Using Cenoz's (2013) Focus on Multilingualism approach, this study explores the L3 phonological growth of 19 German learners of Spanish with prior English ability. Five of them are also heritage language speakers of Italian, Spanish, Croatian, Polish, Israeli Hebrew, and Russian. Results indicate a positive impact of particular bilingual experience (instead of general) on L3 speech acquisition, esp. the generation of commonly tough phonemes. Proof for some L2-L3 phonology ‘coupled growth' extent farther clarifies the outcomes.