I have a set of M-Audio Studiophile DX4 speakers. When I turn them on the right woofer starts going crazy, making a loud thumping noise in the process. This happened when the speakers are plugged in to a sound source and when they are not. What is wrong and how do I go about fixing this issue?

SOURCE: M-AUDIO STUDIOPHILE BX8a (woofer)

Hi David

The fault may be the bass driver itself or the Low Frequency power amp built into the speaker box. hard to determine which it is because it is intermittent. There are a couple of things to try. when the fault occurs.

1. just lightly touch the cone on the bass driver see what happens. If it fires up again, it has failed soldering on the spider wire connections from the terminals to the cone. This can be repaired by a decent sound guy the does speakers, or a specialist near you that can be found easily enough. A new replacement driver is also an immediate option if you don't mind spending the bucks.
2. if the above didn't work, to prove to yourself where the problem may lay, you could swap the bass drivers from one box to the other and see if the fault follows the driver, or remains with the speaker box. If the electronics are faulty, unless you have some decent experience with soldering and fault finding, you may be best to get it to a repair guy,
   

SOURCE: M-Audio StudioPhile DX4 4'' Woofer

The "voice coil" inside the woofer must be rubbing against the "yolk" plate. Meaning = it is mechanically blown(damaged) to a point but electrically intact.
My sugesstion is to take out the damaged woofer and "google" for a mew woofer with the correct impendance and size and mounting holes. If you dont know thw impendance, then you should go with at least 8 ohms. More ohms = less risk of overloading the amp. whick can cause a fire!

Good Luck!!