I've seen electolytic (must be nonpolar or bipolar) bass blockers work in
car doors for years here in Central Florida with no adverse effects.
I've installed for 27 years and do not recall a time where it looked like
bass blockers were heat damaged.

Check out partsexpress.com, they should have a variety of bass blocker
for sale. This should offer you a wider selection and invo

--
John

On Nov 14, 7:36 am, DarthContin...@gmail.com wrote:

I used to work in the industry in *south* Florida...no problems on my
end with the heat and electrolytics, either.

I have to wonder why you're just going to use just capacitors? A
capacitor alone has a 6dB/octave roll-off--which is pretty darn
gradual. This means that you're going to have to choose a pretty high
-3dB (crossover) point to give your speakers the protection they need.
Of course, how high the point has to be depends upon the size of the
speaker and the amount of power your amp is churning out--the more
power you apply to the speaker, the higher the crossover point is going
to have to be.

I would strongly encourage you to consider using a "second-order"
(12db/octave) or even a third-order (18dB/octave) filter  instead.
Using a higher-order filter means that you'll be attenuating
potentially damaging low frequencies much more rapdily, which means
that you'll be able to choose a lower -3dB point and/or apply more
power without damaging your drivers.

There's also something to be said about the quality of the sound you
get when using a higher-ordered filter. Some "golden-eared tweaks"
might argue that the lesser degree of phase shift encountered with
lower-ordered filters leads to a more "pure" (whatever that means)
sound, but this is *highly* debateable. In a typical install, you're
actually likely to do more damage, in my experience, using 6dB/octave
crossovers to your soundstage due to there being less of a clear
"boundary" between the frequencies reproduced by your separates up
front...but this is rather esoteric stuff that the "average Joe"
doesn't care much about. :-)

You also didn't mention what kind of speakers these are...are they
separates (discrete tweeter and woofer) or are they coaxials? Adding a
capacitor (or any passive crossover for that matter) inline with a
coaxial that doesn't have discrete inputs is going to muck with the
crossover point of the tweeter. It's been a long time since I've built
a passive XO network, so I don't remember the precise effect or the
degree thereof, but it's something worth looking into to make sure you
don't do the wrong thing.

In a nutshell, go with a good (mylar capacitor, air-core coil)
second-order (12dB/octave) filter--I think you'll be better off.

-dan

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

They have been using electrolytics in head units for many years. The door
might get hotter, but you don't even have to put them in the door anyway.
Bass blockers are a poor substitute for active crossovers. The bass blocker
increases driving impedance causing the resonant peak of the midrange to
further increase.

greg