Data read October 27, 2026
Gradium TTS vs Cartesia Sonic 3.6: TTS API comparison
On P95 latency, Gradium TTS is faster: 104.3 ms for Gradium TTS against 374.4 ms for Cartesia Sonic 3.6.
On Artificial Analysis listener Elo, Cartesia Sonic 3.6 is ahead (1,174 for Gradium TTS, 1,292 for Cartesia Sonic 3.6). List price per million characters: $36 to $57.80 for Gradium TTS, $39.20 to $50 for Cartesia Sonic 3.6.
Gradium TTS is ranked 1 of 23; Cartesia Sonic 3.6 is ranked 14 of 23. Every comparison on this site uses Gradium TTS as its fixed reference, and no page says either model is better overall.
| Measure | Gradium TTS | Cartesia Sonic 3.6 | Ahead |
|---|---|---|---|
| Rank in the multilingual speed ranking | 1 | 14 | n/a |
| Speed tier | Headroom | Visible delay | n/a |
| Median time to first audio (ms), lower is faster | 53.7 | 285.8 | Gradium TTS |
| P95 time to first audio (ms), lower is faster | 104.3 | 374.4 | Gradium TTS |
| Listener Elo (Artificial Analysis) | 1,174 | 1,292 | Cartesia Sonic 3.6 |
| Customer-service Elo (Artificial Analysis) | 1,241 | 1,331 | Cartesia Sonic 3.6 |
| Naturalness (Speko) | 1,592 | 1,578 | Gradium TTS |
| Naturalness estimate (Cekura, 1 to 5) | 4.51 | 4.41 | Gradium TTS |
| Reading accuracy (Cekura) | 79.5% | 74.9% | Gradium TTS |
| Hard passages judged correct (Artificial Analysis) | n/a | 74.5% | n/a |
| Lowest list price per 1M characters (lower is cheaper) | $36 to $57.80 | $39.20 to $50 | Gradium TTS |
| Languages tested (Artificial Analysis, Speko) | 4 | 9 | Cartesia Sonic 3.6 |
| Access | Proprietary | Proprietary | n/a |
| Streaming status | Measured | Measured | n/a |
Ahead is computed from the figures only. A latency gap under 10 ms is a tie; listener Elo values whose 95% intervals overlap are a tie. A measure one benchmark does not hold is n/a for that model and is never estimated. See the methodology and each model page for sources.
Frequently asked questions
- Is Gradium TTS faster than Cartesia Sonic 3.6?
- On P95 latency, Gradium TTS is faster: 104.3 ms for Gradium TTS against 374.4 ms for Cartesia Sonic 3.6.
- How do Gradium TTS and Cartesia Sonic 3.6 compare on voice quality?
- On Artificial Analysis listener Elo, Cartesia Sonic 3.6 is ahead (1,174 for Gradium TTS, 1,292 for Cartesia Sonic 3.6).
- Which is cheaper, Gradium TTS or Cartesia Sonic 3.6?
- List price per million characters: $36 to $57.80 for Gradium TTS, $39.20 to $50 for Cartesia Sonic 3.6.