Is AssemblyAI-TTS-1 state of the art?Pending benchmarks.Announced Oct 27, 2026; no independent results yet.
AssemblyAI's first text-to-speech model, aimed at voice agents: streaming audio over HTTP or WebSocket, more than 4,000 voices and instant voice cloning, in English, Spanish, French, German, Italian and Portuguese. Generally available on AssemblyAI's API at $15 per 1M characters with no concurrency limit or annual contract. No weights.
The details so far
- Lab
- AssemblyAI
- Announced
- Oct 27, 2026
- API
- Live · assemblyai-tts-1 · assemblyai-tts-1: HTTP POST /v1/speech and WebSocket /v1/ws on tts.us.assemblyai.com, an OpenAI-compatible route, and an EU host
- Open weights
- Closed · None
- Task
- Text-to-speech for voice agents; operates on continuous audio representations rather than discrete audio tokens
- Languages
- English, Spanish, French, German, Italian and Portuguese, with several accents; more languages promised
- Voices
- 4,000+ library voices plus instant voice cloning; no fine-tuned ("Pro") cloning yet; pronunciation dictionaries and emotion tags coming
- Pricing
- $15 per 1M characters; unlimited concurrency, no annual contract
- Training data
- Millions of hours of audio, including real conversational data, per AssemblyAI
Tags marked unsure are not stated on the lab's own pages.
What would let us call it
Verdicts use only independent boards we already track. Two consecutive snapshots are required before any crown.
- Publicly announced with a source
- Usable by the public (API or weights)
- Listed on an independent board we track
- Enough results for a rank in a category
- Holds across two snapshots (crowns only)
What the lab claims
Self-reported. Shown for context; not used in any verdict.
Lab claim: 47 ms median time to first byte in AssemblyAI's head-to-head with five other TTS models (next fastest 119 ms), and 90 ms time to first audio in production.
Lab claim: 99.0% word accuracy, 93.7% entity accuracy, 3.85/5 average on preference predictors such as UTMOSv2, 85.5 on TTSDS prosody and 0.64 cloned-voice speaker similarity.
Sources
LABAssemblyAI blog: AssemblyAI-TTS-1 text-to-speech APIassemblyai.com/blog/text-to-speech-api · Oct 27, 2026LABAssemblyAI docs: text-to-speech voicesassemblyai.com/docs/tts/voicesLABAssemblyAI on X: AssemblyAI-TTS-1x.com/AssemblyAI/status/2115470615583056042 · Oct 28, 2026Tracking continues until an independent board lists it.