SPX to SNDT Converter

Convert Speex audio files to MS-DOS SNDT sound format

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DOS-Era Compatibility

Convert your Speex voice files to SNDT for use with early MS-DOS sound systems and vintage computing projects.

Rapid Conversion

Both SPX and SNDT are compact, lightweight formats — the conversion finishes in seconds.

Secure Processing

Your SPX uploads are deleted immediately. SNDT files are purged from our servers within 24 hours.

How to convert SPX to SNDT

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose sndt or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your sndt file right afterwards

About formats

Speex is an open-source audio codec purpose-built for speech compression, developed by Jean-Marc Valin under the Xiph.Org Foundation. First released in October 2002, it targets voice-over-IP, conferencing, and any scenario where spoken word needs to travel efficiently over a network. SPX files wrap Speex-encoded audio inside an Ogg container, pairing the codec's speech optimization with Ogg's streaming capabilities. Three sampling rates are supported — narrowband at 8 kHz, wideband at 16 kHz, and ultra-wideband at 32 kHz — along with variable bitrate encoding that adapts in real time to speech complexity. A standout advantage is its patent-free, BSD-licensed nature, which allowed developers to embed it freely in both commercial and open-source products. Speex also bundles acoustic echo cancellation, noise suppression, and automatic gain control, features that rival codecs typically delegate to external libraries. Although its creators officially recommend Opus as a successor since 2012, Speex remains deployed in legacy VoIP systems, archived recordings, and embedded devices where its lightweight decoder footprint is still valued.
Initial release: October 15, 2002
SNDT is the audio format associated with Sndtool, an early MS-DOS sound utility from the early 1990s that appeared alongside the spread of Sound Blaster cards in PCs. Unlike the headerless Sounder format, SNDT files include a brief header with the sample rate and data length — a meaningful improvement that let playback software determine timing automatically. Audio data is stored as 8-bit unsigned PCM, typically at 8000 to 22050 Hz in mono. Sndtool functioned as a simple waveform recorder and player, often distributed as shareware or bundled with sound card drivers. A key advantage over competing DOS audio formats was this self-describing header, which eliminated the guesswork of playing unfamiliar files — a real problem before standardized multimedia frameworks existed. The format was also efficient to decode, requiring no decompression and minimal CPU overhead on the 286 and 386 processors of the time. SNDT files served as building blocks for early PC games and multimedia presentations, where developers needed reliable audio across the limited Sound Blaster hardware ecosystem. Today, SNDT survives in retro software archives and is supported by SoX for conversion to modern formats.
Developer: Sndtool (MS-DOS)
Initial release: 1992

Frequently Asked Questions

Why convert SPX to SNDT?

SNDT is needed for certain early MS-DOS audio applications and retro computing setups that only accept this specific format.

What plays SNDT files?

SOX command-line tools and specialized retro computing software can handle SNDT files.

Is SNDT similar to other DOS formats?

Yes — SNDT belongs to the early MS-DOS SND format family, sharing basic PCM storage principles with SND and SNDR.

How is the audio quality?

SNDT supports basic sample rates suitable for voice. SPX speech recordings convert cleanly into this format.

Is it free?

SPX to SNDT conversion is free on convertio.tools.