While Sperber et al. (2019) use a beam of size 1 for the ASR component of their cascade to compare with their two-stage end-to end models, we find that using equal beam sizes of 15 for both ASR and MT improves cascaded performance with the same model by 4-8 BLEU; combining these two parameter changes makes the same cascaded model a much more competitive baseline (compare lines 3 in both Table 2 and Table 3).
widening beam size to yield an equivalent search space for end-to-end models has diminishing returns after a certain point; we did not see further benefits with a larger beam (> 15).