(the stress is on the first syllable; the vowel of the first syllable is the "o" of "dog"; after the "b" sound, you have to pronounce a voiced "s", i. e., a "z" sound, as in "zero"; in the second syllable, -boom, the vowel is a long "o", as in "door").
Hmmm...I've never come across this name before, but I'm a native English speaker, and I'd pronounce it like "hobbz-bawm". "Hobbs" like you're saying the word "hobbies" but take out the "ie" sound, and then "bawm" (which I can't think of another explanation for).