User manual ALPINE SWR-304E

[. . . ] APPLICATION GUIDE Please read this manual to maximize your enjoyment of the outstanding performance and feature capabilities of the equipment, then retain the manual for future reference. Keep the volume at a level where you can still hear outside noises while driving. Driving while unable to hear outside noises could be the cause of accident. [. . . ] Thermal power handling rates how much power the speaker can take without the voice coil melting. This is mostly determined by voice coil size; the SWR-304D/SWR-304E, SWR-254D/SWR-254E uses a 3" coil for high power handling. Mechanical power handling rates how much power the speaker can take without breaking or tearing; this depends on strongly on frequency and on the enclosure. Mechanical power handling is very difficult to evaluate without actual testing. Alpine tests speakers at full power for 96 hours to confirm the mechanical toughness of each woofer. ENCLOSURES (BOXES) : Designing and building the best speaker enclosures takes time, tools, and know-how. If you don't have a lot of experience, consult a professional who has designed and built successful enclosures. If the woofer isn't enclosed, the sound just moves from the front to the back of the speaker, and you won't hear much bass. Tips : For best results, try to make the box rectangular instead of square, and mount the driver(s) off-center. Port ends should be spaced at least one diameter from any obstructions to breathe properly. If the speakers are not connected to the same amplifier channel, they should be in separate cavities. " Please note that rear hatch covers do not isolate very well and are not usually strong enough to support the weight of a subwoofer. disadvantages : In most cars , the trunk leaks to the passenger compartment. Therefore, free air mounting will lose bass output compared to a boxed woofer. Since the woofer is not loaded by box air pressure, it handles less power. Tips : Reinforce the factory rear deck and seat back, and caulk any remaining openings to the passenger compartment. SEALED BOXES : A sealed enclosure is just what it sounds like : a closed box around the woofer to isolate the front and rear sound waves from each other. How they work : The trapped air in the box adds stiffness to the speakers' own stiffness. [. . . ] SPEAKER OUTPUT: Sound pressure level (SPL) is determined by how much air the woofer moves. This is set by the woofer's surface area Sd and by its excursion (motion back and forth). Maximum output at low frequencies is set only by the woofer's excursion (movement)capacity, since most amplifiers have enough power to drive most woofers to full excursion at low frequencies. [. . . ]