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Stenka and stęka - on alleged non-existence of nasal vowels in spoke Polish [17]
I've been wondering about this myself. I'm not Polish but i'll share my thoughts nevertheless.
First of all - same/different and nasal/not nasal are two distinct questions. Obviously it could be pronounced differently whether or not it is nasal.
Often you'll be told <ę> is read, in the middle of words, like /en/ but in more detailed explanations they'll tell you that it's actually /e/ followed by something like a nasal glide. A glide is something like the /j/ sound as in the name Maya. Characteristic of glides is that they can be articulated at different places and act as something like a "bridge" to the surrounding sounds - they "glide" from one to the other. That's why <ę> before back consonants is articulated at the back /eŋ/ which is different from the articulation of <en> like /en/ at the front (alveolar). <ę> before fricatives like /s/ and /z/ does not even touch the roof of the mouth as it just glides to a consonant that doesn't touch the roof either. And finally - before alveolar plosives - /t/ and /d/ - <ę> will sound like /en/ just because it will be forced by the consonants to be articulated in the same way as <n>. In front of the labial plosives /p/ and /b/ it will sound like /em/ for the same reason. So, in some circumstances, it sounds the same as <en> or <em> but in others not. Perhaps in the past it had a more pronounced nasality than today. The language is alive and there're dialects where <ę> at the end of the word is still nasal while most other people pronounce it just /e/. I guess <ę> has lost some of its nasality, especially in certain sound configurations, but the spelling persists so we have to remember for each word if /e/ at the end of a word is written <ę> or <e> (well there're certain rules that help of course) or in other words is it <ent> or <ęt>, etc.. Perhaps in the future <ę> will lose its nasality altogether. As a comparison <ą> is more "stubborn" and is still nasal at the end of words :)
As for the question is it nasal or not - it's more a matter of classification/definition rather than actual difference in opinions about how it's articulated. I mean, probably most phoneticians will agree on the way it is articulated but it's just that they explain it in different terms. It's hard to give discrete/differentiated definitions about linguistic matters when things in linguistics usually exhibit a continuous spectrum of possibilities. Let's say it's a nasal that's in the process of losing its nasality :)
