vowels converge of balm and hot/not

My 1990 edition of the Webster's still lists hot/not as a rounded lip version, which is what you hear from this recording for "not". Now, all three have been listed as the same vowel as in balm. But, some area still pronounces "not" with the rounded lip. My latest longman (2008 editon) actually pronounced them the same as in balm. The Webster online one might not update it faster enough to catch the vowel merging. Longman has most up-to-date pronounced words, but to get a full version, you need to buy one. The Longman one is also recommended by ESL teachers. The Longman also has a both AE/BE pronunications recorded version available.