GT5-12 - JBL

CHOOSING AN ENCLOSUREWarning: Playing loud music inan automobile can permanentlydamage your hearing, as well ashinder your ability to hear traffic.We recommend listening at lowlevels while driving. JBL accepts noliability for hearing loss, bodily injuryor property damage resulting fromuse or misuse of this product.GT Series subwoofers are optimizedto perform best in small, sealed,vented and prefabricated band-passenclosures. While infinite-bafflemounting of GT Series subs ispossible, power handling will begreatly compromised becausethere’s no enclosed volume of air toprevent the speaker’s cone frommoving past its limit. For this reason,we do not recommend infinite-bafflemounting for GT Series subwoofers.You should choose the enclosure youwill use based on the type of musicyou listen to, how much amplifierpower you will use for the subwooferand how much space inside thevehicle you can devote to asubwoofer enclosure.Because a sealed enclosureprovides the most control over thewoofer’s movement, a woofermounted in a sealed enclosure willhandle more power than a woofermounted in another enclosure type.Sealed enclosures provide moreaccuratesonic reproduction thanother enclosure types whenmounted inside a vehicle, so they arewell suited to all types of music.Sealed-enclosure construction isstraightforward, and there are manyprefabricated sealed enclosuresavailable. An optimum sealedenclosure is always smaller thanother types of enclosures optimizedfor a particular speaker, so theyrequire the smallest amount of spaceinside the vehicle.Vented enclosures provide betterefficiency in the 40Hz – 50Hz range,but this efficiency comes at theexpense of sound in the lowestoctave (below 40Hz) and at theexpense of some control and powerhandling at the lowest frequencies. Ifyou are using a small amplifier,a vented box will provide moreperceived bass output from lesspower. Vented enclosures are alsowell suited to a variety of musictypes. Because vented enclosuresrequire the volume of the enclosureand the size of the port to havea specific relationship with thecharacteristics of the woofer, theenclosure must be built exactly to thespecifications provided. While thereare some prefabricated vented boxesavailable, matching a prefabricatedbox to a particular woofer is difficult.If you wish to use a ventedenclosure, we strongly recommendhaving your authorized JBL dealerbuild it or verify that your design iscorrect if you wish to build it yourself.An optimum vented enclosure isalways larger than the optimumsealed box for the same woofer andwill require more space inside thevehicle.Band-pass enclosures often providethe most output available from anyamplifier and subwoofercombination, at the expense of sonicaccuracy.If sheer SPL (sound-pressure level)is what you desire most, choose aband-pass enclosure. Band-passenclosuredesign is very tricky, andthe aid of a computer and enclosuredesign software is necessary. If youare an experienced installer or havesome woodworking experience,you may wish to build the band-passenclosure described in the enclosuredesign sheet included with thiswoofer. Fortunately, there are manyprefabricated band-pass boxesavailable, and they are all optimizedto extract the most output possiblefrom any woofer. Band-passenclosures can be quite large andmay require a lot of space insideyour vehicle.2