How do you pronounce long Japanese vowels?

I know how you pronounce the short vowels, (ah, ee, oo, eh, oh), and I know that the long vowels are written with a macron or as two vowels put together, (like aa, ei, etc.), but like in the case of "aa", or the long a, is that pronounced "ah-ah" or just as one vowel, and is the long vowel e, or "ei" as it is written in romaji, is that pronounced "eh-ee" or some other way? Thanks!~