[TomTheGeek]

I just want to run this by someone to verify that it's working how I
think it is.

I have a sub with a Class D monoblock amp and a stiffening cap. The cap
has the standard voltage meter on the top. With the volume turned low
the voltage meter on the cap shows a steady 12v. With the volume turned
up and the bass really kicking the voltage will fluctuate with the
bass, dropping to around 10v or so occasionally.

My interpretation of this is that at low volumes there is little draw
on the electrical system so the amp doesn't need to pull from the cap
or it's pulling so little the voltage meter isn't sensitive enough to
notice it. At louder volumes the amp is stressing the system and the
cap is doing it's job supplying the extra power therby lowering it's
voltage. If that is correct then you can say that if the voltage meter
was getting to around 0v then I would need a bigger capacitor.

But for all that to be true the voltage meter on the cap would have to
be measuring only the voltage of the cap, not the whole system. To me
this sounds wrong, but I don't know.

Do I need a bigger alternator or a bigger cap, or is it working like it
should and my theory is correct? I bought the cap to ease the load on
the electrical system, not to gain SPL.