The 6x9 inch subwoofer boxes will increase the output of any six by nine inch speaker. If your vehicle does not have room or an opening for 6 X 9 inch speakers you can easily add them by using our 6" x 9" speaker enclosure. The 6x9 inch speaker is great addition to any system because it adds a large frequency range to your system from midbass and up, and if your 6x9's include a tweeter you will be adding huge range to your system.