Cartesia

Cartesia is a voice infrastructure company behind the Sonic text to speech models, built for real time agents where low latency matters, with speech recognition, managed agents, and credit based pricing for developers.

A free tier includes 20,000 credits per month, Pro costs 5 dollars per month with 100,000 credits, Startup is 49 dollars with 1.25 million credits, and Scale is 299 dollars with 8 million credits, with managed agent calls priced separately.

Benchmark comparisons put Sonic at a fraction of the Realtime price with comparable conversational quality and lower latency, which is why comparison sites call it the standard OpenAI Realtime alternative.

The Turbo variant of the Sonic 3 generation pushes generation speed further for latency critical flows such as phone agents and live translation, while keeping natural prosody.

Yes, the Ink model covers speech to text in the same platform, so teams can run the full voice loop from one provider.

Yes, Managed Agents package the models, orchestration, and telephony so teams ship voice agents without assembling their own pipeline, with per call pricing.

Developers building real time voice products such as support lines, drive through and booking flows, and live interpreters, rather than creators producing offline narration.

Yes, real time speech is the core design goal. Sonic streams audio as it generates to keep latency low enough for natural back and forth dialogue, and the Turbo variant of Sonic 3 exists for the most speed critical deployments. Because speech recognition through Ink runs in the same stack, the listen, think, and speak loop avoids stitching together multiple vendors, which keeps round trip time down.

Cartesia runs on a credit model. The free plan includes 20,000 credits per month, Pro at $5 per month raises that to 100,000 credits, and higher tiers add more capacity. Agent call rates are priced separately from the base credits, so a production phone agent should budget for both line items. Track consumption in the dashboard during the first weeks to learn the per minute burn rate of your workload.

Yes. The free plan includes 20,000 credits every month with no time limit, which is enough to run real latency tests against your own scripts rather than canned demos. Build a prototype call flow, measure response gaps, and compare it with your current stack before deciding. Since credits renew monthly, you can iterate across several weeks without entering a card.

Managed Agents package the full voice call loop: speech recognition, the Sonic speech model, and turn taking, so you ship a working phone or in app voice agent without wiring the pipeline yourself. Typical builds include support hotlines, booking lines, and outbound reminder calls. You keep control of the prompt and the escalation rules, and the platform handles the audio plumbing that usually eats the first month of a voice project.

Consumer tools optimize a finished audio file: you paste a script, wait, and download. Cartesia optimizes the live path, where latency decides whether a conversation feels human or broken. That difference shows up in the architecture: low latency streaming, interruption handling, and call oriented pricing. If your output is a podcast episode, a narration tool is fine; if your output is a conversation, this is the category built for it.

The tier ladder is designed for growth: Startup at $49 per month covers early production traffic, and Scale at $299 per month serves sustained high volume. Above that, agent call rates are quoted for the actual workload. The practical test is concurrency: run your peak hour traffic in a staged rollout, watch the latency numbers hold, and then move the real traffic over.