Multilingual Voice AI built for Speed
STT, TTS, and voice agents, up to 3x faster[1] than ElevenLabs and Cartesia in over 50 languages. Built on
Time to first audio
p50, fastest firstTime to first audio by provider, fastest first: Sprag 113 milliseconds (fastest), Cartesia 195 milliseconds, Deepgram 279 milliseconds, ElevenLabs 341 milliseconds, OpenAI 654 milliseconds.
Four ways to make a voice.
Pick one and try it here. Everything on this page runs on the same account you sign up for, and the voices carry between all four.
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Every voice speaks every language.
56 preset voices, each with its own origin and accent. Any of them can be asked for any of the 10 output languages below, and fidelity is strongest in the one they came from.
Output languages: English, Chinese, French, German, Italian, Japanese, Korean, Portuguese, Russian, Spanish.
Eight of 56. Every voice you clone or design joins them.
Browse the full libraryEnterprise-grade infrastructure, built for speed.
Sprag serves its own models on open-source infrastructure rather than reselling somebody else's endpoint. That is where the latency goes, and it is why our audio engineers can tune a voice for you when a stock one will not do.
Time to first agent audio by provider, fastest first: Sprag 1033 milliseconds (fastest), OpenAI 1458 milliseconds, Cartesia 1896 milliseconds, AssemblyAI 3107 milliseconds, Deepgram 3299 milliseconds.
Native speech-to-speech through one model. No transcription and synthesis chained in front of it, which is most of where the time goes on a cascade.
1.18s p50 end-to-end turn latency on agentic_basic, n=30, against OpenAI at 1.76s and Cartesia at 2.24s. Speech in, speech out through a single model, with no transcription and synthesis chained in front of it.
See the methodologyFounded on Open-Source
The inference engine built for every modality.
−91.4%
reduction in job completion time arXiv↗
Omni-modal
Every modality. One surface.
Text, image, audio, and video inference in a single API layer.
Any architecture
AR, DiT, and parallel generation.
Autoregressive, diffusion transformers, and non-autoregressive models in one engine.
OpenAI + ComfyUI
Works with the client you have.
Fully OpenAI-compatible API server. Native ComfyUI support.
KV cache efficiency
vLLM memory management, extended.
State-of-the-art KV cache from vLLM core, applied to multimodal workloads.
Two ways in.
One account covers both. Make a voice in Studio, then call it from your own code.
curl https://api.sprag.ai/v1/audio/speech \
-H "Authorization: Bearer $SPRAG_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "chorus",
"input": "Good morning. The train leaves at nine.",
"voice": "serena",
"response_format": "mp3"
}' --output speech.mp3