SHORT BACK OPEN-MID ROUNDED VOWEL [ɔ]
In unstressed closed syllables, or when accompanied by the shewa/ḥatef sign, Tiberian Hebrew qames is pronounced as a short ɔ-vowel. This sound is between patah /a/ and ḥolem /o/ with the lips rounded.
Note that in unstressed closed syllables, one has to distinguish between qameṣ that derives from the /o/ phoneme (e.g., in חָכְמָה 'wisdom', pronounced as [ħɔχmɔː]) and qameṣ that derives from the /ɔ̄/ phoneme (e.g., שָׁמְרוּ 'they kept', pronounced as [ʃɔːɔmʀ̟uː]). Only the former is pronounced as short [ɔ]. When qameṣ in a closed syllable derives from the long /ɔ̄/ phoneme, it is pronounced extra long as [ɔːɔ] (see below).
LONG BACK OPEN-MID ROUNDED VOWEL [ɔː]
In stressed and/or open syllables, qameṣ is pronounced as a long vowel [ɔː].
(in open or stressed syllable)
EXTRA LONG BACK OPEN-MID ROUNDED VOWEL [ɔː]
In closed syllables, qameṣ that derives from the phoneme /ɔ̄/—rather than qameṣ that derives from the short phoneme /o/ (see above)—is pronounced as an extra long vowel [ɔːɔ].
(in closed syllable, derives from /ɔ̄/)
SOURCES AND FURTHER READING
Khan, Geoffrey. 2020. The Tiberian Pronunciation Tradition of Biblical Hebrew. Cambridge: Cambridge and Open Book Publishers. §I.2.