KRK Rokit 8 GP2 Subwoofer not working

[DuncanWilliam]

The subwoofer for my KRK rokit 8 GP2 studio monitor has no output. The tweeter for the monitor is working though.

How can i go about troubleshooting and repairing this?

Thanks

[coromonadalix]

if you have normally an crossover in it, check the parts, bad solders  etc ... if all seems good remove your speaker and put another one just for tests purposes, it could be any midranges or low frequency ones, car radio speakers etc ... if you hear something, you may have a blown voice coil / speaker ?

[cdev]

The speaker voice coil is easy to test for continuity, also like a meter with a D'Arsonval movement, if you apply a low DC voltage to it it should move, in for one polarity and out for the other. If you get continuity or hear some scratchy sound but dont see some motion, or nothing happens at all, but the voice coil shows continuity and some low resistance, the speaker cone likely needs to be removed and possibly it and or the surround needs to be repaired or the coil needs to be rewound .. it likely will be a fairly straightforward process.

This is actually not that difficult if you have the supplies to do it. There are companies that specialize in speaker components and repair supplies, one is the company ("Parts Express" https://www.parts-express.com/cat/speaker-repair-parts/23 ) (They also make and sell the great inexpensive Dayton Audio speakers). 

Generally, this depends on the speaker, availability of a direct replacement, costs.

Don't assume new is always better. Many older speakers are worth repairing, especially when made with super high quality materials that are rare to see in consumer products today. If these old drivers are repaired with modern materials you may end up with a really good speaker, it may give them a totally new lease on life.

[DuncanWilliam]

thanks for the replies so far, ill check those options out and get back to you both

[DuncanWilliam]

After opening the monitor up and inspecting it i found that black gunk EEVblog talks about in his videos. Ive attached pictures as it seems that at places the gunk has cause a resistor to crumple and a few capacitors to leak dielectric of some sort. let me know if my observations are correct and any suggestions as how to go about fixing it, any cost estimations?. im not too confident in my soldering skills.

Thanks

[Robin]

It indeed is that black gunk like in the video. But the capacitors probably didn't leak. What you see is the gunk turning in some sticky conducting stuff.

At the moment I have a Rokit 6 Gp2 on repair with the same problem. No output. Also had that black gunk and removed it all, but that solved nothing. In my case the amplifier IC receives a mute signal from the control/input board. This signal is an output of an opamp, but I don't know which signals it compares. Some say that the speaker waits for a high enough input signal to unmute…

If your driver measures out to be ok, I suggest measuring/finding the mute/stby pin on that white connector. I bet there will be a negative rail voltage on it and that's probably your problem. The bad news is that I don't know a solution for it yet…

[DuncanWilliam]

Thanks for the info, will do some more research