Manatee

How to convert WAV to MP3 on a Mac

· 6 min read

A WAV file is uncompressed audio, about 10 MB per minute at CD quality, and turning it into an MP3 cuts that by roughly ten times. On a Mac you can do it with the Music app (set the import encoder to MP3, add the file, then File, Convert, Create MP3 Version), with ffmpeg in Terminal, or by dropping a folder of WAVs into Manatee and choosing MP3. Keep the WAV if it is a recording you might edit later; the MP3 is the sharing copy.

Why WAV is so large, and when to keep it

WAV stores raw PCM samples: 44,100 of them per second, two channels, 16 bits each, with no compression at all. That is what makes it the standard for recording, editing, and mastering. Every sample is there, and nothing needs decoding.

It is also why nobody wants to email one. MP3 keeps the parts of the sound your ears attend to and discards the rest. At 320 kbps the result is about 2.4 MB per minute; at 128 kbps, under 1 MB per minute.

The rule that saves regret: if the WAV is something you recorded (an interview, a band rehearsal, a podcast episode, a voiceover), keep it. Converting to MP3 is one-way. If the WAV is a copy of something you also have elsewhere, such as a rip of a CD you own, the MP3 can stand alone. Lossless vs lossy: what happens to audio when you convert it explains the trade in more detail.

Option 1: the Music app

The Music app has an MP3 encoder built in, and it handles WAV input directly. The only wrinkle is that it converts tracks in its library, so you add the file first.

  1. Open Music. Choose Music, then Settings, then Files.
  2. Click Import Settings. Set Import Using to MP3 Encoder. Under Setting, pick Higher Quality (192 kbps) or choose Custom to set 256 or 320 kbps. Click OK twice.
  3. Drag the WAV into the Music window, or use File, then Import.
  4. Select the track. Choose File, then Convert, then Create MP3 Version.
  5. A new entry appears beside the original. Right-click it and choose Show in Finder to locate the MP3 on disk.

You can select a dozen WAVs and convert them together. When you are done, you may want to remove the WAVs from the library so they do not double up; Music will offer to keep the files on disk when you delete the entries.

The limitation is that Music is a library manager, not a file converter. Every WAV you convert becomes a library entry, and the output lands in the Music media folder rather than next to the source.

Option 2: ffmpeg in Terminal

For a folder of files with no library involved, ffmpeg does it in one line. With Homebrew installed, brew install ffmpeg gets you the tool.

  1. Open Terminal. Type cd, drag the folder of WAVs onto the window, press Return.
  2. Convert one file at 320 kbps:
ffmpeg -i "take1.wav" -codec:a libmp3lame -b:a 320k "take1.mp3"
  1. Convert every WAV in the folder:
for f in *.wav; do ffmpeg -i "$f" -codec:a libmp3lame -b:a 320k "${f%.wav}.mp3"; done
  1. For spoken word, add -ac 1 to fold stereo to mono and drop the bitrate: -ac 1 -b:a 96k. Speech recorded in stereo rarely benefits from two channels, and the file halves in size.

WAV files often carry no tags at all, so expect the MP3 to have a blank title and artist. You can fill them in afterward in the Music app with Get Info.

Option 3: Manatee

Manatee is the drag-and-drop version of the ffmpeg route, with the engine bundled in the download.

  1. Open Manatee and choose Convert.
  2. Drop the WAV files, or a folder of them, into the window. Or drag them onto the menu bar icon.
  3. Pick MP3 as the target.
  4. Watch the job list. Each MP3 is written next to its WAV; the source is never modified.

Manatee runs entirely on the Mac, with no upload and no account. It is free for 24 hours with every feature, then $9 once. It does not edit audio, trim silence, or adjust levels, so do that in an audio editor before converting.

If your WAVs come from a field recorder or a voice recorder, Manatee also accepts the odder formats those devices produce (AIFF, CAF, AMR, and others), so you can drop a mixed folder and pick MP3 for all of it.

Bitrate: match it to the content

Content Bitrate Channels
Music, final release 320 kbps Stereo
Music, everyday listening 192 to 256 kbps Stereo
Podcast, interview, lecture 96 to 128 kbps Mono if the source is a single voice
Voice memo for reference 64 kbps Mono

A higher bitrate than the content needs just makes a bigger file. A lower one than it needs produces the swishy, underwater artifacts people associate with bad MP3s, most audibly on cymbals and applause.

Sample rate is the other setting worth a glance. A WAV from a recorder may be 48 kHz or 96 kHz. MP3 supports 48 kHz, but most players are happiest with 44.1 kHz. ffmpeg can set it with -ar 44100; the Music app resamples automatically.

What about WAV files that will not convert

Occasionally a WAV refuses: the Music app says it cannot be imported, or ffmpeg reports an invalid header. Common causes:

  • It is not really PCM. Some recorders and broadcast systems write compressed audio inside a WAV wrapper. ffmpeg usually decodes these anyway; Music often does not.
  • The header is wrong. A recorder that lost power mid-recording writes a WAV whose header says zero length. The audio is usually all there. ffmpeg ignores a bad length field and reads to the end of the file, so converting straight to MP3 usually works, and ffmpeg -i broken.wav -c copy fixed.wav rewrites the header without re-encoding if you want a playable WAV.
  • It is a 32-bit float file from a modern recorder. Convert with ffmpeg; it handles the format.

If the file shows 0 bytes in Finder, the data never made it to disk, and no converter can help. Why files get corrupted and what can actually be recovered covers what is and is not salvageable.

Questions

Will I hear the difference between the WAV and a 320 kbps MP3? On most equipment, no. The MP3 encoder at 320 kbps is designed to be transparent for nearly all listeners. The WAV is still the one to keep for editing, because each further lossy save compounds the losses.

Is M4A (AAC) a better choice than MP3? At the same bitrate, AAC sounds slightly better and the file is slightly smaller. MP3 plays on more devices, including car stereos from fifteen years ago. If compatibility is not a concern, AAC at 256 kbps is a fine choice; both ffmpeg and Manatee can produce it.

Can I convert AIFF the same way? Yes. AIFF is Apple’s equivalent of WAV, also uncompressed, and all three methods handle it identically. How to convert AIFF to MP3 on a Mac has the specifics.

Does the MP3 keep the recording date and other metadata? Only what the WAV carried, which is often nothing. If the WAV has BWF broadcast metadata (recording date, originator), ffmpeg copies what ID3 can represent and drops the rest.