Fish Audio: S2.1 Pro Free (free) vs HeyGen: HeyGen Voice Turbo
A side-by-side comparison of Fish Audio: S2.1 Pro Free (free) (Free) and HeyGen: HeyGen Voice Turbo ($14.00 / 1M characters) using current USD prices and capabilities from the api14 catalog. Both run through the same OpenAI-compatible API.
Specifications
| Fish Audio: S2.1 Pro Free (free) | HeyGen: HeyGen Voice Turbo | |
|---|---|---|
| Provider | Fish Audio | HeyGen |
| Characters | - | $14.00 / 1M characters |
| Context window | - | - |
| Max output | - | - |
| Input | text | text |
| Output | speech | speech |
| Tool calling | ||
| Structured output | ||
| Reasoning control | ||
| Added | Jul 29, 2026 | Oct 26, 2026 |
In depth
Fish Audio: S2.1 Pro Free is a text to speech model from Fish Audio, offered on api14 under the free tier (the model id carries the :free suffix). HeyGen Voice Turbo is a text to speech model from HeyGen. Both sit in the speech category, both take text in, and both return speech. Neither model carries a context length figure in its metadata, so there is no token window to plan around in either case.
The two models are closer than they are different on paper. Both accept text input and produce speech output only, and both list no supported parameters, so things like voice selection, speed or style controls are not exposed through the request body in the way you might expect from a larger audio API. The qualitative comparison fields come back empty or unknown for the cheaper input, cheaper output, bigger context, tools, structured output and reasoning rows, so there is no documented capability that one has and the other lacks. The only concrete dates attached to them are provider release dates: Fish Audio lists 2026-07-29 and HeyGen lists 2026-10-26. That is everything the metadata supports, and it means your choice comes down to output quality on your own material rather than a feature checklist.
For practical selection, treat them as two interchangeable speech endpoints and let a listening test decide. Generate the same script through both, with the same text and punctuation, and compare pronunciation of names, numbers and technical terms, pacing across long sentences, and how each handles pauses. If your pipeline is already producing narration for HeyGen style video content, Voice Turbo is the natural starting point. If you are building voice output on the free tier and cost matters, S2.1 Pro Free is the obvious one to try first, since free is as cheap as it gets and there is no listed feature you would lose by starting there. For anything where the two sound equivalent on your content, default to the free model and only move up when a specific clip fails.
Calling either model through api14 is the same request. Both are OpenAI compatible, so you point your existing client at the api14 base URL, send a normal chat style or audio request with your text, and set the model field. To use Fish Audio, set model to "fish-audio/s2.1-pro-free:free". To use HeyGen, set model to "heygen/heygen-voice-1-turbo". Nothing else in the payload changes: same auth header, same endpoint shape, same response handling. Because supported parameters are empty for both, keep your request minimal and do not add sampling or voice fields expecting them to take effect. Switching between the two is a one line edit, which makes A/B testing on real scripts cheap.
There is no case in the supplied facts where one model is clearly the better pick over the other on capability. The later release date on HeyGen Voice Turbo is the only signal that separates them, and a release date is not a quality claim. Use the free Fish Audio model as your default, keep HeyGen Voice Turbo one string away, and choose per clip based on what you hear.
Switch with one string
Both models use the same endpoint and request shape. Change the model value from "fish-audio/s2.1-pro-free:free" to "heygen/heygen-voice-1-turbo" and prompts, streaming and tools keep working.
import { writeFile } from "node:fs/promises";
import OpenAI from "openai";
const client = new OpenAI({
baseURL: "https://api14.com/api/v1",
apiKey: process.env.API14_API_KEY,
});
const audio = await client.audio.speech.create({
"model": "heygen/heygen-voice-1-turbo",
"input": "Hello from api14! One API for every model.",
"voice": "alloy",
"response_format": "mp3"
});
await writeFile("speech.mp3", Buffer.from(await audio.arrayBuffer()));
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