47.2 ms P50 time-to-first-audio on Coval; ranked 1st of 112 in the TTS for Voice Agents 2026 index.
Benchmark summary: 76.8/100, ranked 1st of 112 in the TTS for Voice Agents 2026 index (Leader). Strongest criterion: real-time speed, 58.7 of 60 points.
Gradium TTS Beta is a proprietary text-to-speech (TTS) API from Gradium, measured by two independent benchmarks: Coval and Speko.
Overall score
76.8 /100
Data checked on September 30, 2026
Updated after each benchmark capture
Every point comes from a public benchmark: sources · methodology
Gradium TTS Beta ranks 1st of 112 in the 2026 text-to-speech (TTS) API benchmark, with a score of 76.8/100.
On Coval's 30-day window ending October 1, 2026 (4,696 runs), Gradium TTS Beta has a P50 (median) time-to-first-audio (TTFA) of 47.2 ms, the lowest of the 31 models Coval measures. Its P99, the slowest 1% of turns, is 108.8 ms (the lowest of the 31 models Coval measures). Latency consistency: a standard deviation of 16.6 ms (2nd lowest of the 31 models Coval measures). Mean time to first byte (TTFB) is 50.2 ms. Speko measures a P50 TTFA of 100 ms from US East (n=30), dated September 16, 2026: 6th lowest of the 29 models Speko measures.
Coval measures an accuracy (word error rate) of 4.5% over 4,696 samples on the same window, 8th lowest of the 31 models Coval measures. Speko rates its pronunciation robustness on numbers, dates and currency at 0.28 on a 0-to-1 scale (16th highest of the 28 models Speko rates).
Speko rates its naturalness at 1,579 Elo from blind A/B votes (10th highest of the 41 models Speko rates).
Speko lists a cost of about $57.8 per 1M characters.
Speko changed its pronunciation robustness between the captures of September 30, 2026 and October 1, 2026 without a new measurement date (0.58, then 0.28): the score uses the average, 0.43. The value shown is the latest.
Alibaba Qwen3 TTS Fast is an open-weights text-to-speech (TTS) API from Alibaba (Qwen), served by Nari Labs, measured by two independent benchmarks: Coval and Speko.
Soniox TTS Real-Time v2 is a proprietary text-to-speech (TTS) API from Soniox, measured by three independent benchmarks: Artificial Analysis, Coval and Speko.
Inworld Realtime TTS-2 is a proprietary text-to-speech (TTS) API from Inworld, measured by three independent benchmarks: Artificial Analysis, Coval and Speko.