Soniox STT-RT v5 vs Speechmatics Linden
Soniox STT-RT v5 is ahead on the Ocular Dataset and final-text delay, and Speechmatics Linden on the Pipecat Dataset and time to first text.
Quality and speed frontier
Every model's error rate on the public clips, against how long its transcript takes to settle.
The four metrics, side by side
Word error rate on 1,000 clips from Pipecat's STT benchmark dataset.
- Soniox STT-RT v5
- 2.54%8th
- Speechmatics Linden
- 2.46%7th
Speechmatics Linden, 0.09 points lower
Word error rate on eight licensed recordings provided by Ocular.
- Soniox STT-RT v5
- 3.92%6th
- Speechmatics Linden
- 3.93%7th
Soniox STT-RT v5, 0.01 points lower
Median delay before the first words arrive, from the first audio packet.
- Soniox STT-RT v5
- 1.20s9th
- Speechmatics Linden
- 1.19s8th
Speechmatics Linden, 5ms sooner
Median delay after the speaker stops before the transcript is final.
- Soniox STT-RT v5
- 38ms1st
- Speechmatics Linden
- 147ms8th
Soniox STT-RT v5, 109ms sooner
Lower is better on every metric. The small figure is each model's place in the whole field.
First text and final text, at three percentiles
Both measured on the same 206 streamed Ocular Dataset turns. P90 and P95 say what a caller meets on a bad turn, which a median hides.
| Measure | Model | P50 | P90 | P95 |
|---|---|---|---|---|
| Time to first text | Soniox STT-RT v5 | 1.20s | 1.67s | 1.71s |
| Speechmatics Linden | 1.19s | 1.56s | 2.52s | |
| Final-text delay | Soniox STT-RT v5 | 38ms | 72ms | 79ms |
| Speechmatics Linden | 147ms | 192ms | 213ms |
Both against every other model
Open on the metric where the two sit furthest apart, with the other three a tab away.
Final-text delay after the speaker stops. Lower is better.
| # | Model | Final text | turns | |
|---|---|---|---|---|
| 1 | Soniox STT-RT v5 | 38ms | 200 | |
| 2 | Inworld STT-1 | 41ms | 206 | |
| 3 | AssemblyAI Universal 3.6 Pro | 91ms | 206 | |
| 4 | Deepgram Nova-3 | 103ms | 202 | |
| 5 | Deepgram Flux English | 108ms | 199 | |
| 6 | Deepgram Flux Multilingual | 114ms | 175 | |
| 7 | Cartesia Ink 2 | 123ms | 198 | |
| 8 | Speechmatics Linden | 147ms | 194 | |
| 9 | AssemblyAI Universal 3.5 Pro | 180ms | 205 | |
| 10 | Smallest Pulse | 201ms | 206 | |
| 11 | Gradium | 212ms | 198 | |
| 12 | Reson8 | 235ms | 201 | |
| 13 | Google Chirp 3 | 475ms | 206 | |
| 14 | GPT Realtime Whisper | 543ms | 206 | |
| 15 | Google Chirp 2 | 568ms | 205 | |
| 16 | GPT-4o Mini Transcribe | 630ms | 206 | |
| 17 | GPT-4o Transcribe | 652ms | 206 |
Median across the same 206 Ocular Dataset turns. Providers finalize differently, so compare models with similar finalization contracts before treating small gaps as meaningful.
Both on the other two views
Pipecat vs Ocular accuracy
Every model's error rate on the public clips, against the same model on real conversations.
Transcription response time
How soon each model returns its first words, against how soon its transcript is final.
What the numbers rest on
| Model | Pipecat clips | Ocular recordings | Turns timed | Failed |
|---|---|---|---|---|
| Soniox STT-RT v5 | 1,000 | 8 | 200 | 6 |
| Speechmatics Linden | 998 | 8 | 194 | 12 |
A clip counts only where the model returned usable text, so counts differ between models. Word error rate is measured the same way throughout: incorrect, missing, and extra words against the reference transcript.
Frequently asked questions
Is Soniox STT-RT v5 or Speechmatics Linden more accurate?
On the 1,000 public Pipecat clips, Soniox STT-RT v5 scores 2.54% and Speechmatics Linden 2.46%, so Speechmatics Linden makes fewer errors by 0.09 points. On the eight licensed Ocular recordings, Soniox STT-RT v5 scores 3.92% and Speechmatics Linden 3.93%, so Soniox STT-RT v5 makes fewer errors by 0.01 points. The two datasets disagree, so the better choice depends on whether your audio looks more like clean public clips or real conversations.
Which is faster, Soniox STT-RT v5 or Speechmatics Linden?
Speechmatics Linden returns first text 5ms sooner, at 1.19s against 1.20s at the median. Soniox STT-RT v5 has the final transcript 109ms sooner, 38ms after the speaker stops against 147ms. Both are measured on the same 206 streamed turns.
How were Soniox STT-RT v5 and Speechmatics Linden compared?
Both ran the same two datasets under the same conditions as every other model in the benchmark: 1,000 public clips from Pipecat's STT benchmark dataset and eight licensed conversation recordings from Ocular. Soniox STT-RT v5 returned usable text for 1,000 of the public clips and Speechmatics Linden for 998. Latency uses each provider's own supported finalization contract.