member devices at matched rates means less resampling overhead overall, and less opportunity for the group to need correcting mid-playback.
Where Chorus fits, and where it does not
Chorus groups outputs using the same multi-output mechanism macOS already provides, the one behind a Multi-Output Device in Audio MIDI Setup, so it shares the identical clock and sample-rate constraint. It cannot fix a genuine sample-rate mismatch or clock-drift stutter: that has to be solved in Audio MIDI Setup with the steps above, whether or not Chorus is involved.
What Chorus does help with is everything after that fix. Once the sample rates match and the group plays cleanly, rebuilding it, or switching to it, is one click or one keyboard shortcut rather than reopening Audio MIDI Setup and re-ticking devices each time. Its per-device balance also holds between sessions, so you are not resetting individual output levels every time you recreate the same group.
For the step-by-step on building a Multi-Output Device, see Apple's own guide to Audio MIDI Setup.
Frequently asked questions
Why does my audio stutter or glitch on a Multi-Output Device?
Because every device in the group has to stay locked to the same clock and sample rate to play the identical stream at once. When they don't, either from mismatched native sample rates or a clock that drifts, macOS has to correct for it as it plays, and that correction is audible as a stutter or brief dropout.
How do I fix a Multi-Output Device that stutters?
Open Audio MIDI Setup, select each device inside the Multi-Output Device and set them all to the same sample rate, typically 44.1kHz or 48kHz, then tick Drift Correction on every device except the one set as primary. Those two checks resolve the two most common causes.
Does mixing Bluetooth and wired speakers cause stuttering?
Often, yes. Bluetooth output buffers audio in larger, more variable chunks and has coarser clock precision than a wired connection, so it usually drifts first and needs the most frequent correction when grouped with wired devices. Two wired devices set to the same sample rate are more stable than a wired-plus-Bluetooth group.
Should the built-in Mac speaker stay in a Multi-Output Device group?
Only if you need sound from it. If its native sample rate does not match the other devices in the group, it adds another device macOS has to resample on the fly and another source of drift, so untick it in Audio MIDI Setup if it is not doing useful work in that group.
Does Chorus fix Multi-Output Device stuttering?
No. Chorus groups outputs using the same underlying clock and sample-rate mechanism as a plain Multi-Output Device, so it cannot fix a genuine mismatch or drift problem, that has to be corrected in Audio MIDI Setup first. Once the group plays cleanly, Chorus makes it faster to rebuild or switch to it without reopening Audio MIDI Setup each time.
