neutts 1.1.0

NeuTTS - a package for text-to-speech generation using Neuphonic's TTS models.

NeuTTS

HuggingFace 🤗:

• NeuTTS-Air (English): Model, Q8 GGUF, Q4 GGUF, Space

• NeuTTS-Nano Multilingual Collection:

  • NeuTTS-Nano (English): Model, Q8 GGUF, Q4 GGUF
  • NeuTTS-Nano-French: Model, Q8 GGUF, Q4 GGUF
  • NeuTTS-Nano-German: Model, Q8 GGUF, Q4 GGUF
  • NeuTTS-Nano-Spanish: Model, Q8 GGUF, Q4 GGUF
  • Multilingual Space

NeuTTS-Nano Demo Video

Created by Neuphonic - building faster, smaller, on-device voice AI

State-of-the-art Voice AI has been locked behind web APIs for too long. NeuTTS is a collection of open source, on-device, TTS speech language models with instant voice cloning. Built off of LLM backbones, NeuTTS brings natural-sounding speech, real-time performance, built-in security and speaker cloning to your local device - unlocking a new category of embedded voice agents, assistants, toys, and compliance-safe apps.

Key Features

• 🗣Best-in-class realism for their size - produce natural, ultra-realistic voices that sound human, at the sweet spot between speed, size, and quality for real-world applications
• 📱Optimised for on-device deployment - quantisations provided in GGUF format, ready to run on phones, laptops, or even Raspberry Pis
• 👫Instant voice cloning - create your own speaker with as little as 3 seconds of audio
• 🚄Simple LM + codec architecture - making development and deployment simple

[!CAUTION] Websites like neutts.com are popping up and they're not affliated with Neuphonic, our github or this repo.

We are on neuphonic.com only. Please be careful out there! 🙏

Model Details

NeuTTS models are built from small LLM backbones - lightweight yet capable language models optimised for text understanding and generation - as well as a powerful combination of technologies designed for efficiency and quality:

• Supported Languages: English, Spanish, German, French (model-dependent)
• Audio Codec: NeuCodec - our 50hz neural audio codec that achieves exceptional audio quality at low bitrates using a single codebook
• Context Window: 2048 tokens, enough for processing ~30 seconds of audio (including prompt duration)
• Format: Quantisations available in GGUF format for efficient on-device inference
• Responsibility: Watermarked outputs
• Inference Speed: Real-time generation on mid-range devices
• Power Consumption: Optimised for mobile and embedded devices

	NeuTTS-Air	NeuTTS-Nano Models
# Params (Active)	~360m	~120m
# Params (Emb + Active)	~552m	~229m
Cloning	Yes	Yes
License	Apache 2.0	NeuTTS Open License 1.0

Throughput Benchmarking

These benchmarks are for the Q4_0 quantisations neutts-air-Q4_0 and neutts-nano-Q4_0. Note that all models in the NeuTTS-Nano Multilingual Collection have an identical architecture, so these results should apply for any Q4_0 model in the collection.

CPU benchmarking used llama-bench (from llama.cpp) to measure prefill and decode throughput at multiple context sizes. For the GPU benchmark (RTX 4090), we leverage vLLM to maximise throughput, using the vLLM benchmark.

We include benchmarks on four devices: Galaxy A25 5G, AMD Ryzen 9HX 370, iMac M4 16GB, NVIDIA GeForce RTX 4090.

	NeuTTS-Air	NeuTTS-Nano
Galaxy A25 5G (CPU only)	20 tokens/s	45 tokens/s
AMD Ryzen 9 HX 370 (CPU only)	119 tokens/s	221 tokens/s
iMAc M4 16 GB (CPU only)	111 tokens/s	195 tokens/s
RTX 4090	16194 tokens/s	19268 tokens/s

[!NOTE] llama-bench used 14 threads for prefill and 16 threads for decode (as configured in the benchmark run) on AMD Ryzen 9HX 370 and iMac M4 16GB, and 6 threads for each on the Galaxy A25 5G. The tokens/s reported are when having 500 prefill tokens and generating 250 output tokens.

[!NOTE] Please note that these benchmarks only include the Speech Language Model and do not include the Codec which is needed for a full audio generation pipeline.

Get Started with NeuTTS

[!NOTE] We have added a streaming example using the llama-cpp-python library as well as a finetuning script. For finetuning, please refer to the finetune guide for more details.

1. Install System Dependencies (required): espeak-ng

[!CAUTION] espeak-ng is an updated version of espeak, as of February 2026 on version 1.52.0. Older versions of espeak and espeak-ng can exhibit significant phonemisation issues, particularly for non-English languages. Updating your system version of espeak-ng to the latest version possible is highly recommended.

