Convert M4A to WAV on iPhone
WAV is the format every audio tool on earth can open. It is also uncompressed, so this conversion makes your file dramatically larger without making it sound any better.
What you are actually doing
An M4A almost always contains AAC — a lossy codec. To make a WAV, Convexy decodes that AAC back to raw PCM samples and writes them out uncompressed.
Note the word decodes. It does not reconstruct. The AAC encoder that produced your M4A permanently threw away audio it decided you would not miss, and that audio does not exist in the file any more. Decoding gives you the samples that survived — nothing else. The WAV is a faithful, uncompressed rendering of a file that already had holes in it.
So: same sound, much bigger file. A 5 MB M4A commonly lands somewhere around 50–100 MB as a WAV. That is not a bug, and it is not a sign of higher quality. It is just what uncompressed audio costs.
Converting lossy to lossless does not recover quality. This is the most persistent myth in audio conversion. WAV, FLAC and AIFF all preserve exactly what you hand them — including everything a lossy encoder already deleted. No app, on any platform, at any price, can undo AAC or MP3 compression.
So why do it?
Because WAV is the lingua franca of audio software and hardware, and quite a lot of things simply refuse to deal with anything else:
- Editing. If you are about to cut, mix, normalise or process the audio, work in WAV. Every edit-and-save cycle on a lossy file adds another generation of damage. Convert once to WAV, do all your work there, and export lossy at the very end — once.
- Tools that demand it. Samplers, transcription software, forensic tools, older DAWs, hardware loopers, some speech-recognition pipelines, plenty of scientific and academic software. WAV or nothing.
- Sound design and sample libraries. Most expect uncompressed PCM and will not import an M4A.
- Anything that has to seek instantly — WAV is trivially seekable because every sample sits at a computable byte offset.
All good reasons. "To make it sound better" is not on the list, and never will be.
What Convexy writes
Convexy writes WAV as 32-bit floating-point PCM. This is the format modern DAWs and editors work in natively, and it gives you enormous headroom — gain changes, mixing and processing will not clip or quantise on the way in.
Two consequences to be aware of. First, the file is about twice the size of the equivalent 16-bit WAV, on top of the size increase from decompressing in the first place. Second, a small number of very old tools and some hardware expect 16-bit integer PCM and will not open a float WAV. If you hit that, it is almost always the tool, not the file.
You can preserve the source sample rate or force 44.1 kHz or 48 kHz, and preserve, downmix to mono, or keep stereo. For a voice recording headed into transcription, mono at 44.1 kHz is a sensible and much smaller choice.
If your M4A is Apple Lossless
An .m4a is a container, not a codec, and it can hold ALAC (Apple Lossless) instead of AAC. If yours does, none of the loss described above applies — ALAC is lossless, so ALAC to WAV preserves the audio exactly and you are simply unpacking it into an uncompressed container.
M4As from Voice Memos, iTunes Store purchases and iPhone video soundtracks are AAC. ALAC almost always comes from a deliberate lossless rip, and you would know if you had made one.
How to do it
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Bring the M4A into Convexy
Tap Browse files and pick it from Files or iCloud Drive, or share it in from Voice Memos or any other app.
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Choose WAV
Convexy shows only the formats your file can actually become, so WAV appears alongside MP3, AIFF, CAF and FLAC.
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Set sample rate and channels
Preserve is usually right. Mono is a large, free saving on a single-microphone voice recording.
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Convert
Decoding runs on your iPhone. Expect a large output file — that is uncompressed audio doing what it does.
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Save or share it
Save to Files, or send it straight into the editor or tool that wanted a WAV in the first place.
Common questions
Does converting M4A to WAV improve the quality?
No. The AAC inside your M4A permanently discarded audio when it was encoded. Decoding it to WAV recovers the samples that survived and nothing more. You end up with an uncompressed file, ten or twenty times the size, that sounds exactly like the M4A. WAV preserves; it does not repair.
Why is the WAV so much bigger than the M4A?
Because WAV stores every sample uncompressed, and AAC's entire job was to avoid doing that. Uncompressed stereo audio costs roughly 10 MB per minute at 16-bit — and Convexy writes 32-bit float WAV, which is about twice that again. A 5 MB M4A becoming an 80 MB WAV is completely normal.
Should I edit the M4A directly instead?
Only if your editor supports it and you are making a single trivial change. Every time you edit and re-save a lossy file, it is decoded and re-encoded — another generation of loss. If there is real work to do, convert to WAV once, do all of it there, and export to a lossy format at the end. One encode, not five.
My tool says it can't open the WAV. Why?
Convexy writes 32-bit floating-point WAV, which every modern DAW and editor handles natively but a few older programs and some hardware do not — they expect 16-bit integer PCM. If a tool refuses the file, that is the likely reason, and it is a limitation of the tool rather than of the audio.
Is WAV or FLAC the better choice here?
Neither improves the audio. Pick WAV if you are heading into an editor or a tool that demands it. Pick FLAC if you just want to store the file losslessly from here on — it is a fraction of the size for identical audio. If you are only listening, keep the M4A and convert nothing.