Cartesia vs OpenAI TTS
Discover key differences between Cartesia and ElevenLabs voice AI models.
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Compare Cartesia and OpenAI TTS Voice Models
Explore the differences between Cartesia and OpenAI TTS voice models. Discover features, pricing, and performance metrics.
Updated on:
Feb 14, 2025
Features
Cartesia
40ms for the Sonic Turbo model, 90ms for the Sonic 2 model
Consistently rated as more natural, expressive, and realistic in blinded human evaluations
Infinite request length
Requires 3 seconds of audio
IPA support with strong contextual understanding
Slider control for speed and emotion + synthetic voice mixing and design
8kHz audio, telephony optimized voices
Supports both on-prem and on-device deployments
15 languages with extensive dialect coverage
Up to 15 on highest self-serve tier (60 parallel conversations), custom for enterprise
OpenAI Speech to Text
200 ms + network time, slower response times
Lower quality ratings in human evaluations, and limited emotional control
Limited character count for longer texts
Requires 13 seconds of audio
Requires 60 minutes of audio
Less contextual awareness in pronunciation
Basic controls for speed, emotion and similarity
Standard audio quality without optimization
No on-device generation available
57
3-200 per mins
Cartesia - Advanced AI Voice Capabilities
Cartesia AI offers the fastest voice model with hallucination-free, ultra-realistic voice generation and cloning.
Voice Clone
Cartesia's voice cloning delivers lifelike, accurate voice replication with unmatched fidelity.
Ultra-Realistic Voices
With a time-to-first-audio of just 40ms, Sonic provides the fastest and most realistic voice generation available.
No Hallucinations
Cartesia's AI text to speech eliminates errors, ensuring authentic and clear audio output every time.
Enterprise Ready
Enterprise-grade reliability with 99.9% uptime, SOC2 compliance, and full on-premises support.
Latency
We measure latency using the Time to First Audio (TTFA) metric and calculate the 90th percentile score from 100 TTFA measurements for each provider. With a TTFA of 199 ms, Cartesia's Sonic model is significantly faster than ElevenLabs' 832 ms at the self-serve tier (with ElevenLabs reserving slightly lower latency for enterprise customers). Cartesia’s Sonic model is built on a radically more efficient architecture, known as State Space Models (SSMs), which allows for far greater latency optimization than the traditional transformer architecture used by ElevenLabs and other providers. For a side by side comparison, watch the latency demonstration in this video on X.
Pronunciation Accuracy
Using the Time to First Audio (TTFA) metric, Cartesia's Sonic model achieves a TTFA of 199 ms, significantly faster than ElevenLabs' 832 ms. This efficiency is due to Cartesia's advanced State Space Models (SSMs), optimizing latency beyond traditional architectures.
Voice Cloning
Cartesia provides unlimited instant voice cloning. In contrast, ElevenLabs restricts cloning capabilities with tiered plans allowing for 10, 30, 160, or 660 custom voices. Additionally, Cartesia utilizes advanced embedding technology to deliver consistent, high-quality voice clones. Cartesia preserves accents and voice quality even if the original audio clip is noisy. Cartesia's voice mixing and design capabilities also open up a more comprehensive set of diverse voices. In the following samples of Engelbart's clones, it's apparent that Cartesia produces a significantly less noisy and higher quality clone than ElevenLabs.
Voice Design Controllability
Cartesia stands out as the only provider offering emotion and speed modulation features, enabling refined voice adjustments while preserving a natural and seamless auditory experience. Cartesia also allows you to localize the voice to match different accents — you can start with an American voice and have it speak in a French accent, for instance. In comparison, ElevenLabs only offers controls for stability, similarity, and style exaggeration, all of which do not offer clear control for the voice. In the following example where the speaker is addressing a customer complaint, we compare the dial effects from ElevenLabs and Cartesia to find that the ElevenLabs voice sounds similar with the various dials applied while Cartesia's emotion and speed dials convey very noticeable changes.
Pricing Plans for Cartesia and OpenAI TTS
Cartesia
Free - $0 per month with 10k free credits
Pro - $5 per month with 100k credits
Startup - $49 per month with 1.25M credits
Scale - $299 per month with 8M credits
Enterprise - trusted by Fortune 500 companies
OpenAI Speech to Text
TTS - $15 per 1M characters
TTS HD - $30 per 1M characters
What Cartesia Customers Say
Join the growing list of companies opting for Sonic.
"Cartesia’s voice API power dynamic and empathetic conversational experiences that are consistently dependable. What really stands out to me is how natural and considerate the responses feel—especially the empathetic tone in statements like ‘I’m sorry, that must be frustrating.’"
Sami Ghoche, CEO of Forethought
"In 1999, Salesforce brought software to the cloud. In 2025, 11x is killing software as we know it and unleashing the era of digital workers. To realise this vision, we needed AI voice technology that feels truly human. Cartesia’s technology gives our AI digital workers reps the speed, reliability, and natural expressiveness required to engage customers at scale.
It's the only solution fit for our relentless drive toward innovation.”
Keith Fearon, Head of Product & Growth, 11x
"Before conversational voice models like Cartesia, Thoughtly relied on legacy text-to-speech APIs from major cloud providers. Nearly two years later, the evolution of this technology is staggering—customers can clone their voice and hear it speaking autonomously over the phone in just 60 seconds.”
Torrey Leonard, CEO, Thoughtly
