SPX is Speex voice audio in an Ogg container — the codec of old VoIP recorders and Asterisk phone systems.
Typical use: Converting SPX to MP3 makes old call recordings and voice prompts playable anywhere.
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
- Compression
- Lossy Speex (Ogg)
- Quality
- Narrowband/wideband speech
- Compatibility
- Legacy VoIP stacks
- Best for
- Call recordings, phone systems
Convert SPX to…
27 direct directions plus 18 workflows, sorted A–Z; 🔥 marks popular targets.
Frequently asked questions
What is a SPX file?
SPX is Speex voice audio in an Ogg container — the codec of old VoIP recorders and Asterisk phone systems.
How do I convert SPX files online?
Pick a target format from the "Convert SPX to…" list below, drop your file and hit convert. Everything runs in your browser — no install, no upload, no watermark, no limits.
Is it safe to convert SPX files here?
Yes. Every conversion is performed by your own device inside the browser — files never leave for a server, and the page keeps working even offline.
Which formats can SPX convert to?
This page lists all 45 directions across documents, images, audio, video, spreadsheets and archives — each one is its own free converter page.