Supertonic: half the storage did not mean faster CPU speech

Inspect the graph before naming the model

Three variants ran the same twelve phrases per language at eight synthesis steps, twice each: FP32, FP16 with the duration component retained, and a mixed INT8 graph. The latter quantized only the verified vector-estimator path; a directory label was not accepted as proof that the whole model used INT8.

Storage and responsiveness

FP32 occupied about 398 MB, FP16 202 MB and mixed INT8 384 MB. Across forty-eight utterances per variant, pooled WER was 1.914%, 2.392% and 2.871%. Median time to first audio was 0.9407, 0.9944 and 0.9238 seconds; median RTF was 0.2965, 0.3175 and 0.2888.

The uncertainty changes the conclusion

Paired bootstrap WER differences for FP16 and INT8 versus FP32 both crossed zero. That does not prove equivalence. The paired FP16 first-audio difference was +0.073 seconds, with interval [+0.059, +0.087], whereas the mixed INT8 interval included zero.

For this workload, FP16 offered storage savings without a latency win. The follow-up question was whether keeping FP32 and moving execution to the GPU could improve responsiveness more convincingly.

Evidence and publication boundary

This is an edited account of the recorded experiment. The linked archive is private; the methods, aggregate findings and limits are included above. Reference recordings, raw conversations, authentication material and workstation configuration are excluded.

• Source record 1