User manual JBL DS120

[. . . ] Your Decade Series subwoofer will also work in infinite baffle applications where there is no space or budget to build a box. Be aware that infinite baffle or "free air" mounting will reduce the power handling of any subwoofer compared to an application using an enclosure. Finally, any deviation from recommended enclosure volumes or port dimensions should be made using dedicated enclosure-design software, such as JBL SpeakershopTM. [. . . ] Decade Series subwoofers are designed to suit a broad range of mobile-audio applications and can be used in a wide variety of enclosure types to produce extended, powerful bass in a limited amount of vehicle space. To ensure maximum subwoofer performance, we strongly recommend that installation be left to a qualified professional. Although these instructions explain how to install a JBL Decade Series subwoofer in a general sense, they do not show box construction details and exact installation methods for your particular vehicle. If you do not feel you have experience, do not attempt the installation yourself, but instead ask your authorized JBL dealer about professional installation options. Remember to keep your sales receipt with this manual in a safe place so both are available for future reference. Enclosure Calculations and Building Boxes Use the recommended box designs on the enclosed data sheet. Choose cabinet dimensions to fit your vehicle, but do not change the enclosure's volume. Doing so will change the tuning frequency of the enclosure and may adversely affect final performance. If you cannot perform the necessary calculations yourself, please contact your authorized JBL dealer for help and for information about JBL Speakershop, a dedicated enclosuredesign software program for experienced car-audio enthusiasts. 2 4. Keep in mind that the openings at either end of the port must be at least one port diameter away from any obstructions, including filling material inside the box. Rectangular vents can be used as long as the cross-section surface area matches the recommended port-area values in the enclosed data sheet. Power-Handling Limitations The power-handling capability of any woofer is related to both its ability to dissipate heat and maximum excursion limits of its cone. Once the speaker's voice coil moves outside the magnetic gap, power can no longer be converted into motion and all the amplifier's power is converted into heat in the voice coil. This voice-coil heating is the largest detriment to speaker longevity, so overexcursion should be avoided. Since speaker-cone excursion is different for each type of enclosure, power handling is different for each enclosure. · Voice-coil overheating and burning, due to overexcursion, are often caused by overdriving an amplifier into "clipping. " A severely clipped signal, or square wave, contains nearly twice the power of a clean sine wave at the same level. Bass that sounds broken up and distorted at higher volumes usually indicates that the amplifier is clipping and is being asked to deliver power beyond its rated power. · Infinite baffle or "free air" mounting applications allow for greater cone excursion than subwoofers mounted in an enclosure. [. . . ] The type and size of box used will produce different excursion demands on the enclosed subwoofer and, consequently, different levels of power handling. As long as recommended parameters are used, the subwoofer will perform properly in its enclosed environment. However, any design deviation may result in less than optimum performance, and may also subject the subwoofer to overexcursion (i. e. , where the voice coil leaves the gap) that can eventually damage the speaker. [. . . ]