The Echobox Explorer sounds excellent, with a neutral reference style tuning. On sound stage, both players have similar width, with a slight edge going to the Opus #3, but the Echobox Explorer has the appearance of more depth due to more forward sounding mids on the Opus #3. The Opus #3 is the more lively sounding of the two, the Explorer is more polite...
On Macy Gray – I Try off of Stripped, probably my favourite stand-up bass recording ever, the Echobox is precise and laid back on the bass. The Opus #3 is groovy on that bass...
Both players do an excellent job driving the HD600. The bass has a bit better definition on the Echobox Explorer and it has more overhead left on the volume.