In May, I bought two brand new LSiM705 for stereo listening (music and movies). Right out the box, there were a problem with the left channel tweeter, but I couldn't pin-point it until I heard solo piano and some women's voice in movies, what I first assumed was bad mixing and poor quality audio in Netflix (for movies). But then, after few days of listening, I could hear it on some other tracks or pieces (FLAC), and on DTS bluray audio track, so I thought there were a problem with the speaker. I swapped the left and right speaker to see if the "issue" was with the speaker or the electronics and it seemed that the LSiM was the culprit. I started a thread on these very forums and someone mentionned that there were some cases of blown LSiM tweeters.
I exchanged the speaker for another one and connected it as the right channel speaker on my amplifier. It seemed that this new one was allright, even if I could hear a slight distorsion in some rare occasions which I assumed, another time, that it was poor audio quality from standard quality Netflix. I couldn't hear it except sometime in movies when people spoke (even with DTS track): there were a slight distorsion, but not too often and far less than the other speaker did in the same conditions. Annoying, but nothing to be too concerned about. For music, it was more than adequate so I didn't make a case.
Yesterday, I moved the speakers in another (smaller and closed 120 sq ft) room. I went from a 9 feet listening distance to 6 feet listening distance. While the room is far from perfect with reverb and all (being non treated), I can clearly hear a distorsion coming from the "new" speaker. Again, it follows the speaker when I swap cables.
I know my amplifier isn't beefy (50w integrated amplifier), but there is no way I am underpowering these speakers, especially when I'm listening at volume levels lower than 80 dB with occasionnal peaks at 85 dB in movies which would require 1 to 5w, tops (can't go any higher with my tinnitus). Given my amplifier has a certain headroom, I wouldn't be too concerned with the lack of power. I doubt I "misused" or abused the speakers in any way as I baby them.
Also, every LSiM705 I owned (the first one, which I returned; this one and the "perfect condition" one) are from the same batch. Only one of them have no distorsion issue right out the box and will probably do just fine. Is it possible that there were some QC issue with that particular batch?
I had no trouble with any of my previous Polk speakers (6 pairs, RTi and LSi) over the years and they're still working fine. Could I be unlucky enough to have two defective speakers out of three, or is there something else causing this?