Guides / Fixing Mac audio recording problems
Why does my Mac recording only capture one channel?
Updated 2026-09-03.
A Mac recording that plays in the left ear only, or shows one flat waveform, has one of two causes: a mono microphone was recorded onto a stereo track, so channel 2 is empty, or a multi-input interface was captured on the wrong channel pair, so the signal on input 3 never reached inputs 1 and 2. Run afinfo on the file to see the channel count, then fix the input mapping before the next take.
How do I check whether my recording is mono or one-sided stereo?
These two look the same in headphones and need different fixes, so check the file first.
- Open Terminal and run
afinfo ~/Music/recording.wav(drag the file into the window to paste its path). - Read the data format line.
2 chis a stereo file;1 chis mono.
What the result tells you:
- 1 ch, plays on both sides: the file is mono and correct. Players send mono to both ears.
- 2 ch, sound on the left only: a mono source was recorded into a stereo file. The right channel is silence. This is the common case with one microphone on inputs 1 and 2.
- 2 ch, silence on both: the interface was captured on the wrong pair. See the interface section.
- 2 ch, different sources left and right: two mono inputs recorded as one stereo pair. Fine for editing, wrong for listening.
afinfo also prints sample rate and bit depth; for what those mean, see 16-bit vs 24-bit audio recording.
Why is my microphone only on the left channel?
Most interfaces present their physical inputs to macOS in pairs: inputs 1 and 2 form the first stereo pair, 3 and 4 the second. A single microphone in input 1 occupies the left half of that pair. A recorder set to a stereo source faithfully records input 1 on the left and the empty input 2 on the right.
Three fixes, best first:
- Record mono at the source. Choose a mono or single-channel input in the recorder if it offers one. The file is 1 ch and plays centered everywhere.
- Record stereo, convert after.
afconvert -f WAVE -d LEI24@48000 -c 1 in.wav out.wavwrites a 24-bit 48 kHz mono WAV. Folding a one-sided stereo file to mono halves its size and loses nothing, because the right channel was empty. - Fix it in the editor. Set the track to mono, or duplicate the left channel, in GarageBand, Logic or Audacity.
Documented failure mode: a stereo-linked pair on the interface itself. Some interfaces have a Stereo Link or Pair control in their vendor software that combines inputs 1 and 2 into one stereo channel. With one mic on input 1, that link is what puts your voice hard left. Unlink the pair for a solo mic.
Why is my interface recording silence on both channels?
An 8-input interface such as a Focusrite Scarlett 8i6 is a single Core Audio device with 8 input channels. Many recorders default to channels 1 and 2. A DJ mixer or synth plugged into line inputs 3 and 4 is then recorded as silence, even though the interface's meters show signal and the permission is granted.
Fix it in the app, not in Audio MIDI Setup. Audio MIDI Setup shows the channel count and lets you "set the sample rate and bit depth" in the Format menu, but it does not choose which channels an app records.
- Open the recorder's input settings and pick the interface.
- Look for a channel, pair, or input mapping control. Select inputs 3 and 4, or whichever pair you are plugged into. Some apps offer "all channels", which writes a multi-channel file you can split later.
- Start a test take and confirm the meter moves.
If the app has no channel picker, it can only record the first pair: move the cable to inputs 1 and 2, or use an app with a picker. The author records his DJ mixer into inputs 3 and 4 of a Scarlett 8i6 for exactly this reason, described in how to record a DJ mix on Mac with an audio interface. If the interface itself is missing, start with USB audio interface not showing up on Mac.
Can system audio recordings come out mono?
Rarely, and then the cause is the output device, not the recorder. System audio capture through ScreenCaptureKit delivers the mix in the format of the current output route. Two situations flatten it:
- Bluetooth headset with the mic open. When any app opens a Bluetooth headset's microphone, the headset switches from stereo A2DP to the Hands-Free Profile, which carries mono playback. A system audio capture made while a call app holds the headset mic can come out mono or narrow. Route output to speakers or a wired device during capture, or close the app using the headset mic. Detail in Bluetooth headphones make Mac recordings sound bad.
- Mono source material. A mono podcast or phone call is mono; the capture is stereo with both channels identical. Nothing is wrong.
A stereo file with identical channels is not a bug, but folding it to mono with the afconvert line above halves its size. The measured size per minute for each format is in how big is an audio recording per minute.
Click the Format pop-up menu, then set the sample rate and bit depth.
Apple, Audio MIDI Setup User Guide, Set up audio devices
One-channel recordings: cause, check, and fix
| What you hear | afinfo shows | Cause | Fix for the next take | Fix for the existing file |
|---|---|---|---|---|
| Voice on the left only | 2 ch | Mono mic on a stereo pair | Choose a mono or single-channel input | afconvert -c 1 to fold to mono |
| Silence both sides, meter on interface moves | 2 ch | Wrong channel pair | Pick inputs 3-4 (or the pair in use) | none, re-record |
| Two different sources left and right | 2 ch | Two mono inputs recorded as a pair | Record each input to its own take, or all channels | Split channels in an editor |
| Centered, sounds fine | 1 ch | Correct mono file | nothing | nothing |
| Narrow or phone-like system audio | 2 ch | Bluetooth HFP output during capture | Play through speakers or wired output | none, re-record |
Where AirCheck fits
AirCheck's input source has a channel-pair picker for multi-channel interfaces, so you can select inputs 3 and 4 of an 8-input Scarlett 8i6, or "all channels", instead of being stuck on the first pair. That solves the silent-on-both-sides case at the source. It records 24-bit AIFF at the device's own rate and exports WAV 16-bit, WAV 24-bit or MP3 320 kbps when the take stops. AirCheck is $39 once and needs macOS 14 Sonoma or newer.
When you do not need it: If your only source is one mic on inputs 1 and 2, any recorder with a mono option, including QuickTime Player, gives you a correct file. AirCheck does not fold a finished stereo file to mono; use afconvert or an editor for that.
AirCheck records what your Mac plays, or any input, to one file. $39 once.
macOS 14 or newer. One-off payment. Fourteen-day refund, no questions asked.
Questions people ask
How do I make a Mac recording play in both ears?
Convert the one-sided stereo file to mono: afconvert -f WAVE -d LEI24@48000 -c 1 in.wav out.wav. Players send a mono file to both sides. For the next take, choose a mono or single-channel input in the recorder.
Does a mono file lose quality compared to stereo?
Not when the source was mono. A single microphone produces one signal; storing it twice adds size, not information. Folding a one-sided stereo file to mono keeps the full bit depth and sample rate of the recorded channel.
Why does my interface show signal but the Mac records silence?
The app is listening to a different channel pair than the one you plugged into. Choose the right pair in the app's input settings. Audio MIDI Setup shows the channels but does not choose them for the app.
Sources
- Apple: Set up audio devices in Audio MIDI Setup on Mac
- Microsoft Learn: Bluetooth Classic Audio (HFP is mono playback and capture)
Related guides
- Why is my USB audio interface not showing up on my Mac?
- Why do my Bluetooth headphones make Mac recordings sound bad?
- Why is my Mac not recording sound?
- How to record a DJ mix on a Mac with an audio interface
- How big is an audio recording per minute on a Mac?
- Why is my app missing from Screen & System Audio Recording on my Mac?
- Fixing Mac audio recording problems: all guides
- Every guide, by topic