Re: Question about stiffening cap
If you were to wire the cap in series, instead of parallel, it is possible to pass enough current through it that you might blow it up.
Do not do this, of course. Besides the obvious issue of it blowing sky high, they contain PCB's and other hazardous materials that can give you cancer.
'65 VW Bus
MA Hippo 122, (2) Aura Sound 8's, (2) SoundStream 6.5 coax, (2) Alpine Type-S 6x9's [rear fill], MBQ DSC1500.1D, RF 501X
'02 BMW 330xi (AWD coupe), every option
Harman/Kardon 12-speaker System Option + Dayton HO D4 10" and PPI Ion 650.1 in sealed box
And many more car audio goodies in storage