Speech to Text

Pulse Pro

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Pulse Pro is the premium Speech-to-Text model in the Pulse family. Built for English transcription where accuracy matters more than streaming. Tied for #2 on the public Open ASR Leaderboard (5.42% average WER), beating ElevenLabs Scribe v2, AssemblyAI Universal-3 Pro, Speechmatics Enhanced, and every Whisper variant. Pre-recorded only, with no streaming worker. Use standard Pulse for live streaming or multilingual audio.

5.42% WER

Open ASR Leaderboard average, English

250–300× RTFx

Long-form transcription, no timestamps

English Only

Pre-recorded HTTP transport

$0.004 / min

Customer rate, non-streaming

Model Overview

Developed bySmallest AI
Model typeSpeech-to-Text
LanguagesEnglish (en)
LicenseProprietary
Versionpulse-large english_v4.1 (ckpt v13-11000)
Recommended GPU1× NVIDIA L4 (24 GB VRAM). Larger GPUs (L40S, A100, H100) supported.
TransportHTTP only (no streaming worker)
Documentationdocs.smallest.ai/waves
Consoleapp.smallest.ai/dashboard
Supportsupport@smallest.ai

How to use it

Pulse Pro is selected via the model query parameter on the unified Speech-to-Text endpoint.

$curl -sL "https://github.com/smallest-inc/cookbook/raw/main/speech-to-text/getting-started/samples/audio.wav" | \
>  curl -X POST "https://api.smallest.ai/waves/v1/stt/?model=pulse-pro&language=en" \
>    -H "Authorization: Bearer $SMALLEST_API_KEY" \
>    -H "Content-Type: application/octet-stream" \
>    --data-binary @-

Replace the inline sample URL with --data-binary "@./your.wav" to send a local file.

Sample response:

1{
2  "status": "success",
3  "transcription": "Hi, how are you doing? ...",
4  "words": [],
5  "language": "en",
6  "metadata": { "duration": 17.643, "processing_time_ms": 482.21, "rtfx": 36.6, "num_chunks": 1 },
7  "request_id": "8c355f4d-bd45-48ee-aa83-d00e4670f6bb"
8}

For long files where you do not want to hold the HTTP connection open, pass a webhook_url:

$curl -sL "https://github.com/smallest-inc/cookbook/raw/main/speech-to-text/getting-started/samples/audio.wav" | \
>  curl -X POST "https://api.smallest.ai/waves/v1/stt/?model=pulse-pro&language=en&webhook_url=https://your-server.com/cb" \
>    -H "Authorization: Bearer $SMALLEST_API_KEY" \
>    -H "Content-Type: application/octet-stream" \
>    --data-binary @-

Returns 200 immediately with {"status": "processing", "request_id": "..."}. The webhook receives the full transcription payload when ready.

Pulse Pro has no streaming worker. Calls to WS /waves/v1/stt/live?model=pulse-pro return 400 with a clear message. For live transcription use standard Pulse (?model=pulse).

Key Capabilities

Leaderboard-Ranked Accuracy

Tied for #2 on the public Open ASR Leaderboard at 5.42% average WER. Outranks every commercial English STT API in our accuracy band.

Domain Wins

Best-in-class on AMI (meetings, 7.32% WER) and SPGISpeech (financial, 2.04% WER). These are workloads enterprise customers actually have.

High Throughput

250–300× real-time factor on long-form audio without timestamps. Around 200× with word timestamps enabled.

Word Timestamps

Per-word timing on every response. Costs roughly one-third of throughput vs no-timestamps mode.

Speaker Diarization

Multi-speaker identification with per-word speaker labels.

Async via Webhook

Pass webhook_url to offload long-file transcription; receive results on your callback when ready.

Performance & Benchmarks

Pulse Pro is evaluated on the public Open ASR Leaderboard (ESB benchmark, Whisper EnglishTextNormalizer) and FLEURS English.

