15 inch active speakers are by far the most popular choice among self-powered speakers on the market today. You will remember that in an active speaker, the amplifier module is built-in to the speaker, so there is no need for an external power amplifier. The 15 inch active speaker is so popular because it is best suited to be the Swiss Army knife of your pro audio speaker needs. The 15" two-way active speaker has a 15 inch woofer to belt out a decent amount of low frequency, without the need for a subwoofer. That is why these are so popular. These 15 inch active speakers can achieve very loud sound pressure levels, and also produce enough low frequency energy to put some get up and go in your venue.
As with all active speakers, you can add as many speakers to your system as you like, simply by daisy-chaining one speaker to the next. The other very obvious advantage is that you do not need truck around stacks and stacks of power amplifiers.