$20.00 Question

zingo

You make a good point. Premium caps usually get a premium price tag in speakers.

Face

I was under the assumption that the higher you move up the chain, the higher the percentage spent on the x-over. For example, the Gemme Tanto($4000-4800) uses over $100 worth of caps.

Polksaladanni

Bennic is a damn good cap. Ala Dayton and the polyester Sounder used on the new RTi series. Although this legend of a man really hates metalized polyesters. He prefers Bennic type metalizied polypropalenes.

http://sound.westhost.com/articles/capacitors.htm

Zing, you should read what he has to say about low voltage, line level coupling caps. Interesting to say the least. But on electrolytics in speaker XO's he's like me, seen it too many times down the road, they die from high voltage/watts and die naturally over time. And they just don't sound good in this particular audio path. Especially in the High pass section of an XO.

As for Vdc. DC voltage is a straight line voltage. Speaker wattage is a form of AC voltage (alternating current). Which means on a scope center it moves up and down from center, meaning you can almost double the Vdc to figure your wattage limits.
IE: 250Vdc=about 400Watts of safe operation.

Polyester, polyproplyene, teflon and the like are different types of plastic. Film in the case of a wound capacitor.They all have different sound properties. Teflon is exlusive to film and foil caps.

The value of a cap (uf) conicides with the value of the coils (mh) and the Z (Imopedence/resistance) of individual drivers. They all work together to get a reference point to use for the crossover slopes.

Also taken into account is the Fs (resonant frequency of each driver) many Ts parameters of the driver, and the volume (cubic feet/inches) of the speaker box.

The XO itself is a very simple AC (alternating current) circuit both there is a millon other parameters involved to make that design sound great.

That's why I KISS (keep it simple , stupid) and replace the old caps with better built and better suited caps with the EXACT values. This includes the coils and resistors also. I know Matt Polk has many more resouces at hand than all of us put together on designing speakers.

Rod Elliott (above has everything there for ya)

Polksaladanni

Oops. Let me finish the last paragraph...

I know Matt Polk has many more resources at hand than all of us put together on designing speakers. He has his R&d Dept and John Hoskins U. I am absolutely convinced they have done everything in thier power to design the best combination of parts, drivers etc for each speaker. (Maybe moreso in the old days) To produce a producrt that sounds great and makes him a tidy profit. I rely on that expertise and go from there to improve/repair or bulletproof the speaker. In 90% of the cases with caps only. I mean how many times do you REALLY play your speakers at a full 100w RMS? 1watt RMS is pretty damn loud.

An XO simply put ,filters either high or low frequencies and directs them to the proper driver. You can set the cut off slope by using different value caps and coils and factoring in the Z/impedence of the speaker. . But when you factor in all the 100's of other parameters, especially the "moving coil transducer" (speaker) you shouldn't play with different specs/values unless you know your speakers sound and what changes, if any that you want to make, plus know the math. The loudspeaker itself is the biggest problem of all. It might have a nominal Z of 4 ohms when you hook a simple DVOM to it but, touch the cone and watch the readings go nuts. There is no set value for Z once it's moving. That's why it's called "nominal impeadence" . Look at it like a variable speed motor. Which is what it's called sometimes.

All that said. you can get away with slight changes in some caps. Example: the RT55, all replacement value I replaced are exact except, the one and only cap in series to the woofer. OE was a 16.5uf. I couldn't find that value so I used a 16.0uf Clarity. My only choice. I did the math using an XO value chart and figured it would raise the LP slope from 2000HZ to about 2200HZ. Giving it an slight "overlap" at that frequency. Lucked out and it sounds fabulous. The smaller value/higher frequency caps though can cause a much bigger change.

I'm tired and sleepy.