Soniox
tts-rt-v1
Measured 2026-07-03
Build voice agents on Speko →tts-rt-v1 is measured here for comparison — it is not one of the models Speko routes.
Naturalness
1569
Win % · 95% CI
63%
56–69%
Drift
24
Synth p50
362ms
362–388 p50–p90
Robustness
0.35
Fined:
• fatal · currency — dropped the minus sign (4 of 7 transcripts)
→ we sent “A refund of -$0.99 was applied.”
→ it said “A refund of $9.99 was applied.”
• fatal · dates — never said “sunday” (40 of 43 transcripts)
→ we sent “The fair runs Fri–Sun, Oct 9–11.”
→ it said “The fair runs Friday to Sun, October ninth to eleventh.”
• fatal · large numbers — never said “three trillion” (48 of 49 transcripts)
→ we sent “National debt passed 3,000,000,000,000 dollars.”
→ it said “National debt passed three billion dollars.”
+ 7 more fined
Cost / 1M chars
$13.0
Token-billed: $4/1M text in, $21.50/1M audio out; the vendor states ~$0.70 per hour of generated speech (soniox.com/pricing). At 900 chars/min (54,000 chars/hour) that is ~$13 per 1M chars.
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