http://www.korgforums.com/forum/phpBB2/

click on the link above. It will take you to the korg forum and somoeone more experienced should be able to handle your enquiry. Certainly the speakers should not be jarring at all.There is a limiter built into the speakers to prevent you from blowing them. However there might be debris that has fallen into the speaker or under the keys of the keyboard into the instrument that might be vibarting when you play deep notes