Polk Rti-A9 speaker buzzing, difficulty finding the problem

Feb 15, 2003
Jupiter, Florida
I have a pair of Polk Rti-A9 tower speakers. Each speaker has 3ea 7 inch woofers and 2ea 5 inch midrange, and 1 dome tweeter. They are powered by an older 120WPC Yamaha receiver.

The RH speaker has a bit of a very occasional buzz (much like a blown speaker sound) on some loud music. Problem is, I can't determine where the problem lies. I believe it's one of the midrange drivers, but despite repeated effort to isolate the noise, it just does not show up when I want it to. I run over to the speaker when it happens, and by the time I get there it's gone. I just can't tell which driver it is (if any).

I've tried using a frequency sweep from 20hz to 20khz. I've also tried using the frequency generator on my phone to drive the amp at various frequencies at high volume to see if I can cause it to act up. Nothing.

I have not tried swapping the speakers Left to Right. I'll do that tomorrow. I suspect the problem will swap sides, as I do think it's a bad driver.

Does anyone have any good guidance or tricks on how to isolate the bad actor?


EDIT: I don't love the speakers. I'd give them 3 stars. Despite internet claims, the bass is weak and flat. I had to add a 12 inch sub, where my previous similarly sized speakers did not need a sub.
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I would try first swapping left and right to rule out the amplifier.. To determine which driver is rattling, remove each speaker one at a time from the enclosure. While holding the speaker (cone side) in one hand, strike the magnet on the palm of your hand. The bad speaker will rattle where a good speaker will produce a deep thud.
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I have had problems with Polk's drivers. Their woofer drivers tend to warp voice coils.
I have had problems with Polk's drivers. Their woofer drivers tend to warp voice coils.
That's kind of what I was thinking. When the voice coil gets warm from use, it acts up a little by rubbing on the magnet. I've pushed on the drivers while operating and do not get anything unusual.
in my experience, a buzz that only happens occasionally is a spider that is starting to separate. Very hard to spot/diagnose until you pull the driver and inspect.