Stephen Benton

Dear fellow mantra devotees, I am interested in knowing your thougths on the correct pronunciation of the basic bija mantras such as: Lam, Vam, Ram, Ham, Yam, and Sham. For all of these is the "a" vowel sound short as in the sound "ah"? I have heard varying ideas that say some of them are pronounced with a short "u" vowel sound, such as Lum, Vum, and soforth. Thank you for your input, Sincerely, Stephen Benton