I got to hear burn-in'ed S4 today morning. Following is relative & short comparison b/w M2 & S4. I thought someone might benefit in deciding between the two.
In S4 Bass has slightly more thump, Midrange is slightly recessed, highs are slightly forward. Soundstage width of both M2 & S4 are similar. Soundstage depth of M2 is more. Bass texture of M2 is better. Realistic vibration feel (caused due to bass) is present in M2 but i couldnt feel it in S4. This all is relative to M2.
In S4 Bass has slightly more thump, Midrange is slightly recessed, highs are slightly forward. Soundstage width of both M2 & S4 are similar. Soundstage depth of M2 is more. Bass texture of M2 is better. Realistic vibration feel (caused due to bass) is present in M2 but i couldnt feel it in S4. This all is relative to M2.