The bass speaker on the rear package shelf of my 98 LS400 has in the last few days developed a very annoying vibration. I don't play music loud or boost bass.... I mainly play NPR podcasts and relatively mellow music. But now with any hint of bass in the sound that speaker buzzes and vibrates.

is the speaker simply worn? Anyone else seen this?

One twist is that (coincidentally?) a month ago I installed an aftermarket radio with the beatsonic amplifier adapter that lets me keep the factory amp. One limitation of the BeatSonic box is that you have no fader control. The BeatSonic instructions say to set your fader at neutral and it will handle it "optimally". I tried adjusting the fader... if I set it full rear I get no sound, any setting with front sound results in front and back both getting about equal sound. This is annoying because I can't temporarily dial my fader all the way forward to stop the vibration and buzzing.

 

i believe on the factory headunit the subwoofer (bass speaker) is on it's own channel where the fader doesn't affect it at all. i could be wrong.

as for your vibration, it could be the speaker cover itself. pry up and remove the cover and see if the buzzing remains. if it's indeed the cover, add some cloth or tape to minimize the rattling.

 

x2 on checking the speaker grill.

The foam for the sub could be dead too.