[!NOTE] brew on macOS Ventura and later, apt in Ubuntu version 25 or Debian version 13, and choco/winget on Windows, install the latest version of espeak-ng with the commands below. If you have a different or older operating system, you may need to install from source: see the following link https://github.com/espeak-ng/espeak-ng/blob/master/docs/building.md

Please refer to the following link for instructions on how to install espeak-ng:

https://github.com/espeak-ng/espeak-ng/blob/master/docs/guide.md

# Mac OS
brew install espeak-ng

# Ubuntu/Debian
sudo apt install espeak-ng

# Windows install
# via chocolatey (https://community.chocolatey.org/packages?page=1&prerelease=False&moderatorQueue=False&tags=espeak)
choco install espeak-ng
# via winget
winget install -e --id eSpeak-NG.eSpeak-NG
# via msi (need to add to path or folow the "Windows users who installed via msi" below)
# find the msi at https://github.com/espeak-ng/espeak-ng/releases

Windows users who installed via msi / do not have their install on path need to run the following (see https://github.com/bootphon/phonemizer/issues/163)

$env:PHONEMIZER_ESPEAK_LIBRARY = "c:\Program Files\eSpeak NG\libespeak-ng.dll"
$env:PHONEMIZER_ESPEAK_PATH = "c:\Program Files\eSpeak NG"
setx PHONEMIZER_ESPEAK_LIBRARY "c:\Program Files\eSpeak NG\libespeak-ng.dll"
setx PHONEMIZER_ESPEAK_PATH "c:\Program Files\eSpeak NG"

2. Install NeuTTS

   pip install neutts
   

   Or for a local editable install, clone this repository and run in the base folder:

   pip install -e .
   

   Alternatively to install all dependencies, including onnxruntime and llama-cpp-python (equivalent to steps 3 and 4 below):

   pip install neutts[all]
   

   or for an editable install:

   pip install -e .[all]
   

3. (Optional) Install llama-cpp-python to use .gguf models.

   pip install "neutts[llama]"
   

   Note that this installs llama-cpp-python without GPU support. To install with GPU support (e.g., CUDA, MPS) please refer to: https://pypi.org/project/llama-cpp-python/

4. (Optional) Install onnxruntime to use the .onnx decoder.

   pip install "neutts[onnx]"
   

Examples

To get started with the example scripts, clone this repository and navigate into the project directory:

git clone https://github.com/neuphonic/neutts.git
cd neutts

Several examples are available, including a Jupyter notebook in the examples folder.

Basic Example

Run the basic example script to synthesize speech:

python -m examples.basic_example \
  --input_text "My name is Andy. I'm 25 and I just moved to London. The underground is pretty confusing, but it gets me around in no time at all." \
  --ref_audio samples/jo.wav \
  --ref_text samples/jo.txt

To specify a particular model repo for the backbone or codec, add the --backbone argument. Available backbones are listed in NeuTTS-Air and NeuTTS-Nano Multilingual Collection huggingface collections.

[!CAUTION] If you are using a non-English backbone, it is highly recommended to use a same-language reference for best performance. See the 'example reference files' section below to select an appropriate example reference.

One-Code Block Usage

from neutts import NeuTTS
import soundfile as sf

tts = NeuTTS(
   backbone_repo="neuphonic/neutts-nano", # or 'neuphonic/neutts-nano-q4-gguf' with llama-cpp-python installed
   backbone_device="cpu",
   codec_repo="neuphonic/neucodec",
   codec_device="cpu"
)
input_text = "My name is Andy. I'm 25 and I just moved to London. The underground is pretty confusing, but it gets me around in no time at all."

ref_text = "samples/jo.txt"
ref_audio_path = "samples/jo.wav"

ref_text = open(ref_text, "r").read().strip()
ref_codes = tts.encode_reference(ref_audio_path)

wav = tts.infer(input_text, ref_codes, ref_text)
sf.write("test.wav", wav, 24000)

Streaming

Speech can also be synthesised in streaming mode, where audio is generated in chunks and plays as generated. Note that this requires pyaudio to be installed. To do this, run:

python -m examples.basic_streaming_example \
  --input_text "My name is Andy. I'm 25 and I just moved to London. The underground is pretty confusing, but it gets me around in no time at all." \
  --ref_codes samples/jo.pt \
  --ref_text samples/jo.txt

Again, a particular model repo can be specified with the --backbone argument - note that for streaming the model must be in GGUF format.

Preparing References for Cloning

NeuTTS requires two inputs:

1. A reference audio sample (.wav file)
2. A text string

The model then synthesises the text as speech in the style of the reference audio. This is what enables NeuTTS models' instant voice cloning capability.

Example Reference Files

You can find some ready-to-use references in the samples folder:

• English:
  • dave.wav
  • jo.wav
• Spanish:
  • mateo.wav
• German:
  • greta.wav
• French:
  • juliette.wav

Guidelines for Best Results

For optimal performance, reference audio samples should be:

1. Mono channel
2. 16-44 kHz sample rate
3. 3–15 seconds in length
4. Saved as a .wav file
5. Clean — minimal to no background noise
6. Natural, continuous speech — like a monologue or conversation, with few pauses, so the model can capture tone effectively

Guidelines for minimizing Latency

For optimal performance on-device:

1. Use the GGUF model backbones
2. Pre-encode references (see examples/encode_reference.py or examples/basic_example.py)
3. Use the onnx codec decoder

Take a look at this example in the examples README to get started.

Responsibility

Every audio file generated by NeuTTS includes Perth (Perceptual Threshold) Watermarker.

Disclaimer

Don't use this model to do bad things… please.

Developer Requirements

To run the pre commit hooks to contribute to this project run:

pip install pre-commit

Then:

pre-commit install

Running Tests

First, install the dev requirements:

pip install -r requirements-dev.txt

To run the tests:

pytest tests/

To test loading of all the official backbone and codecs, use:

RUN_SLOW=true pytest tests/