CONVERT
W64 → SPX
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Fast, secure W64 to SPX conversion. No registration required.
Why this pair exists — W64 is an audio format with specific trade-offs between file size, bitrate flexibility, and device support. Ergo, the SPX route. Turn your W64 audio into a widely-supported SPX file. The conversion happens server-side through FFmpeg — the same engine behind every major audio editor — so the output plays cleanly on phones, car stereos, DJ software and streaming tools. Keep in mind W64 is an audio format with specific trade-offs between file size, bitrate flexibility, and device support. And remember that SPX is an audio format with specific trade-offs between file size, bitrate flexibility, and device support.
Sony Wave64
Source formatWave64 (W64) is an extension of the WAV format developed by Sony that breaks the 4 GB file size limit of standard WAV by using 64-bit chunk sizes. It is used in professional audio production for very long or multi-channel recordings.
Speex Audio
Target formatSpeex is an open-source audio compression format specifically designed for speech encoding. It uses Code-Excited Linear Prediction (CELP) and supports narrowband, wideband, and ultra-wideband modes for different speech quality requirements.
Why convert W64 to SPX
The motivation for a W64 → SPX conversion is almost always practical: a playback device, hosting platform or editing suite that insists on SPX. The audio quality trade-off is controllable via bitrate; the compatibility win is immediate and unambiguous.
HOW TO CONVERT
W64 → SPX
Give us the W64
Select a W64 (or several for batch). We read the header to pick decoder settings automatically.
Re-encode to SPX
The audio is decoded, optionally resampled, and re-encoded as SPX at transparent default bitrate.
Retrieve your SPX
Grab the download as soon as it is ready. Typical jobs finish in seconds for short clips.
Common Use Cases
Share across platforms
Send SPX files to anyone without worrying about whether they have the right software for W64.
Embed in documents
Drop SPX output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
SPX often produces smaller files than W64 for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
W64 vs SPX — Strengths and limitations
What each format does best, and where it falls short.
W64 Strengths
- Unlimited file size (64-bit chunks).
- Professional DAW compatibility.
- Bit-exact lossless.
Limitations
- Less universal than WAV.
- Niche — only matters for very large sessions.
- Competes with RF64.
SPX Strengths
- Patent-free voice codec.
- Three sample-rate modes for voice.
- Low CPU decode.
Limitations
- Deprecated in favor of Opus.
- No music support.
- Rarely used in new projects.
W64 vs SPX — Technical specifications
Side-by-side comparison of the technical details.
W64
- MIME type
- audio/x-w64
- Extension
- .w64
- Max size
- 2^64 bytes
- Relative
- RF64 (EBU 64-bit WAV)
SPX
- MIME type
- audio/speex
- Extension
- .spx
- Container
- Ogg
- Modes
- Narrowband/Wideband/Ultra-wideband
- Successor
- Opus
| Specification | W64 | SPX |
|---|---|---|
| MIME type | audio/x-w64 | audio/speex |
| Extension | .w64 | .spx |
| Max size | 2^64 bytes | — |
| Relative | RF64 (EBU 64-bit WAV) | — |
| Container | — | Ogg |
| Modes | — | Narrowband/Wideband/Ultra-wideband |
| Successor | — | Opus |
W64 vs SPX — Typical file sizes
Approximate file sizes for common scenarios.
W64
- 1-hour 24-bit 48 kHz mono ~620 MB
- 48-hour field recording ~30 GB
SPX
- 1 min voice (wideband 24 kbps) ~180 KB
Quality & Compatibility
The SPX output is as good as the W64 source allows. If the W64 was encoded at 96 kbps, the SPX cannot reconstruct detail the encoder already dropped; picking a very high SPX bitrate just produces a larger file. Match SPX bitrate to the W64 quality for the best balance.
Tips for Best Results
- Sample-rate mismatches between W64 and target device (48 kHz phone output from a 44.1 kHz track) are handled automatically; no manual resampling needed.
- For audiobook delivery, match the platform spec exactly — ACX requires 192 kbps CBR 44.1 kHz stereo, for example.
- Batch-convert an album in one job so every track shares identical encoder settings and loudness normalisation.
Frequently Asked Questions
Lossy-to-lossy conversions (most combinations) re-compress the audio, which technically introduces some loss. At a 192 kbps or higher target it is inaudible on normal equipment. Lossy-to-lossless conversions freeze the existing quality but cannot improve it; lossless-to-lossy transcodes are only as good as the target bitrate you choose.
For voice content (podcasts, audiobooks, lectures) 128 kbps is indistinguishable from higher bitrates. For music, 192-256 kbps covers most listening; 320 kbps is the ceiling for SPX and the right choice for audio you plan to edit further. Above that, prefer a lossless target instead.
Yes. Title, artist, album, year and cover art travel from the W64 container to the SPX container automatically where both formats support them. If a tag field has no SPX equivalent, it is dropped silently. Use any tag editor (Mp3tag, MusicBrainz Picard) to fine-tune afterwards.
RELATED CONVERSIONS
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See these formats side by side to understand which fits your use case best.
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