I have not tried the Orcas on 4 ohms. But I agree the speakers sound different. I find the Orcas have that Fostex/Lowther high quality pulp cone presentation of a prominent sense of presence that adds some excitement to the original tonal balance of a song and can indeed emphasize frequencies in the vocal range. It's likely that a 4 ohm setting might emphasize this a bit more, but you just have to smoke it and see. To my ear the Pipettes are oriented to a more laid back, perhaps more wideband presentation more typical of metal cone drivers. They can get a little full in the upper bass on 8 ohms and the 4 ohm secondary can help eliminate this.