Complex sentence: When cold, Naim equipment has a tendency to harshness and never gives optimal performance straight out of the box, thus reviewers will usually deliver their assessment based on listening to samples warmed-up for days, if not weeks.
Split into simpler sentences: When cold, Naim equipment has a tendency to harshness and never gives optimal performance straight out of the box. Reviewers will usually deliver their assessment based on listening to samples warmed-up for days, if not weeks.