I purchased a new set of JBL lsr308 speakers for my music producing. When I plugged them in no matter what I did I cannot get any frequencies below 100hz, they are good down to 37hz. The only things I can conclude is that the monitors are broken in some way or my setup is wrong. I am using a 1/4" to 3.5mm converter and 3.5mm cable that runs into the back of my motherboard. I have tested this with other speakers and they work just fine. I have also tested the new ones in my laptop and the same problem occurs. I have never had studio quality monitors before so I'm not sure if I need a higher quality sound card to use them. I still get sound out of them but anything below 100hz doesn't exist. My assumption is that the amp or speakers are dead. I have also made sure that I have the most current audio drivers for my pc as well. Any advice?