Stem-initial accent has been identified in a number of NW Bantu languages. Phonetically, stem-initial accent appears to be realised only or mainly through consonant length. In order to evaluate this hypothesis, we recorded questionnaires for seven NW Bantu languages (Bapuku, Basaa, Eton, Fang, Kota, Kwasio, Bagyeli), with a particular focus on different regional varieties of A70 languages. The acoustic analysis of the data confirms the role of consonant lengthening and suggests that it is in origin an utterance-level prosodic phenomenon, which we refer to as C-emphasis prosody.