[Matt Ion]

wrote:
I need to install some capacitors to serve as bass blockers for door
speakers in my car.

Since my car is parked outside a lot, it seems like it may not be a
good idea to use electrolytic capacitors, but instead use something
like ceramic or mylar which don't have a paste that could dry up in the
heat.

Can anyone help me determine whether this would work? Or must
capacitors in this role be electrolytic?

Just to clarify: no, they don't HAVE to be electrolytics. HOWEVER, about the
only caps you'll find in the capacitance range you need (several hundred
microfarads - a 200Hz cutoff on a 4-ohm speaker should have about a 200uF cap)
for a reasonable cost, will be electrolytics.

Most other types (ceramic, mylar, tantalum, etc.) are not generally available in
those values (tatalum caps, IIRC, tend to be relatively high-value,
high-tolerance, high-voltage for a fairly small size, but also tend to be
comparitively expensive).

If you can't find a non-polarized cap, you can always connect two standard
electrolytics back-to-back (ie. negative of each cap connected together;
positive of one to the speaker, positive of the other to the feed wire), just
remember that doing so will cut the total capacitance in half... so if you need
200uF total, you'd have to use two 400uF caps.

See here for some useful charts/calculators:
http://www.carstereo.com/help/Articles.cfm?id=1