4 12" L7s on 4,000 watts should be a lot louder than a single 12" XXX. MUCH MUCH more air movement. May I add I stated earlier about proper enclosurement/power. It does seem pretty hard to believe that.Yeah it is hard to believe but this guy seems credible to me so ill take his word for it. And even if its not louder, so come close with a single sub is still impressive.