Canton 80 cx subwoofer defekt

Hello,

My german isn't so good but because Canton is a german brand I figured someone maybe have some details about it.

My canton 80cx subwoofer have very very low sound output even at max level +9. I tested the subwoofer at a friends place with the same results so it's not anything wrong with my amp or cable. The green led on the back is on. I'm new to electronics but I opened it up and the board looks OK, no visible burned or swollen components.

I meassured the sound level potentiometer with the results (legpair 1-2 & 1-3 but not from 2-3 (zero K)):
-80 = zero K
-18= 0,26 K
-12=0,72 K
-6=1,78K
0=3.12K
+6=8,12K
+9(max)=12,85K

The crossover potentiometer goes from 65 to 150 Hz. It has 6 legs A1,A2,A3,L1,L2,L3. At all Hz levels (65 - 150 Hz) I got the same result 9.85 K ohm for pairs A2 & L2 and A1 & L2, all other combination were zero.
My meter can't meassure the capacitors.