the spider in the sub cause soft , which caused distortion ,
while 2nd voice coil was not giving much response as compare to 1st voice coil
third d4 have 2 , 8 ohms
yuck for 8 ohms , great for 2 ohms , my previous amp support load of 2 ohms but ,i don't wanna use it on 2 ohms , it could end up the lifetime of my sub and amplifier