less volume in mixdown file

Hi guys: Recently I have this issue when mixing down even just 2 tracks, say 1 complete track from beginning to end and just a piece of another; I mean when playing back the mixdown wav file in n, not using wmp or other media players. So it’s surely a problem within n itself, which is confirmed by simply visually comparing the sizes of the waveforms, the complete original one and the mixed one. I’m still using v 3.2 but this is a new issue, never happened before.
Thanks to your kind replies.

So, the mixdown is lower in volume in n than in other apps? I take it that you imported the final mix into n with nothing else on the track? No plug ins or anything?

No, what I mean is that when I open the mixdown wav file within the sng song file (mixdown offline without substitution of the mixed tracks) and compare its audio and waveform with the original mixed tracks, it sounds and looks as the level is significantly lower, so I have to turn up the volume of the new mixdown track to compensate, but I want it to be equally loud.