"The device is not set up to transmit."
Klingon for the Galactic Traveler has a long section on this very question. The answer is that it typically depends on the age or hipness of the speaker. Older or more formal speakers tend to either pronounce both consonants separately, aspirating each b, or lengthen a single consonant. Younger or more casual speakers tend to contract the cluster into a single consonant at normal length. A younger speaker would pronounce it more like labeH.