"Large" midrange doesn't mean anything, it is the capability of the specific driver in question. Just because a driver is larger doesn't mean it won't play higher, though the larger you go, the harder it is to find one that will play well higher up. So if a proper driver is chosen, it may be able to do this.
On the other side of that, and far more likely, is having tweeters that can extend low enough to handle that range or in order to use a larger midbass driver that does not extend as high. OR, as mentioned earlier, having another midrange that is crossed between the tweeter and bass driver, aka a 3-way design. Not every speaker is just a woofer and tweeter.
