Crossover networks - electrolytic capacitors - advice from the experts

Hello,

Okay, here's the translation:

"I'm sure this is a really stupid question, especially for anyone who has studied electrical engineering... But I've repeatedly repaired the standard tweeters in VAG vehicles when they've been distorted, by removing the standard electrolytic capacitor (which acts as a crossover) and replacing it with bipolar Hi-Fi capacitors that our Hi-Fi store sold me."

Okay, I now have more speakers lying around that need to be refurbished as soon as possible... They currently have 6.8µF capacitors installed. The root of my problem is that the Hi-Fi store is about 80km away, making the trip not worthwhile, and I have several hundred of regular electrolytic capacitors lying around.


Therefore, my questions are:

- How is the cutoff frequency calculated from the capacitance (for example, I have a 4.6 µF capacitor available)?
- Do they have to be bipolar, or can you use regular electrolytic capacitors?



I have already searched on Google, but I have found 3 statements:

- it doesn't work.
- it works, because the electrolytic capacitors can tolerate a certain degree of reverse polarity.
- You can connect two capacitors of double the capacitance in opposite polarity to create a bipolar capacitor.


These statements are NOT from me, but were found through a Google search, and they are not helping me feel calmer.


"In my opinion, the installed electrolytic capacitor is NOT a bipolar capacitor, because it has a notch on one side, and both legs are on the same side. The bipolar capacitors I have used previously did not have a notch and had the legs on the left and right sides."



I hope someone can help me .


Greetings.
Georg.

Ibiza1986 wrote:

- How is the cutoff frequency calculated from the capacitance (for example, if I have 4.6 µF)

The crossover frequency is directly proportional to the capacitor used. So, if you go from 6.8 to 4.6, you'll reduce the crossover frequency by about 1/3. I wouldn't necessarily do that to the tweeter. (Although, even now, it's only decoupled with a 6dB slope, so it's still receiving relatively low frequencies in its original state. An LC combination would offer double the decoupling, but accordingly, the woofer would also need to be decoupled, which I wouldn't do for a standard setup.)

If you want to use existing capacitors and don't have suitable ones on hand: In a parallel configuration, the capacitance increases (doubles, triples, etc., depending on the number of capacitors). In a series configuration, it decreases accordingly (halves, etc.). Three 4.6-inch parallel lines, along with three more parallel 4.6-inch lines connected in series, come close to the 6.8-inch mark.

Ibiza1986 wrote:

Do they have to be bipolar, or can you use regular, non-polarized electrolytic capacitors? - it works, because the electrolytic capacitors can tolerate a certain degree of reverse polarity. - you can connect two capacitors with double the capacitance in opposite polarity to create a bipolar capacitor

There is a certain voltage present in the case of reverse polarity, but the voltage level is not specified and is therefore random. I wouldn't install it like that.

The second statement is correct, and that's how I would proceed if I didn't have access to bipolar transistors. (In your case, the best approach would be to connect three 4.6-ohm resistors in parallel in one direction, and then connect another three 4.6-ohm resistors in series to that, reversing the polarity.)

Ibiza1986 wrote:

The electrolytic capacitor used is, in my opinion, NOT a bipolar electrolytic capacitor, because it has a notch on one side, and both legs are on the same side - the bipolar ones I have used so far have no notch and have the legs on the left and right.

Notch? Typically, polarized electrolytic capacitors have a minus sign printed on them, with an arrow pointing to one of the legs.
The "leg arrangement" (axial/radial) has nothing to do with polarity. Both types are available in both versions.

Sure.
Guste.

hi,

Thank you for the detailed answer .

By "kerbe," I mean a constriction or narrowing all the way around. There's no marking or text on the part itself, nor at the point where it's attached to the HT (presumably, "HT" refers to a specific component or device).
While I was thinking about it, I also realized that this has nothing to do with the signs indicating positive or negative values; it's just "like that."


Okay, I'll take a precise inventory of the electrolytic capacitors I have tomorrow. Maybe I'll even find one with 6.8µF... and then I should switch in a "sorum," right? Like the quick sketch in the diagram below?

I hope I haven't made any mistakes in my thinking.

Ibiza1986 wrote:

Maybe I'll even find one with 6.8µ... and then I should switch a sorum, a sorum switch, or? So, like in the circuit below, quickly sketched out, yes?

No.

Because:

Ibiza1986 wrote:

I have already searched for: - You can connect two capacitors of double capacitance in opposite polarity to create a bipolar capacitor.

respectively

Ibiza1986 wrote:

In a parallel circuit, the capacitance increases (doubles, triples... depending on the number of capacitors). In a series circuit, they decrease accordingly (are halved, ...).

You've correctly identified the polarity.

Regards,
Guste.

Okay, then just double every electrolytic capacitor... I must have missed that, I was probably too late... see the current setup.

Hopefully, this is correct now... This applies again to the same electrolytic capacitors mentioned above; I was just too lazy to add the capacitance values four more times.

Yep, that's the way to do it if you can find 6.8µF electrolytic capacitors.

If you can only find 4.6µF capacitors, use three instead of two in parallel. It roughly amounts to about double the value of 6.8.

Best regards,

yes.

I found a 6.8µF capacitor that works. Thank you for your advice . Unfortunately, you're a rank above me, otherwise you would have gotten a +point - so at least feel that way .