The Koel has moderate sub-bass quantity and it is extended fairly. The sub-bass reproduction is not very punchy. Each bass note is articulated with a smooth hit. Bass decay is rather quick. The bass texture is rendered smoothly. The mid-bass has fair quantity and the slam is expressed with some weight. The bass performance is controlled with little impact.
The midrange is expressed in a laid-back manner. The transparency is at a moderate level with fair details retrieval. The lower mids has moderate amount of body and male vocals are presented without too much presence. The upper mids is not very forward and female vocals are expressed in a relaxing manner. The finesse is great which helps to prevent vocals from being shouty.
The treble is extended moderately and there is no sibilance and harshness. It takes on a smooth approach for a fatigue-free listening. The sparkle is lacking and expression is not very energetic. The amount of air rendered is fair with decent crisp. Treble is articulated smoothly with body and it provides a soothing listen.
The soundstage expands quite naturally. The width magnitude is fair and the depth is slightly closed in. There is some congestion at times.