Capacitor Replacement in Crossovers

[Old70z]

Can axial non-polarized caps be used to replace electrolytic polarized caps as long as the replacement cap values are sufficient? In summary my question is: does the change from polarized to non-polarized matter? Thanks in advance

 

[Galu]

It is safe to replace a polarised electrolytic capacitor with a non-polarised electrolytic.

Think of a non-polarised electrolytic as two polarised electrolytics connected back to back in series. When a dc voltage is applied, the correct polarity capacitor gets the full voltage. When two such capacitors are connected back to back, they will block the voltage in both polarities.

 

[Galu]

P.S. I've just noticed the reference to crossovers in your title.

ALL crossover capacitors MUST be non-polar (NP) types, whether that be NP electrolytic or NP plastic film type capacitors.

 

[Tweet]

If you are going to use Non Polar Electrolytic capacitors make sure you use 100 volt working and avoid using the very small circuit board types as they tend to over heat and deteriorate more quickly. Physically large capacitors of this type are a better choice if used in the low frequency circuit of a bass driver.


C.M

 

[eriksquires]

It is safe, but you have to wonder why.



That is, caps in series divide, so you could replace 2 back to back polars with a single bipolar/nonpolar cap half their uF.




It's worth measuring the ESR if replacing very old (1980's or before) caps as new ones may change this.

 

[eriksquires]

Er, if you have 2 polarized 50uF caps in series you can replace them with a single 50uF non polar.



Sorry for the confusion.

 

[Tweet]

Er, if you have 2 polarized 50uF caps in series you can replace them with a single 50uF non polar.



Sorry for the confusion.

Sorry for the correction, but 25uF is probably what was meant.


C.M

 

[wintermute]

I think it would be good if the OP posted the circuit. The original post can be interpreted a number of ways and depending on the interpretation the answers are different. Showing the existing circuit will help clarify things.

Tony.

 

[eriksquires]

Gah.



Yes, 25uF would be the end result of two 50 in series. I need sleep.

 

[asuslover]

I would not use regular non polar electrolytic capacitor or 2 regular polarized electrolytic capacitors for speakers crossovers .

 

[system7]

I would not use regular non polar electrolytic capacitor or 2 regular polarized electrolytic capacitors for speakers crossovers .

TBH, i think advice depends on circumstances.

What we know about wet Electrolytic Capacitors is that they age badly, overheat and have a significant resistance. Alan Shaw of Harbeth admits this.

After 25 years or so, the wet electrolyte dries out and they cease to behave as origonally intended! Evaporation of liquids, an' all that.

Nevertheless, they had a place in early Harbeth designs, along with MKT capacitors, this being a Harbeth HL5 IIRC:

The blue thing on the left. Way cheaper than a (MKP) polypropylene capacitor of the same value.

What I find interesting about Harbeth, is they use ferrite inductors in the tweeter circuit. Ferite is demonstratably non-linear. Capacitors are far easier.

 

[Galu]

I think it would be good if the OP posted the circuit. The original post can be interpreted a number of ways and depending on the interpretation the answers are different.

This is the OP's first post on the forum. Let's hope he returns with either clarification of his question or confirmation that it has been answered to his satisfaction.

 

[wintermute]

lets hope so I think probably all variations have been covered, but it would be nice to know!

Tony.