There will be a lot of issues to cause a rattle. So now just do some tests to eliminate which factors may cause the problem, of cause some of test must be done while speaker playing and required handy skills.
1.) Check fit all the fittings, floor, make sure speaker stand stablely, speaker connector must be tighten up..., front cover must be removed. No decorative object is put on top of the speaker. If it still rattle?
2.) presse and hold the front plate of super tweeter, then move to tweeter and finaly the bass driver. they might cause rattle by some screws were loosing thread, press and hold the front plate may help to know which driver needs to be tighten up again. If it still rattle?
3.)gentle touch on center piece of tweeter (coated dome), make sure that you will not put the cone pops in. if rattle disappears every time you touch on the center piece of tweeter means your driver is bad, it must be reconed or replaced. Do the same with the bass driver. In the case of replacement, the drivers must be in matching pair even another driver still good.
4.) the bolts at bottom base stand is the way to access to x-over MDF board for the original Khorus, its was mounted by 4 #10 flat head wood screws. no thing esle is in this separate compartment, this may be the last stop in the case you like to check x-over components. Another factor may cause is the concentric woofer was placed inside the cabinet, it may also loose screw thread or damping materials were put to close to the woofer. If you want to get in there you have to remove the front woofer to access into it.
the rattle in my speaker was caused by the bad tweeter, it was over drove, the rattle came along with the music, it's hard to tell untill i turned them lound. i replaced them with new pair of driver at Madisound. i also replaced the stock capacitors and resistors by Jensen, Auricap, Wondercap and Mill resistors. Now sound is so much different, clear, warm and more midrange. Yours may be caused by some thing very simple that we never know untill we try. I hope all those above will help. Good lucks and drop me a mail if you have question.