Open ASR Leaderboard, head-to-head

WER % on the eight ESB datasets. Bold = winner per row. Whisper EnglishTextNormalizer, normalized.

DatasetPulse ProGranite 4.1 2BCohere Transcribe
AMI7.328.098.13
Earnings229.048.3710.86
GigaSpeech9.529.809.34
LibriSpeech clean1.731.331.25
LibriSpeech other3.742.502.37
SPGISpeech2.043.783.08
TED-LIUM3.683.072.49
VoxPopuli6.325.705.87
Average (8 datasets)5.425.335.42
Open ASR rank🥈 #2 (tied)🥇 #1🥈 #2 (tied)

Pulse Pro and Cohere Transcribe are a statistical tie on aggregate WER. Pulse Pro leads on conversational and financial workloads (AMI, SPGISpeech); Cohere edges ahead on read speech (LibriSpeech, TED-LIUM).

Position on the public leaderboard

Sorted by ESB average WER. Source: HF Open ASR Leaderboard.

RankModelESB Avg WER ↓Pricing
1IBM Granite Speech 4.1 2B5.33self-host
2Pulse Pro5.42$0.004 / min
2Cohere Labs Transcribe (tied)5.42self-host
3Zoom Scribe v15.47API
4IBM Granite Speech 4.0 1B5.52self-host
5NVIDIA Canary Qwen 2.5B5.63API
8ElevenLabs Scribe v25.83API
12AssemblyAI Universal-3 Pro6.21API
18Speechmatics Enhanced6.91API
23OpenAI Whisper Large v37.44API

FLEURS English

MetricPulse Pro
WER (FLEURS en_us)3.92%
CER (FLEURS en_us)1.73%

Per-language FLEURS tables for the broader European and Indic sets are tracked on standard Pulse.

Performance notes. Two caveats that matter for accurate expectation-setting:

  • RTFx hardware reference: the public leaderboard measures throughput on A100-80GB. Pulse Pro’s published 250–300× was measured on L40S; the recommended L4 deployment delivers lower throughput than L40S, and A100 delivers higher. Re-benchmark on your target GPU before locking SLOs.
  • Long-form single-file RTFx is lower than batched. On a challenging 1.92-hour Earnings22 sample we measured 68×. The 250–300× headline assumes optimal batching of typical-length audio. Plan for the lower bound on single very-long-form files.

Throughput, latency, and pricing

ModeThroughput (RTFx, long-form)2 hr file latency
No word timestamps250–300×~24–29 sec
With word timestamps~200×~36 sec

Customer pricing: $0.004 per minute of audio (Standard plan, non-streaming HTTP). Standard plan rate-limit defaults: 25 RPM per model. Enterprise tier is unlimited and configurable per-customer.

Supported Languages

Pulse Pro is English-only. For multilingual transcription, use standard Pulse (17 streaming + 26 pre-recorded languages).

LanguageCodeAvailable
EnglishenYes

API Reference

Endpoint

EndpointMethodUse case
https://api.smallest.ai/waves/v1/stt/?model=pulse-proPOSTSynchronous (or async via webhook_url) transcription

Query parameters

ParameterTypeRequiredDescription
modelpulse-proYesRequired selector. Omitting it or passing pulse-pro to the streaming endpoint returns 400.
languageenYesEnglish only.
word_timestampsbooleanNoPer-word timestamps. Costs roughly one-third of throughput.
diarizebooleanNoSpeaker identification.
webhook_urlURLNoReceive the transcription asynchronously; endpoint returns 200 with {"status": "processing", "request_id": "..."} immediately.
webhook_methodGET | POSTNoDefault POST.
webhook_extrastringNoArbitrary metadata passed back on the webhook.

Request body

  • Raw audio bytes: Content-Type: application/octet-stream
  • Audio-by-URL is not supported on Pulse Pro. For URL-based input use standard Pulse.
Pre-recorded quickstart

Pre-recorded STT setup, with both Pulse and Pulse Pro examples.

