Have received a replacement set of capacitors for my loudspeakers.  Have been sorting them out and comparing to the existing caps on the xover boards.

I note that several caps, while having the correct micro farad spec, have a different V to the original.

For example existing cap at C4, and also as per a schematic I have downloaded, should be 600MF and 50V, whereas the replacement is the correct 600MF but rated at 100V.  Is that an issue?

Also, the cap at C9 should be 240MF and 50V, whereas the replacements are two 120MF at 100V, with an accompanying note saying to mount in series to reach 240MF.  Again, is that an issue to be concerned about?

OK.. a couple of Qs here:

Capacitor voltage - is usually specified higher than the maximum expected working voltage, by a factor of say 1.5x to 2x, depending on the type of cap, the type of cct, etc.
So, the original 50v spec should have been already overrated & the newer 100v one will be fine too. (The downside sometimes is that the higher V cap may be larger, but probably not a problem on a sparsely laid out xover bd.

Capacitance value, micro-Farad (uF) - normally if you want to add together say 2 x 120uF caps to achieve 240uF, you would connect them in parallel (not series)
(Their voltage rating is unchanged, same as the lowest voltage cap used.)

If 2 x equal uF caps are connected in series, the capacitance value is halved - but voltage rating of the 2 in series is doubled (added).

DarkLantern blog - darklanternforowen.wordpress.com

The rated voltage of a capacitor can be higher than specified, so what you have received is OK
They are wrong to say connecting two 120 uF caps in series will amount to 240 uF. They should be connected in parallel to get 240 uF

See attached calculator, it also shows how to connect them together

ThanKs guys, Series was my interpretation- their instructions were to couple together.

My experience with series and parallel, is with my off grid battery bank, where two batteries connected in series doubles the voltage, and in parallel keeps V same but increases amperage. A little knowledge is a dangerous thing!

A 100 watt amp powering a 4 ohm speaker results in a peak voltage of just over 28 volts. If it were an 8 ohm speaker 100w would be 40 volts.
So on the 4 ohm Kefs the 50 volt capacitor rating was fine. Newer caps for crossovers are generally rated 100v as it’s now easier to manufacture that voltage rating in a capacitor the same size an an older 50 volt one.
The physical size of the cap is influenced by how much energy it can hold. Joules = 1/2 x C (in Farads) x V^2. But modern caps have more intense etching on the aluminium foil than older caps and can be the same size as them, even though the potential energy storage is quadrupled from 50v rating to 100v rating.

AMR-iFi R&D

Colin is right, Falcon Acoustics has confirmed 50V versions are no longer made.

I was possibly wrong in my first post to refer to a 600uF cap as 600MF, but I note that half of my replacement caps all use that abbreviation. Which could be a bit confusing, as I see mF = millifarad = 1000th of a farad, whereas uF = microfarad = one millionth of a farad

Just been researching “farad” and discovered information that I am sure all you knowledgeable DIY chaps already know!

This link explains it rather well...

www.westfloridacomponents.com/blog/is-mf-mfd-the-same-as-uf/

Yes, confusing for newbies! If it’s 600MF and 50 volts and it’s a smallish electrolytic cap, the translation is 600uF.
You don’t see a 1000uF cap being labeled as 1mF for reasons of clarity. Electrolytics are almost always in uF, despite what it says outside, unless it specifically says F, meaning Farads. There are tiny 5 volt 1F caps out there, mainly used as memory backup for clocks when the power goes off.

AMR-iFi R&D