hi. some people would just look at the distributor which is only Pro ICE in Malaysia. they are the only authorized distributor of JL Audio in Malaysia. some sellers would claim that they imported the sets themselves from various of countries(not distributed by Pro ICE) and yes, those MIGHT be original too. however, the workmanship of a subwoofer would be easily identified if you have an original model next to the imitation one. some imitation ones would have different terminals, poor material used, poor workmanship(example: glue stains around the subwoofer), your ears, the specifications. lets say an original JL Audio 12W3V3 is rated at 500W RMS, hook it up with a recommended amplifier, and play till the volume below distortion. then change the subwoofer to the imitation one. you can smell something after playing some music for a while. the imitation one wrote "500W RMS" too but i doubt that it could reach it as we have tried it. the coil of the imitation unit would be damaged as it could not handle the rated power as an original unit.
i hope that it would clear some of the doubts.
thanks for your question. :)