Quick Verdict
Use Speex when…
Don't use Speex for new work — it's deprecated. Use Opus for voice instead.
Use MP3 when…
Use MP3 for general audio — voice notes, music, anything. Universal compatibility and good quality at all bitrates make MP3 the practical choice for general audio storage.
Convert Speex and MP3 files
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Speex vs MP3: Feature Comparison
| Feature | Speex | MP3 |
|---|---|---|
| Optimization | Voice only | All audio |
| Typical bitrate | 8–24 kbps | 128–320 kbps |
| Music quality | Unusable | Excellent |
| File size (1 min voice) | ~120 KB | ~960 KB at 128 kbps |
| Compatibility | Limited (deprecated) | Universal |
| Modern status | Replaced by Opus | Universal |
When Speex wins
- ✓Optimization: Voice only
- ✓Typical bitrate: 8–24 kbps
- ✓Music quality: Unusable
When MP3 wins
- ✓Optimization: All audio
- ✓Typical bitrate: 128–320 kbps
- ✓Music quality: Excellent
Frequently asked questions
How do I convert Speex (.spx) to MP3?
FFmpeg: `ffmpeg -i input.spx -c:a libmp3lame -b:a 64k -ac 1 output.mp3` for voice (mono, low bitrate). The output sounds about the same as Speex source — Speex was already lossy at low bitrates.
When did Speex become deprecated?
The Speex project announced in 2012 that all new development should use Opus instead. Existing Speex files remain playable, but no new applications should adopt Speex. Some legacy systems (older voicemail, ham radio software) still use it.
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