SPX to AAC 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. AAC is the sweet spot when you want modern compression in an open, non-Apple container.
iLoveConverter processes everything locally on your computer, which makes it private and fast: no upload wait, no server storage, no limits. Add as many files as you like — batch conversion is built in.
How SPX compares to AAC
| SPX | AAC | |
|---|---|---|
| Compression | Lossy Speex (Ogg) | Lossy (LC/HE/xHE profiles) |
| Quality | Narrowband/wideband speech | Best-in-class at low bitrates |
| Compatibility | Legacy VoIP stacks | Streaming/broadcast standard |
| Best for | Call recordings, phone systems | Streaming and mobile audio |
How to convert SPX to AAC
- 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 AAC". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted AAC 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 AAC format
AAC (Advanced Audio Coding) is MP3's official successor, standardized in MPEG-2 and MPEG-4 and refined over two decades. It is the audio track of YouTube, iPhone voice memos, digital radio and HE-AAC streaming — arguably the most-played codec in history. Files appear either raw (.aac, ADTS stream) or inside M4A/MP4 containers.
Its claim to fame is low-bitrate performance: HE-AAC v1/v2 keep speech and music listenable at 24–64 kbps, where MP3 collapses. Raw .aac streams carry weaker tagging than the M4A container, which is why music libraries prefer M4A even when the codec is identical.
+ Strengths
- ✓The standard of streaming, mobile and broadcast
- ✓Excellent low-bitrate behavior (HE-AAC)
- ✓Better than MP3 at equal bitrate
! Limitations
- −Raw .aac files tag poorly
- −Flavor fragmentation (LC/HE/xHE) confuses tooling
Why convert SPX to AAC?
There is a concrete reason this conversion exists: Speech-only: music is unusable AAC sidesteps that — The standard of streaming, mobile and broadcast If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this SPX to AAC 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 AAC?
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.
Will converting SPX to AAC reduce audio quality?
If AAC is lossless, the output contains everything the SPX file contains — no further loss is added. If AAC 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.
Can I convert a whole folder of SPX files?
You can select many files at once and they are processed in a single batch. Output files land in one ZIP download when there is more than one result.