Voice AI BenchmarksBy

ASSEMBLYAITEXT-TO-SPEECH2,882 SAMPLES / 30 DAYSLAST RUN NOV 2, 2026, 09:00 UTC

Assemblyai TTS 1 text-to-speech benchmarks

Assemblyai TTS 1, hosted by AssemblyAI (Assembly AI, assemblyai.com), measures mean 224 ms time to first audio (16th of 32) and 1.6% word error rate (7th of 32) among TTS systems. Results cover the last 30 days. Last measured .

Coval has active text-to-speech measurements for Assemblyai TTS 1, created by AssemblyAI and served through AssemblyAI's own API.

Time to First Audio#16 / 32
224ms
TTFA Network Roundtrip#6 / 32
80ms
TTFA Leading Silence#29 / 32
143ms
Word Error Rate#7 / 32
1.6%

Overview

Assemblyai TTS 1 is tested every day on a fixed set of text prompts, measuring how quickly audible speech starts and how intelligible the result is.

Technical specifications

Made by
AssemblyAI
Hosted by
AssemblyAI
Source
Official API
Licensing
Proprietary
Deployment
Cloud
Region
US

How Assemblyai TTS 1 ranks

Full TTS dashboard
Time to First Audio — every measured TTS modelMilliseconds · lower is better · 30-day averageEvery TTS model ranked on Time to First Audio, with Assemblyai TTS 1 highlighted.
  1. #1vui42 ms
  2. #2Default64 ms
  3. #3Qwen3 TTS Fast68 ms
  4. #4TTS Flash 283 ms
  5. #5Qwen3 TTS 1.7b105 ms
  6. #6Simba 3.0110 ms
  7. #7Simba 3.2118 ms
  8. #8Palabra TTS123 ms
  9. #9PhantomZ 4.0141 ms
  10. #10TTS 2163 ms
  11. #11drama3-preview165 ms
  12. #12Falcon 2177 ms
  13. #13Eleven v4 Turbo194 ms
  14. #14Flash v2.5202 ms
  15. #15Flux TTS207 ms
  16. #16Assemblyai TTS 1224 ms
Show all 32 models
  1. #17TTS RT v1261 ms
  2. #18TTS Rt v2264 ms
  3. #19Airy TTS281 ms
  4. #20Sonic 3.6287 ms
  5. #21Sonic 3.5291 ms
  6. #22Aura 2303 ms
  7. #23Grok TTS342 ms
  8. #24S2.1 Pro367 ms
  9. #25Coda378 ms
  10. #26Lightning v3.1 Pro383 ms
  11. #27Mist v3387 ms
  12. #28Daytona TTS439 ms
  13. #29Aura 2 En546 ms
  14. #30Chirp 3 HD588 ms
  15. #31Qwen3 TTS Flash Realtime727 ms
  16. #32S2.1 Pro Free802 ms
median of all models · 242 ms
TTS models over the last 30 days, ranked on Time to First Audio.
#ModelHostTTFAWERSamples
1vuiFluxions42 ms2,663
2Gradium TTS Beta 202609Gradium64 ms2,878
3Qwen3 TTS FastNari Labs68 ms2,878
4TTS Flash 2Inworld AI83 ms2,878
5Qwen3 TTS 1.7bBaseten105 ms2,875
6Simba 3.0SpeechifyAI110 ms2,875
7Simba 3.2SpeechifyAI118 ms2,875
8Palabra TTS v1Palabra123 ms2,351
9Phantom Z 3.4 conversationalDeepdub141 ms2,866
10TTS 2Inworld AI163 ms2,876
11Drama 3 Preview Us EastFish Audio165 ms1,955
12Falcon 2Murf177 ms2,875
13Eleven v4 TurboElevenLabs194 ms2,878
14Flash v2.5ElevenLabs202 ms2,869
15Flux TTSDeepgram207 ms2,754
16Assemblyai TTS 1AssemblyAI224 ms727
17TTS RT v1Soniox261 ms2,418
18TTS Rt v2Soniox264 ms2,405
19Airy TTSOut of Set281 ms2,177
20Sonic 3.6Cartesia287 ms2,877
21Sonic 3.5Cartesia291 ms2,877
22Aura 2Deepgram303 ms2,878
23Grok TTSSpaceXAI342 ms2,876
24S2.1 ProFish Audio367 ms2,873
25CodaRime378 ms506
26Lightning v3.1 ProSmallest383 ms2,867
27Mist v3Rime387 ms506
28Daytona TTSGuava439 ms2,880
29Aura 2 EnCloudflare546 ms2,875
30Chirp 3 HDGoogle588 ms2,878
31Qwen3 TTS Flash RealtimeAlibaba727 ms2,877
32S2.1 Pro FreeFish Audio802 ms2,860
Under-sampled models are excluded; tied models share a place. Dotted WER values split into substitutions, deletions and insertions on hover or tap.

Highest relative placement: 7th of 32 on Word Error Rate.

