Rogue Amoeba's Loopback is one of the best-built utilities on the Mac. If you need to capture app audio, merge a mic with your system sound for a livestream, or build a virtual device that feeds one app's output into another's input, it is the tool professionals reach for — and it earns that reputation.
Which is exactly why so many people try to use it for a different job: pointing several microphones at one person and combining them into a single input. It seems like the same problem. It is not, and the reason is physics, not software quality.
What Loopback actually does with multiple mics
Loopback is a routing tool. When you add two microphones to a virtual device, it does precisely what you asked: it sums them. Both signals, mixed together, all the time. For two different sound sources — your voice plus a guitar amp, a host mic plus a guest mic — that is exactly right.
For two microphones capturing the same voice, summing is the one thing you should never do. Your voice arrives at each mic at slightly different times — sound covers only about 34 centimeters per millisecond. When two time-shifted copies of the same signal are added together, some frequencies reinforce and others cancel. Audio engineers call the result comb filtering: a hollow, phasey, "talking into a pipe" coloration that gets worse as you move, because the delay between the mics keeps changing.
This isn't a Loopback flaw. Any tool that sums same-source mics — Aggregate Devices, a hardware mixer with both faders up, a DAW bus — produces the same artifact. Broadcast engineers solved it decades ago with a rule of thumb: when several mics hear the same source, one mic should be live and the rest should be down.
The job you're actually trying to do
If you're setting up a desk mic plus a lav, or mics at different angles of your workspace, what you want isn't a mix — it's whichever mic hears you best right now, switching automatically as you turn, lean, and move, without you touching anything mid-call.
That is a decision-making problem, not a wiring problem, and it's the job SoundMesh was built for. It listens to every connected mic, continuously scores which one is capturing your voice most clearly, and hands off between them with a fast crossfade — then presents the result to Zoom, Meet, or your dictation app as one ordinary virtual microphone. One mic live at a time, so there is nothing to comb-filter.
When Loopback is the right choice
Honesty matters here, because these tools genuinely serve different jobs:
Choose Loopback when you need to capture application audio, route sound between apps, combine different sources (voice + music + game audio) into one feed, or build custom multi-channel virtual devices for broadcast software. SoundMesh does none of that today.
Choose SoundMesh when the problem is one voice and several microphones — a desk you move around, dictation while pacing, calls where you keep turning to a second monitor. Routing tools make you the audio engineer; SoundMesh's whole point is that nobody is riding faders while you work.
Some setups legitimately use both: Loopback to bring app audio into a stream, SoundMesh as the microphone source feeding it.
What about just using an Aggregate Device?
macOS's built-in Aggregate Devices get suggested in every forum thread on this topic. They combine mics into one multi-channel device — but most call apps only read the first channels, and if the channels are summed you're back to comb filtering. We've covered the details in our guide to using multiple microphones on a Mac.
If you've been fighting hollow, phasey audio from a summed multi-mic setup, the fix isn't a better mixer — it's switching instead of summing. We keep a shorter buyer's version of this comparison if you're deciding today. That's the product. SoundMesh is a one-time purchase, and you can hear the difference on your own setup before paying anything.