Use Cases

Strong fit

  • High-volume English batch transcription (call center QA, meeting platforms, media archives, compliance audits)
  • Meeting and financial audio workloads where Pulse Pro leads the leaderboard (AMI, SPGISpeech)
  • Regulated industries needing on-prem or VPC deployment
  • Customers with budget pressure at scale (>1M minutes per month)

Not a fit

  • Multilingual workloads; use standard Pulse (17 streaming + 26 pre-recorded languages)
  • Live streaming or sub-100ms conversational AI; use standard Pulse streaming
  • Audiobook or broadcast read-speech transcription where Cohere Transcribe and IBM Granite edge ahead on LibriSpeech and TED-LIUM

FAQ

Whisper Large v3 ranks 23rd on the Open ASR Leaderboard at 7.44% WER. Pulse Pro is tied for #2 at 5.42%, roughly a 27% relative WER improvement. Pulse Pro is also cheaper per minute than every hosted Whisper API.

Pulse Pro and Cohere Transcribe are tied on aggregate ESB WER (both 5.42%). Pulse Pro wins on AMI (meetings, 7.32 vs 8.13) and SPGISpeech (financial, 2.04 vs 3.08); Cohere wins on LibriSpeech and TED-LIUM (read speech). Pulse Pro ships as a managed API at $0.004/min; Cohere is open-weights and requires you to self-host.

Granite 4.1 2B is 0.09 WER points ahead on aggregate (5.33 vs 5.42). For most workloads the gap is operationally invisible. Pulse Pro is managed, hosted, and metered per minute. Granite is open-weights, with the same self-hosting cost basis as our infrastructure, but you take on the deployment, autoscaling, and operations cost.

Scribe v2 ranks 8th on the Open ASR Leaderboard at 5.83% WER, behind Pulse Pro by 0.41 points. The “Scribe v2 is #1 for accuracy” talking point comes from a different (smaller) benchmark. On the public, reproducible ESB benchmark Pulse Pro is more accurate and ~1,500× cheaper per minute.

Universal-3 Pro ranks 12th on ESB at 6.21% WER, behind Pulse Pro by 0.79 points. AssemblyAI is 3.50per1,000minutes;PulseProis3.50 per 1,000 minutes; Pulse Pro is 0.004/min ($4 per 1,000 minutes). Pulse Pro is more accurate at a comparable price.

Parakeet TDT 0.6B v3 runs at ~3,300× RTFx on A100, roughly 10× the published Pulse Pro throughput. But it ranks 13th on ESB at 6.32% WER, behind Pulse Pro by 0.90 WER points. For pure overnight bulk transcription where throughput dominates, Parakeet is competitive. For accuracy-sensitive workloads (meetings, finance, compliance), the WER gap matters.

Pulse Pro v4.1 is trained exclusively on English. For multilingual transcription, use standard Pulse (17 streaming + 26 pre-recorded languages). Pulse Pro and Pulse share the same /waves/v1/stt/ endpoint, so adding multilingual capability is a one-line ?model= swap.

Word timestamps require an alignment pass after acoustic decoding. Pulse Pro currently runs alignment in the standard pipeline, which costs roughly one-third of overall throughput (~200× with timestamps vs 250–300× without). A vLLM-backed alignment port is in development to close this gap.

The streaming worker for Pulse Pro is on the roadmap but not yet deployed. Today, calls to WS /waves/v1/stt/live?model=pulse-pro return 400 before the WebSocket upgrades, with a message directing you to the HTTP endpoint. For streaming use the standard Pulse model (?model=pulse).

Safety & Compliance

Pulse Pro must not be used for:

  • Recording or transcribing individuals without their explicit consent
  • Surveillance, stalking, or any form of unauthorized monitoring
  • Any illegal or unethical purposes

Additionally:

  • Usage is monitored for policy compliance
  • For compliance documentation (GDPR, SOC2, HIPAA), contact support@smallest.ai

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