Latency vs accuracy

TTFA vs WEREach point is one measured model · Assemblyai TTS 1 highlighted · 30-day averagesTime to First Audio against Word Error Rate for every measured TTS model, with Assemblyai TTS 1 highlighted.
vui — 42 ms, 2.0%Default — 64 ms, 1.9%Qwen3 TTS Fast — 68 ms, 1.8%TTS Flash 2 — 83 ms, 1.7%Qwen3 TTS 1.7b — 105 ms, 1.9%Simba 3.0 — 110 ms, 1.6%Simba 3.2 — 118 ms, 2.0%Palabra TTS — 123 ms, 2.7%PhantomZ 4.0 — 141 ms, 2.2%TTS 2 — 163 ms, 1.6%drama3-preview — 165 ms, 1.6%Falcon 2 — 177 ms, 1.6%Eleven v4 Turbo — 194 ms, 1.7%Flash v2.5 — 202 ms, 1.9%Flux TTS — 207 ms, 1.8%TTS RT v1 — 261 ms, 2.6%TTS Rt v2 — 264 ms, 2.7%Airy TTS — 281 ms, 1.6%Sonic 3.6 — 287 ms, 1.5%Sonic 3.5 — 291 ms, 1.5%Aura 2 — 303 ms, 1.9%Grok TTS — 342 ms, 1.7%S2.1 Pro — 367 ms, 1.6%Coda — 378 ms, 2.4%Lightning v3.1 Pro — 383 ms, 1.6%Mist v3 — 387 ms, 2.0%Daytona TTS — 439 ms, 1.8%Aura 2 En — 546 ms, 2.1%Chirp 3 HD — 588 ms, 1.6%Qwen3 TTS Flash Realtime — 727 ms, 3.0%S2.1 Pro Free — 802 ms, 1.6%Assemblyai TTS 1 — 224 ms, 1.6%

Where the errors come from

WER compositionAssemblyai TTS 1's Word Error Rate split by error type · 30-day averageAssemblyai TTS 1's WER split into substitutions, deletions and insertions.
  • Assemblyai TTS 11.6%
SubstitutionsDeletionsInsertions

Averages and tail latency

Averages hide slow outliers — these are the distributions behind each figure.

Assemblyai TTS 1 latency distributionMilliseconds · shared axis across metrics · last 30 daysAssemblyai TTS 1's latency percentiles per metric: p25–p75 band, p50 tick, whisker to max.
  • Time to First Audiop50 206 ms · Max 422 ms
  • TTFA Network Roundtripp50 76 ms · Max 321 ms
  • TTFA Leading Silencep50 122 ms · Max 316 ms
band p25–p75 · tick p50 · whisker to max with p90 and p95 stops
Average and percentile values per metric, with the number of samples behind each row.
MetricAveragep25p50p75p90p95MaxSamples
Time to First Audio224 ms187 ms206 ms235 ms321 ms339 ms422 ms727
TTFA Network Roundtrip80 ms72 ms76 ms86 ms103 ms118 ms321 ms727
TTFA Leading Silence143 ms106 ms122 ms146 ms258 ms274 ms316 ms727
Word Error Rate1.6%0.0%0.0%2.3%6.9%15.2%43.8%701

Last 30 days

Daily medians from the same measurement runs · gaps are days without qualifying runs.

Time to First Audio — daily p50Line p50 · band p25–p75 · UTC daysAssemblyai TTS 1's daily median Time to First Audio over the last 30 days.
Assemblyai TTS 1 · Oct 22: 204 msAssemblyai TTS 1 · Oct 23: 220 msAssemblyai TTS 1 · Oct 24: 211 msAssemblyai TTS 1 · Oct 25: 223 msAssemblyai TTS 1 · Oct 26: 212 msAssemblyai TTS 1 · Oct 27: 192 msAssemblyai TTS 1 · Oct 28: 203 msAssemblyai TTS 1 · Oct 29: 230 msAssemblyai TTS 1 · Oct 30: 199 msAssemblyai TTS 1 · Oct 31: 209 msAssemblyai TTS 1 · Nov 1: 206 msAssemblyai TTS 1 · Nov 2: 198 ms
Word Error Rate — daily averageDaily average · UTC daysAssemblyai TTS 1's daily Word Error Rate over the last 30 days.
Assemblyai TTS 1 · Oct 22: 1.3%Assemblyai TTS 1 · Oct 23: 3.5%Assemblyai TTS 1 · Oct 24: 4.8%Assemblyai TTS 1 · Oct 25: 5.8%Assemblyai TTS 1 · Oct 26: 6.2%Assemblyai TTS 1 · Oct 27: 2.0%Assemblyai TTS 1 · Oct 28: 3.7%Assemblyai TTS 1 · Oct 29: 2.3%Assemblyai TTS 1 · Oct 30: 3.3%Assemblyai TTS 1 · Oct 31: 3.6%Assemblyai TTS 1 · Nov 1: 4.2%Assemblyai TTS 1 · Nov 2: 3.0%

How fast is Assemblyai TTS 1?

On AssemblyAI, Assemblyai TTS 1 measures mean 224 ms time to first audio (16th of 32). Last measured 2026-11-02.

How accurate is Assemblyai TTS 1?

On AssemblyAI, Assemblyai TTS 1 measures 1.6% word error rate (7th of 32). Last measured 2026-11-02.

Who hosts Assemblyai TTS 1?

Assemblyai TTS 1 is created by AssemblyAI and served by AssemblyAI. Coval measures each hosted endpoint separately.

Results are re-measured daily using fixed datasets and reported over a rolling 30-day window. Same datasets, prompts and metric definitions for every model, measured by Coval’s open-source runner. Full methodology on the overview.

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