User manual ALPINE SWR-1241D

[. . . ] Driving while unable to hear outside noises could be the cause of accident. Do not use only one jack as shown in Fig. Doing so may lead to accident, fire or electric shock. Arrange wiring and cables in compliance with the installation manual to prevent obstructions when dirving. [. . . ] dEFINITION OF TERMS: Resonance: Most objects vibrate naturally at certain frequencies. If you hang a weight on a spring, then pull it and let go, the weight will bob up and down at a certain frequency determined by the amount of mass and by the stiffness of the spring. Generally, Q denotes how well controlled the movement of the speaker cone is near resonance. qts is the Q , total , of the speaker by itself. When the speaker is placed in a sealed box, the stiffness of the trapped air raises total Q. qtc stands for Q , total , of the closed box system. POWER HANDLING: There are really two completely different types of power handling. 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-1241D/SWR-254ED uses at 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. How they work: The trapped air in the box adds stiffness to the speakers' own stiffness. This raises the resonance frequency and Q from free air values. The smaller the box, the stiffer the trapped air acts, and the more Qtc and Fc increase. Cone motion tends to "ring" (keep moving after the amplifier signal stops) more because the box in "springier". As you can see from the graph and table on page five, low frequency output decreases, because the amplifier has to push the speaker against a stiffer air spring. Advantages: Closed box designs are easiest to get good results with. Simply decide whether you want a tight sound (low Q) or a boomy sound (high Q), then size the box accordingly (see table). sealed boxes control cone motion the best. Disadvantages: Compared to free air, a sealed box takes up more room in the trunk. Around 20 to 80 hertz, a ported box can have a higher maximum output. alignments: System Q determines the sound quality. [. . . ] disadvantages: Below Fb , the port acts like a big leak. The enclosure cannot provide stiffness to the woofer, so the unloaded woofer moves a lot, like it was mounted free air. output bellow Fb is less than free air or a sealed box. Also, ported systems are much easier to get bad results from than a sealed box. [. . . ]