Capacitor

Hi there,

This really depends.  With a value this high I have to assume it's a low pass filter.  If so it is likely to go to ground. If so these rarely matter as much as caps in series.  They DO matter, but it's hard to really judge their sonic worth as much.  To hear the difference here you might want to try a non-polarized electrolytic before you spend too much money.  Here's one that costs $2.

https://www.parts-express.com/100uF-100V-Non-Polarized-Capacitor-027-360

Try it and see if you feel it's an important capacitor in your circuit.

What value is important the uf or the vdc

The uF determines the frequency of the crossover filter (gross oversimplification) the VDC determines the maximum voltage.  If you apply too much it will short the capacitor and it will no longer work as expected.  That's a very high value for a speaker where I can't imagine ever needing more than 200 VDC rating in extreme high power speakers but with film caps it's hard to make a lower voltage cap sometimes, do don't go looking to optimize this. 

Best,

Erik

What value is important the uf or the vdc

The critical value is uF, micro-Farads, the unit of capacitance. VDC is voltage, which matters only in that you do not want to use a low voltage cap with high voltage as it can destroy the cap. Crossovers are in the single digits to tens of volts, not hundreds, so this number 630VDC is irrelevant. You just don't want one that is too low. 

Capacitors in crossovers are sometimes called filter caps because that is what they do, filter lower frequencies. The greater the capacitance the more energy the cap stores. Because of this, if you change the value from say 100uF to 150uF this will shift the frequency and this will cause the speaker to sound different.

All caps and resistors have a tolerance, typically of a few percent, often printed on the part along with the value. So if your cap is 100uF +/- 5% it can be 95 to 105uF. If the manufacturer specs this cap that alone should be enough to tell you one or two uF one way or the other is not critical. If you really want to know you can buy a LCR meter and measure actual capacitance and inductance yourself.

The idea someone had that the only thing that matters is the measured value and gives as his "reason" because, physics, is patently false. The better caps do indeed sound better even though they measure the same. And you want to know why? PHYSICS!

What is actually happening inside a cap is electron charges are constantly shifting one way and another, in and out, according to the music signal. When we measure all we get is a static, fixed state number. There is nothing in it having anything to do with how fast and smooth these charges shift back and forth. Which with music is EVERYTHING! That is why some of these expensive caps use such an elaborate manufacturing process, to ensure extreme consistency and sensitivity down to the electron level.

It ain’t cheap. It ain’t easy. And it can’t be measured by no meter. Thus the link to the cap comparison page above.

What are you trying to achieve? You have a pretty good film cap already. The only identified issue with film caps is a potential for mechanical resonance specific to a frequency but audiophiles make up all kinds of things like posts in this thread. Caps can be in high or low pass filter networks. They are critical in both. That's simple circuits. Whether the signal passes through them or is shunted to ground through them the effect is the same. You don't have a cheap electrolytic so temper your expectations. There is a reason some quite expensive speakers use sort of average capacities.

Here's a link to a guy that did extensive listening tests for crossover caps. 

http://www.humblehomemadehifi.com/Cap.html

I've found the copper foil in oil caps from companies such as dueland, Jupiter and miflex sound the best, but these can get quite expensive and are quite large.

The only identified issue with film caps is a potential for mechanical resonance specific to a frequency but audiophiles make up all kinds of things like posts in this thread. Caps can be in high or low pass filter networks. They are critical in both.

So which is it then? Because if they are so critical then it would seem we would want the best ones, and you already admitted there are problems like mechanical resonance. Which is indeed a factor. So how can you be sure we are just "making up all kinds of things" about which is best? Help me understand your, uh, reasoning.