Philips SHE3595WT/28 In-Ear Headset with Mic White

I got the same kind but of course in purple Philips SHE3590PP/28 In-Ear Headphones (Purple) - there is basically no based and I had to turn the volume way up to hear sound that didn't sound cheap.

I have previously given a positive review for the Philips SHE3590, a cheap IEM that sounds good.
 
I purchased the Philips SHE3595 because it looks like the SHE3590, has a microphone and it was cheap at Dick Smith's closing down sale (a major Australian retailer).
 
While they look similar, the SHE3595 has a rounded protrusion and doesn't fit so well as the oval protrusion on the SHE3590. The SHE3595 sounds tinny and ragged in comparison to my SHE3590 and AKG K324P IEMs. Why can't an IEM with microphone sound as good as an IEM without mic?