replacing capacitors in speaker crossover

[kevink]

Hi folks new here to forum..got a pair of 70's vintage advent speakers and I want to replace the capacitor in the crossover..the capacitor is a 13uf 50volt ...I have not been able to find a 13uf 50volt replacement (no 13uf regardless of voltage) what is the impact if I replace with a 12uf or 15 uf...have not been able to find much discussion on this topic..

 

[XEagleDriver]

Hi folks new here to forum..got a pair of 70's vintage advent speakers and I want to replace the capacitor in the crossover..the capacitor is a 13uf 50volt ...I have not been able to find a 13uf 50volt replacement (no 13uf regardless of voltage) what is the impact if I replace with a 12uf or 15 uf...have not been able to find much discussion on this topic..

Do not go below the 50V of the original, that is a safety issue to ensure the cap can handle expected power requirement.
- A 12uf replacement should work just fine. If you can find the schematic of the crossover, a Goo search can give you the formula to compare 13 vs 12uf effect on x-over frequency.
- All components have a statistical range of performance, not a precise value, so you should be OK.
Cheers,
XEagleDriver

Sent from my SM-G975U using Tapatalk

 

[Verdinut]

You can use a higher voltage capacitor without any worry. A 12 µF polypropylene cap will do the job and is of better quality than the original electrolytic one:

Home

Dayton Audio DMPC-12 12uF 250V Polypropylene CapacitorMake the Dayton Audio line of metallized polypropylene capacitors your standard choice for all of your loudspeaker projects! The same high quality as the competing brands ... but at a much lower price. They are suitable for a wide range of...

www.parts-express.com

 

[Swerd]

I agree with both of the above posts from XEagleDriver and Verdinut.

A voltage rating, such as 50V, indicates a voltage below which the capacitor has been tested and shown to resist failure for a defined time span. Above 50V, it can fail. A voltage failure rating tells us nothing about other capacitor qualities.

Most all crossover designs have a range of capacitor and inductor values that will work. Crossovers as old as those from the 1970s probably had a range no smaller than plus or minus (±) 10%, maybe as high as ±20%. If the original capacitor is 13 µF, any replacement capacitor within 10% of 13 µF should work. That would include anything from 12 to 14 µF. That inexpensive ($4.55) capacitor Verdinut suggests would be a good choice. It's 250V (DC) rating means it didn't fail when tested for 1000 hours, at 85°C, at 150% of the rated voltage.

Be aware the dimensions of your old 13 µF cap and any replacement cap. That replacement capacitor is 22×55 mm. It probably will not fit in the same space as your old capacitor. It will not hurt performance if you locate the new cap further away and use some short extensions to it's leads.

 

[D Murphy]

You can use a higher voltage capacitor without any worry. A 12 µF polypropylene cap will do the job and is of better quality than the original electrolytic one:

Home

Dayton Audio DMPC-12 12uF 250V Polypropylene CapacitorMake the Dayton Audio line of metallized polypropylene capacitors your standard choice for all of your loudspeaker projects! The same high quality as the competing brands ... but at a much lower price. They are suitable for a wide range of...

www.parts-express.com

 

[D Murphy]

There's no need to need to use a 12 uF capacitor. After all, with a 10% tolerance it could be as low as 10.8 uF. Just order an inexpensive 12 uF poly and a 1 uF poly, and wire them in parallel for a combined value of 13 uF. I use Audyn from Parts Express because they're red. https://www.parts-express.com/audyn-cap-q4-12uf-400v-mkp-foil-capacitor--027-162 https://www.parts-express.com/audyn-cap-q4-10uf-400v-mkp-metalized-polypropylene-foil-crossover-capacitor--027-108

 

[Verdinut]

There's no absolute need to use a capacitance of 13 µF either. Isn't using only one component somehow simpler, with no noticeable audio response difference for anyyone except for the ones who have golden ears?

 

[lovinthehd]

Then again does the cap actually need replacement at all?

 

[D Murphy]

Then again does the cap actually need replacement at all?

I don't know specifically why the OP wants to replace the Electrolytic capacitors, but given that the speakers must be over 40 years old and NPE caps can drift and even dry out over time, it's not a bad idea. Why wouldn't you want to choose the same value cap as factory spec? That's the entire crossover on the Advents. The woofer runs free. There are some resistors in the tweeter circuit to allow a choice of level settings, but that doesn't affect the crossover point. It takes maybe 30 seconds to twist the 12 uF and 1 uF together to form one unit. It seems like a no brainer to me.

