TTS API comparison 2026
Gradium TTS Beta vs Soniox TTS RT v1 Gradium vs Soniox · text-to-speech for voice agents
Gradium TTS Beta ranks 1st of 112 with 76.8/100; Soniox TTS RT v1 ranks 9th with 57.2/100: a gap of 19.6 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 | Soniox TTS RT v1 |
|---|---|---|
| Overall score | 76.8/100 | 57.2/100 |
| Rank | 1st of 112 | 9th of 112 |
| Real-time speed /60 | 58.7 | 37.9 |
| Voice quality /20 | 7.8 | 6.6 |
| Accuracy /15 | 9.8 | 10.6 |
| Price /5 | 0.5 | 2.1 |
| P50 / median time-to-first-audio Coval, 30-day window | 47.2 ms | 247.2 ms |
| P99 time-to-first-audio (slowest turns) Coval, 30-day window | 108.8 ms | 339.8 ms |
| Latency consistency (standard deviation) Coval, 30-day window | 16.6 ms | 104.8 ms |
| P50 time-to-first-audio, US East Speko | 100 ms | 362 ms |
| Accuracy: word error rate (WER) Coval, 30-day window | 4.5% | 4% |
| Pronunciation robustness (0 to 1) Speko | 0.3 | 0.4 |
| Speech Arena Elo (blind listener preference) Artificial Analysis | not measured | not measured |
| Naturalness (Elo) Speko | 1579 | 1569 |
| Price per 1M characters Artificial Analysis | not measured | not measured |
Choose Gradium TTS Beta if…
- → Ranks 1st of 112 in the overall benchmark, against 9th for Soniox TTS RT v1
- → Better P50 / median time-to-first-audio: 47.2 ms vs 247.2 ms (Coval, 30-day window)
- → Better P99 time-to-first-audio (slowest turns): 108.8 ms vs 339.8 ms (Coval, 30-day window)
- → Better latency consistency (standard deviation): 16.6 ms vs 104.8 ms (Coval, 30-day window)
- → Better P50 time-to-first-audio, US East: 100 ms vs 362 ms (Speko)
- → Better naturalness (Elo): 1579 vs 1569 (Speko)
Choose Soniox TTS RT v1 if…
- → Better accuracy: word error rate (WER): 4% vs 4.5% (Coval, 30-day window)
- → Better pronunciation robustness (0 to 1): 0.4 vs 0.3 (Speko)
Frequently asked questions
- What is the difference between Gradium TTS Beta and Soniox TTS RT v1?
- In the 2026 TTS API benchmark, Gradium TTS Beta ranks 1st of 112 with 76.8/100 and Soniox TTS RT v1 ranks 9th with 57.2/100, a gap of 19.6 points on the same rules.
- Which is faster for real-time voice agents, Gradium TTS Beta or Soniox TTS RT v1?
- 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 247.2 ms for Soniox TTS RT v1; the P99 is 108.8 ms and 339.8 ms.
- On which criteria does Soniox TTS RT v1 beat Gradium TTS Beta?
- Soniox TTS RT v1 scores higher on Accuracy (10.6 vs 9.8 out of 15), Price (2.1 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.