I am not an expert in phonetics, but I don't understand your question. The stress is on the first syllable in "utter". It is not an exception as far as I know.
I was always under the impression that reduced syllable sounds can not have stress on them because they are lax vowels. however, the word "utter (/ˈʌtər/" has first syllable stress which is a reduced sound. please tell me the reason why.
Reduced sounds are not suppose to have stress, i.e schwa sounds ,etc. hence the meaning; reduced sounds.
I am not a teacher.
I don't think the 'ʌ' is a reduced vowel. It is an unreduced short vowel and appears in stressed syllables quite frequently.
Take the word 'reduction' ɾiˈdʌkʃ(ə)n for example.
/ɛ/ is surly a reduce sound (according to American Accent Training by Ann Cook). Notice the streets on the word empty /ˈɛmpti/
I know exactly what a schwa is. The point is that although I know /ɛ/ is short "e" , I read it is also "reduced sound, or a lax vowel".
Maybe because of “American Accent Training,” I think you misunderstand the meanings of those technical terms. Actually, I skimmed through this book about a year ago, and I found that its content was not always phonetically accurate (judging from the reviews on Amazon, it seems to be quite popular though), so I recommend you check the meanings of “lax” and “reduced” once again with other sources, preferably textbooks on phonetics and phonology. Probably they say both /ʌ/ and /ɛ/ are “lax vowels,” and they CAN occur in stressed syllables. And as MikeNewYork and Roman55 said, neither /ʌ/ nor /ɛ/ is a “reduced vowel” but a “full (unreduced) vowel.”
In utter, the u is not a schwa, It's a short u. The e is a schwa. It's silent and just provides a vowel for the syllable.
In empty, the e is not a schwa. It's a short e.
In both, the stress is very definitely on the first syllable - as it is in butter, gutter, stutter, mutter, clutter, cutter, and putter.
As you can see, all of us who responded agree. Trust us on this.