oh btw i know this doesn't make sense : but the buttkicker really surprised me today.
the 3.5mm to RCA(red and white) , you know only either one that connects to the BKA Amp right?
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now the one i plugged in is the red one if im not mistaken which translate to be "right side" speaker that goes to the BK
So you see the pic the BK was on my right side, Now every time I was running rumble strip on the right the BK rummbles hard, while if it's on the left I kind of felt it on the left of the seat.
I know this doesnt' make sense but you know when you take out one side of the headphone say the right side and the left side still on your ear, if the stereo sound is meant on the right side you can still hear it abit on your left headphone?, even though only alittle bit, but you know that it is sound for the right side.
now that is what happen to the BK at the moment, when I was rammed from teh left, the BK on the rigth can rumble enough Low Frequency Effect that My left side is rumbling.
Its weird . but it works

so it doesnt' matter which side you mount the BK at as long as it is connected to the right side of the RCA on the Amplifier.
hmm Imagine if you have 2 and the 3.5mm to RCA -> white goes to left AMp and Red goes to right amp and each amp goes to each Buttkicker on the correct side.
translation : you get bumps and rumble on the correct side like you are in a real car
but i need the other side latter on for the keyboard and mouse mount so , it works right now.
Sorry for the Long post but for people who asked the question if it's biased or not putting Buttkicker on one side, the answer is NO, It can work properly as long as you plug the correct RCA side from your AUdio source to the corresponding Buttkicker Amp.
ie: if red RCA means right-side speaker, and you plug red in to the input on the BK Amp, the you need to mount the buttkicker rumbler on the right side. it will simulate the correct effect on your chair. Try it !