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So... My sub is blown?

709 Views 7 Replies 5 Participants Last post by drdoan, Feb 21, 2005

Cryofax

Discussion Starter · Feb 17, 2005

Howdy,

I've been using a little Polk 202 sub for about 2 years. I don't think I have EVER turned it more than a third of the way up (its self powered), and its always sounded great and could put out more than enough chest vibrating power even at that level...

Well yesterday I'm watching TV with my family and I start hearing these little slight background noises, almost like a geiger radiation counter. I thought it was the local TV signal so i ignored it.

Later we watched a movie and it was more pronounced. I realized I was only hearing these noises when the sub was kicking in.

Also I notice the thing has a distinctive "hum" it never had before. So does the crackly geieger counter noise = blown speaker? And since I never crank it up what may have accounted for it? I'm not adverse to upgrading my sub (heh heh) but am a little concerned as to how it could be blown out when I never really had it turned up that loud

- Cryo

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thomasmiller

· #2 · Feb 17, 2005

Call Polk. I recently had a great experience with them on a service issue -- blown speaker, as a matter of fact. The Baltimore folks were very responsive and the west coast repair shop was quick and fairly priced.

Customer Service
[email protected]

9am - 6pm, M-F, EST (USA)

800-377-7655 toll free phone

410-764-4817 fax

they will want your model# & serial#, so have that handy.

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YeuEmMaiMai

· #3 · Feb 18, 2005

sounds like something may be starting to short out.

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M NEWMAN

· #4 · Feb 18, 2005

Quote:

Originally posted by YeuEmMaiMai
sounds like something may be starting to short out.

Sorry, but shorts typically result in smoke and fire...at the very least a blown fuse.

It actually sounds like either the woofer voice coil is partially blown (scratchy, crackly, rattley racket coming from the driver), or the plate amp has developed a problem in the preamp driver section of the circuitry. Your sub needs servicing or replacement.

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Cryofax

Discussion Starter · #5 · Feb 20, 2005

Thanks to Polk's 3-year warranty on my sub they are fixing it. The place I bought it had to ship it to Polk so I am without a sub for a good month. I'm tempted to buy one and return it when my other one comes back : ) And no they wouldn't give me a loaner... Bastards...

- Cryo

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YeuEmMaiMai

· #6 · Feb 20, 2005

I beg to differ,

you can have something such as an input that is shorted to or intermittently shorting to ground and you would then pick up ac hum crackling, etc . You could also have other items shorting out like inductors that would allow ac to pass or caps that are dying allowing DC current to jump accross.

Those types of short do not produce smoke or fire, they just show up as unwanted noise or erratic behavior in the electronic device.

Don't be so quick to judge someone as I do have a degree in electronics engineering and have some clue as to what I am talking about.

Quote:

Originally posted by M NEWMAN
Sorry, but shorts typically result in smoke and fire...at the very least a blown fuse.

It actually sounds like either the woofer voice coil is partially blown (scratchy, crackly, rattley racket coming from the driver), or the plate amp has developed a problem in the preamp driver section of the circuitry. Your sub needs servicing or replacement.

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M NEWMAN

· #7 · Feb 21, 2005

Quote:

Originally posted by YeuEmMaiMai
I beg to differ,

you can have something such as an input that is shorted to or intermittently shorting to ground and you would then pick up ac hum crackling, etc . You could also have other items shorting out like inductors that would allow ac to pass or caps that are dying allowing DC current to jump accross.

Those types of short do not produce smoke or fire, they just show up as unwanted noise or erratic behavior in the electronic device.

Don't be so quick to judge someone as I do have a degree in electronics engineering and have some clue as to what I am talking about.

It was your general (and pretty much useless comment on some mystery short) that was what led me to "be so quick to judge" you. Typically, people who just "toss" out the "something is shorting out" explanation are, in fact, quite ignorant of electronics. Since you have now revealed that you're not the average electronic dolt, it is doubly ridiculous that you would have tossed out such a general and useless bit of advice. All the things you mentioned above are legitimate issues that "could" qualify under the "something's shorted" theory, although, based on the poster's explanation of the symptoms, didn't necessarily sound like the problem. However, since you have this knowledge, why didn't you elaborate, and give Cryo something that was actually useful?

By the way, the scenario of dried caps or shorted inductors you mentioned are just as likely to create high current flow (smoke and/or fire) as they are not, depending on circuit configuration. The only example that you gave above that truly would not create an excess current flow is the shorting interconnect or input.

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drdoan

· #8 · Feb 21, 2005

Usually crackling sounds are generally electronic in nature. Although it could be the speaker's voice coil warping and causing the sound. To find out if it is the speaker, try carefully pushing in the speaker cone using even pressure around the dust cap. if the back and forth motion is rough or restricted, it could be the speaker. Otherwise the most likely cause is a leaky capacitor in the power supply, or a noisy transistor. Coils (inductors) rarely "short" unless a large current is applied to them. It has to break down the coating on the windings. Capacitors are much more likely to leak. Dennis

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