Cartesia alternative for realtime text to speech
Give your product a voice with Lightning TTS. Stream responses as text arrives, tune pronunciation for your business, and add Smallest voice agents when you need a complete calling workflow.
Is Smallest a Cartesia alternative for realtime TTS?
Yes. Smallest Lightning is a Cartesia alternative for applications that need streaming text to speech and pronunciation control. Use Lightning as the speech layer in your existing stack, or evaluate Atoms separately for phone agents. Cartesia Sonic may fit better if your product depends on a specific Sonic voice, locale, or dated model snapshot.
Smallest Lightning vs Cartesia Sonic: features compared
Compare the speech models, streaming interfaces, and release controls your application will use. Both providers also offer separate products for complete phone agents.
| Smallest AI | Cartesia | |
|---|---|---|
| Speech models | Lightning standard and Pro | Sonic model family |
| Streaming | HTTP, SSE, and WebSocket | WebSocket with text continuations |
| Voice selection | Separate catalogs for standard and Pro | Voice catalog with regional locale selection |
| Pronunciation | Per-request pronunciation dictionaries | Pronunciation and normalization controls |
| Model releases | Select the Lightning model in each request | Dated Sonic snapshots are documented |
| Complete phone agents | Separate Atoms platform | Separate managed phone-agent product |
Streaming TTS and pronunciation control with Lightning
Turn incoming text into spoken replies
Connect a live text stream to Lightning over WebSocket, or use HTTP synthesis for messages you already have. Choose the delivery method around your product’s response flow.
Make names and numbers part of your voice
Use pronunciation dictionaries for product names and specialist vocabulary, and set language and speaking speed per request, so delivery follows your application’s needs.
Grow from a voice API to a working agent
Keep Lightning as the speech layer in your existing application, or use Atoms for phone workflows. Smallest offers separate products for synthesis and agent workflows.
Use Lightning for spoken order updates
An order update needs more than a friendly greeting. Your application passes the current delivery details to Lightning and speaks the answer in the customer’s selected voice and language.
1
Fetch the order status in your application.
2
Send the reply with the required pronunciation dictionary.
3
Play streamed audio while the response is generated.
Smallest TTS pricing for Cartesia users
A voice-only change and a platform migration have different bills. If you keep Vapi, include its platform and other provider costs in the estimate. If you move to Atoms, build the estimate around the Smallest architecture you choose.
Lightning v3.1
Approximately $0.175 per 10,000 characters on the published pay-as-you-go model plan.
Lightning v3.1 Pro
Approximately $0.195 per 10,000 characters on the published pay-as-you-go model plan.
Your complete application
Listen to names, prices, and interrupted responses in the application. Expand usage after playback and business-critical wording are verified.
Should you choose Smallest or Cartesia?
Choose Smallest AI when
Build speech into your existing application
Choose Lightning for streaming speech with pronunciation controls, alongside the option to add transcription and hosted phone agents as your product grows.
Choose
Cartesia
When
When Cartesia may be the better fit
Stay with Sonic when a particular Cartesia voice, locale, or dated model snapshot is central to your product. Changing providers should preserve the listening experience and release controls your users already depend on.
Frequently asked questions
Is Smallest a Cartesia alternative for realtime voice applications?
Can I use Lightning without moving my whole voice stack?
Does Smallest support pronunciation dictionaries?
How do model and voice selection differ?
Can Smallest run phone agents as well as generate speech?