English scores do not establish multilingual performance
The authors caution that English performance does not necessarily carry over to other languages. The leaderboard reports CER for Chinese, Japanese, and Korean, and computes a macro-average across languages. Seed TTS Eval covers English and Chinese; other languages use CV3 Eval (zero shot).
Supporting evidence
Open TTS Leaderboard: Scalable Evaluation for Multilingual Text-to-Speech and Voice Cloning
Original excerpt
English performance doesn't necessarily translate to other languages. Multiple languages can be toggled to rank models on multilingual performance. Seed TTS Eval only has audio for English and Chinese, so the other languages are simply the score on CV3 Eval (zero shot). Note that Chinese, Japanese, and Korean are character-based languages and so character error rate (CER) is reported, and the “Average WER” across languages is a macro-average across languages.