Bonus: Top up now and we'll double your first deposit — get x2 credits instantly.
Get Started
Sign Up
Sign Up

Cartesia Sonic 3.5

Up to 30%

Synthesize speech with Cartesia Sonic 3.5 on LLM.API—text in, audio out, billed and authenticated like the rest of your model fleet.

Start Using API

What is Cartesia Sonic 3.5?

Cartesia Sonic 3.5 is a text-to-speech model on LLM.API (`sonic-3.5`). Text-to-speech model by Cartesia. It converts text into audio for assistants, narration, and accessibility.

Providers

LLM.API routes Cartesia Sonic 3.5 to the providers below, with discounted effective rates versus list price.

ProviderPricingContextCapabilities
cartesia30% offin $78; out — per 1M characters——

Prices and availability from the LLMAPI catalogue, updated nightly. Last updated 21 Sept 2026.

Try this model

Test Cartesia Sonic 3.5 right here — free to start.

Cartesia Sonic 3.5
Hi! Want to test the model?

Suggestions for your first prompt

Code snippet

Call Cartesia Sonic 3.5 through the OpenAI-compatible API — TTS via LLM.API (see docs for audio endpoints).

python
from openai import OpenAI

client = OpenAI(
    api_key="YOUR_LLMAP_KEY",
    base_url="https://api.llmapi.ai/v1",
)

resp = client.chat.completions.create(
    model="sonic-3.5",
    messages=[
        {"role": "system", "content": "You are a precise product assistant."},
        {"role": "user", "content": "Give me three crisp launch checklist items."},
    ],
)
print(resp.choices[0].message.content)
{
  "model": "sonic-3.5",
  "messages": [
    {"role": "system", "content": "You are a precise product assistant."},
    {"role": "user", "content": "Give me three crisp launch checklist items."}
  ]
}

5 Core Capabilities

  • Voice product UX

    Enables talk-back experiences in apps and devices. Grounded in the model's tts role rather than generic chat claims.

  • Multilingual voices

    Supports multiple languages where the provider catalog allows. Tuned to how teams typically call Cartesia Sonic 3.5.

  • IVR and alerts

    Generates spoken prompts for support and notification flows. Reflects text-to-speech positioning for this endpoint.

  • Natural speech synthesis

    Turns text into spoken audio for assistants, accessibility, and media. Grounded in the model's tts role rather than generic chat claims.

  • Promptable delivery

    Responds to punctuation and phrasing cues for pacing. Relevant for `sonic-3.5` workloads on LLM.API.

6 Most Valuable Use Cases

  • Alert and notification spoken prompts with Cartesia Sonic 3.5
  • Multilingual demo voiceovers
  • Course and help-center narration with Cartesia Sonic 3.5
  • Voice assistants and talk-back UIs
  • Game and app character voice drafts with Cartesia Sonic 3.5
  • Rapid podcast intro/outro prototypes

Why Build on LLM.API?

One unified API. Every major model. Built-in reliability, cost control, and observability.

  • Intelligent AI Routing

    Automatically route each request to the best model across providers based on latency, cost, and quality—without changing your integration or redeploying code.

    One endpoint, every model.

  • Cost-Aware Execution

    Control spend with per-request cost estimation, smart model selection, and centralized quotas so teams can experiment fast without runaway bills or manual tracking.

    More performance, less spend.

  • Resilient Fallback Flows

    Define automatic, provider-agnostic fallbacks to keep your app up during outages, rate limits, or timeouts—no brittle failover logic scattered through your codebase.

    Never go dark on users.

  • Deep LLM Observability

    Trace every call across providers with logs, metrics, and request replay so you can debug, tune prompts, and optimize model choices from one unified dashboard.

    See every token, everywhere.

  • Task-Level Orchestration

    Describe tasks, not models. LLM.API maps them to the right tools, models, and prompts so you ship complex AI workflows with minimal glue code.

    Think tasks, not models.

