The use of Mylar Caps in RC contour applications

dcmeigs

Perhaps you've seen the guy on ebay that sells the capacitor kits for vintage Polks. If not, a polk search should turn him up if you are interested.

He makes an arguement that I find much more interesting than his kits. I suspect it is specious, but I really don't have the experience to know. I solicit your opinions and experience.

It concerns the use of various types of caps for different purposes in the crossover:

\\ In the signal path, in series with the tweeter in the high pass, a polypropylene cap is offered. No arguement there.

\\ He offers that a good electrolytic cap will work well in the low pass in series with the inductor and both in parallel with the tweeter. (this happens to concern the Monitor 10 crossover). I really have no problem with this because he doesn't make any claims to sonic excellence and we all know it will work.

\\ **THIS IS THE INTERESTING ONE** In the RC contour application in the high pass, a mylar cap is offered. It is presented not as an economy, but as the best option. I quote from the ad:

Some may assume that using a Polypropylene capacitor in this RC Contour Network could or should sound better, because this capacitor is in series with the tweeter, as is the capacitor of the 12dB/octave high pass filter. Not so! Keep in mind that the resistor in this RC Contour Network is also at work here! The Mylar capacitor in this application, with these loudspeakers, provides superior results over Polypropylene.

I wonder if there is any merrit to this claim? Comments?

Systems

dcmeigs wrote: »

I wonder if there is any merrit to this claim? Comments?

Humm being that they are both film caps I cant see where the mylar would have an advantage over the polyprop.

geoff727

If it's the same ebay listing I'm thinking of, I was wondering why he didn't spring for some better series resistors for the tweeters. Even the Mills are only about, what, $3.50 or so? It would only add 7 or 8 bucks to the price of the kit.

geoff727

Maybe he's built several crossovers for the same speaker, swapped them in and out during listening tests, and the Mylar cap in that position is what pleased his ears the most.

dcmeigs

Perhaps so, or maybe it's a matter of cost.

I found a couple of good articles on the subject I had missed earlier. There seems to be agreement that there is a hierarchy: Electolytic, mylar and polypropylene film. This is from this site:

For capacitors, an Electrolytic capacitor is your basic type. They are cheap, but do not pass high frequencies well. Mylar capacitors are more expensive, but they are better for audio because they work better at the high frequencies, and have less inductance and resistance. Polypropylene capacitors are the best, but are also much more expensive.

Probably just that simple.