Bass Vibration seems to be coming from rear speakers

[caoiii]

I have a 2001 Solara SLE convertible that has a heavy bass vibration that seems to be coming from the rear speaker unit every time the stereo system is turned off.
At first I thought it was the speaker itself because after examining the old speaker I found that the paper coning was torn so I bought a new speaker and replaced it.
The vibration is still there and only happens when the system is turned off.
Has anyone had this experience or know what the cause might be?

[iovaykind]

What kind of vibrations are you talking about? How can the speaker produce sound without the stereo being turned on?

[caoiii]

The speaker is mounted in some sort of black box located behind the rear seatback in the center. The sound comes from that area and the vibration is heard when the radio/stero/cd/tape player is turned off.
I just worried that this vibration will damage the new speaker.
I wondered if any other solara owner has had this happen before or maybe knows what causes it.

[iovaykind]

What kind of vibration is it? Constant.. once in awhile? More details would help. Also, is it a factory speaker or is there a subwoofer there?

[caoiii]

Let me clarify what I mean by "turned off".
The vibration happen at the time you press the button to turn off the stereo.
I think that maybe I gave the impression that the unit was already off for a period of time when the vibration is heard.
This is not the case,it happens just after the power switch is pressed to turn off the stereo.
The system is JBL

[caoiii]

It only lasts a couple seconds,and just when unit is powered down.

[iovaykind]

You don't have to worry about it.. might be residual current from amps being drained out. Try this, have your stereo on mute and then turn it off. If it still produces that bass vibration you're talking about then I'm out of ideas. But if you're playing music and turn it off, it might be extra juice still running through the speakers.

[Chris Crash]

Try insulating between the speaker and the mating surface.

[73sport]

I'd venture to guess the final output circuit (amp) has a faulty component. Electronic components fail for having leakage when no input is applied which is likely the case here. Ahead of the amp is a power supply which has capacitors holding a current which was previously driving the amps circuits. When the input is cut off, the output should be zero. In your case it's not. Here is how you can test that.

I'd measure the voltage across the speakers input in DC volts and have someone turn it off while in use just as you normally use it and listen to it volume wise. If the meters reads a positve number (assuming you have the polarity correct) and you get like 3 plus volts contineous until the sound is gone, the amp is likely going bad. Direct DC applied to a speaker will kill it over time so be advised that it could kill again.