Simple crossover repair - matching capacitors

[The Documentary Sound Guy]

My project is about as simple as could be: I'm repairing a crossover in speaker with no high frequency response. The crossover is two caps and a transformer on a PCB. One of the capacitors has failed open, and I'm going to replace it.
What I'm wondering is how strictly I need to match the capacitor, both in terms of electrical specs, and also in terms of chemistry and brand.

Here's a photo:


The dead cap is the one that is lifted with the specs visible. On that basis, this is what I can tell from the original:

• 330µF
• 85°C
• 100V
• NP?
• Electrolytic???
• Nihtin ??? Brand?

Knowing that, this is what I think I should be looking for:

• 330µF (exact value)
• ≥ 85°C (at least)
• ≥ 100V (at least)
• NP? (not relevant?)
• Electrolytic??? (replace with electrolytic)
• Nihtin ??? Brand? (brand not relevant)

Can anyone confirm my assumptions about specs here? Are there any specs missing that I should be considering?

 

[abbey road d enfer]

• 330µF (exact value)

Yes, however the typical tolerance is +/-20% on these old caps.
If you buy from a specialized shop, they have a choice of tolerance, from +/- 10% to +/-2%.

• ≥ 85°C (at least)

Actually I would prefer 105°C, but it seems the most common are 85.

• ≥ 100V (at least)

Not necessarily. It depends very much on the expected signal level.
For a 100W speaker, the peak voltage is 40V.
That's what you need to check.
Typical x-over caps are rated for DC and AC, with the AC rating bout 40% of the DC rating.
I'd rather have a good quality 63V cap than a poor 100V.

• NP? (not relevant?)

Extremely important and necessary, since the loudspeaker signal is AC.

• Electrolytic??? (replace with electrolytic)

Actually, a film capacitor would be a better choice, but for 330uF, it would be huge and expensive and you would need to replace it on the other speaker (which I recommend in any case if you want decent stereo pairing).
Note that most of the commonly available caps are axial so you would have to adapt the wiring.

• Nihtin ??? Brand? (brand not relevant)

Yes, it's the brand. Irrelevant.

 

[The Documentary Sound Guy]

Thanks for flagging the NP for me. I missed the importance of that.
I'd rather avoid re-capping all the speakers if possible. This is a centre channel speaker from a 5.1 set, so it's already a slightly different design (this crossover is driving two 3" "woofers" in series; the rest of the speakers only have one woofer). Given that this is mainly a learning project, I'd rather not duplicate the repair five more times.
Is there a good way to estimate the tolerance of the original cap? The only marking I didn't document is the number "2405" written on the opposite side.
Since you bring up quality, how can I identify good quality caps if not by the specs? I'd prefer to buy locally, so I was going to trust my local shop, but I don't think they have non-polarized caps, so I may have to chase something down on Mouser.

 

[abbey road d enfer]

I'd rather avoid re-capping all the speakers if possible. This is a centre channel speaker from a 5.1 set, so it's already a slightly different design (this crossover is driving two 3" "woofers" in series; the rest of the speakers only have one woofer). Given that this is mainly a learning project, I'd rather not duplicate the repair five more times.

OK I get that. However, statistics show that when one type of caps fails, the others will also fail, not tomorrow, but one day, so you'd better be prepared.

Is there a good way to estimate the tolerance of the original cap?

No, but typically these cheap capacitors were 20%.

The only marking I didn't document is the number "2405" written on the opposite side.

I think it's the mfg date code, likely 24th week of 2005.

Since you bring up quality, how can I identify good quality caps if not by the specs?

Unfortunately, specs are often doctored by the mktg dept, so are not totally credible.

I'd prefer to buy locally, so I was going to trust my local shop, but I don't think they have non-polarized caps, so I may have to chase something down on Mouser.

Mouser actually have suitable Panasonic and Nichicon. They all seem to be +/-20%.
You may want to try a specialized shop, where they handle Monacor, Mundorf, Jantzen or SCR.
They have up to 2% tolerance ($$)

 

[The Documentary Sound Guy]

Ok, thanks, I'll see what I can get from Mouser. I don't think this speaker is worthy of 2% parts, especially if the original can be assumed to be a 20% tolerance. For the moment, I'll just be happy if I can fix it and learn a bit about capacitors and filters in the process.

 

[The Documentary Sound Guy]

Unfortunately, specs are often doctored by the mktg dept, so are not totally credible.

Absolutely, that is my fear. But it's not helping me identify the good ones ... I guess this becomes an issue of brand trust?

 

[The Documentary Sound Guy]

I'd rather have a good quality 63V cap than a poor 100V.

Taking that advice, would this be a good choice? https://www.digikey.ca/en/products/detail/nichicon/UEP1J331MHD/2597840
I'm having trouble finding parts rated 100V on non-specialty sites.

I also found this: Jantzen Electrolytic Capacitor 330.00µF 100VDC M.D.L. Series Non-Polar "Discontinued"
But Jantzen's website gives me more than a whiff of audiophile technobabble that gives me snake-oil vibes.