 

[lovinthehd]

I don't know specifically why the OP wants to replace the Electrolytic capacitors, but given that the speakers must be over 40 years old and NPE caps can drift and even dry out over time, it's not a bad idea. Why wouldn't you want to choose the same value cap as factory spec? That's the entire crossover on the Advents. The woofer runs free. There are some resistors in the tweeter circuit to allow a choice of level settings, but that doesn't affect the crossover point. It takes maybe 30 seconds to twist the 12 uF and 1 uF together to form one unit. It seems like a no brainer to me.

I just like throwing out that question anytime someone gets some old gear and wants to replace the caps It might be a good idea, it could be a good exercise, it might not be necessary....but I'd sure like to see the spec on the old cap after replacement.

 

[Verdinut]

A lot of commercial speaker manufacturers, and that includes some expensive consoles, use electrolytic capacitors in their passive crossovers. IMO, a passive crossover should be built without the use of electrolytic caps which change values with time, since the cost of polypropylene ones is very reasonable.
Also, for the passive crossovers, many commercial speaker manufacturers use steel core inductors, instead of air core coils which operate in a more linear fashion and don't saturate at high power levels. Of course, manufacturers want to maximize their profits and they cut on quality for some components which are hidden.

 

[Swerd]

I just like throwing out that question anytime someone gets some old gear and wants to replace the caps It might be a good idea, it could be a good exercise, it might not be necessary....but I'd sure like to see the spec on the old cap after replacement.

With most capacitance measuring tools, you have to first cut the connections between the cap and the rest of the circuit. Once you've done that with a 30- or 40-year-old electrolytic cap, why not replace it?

If I understand correctly, there are ESR-type meters that allow you to measure a cap while it remains connected. But what does one of those cost, and how many non-electrolytic 5% 250V caps can you buy for that same cost?

 

[lovinthehd]

With most capacitance measuring tools, you have to first cut the connections between the cap and the rest of the circuit. Once you've done that with a 30- or 40-year-old electrolytic cap, why not replace it?

If I understand correctly, there are ESR-type meters that allow you to measure a cap while it remains connected. But what does one of those cost, and how many non-electrolytic 5% 250V caps can you buy for that same cost?

I thought they always required to be taken off for testing, hadn't heard about the meters where you can leave them in place. I suppose depends how many you need to test whether the special gear would be worth it to get one....what is the typical cost of a good unit?

 

[Swerd]

I thought they always required to be taken off for testing, hadn't heard about the meters where you can leave them in place. I suppose depends how many you need to test whether the special gear would be worth it to get one....what is the typical cost of a good unit?

I don't know what they cost.

I've only heard about them, indirectly, from an internet audio forum that I wouldn't call entirely reliable – Audiokarma. Maybe PENG could tell us more. I have a ~$30 LC meter I bought years ago from Amazon. It's all I need or want.

 

[Swerd]

If I understand correctly, there are ESR-type meters that allow you to measure a cap while it remains connected.

I was wrong. These meters measure equivalent series resistance (ESR) of capacitors without the need to disconnect them from a circuit. The do not measure the capacitance of a capacitor.

See https://en.wikipedia.org/wiki/ESR_meter

"An ESR meter does not measure the capacitance of a capacitor; the capacitor must be disconnected from the circuit and measured with a capacitance meter (or a multimeter with this capability). Excessive ESR is far more likely to be an identifiable problem with aluminium electrolytics rather than out-of-tolerance capacitance, which is rare in capacitors with acceptable ESR."

 

[kevink]

Do not go below the 50V of the original, that is a safety issue to ensure the cap can handle expected power requirement.
- A 12uf replacement should work just fine. If you can find the schematic of the crossover, a Goo search can give you the formula to compare 13 vs 12uf effect on x-over frequency.
- All components have a statistical range of performance, not a precise value, so you should be OK.
Cheers,
XEagleDriver

Sent from my SM-G975U using Tapatalk

thanks for your feedback...I was able to obtain the exact value by using two caps in parallel to add up to 13...