Speech Revolutions vs AssemblyAI
AssemblyAI is batch-first and developer-focused, with audio-intelligence features layered on top — summarisation, topic detection, content moderation. We build transcription, diarization and timestamps only, and that focus is where the measured gap appears.
Where we differ measurably is speaker diarization — telling apart who said what — and that gap is large enough to decide the question for meetings, interviews and contact-centre audio.
Diarization error rate
Lower is better. Overlap-aware at a 0.25 s collar, on public datasets, measured 2026-07-12 against AssemblyAI (their API default at the time of the run).
| Dataset | Speech Revolutions | AssemblyAI |
|---|---|---|
| AMI-SDM | 9.7% | 25.3% |
| NotSoFar | 10.9% | 23.3% |
| DiPCo | 26.7% | 28.9% |
The harness that produced these is public, and so are the datasets — so this is a number you can reproduce or contest rather than take on trust. Full benchmarks and methodology.
Differences that matter in practice
| Speech Revolutions | AssemblyAI | |
|---|---|---|
| Audio intelligence | Not offered. Transcription, diarization and timestamps only. | Summarisation, topic detection, content moderation. |
| Progress reporting | Live progress over SSE while a file is processed. | Poll for status. |
| Language handling | Always auto-detects, including switching mid-file. | language_code, or language_detection to auto-detect. |
| Keyword biasing | custom_vocabulary. | keyterms_prompt (word_boost is deprecated). |
Pricing
We charge $0.003 per audio minute — $0.18 an hour — with speaker diarization, word timestamps, punctuation and keyword biasing included rather than priced separately.
We deliberately do not quote AssemblyAI's prices here. They are tiered, they change without notice, and a stale number on a page like this is worse than no number at all. The comparison worth making is the effective cost of one audio hour with the features you actually need switched on — check theirs against ours directly.
What switching involves
Auth moves from the Authorization header to X-API-Key, and the submit-then-poll loop becomes upload, complete, then either poll or watch the SSE stream. The SDKs expose an AssemblyAI-shaped result.text, so much of a response parser carries over unchanged.
The migration guide maps every field, side by side, in four languages.