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Open article · Retrieved 2026-09-14T18:22:36.262441+00:00
## TL;DR
**Nari Labs leads Coval’s voice AI benchmark by sitting on the quality-latency Pareto Frontier for both Text-to-Speech and Speech-to-Text. We also lead the latency-cost and quality-cost Pareto Frontier out of all publicly available models on the benchmark.**
[Coval](https://www.coval.ai/) is a leading provider of voice AI evaluation and benchmarks. They help speech AI agents perform better in production and publish one of the most widely cited benchmarks in the industry.
The [Text-to-Speech (TTS) benchmark](https://benchmarks.coval.ai/tts) evaluates latency from text input to first audible chunk of audio (time-to-first-audio or TTFA) and Word Error Rate (WER). The [Speech-to-Text (STT) benchmark](https://benchmarks.coval.ai/stt) evaluates latency from user’s finalize request to the final text output (time-to-final-segment or TTFS) and Word Error Rate (WER).
TTFA and TTFS are critical for voice agents, where latency can make a voice AI agent feel unresponsive. Low WER is an obvious key factor for model performance as well.
As of mid September 2026, Nari Labs tops both the Speech-to-Text and Text-to-Speech benchmarks. **STT: #1 Latency, #2 WER**. **TTS: #2 Latency, #1 WER**. Note that [Coval’s benchmarks](https://benchmarks.coval.ai/) can fluctuate every 30 minutes[\*](https://narilabs.com/blog/nari-labs-leads-coval-voice-ai-benchmarks/#coval-snapshot-note). We only include publicly available endpoints in our rankings and charts.
## Speech-to-Text
**Our [Qwen3-ASR Fast](https://narilabs.com/product/stt/) model is ranked #1 in Time-to-Final-Segment (TTFS), at p50 of 44 ms and WER of 3.6%, placing #2 behind AssemblyAI’s Universal 3.5 Pro at 3.5%.**
The pricing makes it even better. At **$0.12 / hour**, our Fast endpoint ties for the **2nd-lowest price** among models with known public rates in [Coval’s pricing directory](https://benchmarks.coval.ai/pricing). Universal 3.5 Pro costs 3.75× more, and Deepgram Nova 3 costs 2.4× more. Our Standard endpoint would be the cheapest at **$0.06 / hour**.
[Coval STT latency and accuracy: Nari Qwen3-ASR Fast on the Pareto frontier at 44 ms median TTFS and 3.6% WER.Nari Labs](https://narilabs.com/blog/nari-labs-leads-coval-voice-ai-benchmarks/assets/stt-latency-accuracy.png)
[Coval STT word error rates: Nari Qwen3-ASR Fast ranks second at 3.6%, behind AssemblyAI Universal 3.5 Pro at 3.5%.Nari Labs](https://narilabs.com/blog/nari-labs-leads-coval-voice-ai-benchmarks/assets/stt-word-error-rate.png)
## Text-to-Speech
**Our [Qwen3-TTS Fast](https://narilabs.com/product/qwen3-tts/) model is ranked #2 in Time-to-First-Audio (TTFA), at p50 of 63 ms and WER of 3.8%, coming in at #1.**
The only model with a lower median TTFA than ours is vui from Fluxions, at 49 ms. It is a 300M parameter model, compared to the 1.7B Qwen3-TTS that we serve.
At **$10 per 1M characters**, our Fast endpoint is tied for the **#1 cheapest** model on [Coval’s pricing directory](https://benchmarks.coval.ai/pricing). ElevenLabs Eleven v3 Conversational costs 5x more, and Cartesia Sonic 3.6 costs 6.5x more. Our Standard endpoint would be the cheapest at **$5 per 1M characters**.
[Coval TTS latency and accuracy: Nari Qwen3-TTS Fast on the Pareto frontier at 63 ms median TTFA and 3.8% WER.Nari Labs](https://narilabs.com/blog/nari-labs-leads-coval-voice-ai-benchmarks/assets/tts-latency-accuracy.png)
[Coval TTS word error rates: Nari Qwen3-TTS Fast leads at 3.8%.Nari Labs](https://narilabs.com/blog/nari-labs-leads-coval-voice-ai-benchmarks/assets/tts-word-error-rate.png)
Interestingly, the official Qwen3 TTS Flash Realtime endpoint sits at 8.8% WER and 692 ms median TTFA. We both serve the same model.
We also surpass Baseten’s dedicated Qwen3-TTS endpoint, which records 6.0% WER and 101 ms median TTFA.
## Get Started
Try both our [Speech-to-Text](https://narilabs.com/product/stt/) and [Text-to-Speech](https://narilabs.com/product/qwen3-tts/) models for free for a limited period of time. We are moving our Public Beta APIs to a paid GA within this week and will provide **$20 in credits** for everyone who has created an account when the switch happens.
[Try STT and TTS](https://app.narilabs.com/)
Need help meeting the latency and capacity requirements of your voice application? [Talk to our engineers](https://cal.com/toby-kim/30min?utm_source=nari-labs&utm_medium=blog&utm_campaign=coval-voice-ai-benchmarks)
[\*](https://narilabs.com/blog/nari-labs-leads-coval-voice-ai-benchmarks/#coval-snapshot-ref) Benchmark values in this post are based on Coval’s **1-day view as of September 14, 2026, at 15:00 UTC**. WER is pooled across datasets. Rankings exclude dedicated inference endpoints. Prices compare Nari’s published rates with known public rates in Coval’s pricing directory.