STT Engines¶

Kiwi supports three speech-to-text engines. Switch between them in config.yaml or via environment variable.

Comparison¶

Engine	Quality	Latency	Cost	Local	GPU
Faster Whisper	Excellent	~1–3s	Free	Yes	Optional (CUDA)
ElevenLabs	Excellent	~0.3–0.5s	~$0.018/min	No	No
MLX Whisper	Excellent	~0.5–1s	Free	Yes	Apple Silicon

Faster Whisper¶

FREE DEFAULT

Local STT using CTranslate2-optimized Whisper models. Works on CPU or CUDA GPU.

stt:
  engine: "faster-whisper"
  model: "small"             # tiny, base, small, medium, large
  device: "cuda"             # cuda or cpu
  compute_type: "float16"    # float16 (GPU) or int8 (CPU)
  language: "ru"

Model size tradeoff

small is the sweet spot — fast with good accuracy. Use large for best accuracy (slower startup), tiny for minimal resources.

ElevenLabs¶

PAID CLOUD

Cloud-based STT via WebSocket (Scribe v2 model). Lowest latency, no local resources needed. Uses the same API key as ElevenLabs TTS.

stt:
  engine: "elevenlabs"
  elevenlabs:
    model_id: "scribe_v2"
    language_code: ""        # auto-detect if empty; or "ru", "en", etc.

# .env — same key for both TTS and STT
KIWI_ELEVENLABS_API_KEY=sk-...

How it works

Kiwi collects audio using the same VAD pipeline (energy + Silero), then sends the full buffer to ElevenLabs via WebSocket for transcription. All existing hallucination filtering and wake word detection still applies.

Pricing

ElevenLabs STT costs ~$0.018/min (~$1.05/hr). With typical voice assistant usage (a few minutes of speech per hour), the cost is minimal.

MLX Whisper¶

FREE APPLE SILICON

Local STT optimized for Apple Silicon using Lightning Whisper MLX. ~10x faster than standard Whisper on M-series chips.

stt:
  engine: "mlx-whisper"
  model: "distil-medium.en"
  mlx_batch_size: 12

Requires lightning-whisper-mlx — only available on macOS with Apple Silicon (M1/M2/M3/M4).

Switching Engines¶

Via config.yaml¶

stt:
  engine: "elevenlabs"   # faster-whisper, elevenlabs, mlx-whisper

Via environment variable¶

KIWI_STT_ENGINE=elevenlabs python -m kiwi

Engine aliases¶

For convenience, these aliases are also accepted:

Alias	Resolves to
`whisper`	`faster-whisper`
`eleven`	`elevenlabs`
`11labs`	`elevenlabs`