It's amazing really. Any decent speaker manufacturer will take excruciating pains in designing and executing the crossover between tweeter and woofer. Most go on to devote pages in their literature to tell you about it, offering up trademarked ways to all say the same thing.
In 5.1 digital surround sound, the 0.1 channel is called the LFE or Low Frequency Effects channel. While in the commercial system it is referred to as the subwoofer channel, this is not necessarily true for home theater setups.
Many surround sound receivers and processors these days offer an "Auto" set-up routine that attempts to configure the basic set-up for the consumer, including whether a speaker should be high-passed or not, which frequency to high-pass it at if applicable . . .