Cartesia
sonic-3.5
Measured 2026-07-03
Run sonic-3.5 on Speko →One API, every model on this board.
Naturalness
1574
Win % · 95% CI
65%
58–71%
Drift
13
Synth p50
121ms
121–236 p50–p90
Robustness
0.18
Fined:
• fatal · currency — dropped the minus sign (7 of 7 transcripts)
→ we sent “The balance is -$12.50.”
→ it said “The balance is $12.50.”
• fatal · dates — never said “friday” or “sunday” (41 of 49 transcripts)
→ we sent “The fair runs Fri–Sun, Oct 9–11.”
→ it said “The fair runs Fryson, October ninth, eleven.”
• fatal · large numbers — never said “three point four million” (21 of 49 transcripts)
→ we sent “The clip hit 3.4M views and 1.2k shares.”
→ it said “The clip hit three point four M views and one point two K shares.”
+ 22 more fined
Cost / 1M chars
$50.0
1 credit/char on Pro, the cheapest paid plan; $39.2 at Startup, $37.4 at Scale. Cloned voices bill 1.5x.
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