Free online FLAC to SPX converter

Brief explanation of the source format

FLAC (Free Lossless Audio Codec) is a widely used lossless audio format that compresses sound without removing any audio data. It is popular with music collectors, archivists, podcasters, and anyone who wants high-quality audio with smaller file sizes than WAV or AIFF. FLAC is commonly used for music libraries, archival storage, and distribution of high-fidelity audio.

Brief explanation of the target format

SPX usually refers to audio encoded with the Speex codec, typically stored in an Ogg container as .spx or sometimes .ogg. Speex is a lossy speech codec designed for voice, not music. Its main advantages are small file size, low bitrate operation, and good performance for speech recording, VoIP, and voice notes. Compared with FLAC, SPX is much more compressed but sacrifices audio fidelity, especially for music and complex sounds.

How to perform the conversion

The best practical tool for this conversion is FFmpeg, which supports both FLAC input and Speex output in many builds. Because FLAC is lossless and SPX is lossy, the conversion is straightforward, but you should choose settings appropriate for speech.

1. Install FFmpeg if it is not already available on your system.
2. Open a terminal or command prompt in the folder containing your FLAC file.
3. Run a command such as ffmpeg -i input.flac -c:a libspeex -ar 16000 -ac 1 output.spx.
4. If your FFmpeg build does not include libspeex, try ffmpeg -i input.flac -c:a speex -ar 16000 -ac 1 output.spx instead.
5. For speech, 16 kHz mono is a common choice; for higher voice quality, you can experiment with higher sample rates if your encoder and playback target support them.
6. Test the resulting file in a player that supports Speex/Ogg playback.

If you prefer a graphical workflow, some audio editors and converters can export to Speex if the codec is installed, but support is less common than for MP3, AAC, or FLAC. You can also convert the file on 101convert.com for free, without installing any software.

Notes on quality, compatibility, or limitations

This is a lossy conversion: converting FLAC to SPX permanently discards audio detail, so it is not suitable if you want to preserve music quality or keep an archival master. SPX is best for speech-only content such as interviews, voice memos, and narration. Compatibility is also more limited than with mainstream formats; some players recognize Speex only when it is stored in an Ogg container. If your goal is general playback compatibility, consider whether MP3, AAC, or Opus would be a better target than SPX. For archival purposes, keep the original FLAC file because you cannot recover the lost quality from the converted file.