  • High-Throughput Batch APIs

    Process millions of inferences efficiently with optimized batch pipelines, concurrency controls, and retry logic—all behind the same simple interface you use for single calls.

    Scale from 1 to millions.

Why run Cartesia Sonic 3.5 on LLM.API?

  • Unified AI Routing

    Practical: Reach Cartesia Sonic 3.5 and sibling models through one OpenAI-compatible endpoint.

  • Cost Control

    Production: Compare provider price points and keep spend visible as you scale Cartesia Sonic 3.5.

  • Reliability Layer

    Retry and route across configured providers when a single upstream blips.

  • Observability

    Trace prompts, tokens, and errors for Cartesia Sonic 3.5 alongside the rest of your stack.

  • Drop-in SDKs

    Keep using familiar OpenAI client patterns with base URL https://api.llmapi.ai/v1.

  • Model Breadth

    Production: Swap Cartesia Sonic 3.5 for chat, media, or embedding alternatives without rewriting auth.

When to Use — When NOT to Use

Use it if...

  • You need text-to-speech without managing voice infrastructure (Cartesia Sonic 3.5)
  • Your UX requires spoken responses or narration (Cartesia Sonic 3.5)
  • You want API-driven voice prototypes that can go to production (Cartesia Sonic 3.5)

Avoid if...

  • You require a specific celebrity voice you do not have rights to
  • You only need embeddings or OCR
  • You need speech recognition rather than synthesis

COMMUNITY

What developers say about text-to-speech models

Summarised from publicly published developer and community reviews of this model family. Opinions are the sources’, not LLM.API’s, and may not be specific to Cartesia Sonic 3.5.

  • Community consensus still puts ElevenLabs-class voices at the top for realism and emotional range.
  • The debate has shifted from quality to value, as open-source voices mature and heavy usage pushes teams to higher tiers.
  • Developers advise designing for rate limits early — 429 handling on generation calls is a common production surprise.

SOURCES

Frequently Asked Questions

  • How is Cartesia Sonic 3.5 priced on LLM.API?

    Listed pricing metadata shows: In $78.00 / 1M tokens. LLM.API may offer discounted effective rates (illustrative ~30% callout vs list when available).. Confirm live rates in the LLM.API dashboard or docs before production budgeting.

  • Can I use tools or structured outputs with Cartesia Sonic 3.5?

    Tooling support varies; for pure tts models, prefer the modalities listed rather than assuming chat tools.

  • Is Cartesia Sonic 3.5 a chat model?

    No—Cartesia Sonic 3.5 is categorized as a tts model. Use the matching API surface rather than assuming chat completions.

  • What is the context length for Cartesia Sonic 3.5?

    Reported context for Cartesia Sonic 3.5 is See provider specs. Always verify the active provider row if multiple providers are listed.

  • What are limitations of Cartesia Sonic 3.5?

    Like other API models, Cartesia Sonic 3.5 can be wrong, incomplete, or uneven on edge cases. Validate outputs for high-stakes use. Media/OCR/STT models additionally depend on input quality.

  • How do I call Cartesia Sonic 3.5 via API?

    Send OpenAI-compatible requests to https://api.llmapi.ai/v1 with model "sonic-3.5" and your LLM.API key. See the code snippet on this page.

  • What is Cartesia Sonic 3.5?

    Text-to-speech model by Cartesia. On LLM.API it is addressed as `sonic-3.5`.

  • When should I choose Cartesia Sonic 3.5?

    You need text-to-speech without managing voice infrastructure — especially when you specifically need Cartesia Sonic 3.5.

  • Where is the canonical page for Cartesia Sonic 3.5?

    https://llmapi.ai/models/sonic-3-5/

  • Does Cartesia Sonic 3.5 support streaming?

    Streaming depends on the active provider; check the providers table on this page for flags.

COMPARE

Competitive Models

Get one key to every model

Swap your API key. Keep your code.

Start for free Talk to sales