[D.Kreft]

On Nov 14, 7:36 am, wrote:

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.

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

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

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