Earthquake Sound corporation is the original Inventor of the shallow woofer system (sws) that produces a lot of bass from a small space. Designed to replace the BMW factory speakers that are located under the front seats, the X84SWS pair requires No modification. Simply remove the seats and replace the factory woofers with the exact-fitting sws woofers to improve the sound quality of your mobile audio. In addition to BMW cars, the sws Series are the perfect bass solution for any car. Many factories are now using woofers in small areas. To improve your bass, simply replace the factory speakers with the sws woofers.