F5-TTS vs Cartesia Sonic: Which AI Model Should You Choose?

Pricing, context windows, latency, capabilities, and a one-line code switch โ€” everything you need to pick the right model.

Replicate
Text-to-Speech
vs
xAI
Text-to-Speech
Verdict

F5-TTS and Cartesia Sonic are closely matched on pricing and context. The right choice depends on your specific workload โ€” see the table below for the full breakdown.

Side-by-side specs

SpecF5-TTSCartesia Sonic
ProviderReplicatexAI
CategoryText-to-SpeechText-to-Speech
Input cost / 1M tokensFreeโ‚ฌ0.030
Output cost / 1M tokensFreeFree
Context windowโ€”โ€”
Max output tokensโ€”โ€”
Avg. latencyโ€”โ€”
Featuredโ€”โ€”
Newโ€”โ€”
Capabilities
text
audio
text

Pricing example

A typical chat workload of 100,000 input tokens plus 50,000 output tokens.

F5-TTS
โ‚ฌ0.0000

100K in ร— Free + 50K out ร— Free

Cartesia Sonic
โ‚ฌ0.0030

100K in ร— โ‚ฌ0.030 + 50K out ร— Free

For this workload, F5-TTS is cheaper than Cartesia Sonic by โ‚ฌ0.0030 per request.

Switch in one line

Both models live behind Railwail's OpenAI-compatible endpoint. Replace the model string and you are done.

JavaScript / TypeScript
import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.RAILWAIL_API_KEY,
  baseURL: "https://railwail.com/v1",
});

// Before โ€” using F5-TTS
let r = await client.chat.completions.create({
  model: "SWivid/F5-TTS",
  messages: [{ role: "user", content: "Hello" }],
});

// After โ€” switched to Cartesia Sonic
r = await client.chat.completions.create({
  model: "sonic",
  messages: [{ role: "user", content: "Hello" }],
});
Python
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["RAILWAIL_API_KEY"],
    base_url="https://railwail.com/v1",
)

# Before โ€” using F5-TTS
r = client.chat.completions.create(
    model="SWivid/F5-TTS",
    messages=[{"role": "user", "content": "Hello"}],
)

# After โ€” switched to Cartesia Sonic
r = client.chat.completions.create(
    model="sonic",
    messages=[{"role": "user", "content": "Hello"}],
)
cURL
# Before โ€” using F5-TTS
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "SWivid/F5-TTS",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

# After โ€” switched to Cartesia Sonic
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "sonic",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

Which one wins for...

Quick verdicts derived from public specs. Always validate on your own workload.

Coding
F5-TTS

Higher coding category match or larger context wins.

Writing
F5-TTS

Bigger context window helps maintain long-form coherence.

Long documents
F5-TTS

The larger context window is the deciding factor.

Vision
Tie

Multimodal/vision support is required for image inputs.

Real-time chat
Tie

Lower average latency wins for interactive UX.

Cost-sensitive
Tie

The model with the lower input-token price wins.

Frequently asked questions

Which is cheaper, F5-TTS or Cartesia Sonic?
Pricing for F5-TTS and Cartesia Sonic is comparable on input tokens. For a 100K input + 50K output workload, F5-TTS costs about โ‚ฌ0.0000 and Cartesia Sonic costs about โ‚ฌ0.0030.
Which has more context, F5-TTS or Cartesia Sonic?
F5-TTS and Cartesia Sonic have similar context windows (โ€” vs โ€”).
Is F5-TTS better than Cartesia Sonic for coding?
For coding-heavy workloads we lean toward F5-TTS on this comparison โ€” it scores higher on the relevant heuristics (category, tags, or context window). Both models are usable for code via Railwail's OpenAI-compatible endpoint, so the safest path is to A/B test on your own prompts.
Can I use both F5-TTS and Cartesia Sonic via Railwail?
Yes. Both F5-TTS and Cartesia Sonic are accessible through a single Railwail API key and the OpenAI-compatible /v1/chat/completions endpoint. You only change the "model" parameter to switch between them โ€” no SDK swap, no separate billing.
How do I switch from F5-TTS to Cartesia Sonic?
Replace the model identifier "SWivid/F5-TTS" with "sonic" in your request payload. Everything else โ€” API key, base URL, request shape โ€” stays the same. See the code example on this page for the exact one-line change.

Try F5-TTS and Cartesia Sonic side by side

One API key, one endpoint, both models. Start free โ€” no credit card required.