Vireo TTS 3B for Apple Silicon

Vireo is my unofficial MLX build of Breeze TTS 2, a 3B speech model by BreezeBlue. BreezeBlue has not reviewed or endorsed it. It comes in two builds. The bfloat16 build converts the released checkpoint to MLX at unchanged precision, as the quality reference. The mixed 4-bit build adds activation-calibrated pruning and per-stage low-bit quantization, and it is the one I optimised and measured end to end.

mixed 4-bit, real time

1.15×

bf16 reference, real time

0.41×

peak GPU memory

3.0 / 7.0 GB

warm first audio

285–322 ms

Limits. Speed is the best of three runs on one M2 and does not transfer to other machines. I picked the 4-bit build from more than sixty candidates against one probe set: its development word error rate is 0.0093, but 0.0368 on held-out text. Its worst speaker similarity, 0.856, is below the bf16 build's 0.903. The two builds are close on quality and far apart on cost; the compressed one is not uniformly better. The calibration clip is private, so nobody else can rebuild the 4-bit weights bit for bit.

Weights: BreezeBlue Research and Non-Commercial License, gated, no commercial use. Runtime code: Apache-2.0. mixed 4-bit card · bf16 card · upstream Breeze TTS 2