Soniox STT-RT v5 vs Speechmatics Linden
Soniox STT-RT v5 is ahead on final-text delay, and Speechmatics Linden on time to first text. The Pipecat Dataset and The Ocular Dataset are too close to call.
Last updated Methodology by Dileep Chagam
Accuracy vs speed
Each dot is one model. Bottom-left is best: fewer errors and a faster final transcript.
Which to pick
Pick Soniox STT-RT v5 for quick turn-taking once the caller stops (109ms sooner). Pick Speechmatics Linden for showing words while the caller is still talking (5ms sooner). For accuracy on clean, scripted audio and accuracy on real phone conversations, the gap is inside the margin of error, so neither is ahead.
The four metrics, side by side
- Soniox STT-RT v5
- 2.54%8th
- Speechmatics Linden
- 2.46%7th
Too close to call: inside the margin of error
- Soniox STT-RT v5
- 3.92%6th
- Speechmatics Linden
- 3.93%7th
Too close to call: inside the margin of error
- Soniox STT-RT v5
- 1.20s9th
- Speechmatics Linden
- 1.19s8th
Speechmatics Linden, 5ms sooner
- 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. What each metric measures.
- WER · Word error rate
- Share of words the model got wrong: replaced, missing or added. Lower is better.
- Pipecat Dataset
- 1,000 short public clips from Pipecat's STT benchmark dataset.
- Ocular Dataset
- 8 recordings from 4 real phone conversations, licensed from Ocular.
- TTFT · Time to first text
- How long after the audio starts streaming until the first words appear.
- TTFS · Final-text delay
- How long after the caller stops until the full transcript arrives. A voice agent waits for this before it replies.
First text and final text, at three percentiles
Soniox STT-RT v5 shows first text after 1.71s and final text after 79ms, and Speechmatics Linden shows first text after 2.52s and final text after 213ms, on a bad turn (P95) across the same streamed turns.
| 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 |
- P50 / P90 / P95 · Typical, slow and slowest turns
- Half of turns are faster than P50. Only 1 in 10 is slower than P90, and 1 in 20 slower than P95.
How each ranks among all 17 models
Place among the 17 models on each metric. Lower is better on all four.
| Metric | STT-RT v5 | Linden |
|---|---|---|
| Pipecat Dataset WER | 2.54%8th of 17 | 2.46%7th of 17 |
| Ocular Dataset WER | 3.92%6th of 17 | 3.93%7th of 17 |
| Time to first text | 1.20s9th of 15 | 1.19s8th of 15 |
| Final-text delay | 38ms1st of 17 | 147ms8th of 17 |
How much audio each model was tested on
| Model | Pipecat clips | Ocular recordings | Turns timed | Failed |
|---|---|---|---|---|
| Soniox STT-RT v5 | 1,000 | 8 | 200 | 6 |
| Speechmatics Linden | 998 | 8 | 194 | 12 |
Only clips with usable text count, so the two totals can differ. How WER is scored.
Related comparisons
- Soniox STT-RT v5 vs Cartesia Ink 2
- Soniox STT-RT v5 vs Inworld STT-1
- Soniox STT-RT v5 vs GPT Realtime Whisper
- Soniox STT-RT v5 vs Reson8
- Soniox STT-RT v5 vs Google Chirp 3
- Soniox STT-RT v5 vs AssemblyAI Universal 3.6 Pro
- Soniox STT-RT v5 vs GPT-4o Mini Transcribe
- Soniox STT-RT v5 vs Deepgram Nova-3
- Soniox STT-RT v5 vs Smallest Pulse
- Soniox STT-RT v5 vs GPT-4o Transcribe
- Soniox STT-RT v5 vs Deepgram Flux English
- Soniox STT-RT v5 vs Deepgram Flux Multilingual
- Soniox STT-RT v5 vs Gradium
- Speechmatics Linden vs Cartesia Ink 2
- Speechmatics Linden vs Inworld STT-1
- Speechmatics Linden vs GPT Realtime Whisper
- Speechmatics Linden vs Reson8
- Speechmatics Linden vs Google Chirp 3
- Speechmatics Linden vs AssemblyAI Universal 3.6 Pro
- Speechmatics Linden vs GPT-4o Mini Transcribe
- Speechmatics Linden vs Deepgram Nova-3
- Speechmatics Linden vs Smallest Pulse
- Speechmatics Linden vs GPT-4o Transcribe
- Speechmatics Linden vs Deepgram Flux English
- Speechmatics Linden vs Deepgram Flux Multilingual
- Speechmatics Linden vs Gradium
Frequently asked questions
Which is more accurate, Soniox STT-RT v5 or Speechmatics Linden?
Soniox STT-RT v5 and Speechmatics Linden are too close to call on accuracy. On the 1,000 public Pipecat clips, Soniox STT-RT v5 scores 2.54% and Speechmatics Linden 2.46%, with likely ranges of 2.27 to 2.83% and 2.19 to 2.73%. The ranges overlap, so the difference is too close to call. On the eight licensed Ocular recordings, Soniox STT-RT v5 scores 3.92% and Speechmatics Linden 3.93%, with likely ranges of 2.60 to 4.86% and 2.94 to 5.19%. The ranges overlap, so the difference is too close to call. Word error rate counts incorrect, missing, and extra words, so lower is better.
Is Soniox STT-RT v5 faster than Speechmatics Linden?
Yes. Soniox STT-RT v5 finishes the transcript 109ms sooner. Soniox STT-RT v5 has the final transcript 38ms after the speaker stops and Speechmatics Linden 147ms, at the median. Both are measured on the same 206 streamed turns.
Is Soniox STT-RT v5 or Speechmatics Linden better for voice agents?
Soniox STT-RT v5 finishes the transcript 109ms sooner, and the two are too close to call on real conversations. A voice agent cannot reply until the final transcript arrives, and the Ocular recordings are real conversations.
Do Soniox STT-RT v5 and Speechmatics Linden stream text while the speaker is talking?
Yes, both return partial text before the speaker stops. Soniox STT-RT v5 shows first text after 1.20s and Speechmatics Linden after 1.19s, at the median, so Speechmatics Linden is 5ms sooner.