Well with this tape mod the S400s sounds more dynamic and less laid back. It brings the bass up a little bit so the entire sound is more engaging.
The tape mod with the S500s makes the bass really deep and hard hitting without it bleeding into the mids or highs.
BUT you only get these results IF and ONLY IF you stuff the stock pads with paper towels combined with the tape mod. Once you stuff the pads and tape the ports, the sound on both the S400s and S500s get elevated to another level. There is less congestion which makes them sound just "right" to me.
Stuffing the pads ARE CRUCIAL!!!
That being said the S400s will always sound more laid back and smoother compared to the S500s. The S500s like many have said has this WOW factor to them and their sound is a lot more engaging/ dynamic than the S400s. More of a in you face type of sound while the S400s are more like sit back and relax type. So they compliment each other really well, like you can't already tell I love them both. haha
Sorry i had to be so subtle about this.
Edited by sfwalcer - 11/8/12 at 10:50am