Advice - Diagnose and Repair Polk VM20

whovous

I have a 7.1 system with two VM30s, five VM20s, and an SVS PC13Ultra subwoofer. The VM20 center channel is mounted on the wall beneath a 50" Panny plasma. Until Sunday, everything worked fine.

On Sunday, I had to move things around in very awkward fashion while leaving the center VM20 connected on the wall. When I put things back in place, a few speakers did not work. I checked all of the connections and got down to where only the center speaker did not work, and now I am out of ideas. If I send the center feed to another speaker, it works, so the output is OK all the way to the binding post. But if I send the same feed to the center speaker, I hear nothing. Connecting the working right channel speaker cable to the center channel likewise produces silence.

I have removed the screws on the back from the box surrounding the binding post and I have removed the passive radiator from the front, so that the crossover board is loose and exposed. I see nothing resembling a bad connection, and have no idea of what else to look for.

Does anyone have any advice for me?

[Deleted User]

Hello,
Usually the cause of a speaker not working is either a tweeter or driver not functioning. One way to test these components would be to remove them from the enclosure, disconnect the crossover and at a low playing volume try playing the tweeter and driver directly.
Regards

whovous

Thanks for the reply. I do not understand. I have VM10s in a separate system; one arrived with a disconnected tweeter. In that case, the other driver still worked. Why does the VM20 react differently? How can failure of one driver stop the other drivers from working? Don't they still receive a signal? It seems like they should work if they get juice.

[Deleted User]

For me the best approach is to make sure each of the components, the tweeter and drivers, function. Take each one, disconnect it from the crossover and play it directly with your receiver at a very low volume. The other method is to substitute a component from the non-working speaker into a working speaker, one at a time. I don't have the crossover's schematic, if the drivers are connected in a series/parallel connection then if one has a burned out voice coil then neither one will operate.

whovous

I will give it a try, thanks. I only just now noticed how the drivers are connected to the front panel. That is a lot of screws.

whovous

This is a very belated followup. I removed the many screws and fed a signal to each of the three drivers, one at a time. All three drivers work. When I direct the same signal to the binding posts, I get nothing. I feel like I have narrowed things down quite a bit, but I have not solved the problem. Is there anything else I can try?

[Deleted User]

From what you've described it would appear the crossover is the cause. That's the only component left in the speaker. It would be best to contact Polk at: 1-800-377-7655 select option 1. If you're within the speaker's five year warranty they'll need the serial number and place of purchase. They will be able to help.

whovous

Thank you.