I did experience this at first. Give them burn in time and they'll relax, but still be a bit harsh as that's just the nature of this product. Indeed, though you're comparing two different driver IEMs that don't sound much the same. Moving Coil Dynamic Driver in my time produce a more brighter sound, and something a little bit more musical. Symphonic Drivers are known to be a bit more warm, and resemble the warmth a speaker gives off, and stick to the warmer sounding side. Though arguably, I think the IM series in AudioTechnica's lineup carries a different sound due to the shape of the In Ear itself. I own the IM50, and it's a bit more warm sounding than the IM70 and carry lass bass, but more sub bass. The IM70 is described a bit more bassier, but carry clarity, which I don't see. They're both great! The A151P is just a bit more bassier. I told them on their Facebook that we need a detachable cable version! I think it'd be a lovely piece to buy then, I don't care for non detachables.