SPX to M4A Converter
Processing entirely on your device — large files may take a moment.
SPX is Speex voice audio in an Ogg container — the codec of old VoIP recorders and Asterisk phone systems. M4A sounds better than MP3 at the same bitrate, and Apple users never have compatibility worries.
Because the whole conversion happens on your device, it is instant, unlimited and genuinely private — no accounts, no watermarks, no files on anyone's server. Multiple files are converted in one go.
How SPX compares to M4A
| SPX | M4A | |
|---|---|---|
| Compression | Lossy Speex (Ogg) | Lossy AAC (ALAC for lossless) |
| Quality | Narrowband/wideband speech | Strong at 128–256 kbps |
| Compatibility | Legacy VoIP stacks | Apple-first, modern platforms |
| Best for | Call recordings, phone systems | Music libraries and voice memos |
How to convert SPX to M4A
- 1
Select your files
Drag & drop your SPX files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to M4A". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted M4A file individually, or grab everything at once as a ZIP archive.
About the SPX format
SPX is Speex speech audio in an Ogg container — the open voice codec of the 2000s VoIP wave, tuned for telephone-band speech at absurdly low bitrates. Asterisk PBX call recordings and old conferencing archives are where you meet it.
Speex was formally retired in favor of Opus, and players have followed. Converting SPX to MP3 (or Opus for the adventurous) rescues call archives before they become unplayable.
+ Strengths
- ✓Extremely compact for speech
- ✓Open-source lineage
! Limitations
- −Speech-only: music is unusable
- −Format officially retired
About the M4A format
M4A is MPEG-4 audio: AAC (or ALAC) inside the MP4 container, minus the video. It became the iTunes Store's format in 2003 and never left — Apple Music downloads, voice memos and most phone recordings are M4A. At the same bitrate, AAC sounds distinctly better than MP3, which is why 128 kbps M4A competes with 192 kbps MP3.
Support is excellent across Apple devices, modern Android, Windows and every streaming SDK. The one historical caveat: iTunes Store music bought before 2009 carried FairPlay DRM; everything since (and everything you record yourself) is DRM-free.
+ Strengths
- ✓Better quality than MP3 at the same bitrate
- ✓First-class on Apple and modern platforms
- ✓ALAC variant covers lossless needs
! Limitations
- −Very old feature phones and players miss it
- −Pre-2009 store purchases may carry DRM
Why convert SPX to M4A?
There is a concrete reason this conversion exists: Speech-only: music is unusable M4A sidesteps that — Better quality than MP3 at the same bitrate If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this SPX to M4A converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for SPX to M4A?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.
Are tags like title and artist preserved?
Tag handling varies between target formats and this conversion focuses on the audio itself. For archival copies where tags matter, keep the original file; the converted copy is for playback and sharing.
Will converting SPX to M4A reduce audio quality?
If M4A is lossless, the output contains everything the SPX file contains — no further loss is added. If M4A is lossy, one recompression pass is unavoidable; the quality slider controls how much. Loss that already happened in the source file can never be undone by converting.