Depth of insertion makes a big difference to the sound. The further away from the ear drum the transducer sits the bigger the soundstage but that also leaves a bigger cavity for the sound to do things in and that is the brilliance of the spacer mod in that it takes the driver further away from the eardrum but maintains the seal to the inner ear. I ram them in as far as they can go, wait till the tip has softened up and the ram it a bit further (using Shure black olives or Comply T100x). Same goes for my HF2 headset with the iPhone.