TTS API comparison 2026
Gradium TTS Beta vs Fish Audio S2.1 Pro Gradium vs Fish Audio · text-to-speech for voice agents
Gradium TTS Beta ranks 1st of 112 with 76.8/100; Fish Audio S2.1 Pro ranks 23rd with 33.2/100: a gap of 43.6 points on the same public rules, built on Coval, Speko and Artificial Analysis.
Data checked on September 30, 2026 · Coval 30-day window ending October 1, 2026 · updated after each benchmark capture
Side-by-side benchmark
| Measure | Gradium TTS Beta | Fish Audio S2.1 Pro |
|---|---|---|
| Overall score | 76.8/100 | 33.2/100 |
| Rank | 1st of 112 | 23rd of 112 |
| Real-time speed /60 | 58.7 | 18.6 |
| Voice quality /20 | 7.8 | 7.7 |
| Accuracy /15 | 9.8 | 5.1 |
| Price /5 | 0.5 | 1.8 |
| P50 / median time-to-first-audio Coval, 30-day window | 47.2 ms | 300.1 ms |
| P99 time-to-first-audio (slowest turns) Coval, 30-day window | 108.8 ms | 885.9 ms |
| Latency consistency (standard deviation) Coval, 30-day window | 16.6 ms | 193.9 ms |
| P50 time-to-first-audio, US East Speko | 100 ms | not measured |
| Accuracy: word error rate (WER) Coval, 30-day window | 4.5% | 4.6% |
| Pronunciation robustness (0 to 1) Speko | 0.3 | not measured |
| Speech Arena Elo (blind listener preference) Artificial Analysis | not measured | 1137 |
| Naturalness (Elo) Speko | 1579 | not measured |
| Price per 1M characters Artificial Analysis | not measured | 15 USD |
Choose Gradium TTS Beta if…
- → Ranks 1st of 112 in the overall benchmark, against 23rd for Fish Audio S2.1 Pro
- → Better P50 / median time-to-first-audio: 47.2 ms vs 300.1 ms (Coval, 30-day window)
- → Better P99 time-to-first-audio (slowest turns): 108.8 ms vs 885.9 ms (Coval, 30-day window)
- → Better latency consistency (standard deviation): 16.6 ms vs 193.9 ms (Coval, 30-day window)
- → Better accuracy: word error rate (WER): 4.5% vs 4.6% (Coval, 30-day window)
Choose Fish Audio S2.1 Pro if…
On the published benchmarks, Fish Audio S2.1 Pro wins none of the measurements above against Gradium TTS Beta. This says nothing about features the benchmarks do not measure.
Fish Audio S2.1 Pro: all measurements →Frequently asked questions
- What is the difference between Gradium TTS Beta and Fish Audio S2.1 Pro?
- In the 2026 TTS API benchmark, Gradium TTS Beta ranks 1st of 112 with 76.8/100 and Fish Audio S2.1 Pro ranks 23rd with 33.2/100, a gap of 43.6 points on the same rules.
- Which is faster for real-time voice agents, Gradium TTS Beta or Fish Audio S2.1 Pro?
- On Coval's 30-day window ending October 1, 2026, the P50 time-to-first-audio is 47.2 ms for Gradium TTS Beta and 300.1 ms for Fish Audio S2.1 Pro; the P99 is 108.8 ms and 885.9 ms.
- On which criteria does Fish Audio S2.1 Pro beat Gradium TTS Beta?
- Fish Audio S2.1 Pro scores higher on Price (1.8 vs 0.5 out of 5).
- How are these two text-to-speech APIs scored?
- Both are scored by the same public rules: 4 criteria, 100 points (Real-time speed 60, Voice quality 20, Accuracy 15, Price 5), computed from three independent benchmarks: Coval, Speko and Artificial Analysis. A measurement a benchmark does not publish counts zero, and the model page says why.
- Can these numbers be checked?
- Yes. Each model page lists every measurement with its source and date, and links to the benchmark page it comes from. The rules are on the methodology page.