Seemingly dead speakers

Hey all,

I have an '04 (ZZW30) MR2, with a slight speaker issue. The larger speakers in the door pretty much don't work 99% of the time. They come back to life sometimes, but very rarely. The tweeters do work, it's just the larger door speakers that don't. Its doesn't have the premium stereo (no speakers behind the seats) and has the standard factory head unit. Has anyone had this problem before, or managed to find a fix? Thanks!