Can someone help explain why my kappa door speakers sound so bad?

I have some kappa 6x9 3-way components in the front that sound amazing. So good that I got rid of my sub. They are on a 125w x4 RMS amp.

My rear speakers are another story. They are 60csx. The bass response falls off around 200Hz. The stock non-jbl speakers by comparison, had wayyyy better bass on a 125w amp. https://my.infinityspeakers.com/KAPPA+60CSX_.html

VAS: 7.45L
QTS: 0.77
QMS: 8.39
QES: 0.85
FS: 78
CMS: 301

 

Don't run rears.

Hardly anyone does as it affects the front soundstage.

 

What headunit you using? Stock 3rd gen puts very little power to the rear. I put a small 400w amp behind head unit to help with the rears…

 

He's running external amplification, literally nothing to do with the head unit's power output.

Says so in his post.

 

My first guess would be to make sure there’s not a hi-pass filter set on the amp.

another little test is to swap your front and rear inputs on the amp. If everything still sounds the same, at least you know it’s not an amp issue.

 

^+1.

the last test i would run would be to swap the polarity of one of the rear speakers at the amp. it's possible one of them is wired reversed, which would cancel out the rear bass frequencies the most. though that said, the rear locations really suck for acoustics, so a lot of it just how they are.