I have a 400 watt 410 cab that gets a fair amount of abuse. Recently the top right speaker started making a subtle crackling on low notes at high volume, then yesterday it went to all out loudcrackling on all playing. So knowing nothing about speakers or cabinets i unscrewed the speaker looked at it saw nothing, shook it a bit then put it back in and now it works just fine?? Any thoughts? Can I rely on this for my gig next week?