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ElevenLabs vs OpenAI TTS

Compare ElevenLabs with OpenAI's speech API. Review model choice, custom voices, streaming and character versus token-based billing.

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ElevenLabs vs OpenAI TTS at a glance

Compare ElevenLabs speech models with OpenAI's text-to-speech endpoint when your application already has text to speak. OpenAI Realtime handles a broader conversation and needs a separate evaluation. Model choice, custom-voice access and billing units matter more than a single provider-wide quality or latency score.

ElevenLabsOpenAI TTS

  1. Model selection

    ElevenLabs
    Flash v2.5 for low latency, Multilingual v2 for long-form speech, and Eleven v3 for expressive delivery.
    OpenAI TTS
    GPT-4o mini TTS converts supplied text into audio through the speech endpoint.

  2. Custom voices

    ElevenLabs
    Instant and Professional Voice Cloning are separate workflows with plan and recording requirements.
    OpenAI TTS
    Custom voices are limited to eligible customers and require a consent recording plus a matching voice sample.

  3. Delivery controls

    ElevenLabs
    Controls depend on the selected model. Test expressive delivery separately from low-latency generation.
    OpenAI TTS
    GPT-4o mini TTS accepts natural-language instructions for how the text should be spoken.

  4. Languages

    ElevenLabs
    Flash v2.5 lists 32 languages; Multilingual v2 lists 29. Check the selected model's language list.
    OpenAI TTS
    The speech guide documents multilingual output and notes that the built-in voices are optimized for English.

  5. Streaming output

    ElevenLabs
    Measure first playable audio using the model and playback path your application will deploy.
    OpenAI TTS
    The speech API can stream output. Choose an output format that matches your player and latency needs.

  6. Conversation scope

    ElevenLabs
    Compare TTS when replacing speech output; assess an agent platform separately for conversation handling.
    OpenAI TTS
    The speech endpoint speaks supplied text. Realtime also handles audio input, conversation state and tools.

  7. Billing unit

    ElevenLabs
    ElevenAPI meters TTS by characters. The selected model and offer affect the rate.
    OpenAI TTS
    GPT-4o mini TTS bills text input tokens and audio output tokens. Older TTS model rates use different units.

Why teams choose Cartesia

Rated first by listeners

Sonic 3.6 ranks first on the Artificial Analysis Provider Voice Arena, a blind listening test.

First audio in under 90ms

Sonic streams speech fast enough for a live phone call, on the public API.

44 languages, one model

Native accents in every language, with no model to switch when a caller does.

Enterprise ready

SOC 2 Type II, HIPAA-eligible, on-prem and air-gapped deployment, and a 99.9% uptime SLA.

How they stack up

Match the endpoint to the job

  • Use a TTS comparison when your application already produces response text.
  • Evaluate OpenAI Realtime separately when it owns voice input, conversation state and tool calls.
  • Compare the same scripts in named models. Keep playback format and network region constant when measuring first audible output.

Confirm the voice workflow

  • Follow the ElevenLabs cloning guide for Instant or Professional cloning requirements.
  • Confirm OpenAI custom-voice eligibility before making it a dependency of your launch.
  • Test names, numbers and long passages in every required language. A voice demo does not establish pronunciation accuracy for your application.

Budget using the actual units

  • Use the current ElevenAPI prices and OpenAI model pricing for the same expected workload.
  • Measure token usage and generated audio rather than assuming a fixed conversion between characters and audio tokens.
  • For Realtime, include session input and output usage. A standalone speech-output price does not cover the whole conversation.

If you are also evaluating Sonic, the Cartesia vs OpenAI comparison separates speech output from a full Realtime conversation.

Trusted by leading enterprises. Speaking from experience.

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“Cartesia’s state-space models bring enterprise-grade speed and quality to our AI Voice Agents… making it possible for businesses to deploy secure, scalable voice agents that can understand, act, and adapt in real time.”

Ravi Krishnamurthy

VP Product

“With Cartesia's Sonic model, users can interact with a wide range of high-quality, human-like voices in multiple languages, enhancing their experience on our platform.”

Spencer Chan

Head of Poe Product

“Cartesia is leading the charge of building efficient, multimodal models from first principles, starting with their Sonic TTS model.”

Vipul Ved Prakash

CEO

“We didn’t switch to Sonic because it was incrementally better, we switched because nothing else came close… we’ve seen a 2.9% lift in our conversion and a 12.2% increase in customer engagement.”

Akshay Ramaswamy

Staff Product Manager

“Sonic represents a significant evolution over previous TTS models, delivering refined prosodic rhythm, natural intonation, superior pacing and wider emotional range for more “human” sounding voices.”

Tyler Brown

Voice Expert

“Cartesia Sonic is the best voice model today for real-time multimodal use cases.”

Kwindla Hultman

CEO

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