Crossover Capacitor Replacement Questions

[DangerBoy]

Case 1:

I have a set of 2 way speakers (PSB Image 2B) that I want to upgrade capacitors in. The 3rd order XOvers have a 1.5 uF, 8.0 uF and a 12 uF cap. They are all 10% tolerance caps.

It's easy to match the 1.5 and 12 uF with identical capacitance caps within my price range for this project. Not so much with the 8 uF. I can either go for an 8.2 uF or I could put two 4.0 uF caps in parallel for just a couple bucks more.

8.0 uF + or - 10% is 7.2 - 8.8 uF. An 8.2 uF 5% cap is 7.81 - 8.63 uF which falls well within the previous cap's range so I figure an 8.2 uF 5% or 1% cap should be just fine as a substitute for the 8.0 uF.

Is my reasoning sound here? Would the 8.2 uF 5% or 1% be okay or would I be better off getting two 4.0 uF 5% or 1% caps instead?

Case 2:

I have a subwoofer/Bass unit from an old (1970s) set of trio speakers that has a 120 - 128 uF cap wired in parallel with a 50 uF so total capacitance is 170 - 178 uF. I want to replace these caps with modern audio quality caps.

I can easily go with a 100 uF and a 75 uF but is it better to use two caps that are closer in capacitance rather than two that are further apart or does it not make much difference either way? Another option I have is an 82 and a 90 uF.

Cost-wise here are my options:

Dayton 100 uF 5% $32.49 or
Audyn 100 uF 5% $24.30
Dayton 75 uF 5% $22.62

OR

Audyn 82 uF 5% $19.99
Dayton 90 uF 5% $24.99

Cost-wise there's not much difference between the two options if I go for the Audyn 100 uF cap in the first option. Please note that all of these costs will be doubled because there are two woofers in this bass unit and each has its own crossover because the signal out of the bass unit goes to the two treble units/satellites.

I guess this question almost comes down to whether one has a strong preference for Dayton over Audyn. I've never tried either so I'd like to hear from anyone who has tried both.

Which way would you go on this and why?

 

[datafone]

I'll only address one aspect here.

Of course you want to use the same type of cap, I personally would use Audyn.

Are those values you state what is printed on the original caps? As this is what you need to aim for.

 

[DangerBoy]

If you are referring to the capacitors in the second case, yes those are the values of the capacitors used in the original crossover but the builder has wired them in parallel so it's the total capacitance that counts. I looked again and the big capacitor states 124 - 138 uFD on the case. The other is 50uF. That makes the total capacitance 174 - 188. Go for the average and that's 181. I can get a 130 uF capacitor from Parts Express but it's a Solen and it's $55. Parts Express only offers one 50 uF cap and that's by Dayton at $15 each. That brings my total cost to $140 USD because there are two of these crossovers in the bass unit.

Alternatively, PE offers a Dayton 90 uF 5% cap at just shy of $25 each. I would need 4 of them then so that's about $100 even.

If I went for 175 uF, I would have to use a Dayton and an Audyn whichever combination I go for (i.e. 100 + 75 or 90 + 82)

The only way I could do it using all Audyn Caps would be to go 82 + 82+ 15. The total cost of that would be $45.25 per crossover or $90.50 total.

So I can save $9.50 by going with Audyn vs Dayton. I've heard good things about both brands. I would like to hear some feedback from folks who've tried both.

 

[TudorTurtle]

Regarding caps in parallel; all the textbooks I can remember, say the 2 cap's values (wired in parallel ) are just added together.
I always make the two caps the same value, but it's probably more OCD than EE.

 

[MCM_Fan]

Are the two large caps in parallel a shunt circuit (to ground) for the woofer (i.e. not in the signal path). If so, I generally use NPE (non-polarized electrolytic) capacitors for this application. They are much smaller and considerably cheaper than film caps of comparable value.

My favorite NPE caps for woofer shunt circuits are the Mundorf E-Cap Plain series. These are much higher quality electrolytic caps than those originally used in 30 - 50-year old vintage speakers. They are 5% tolerance (most older electrolytic caps are +/- 20%) and should be good for another 25 or 30 years before they drift out of spec.

I buy mine from AK sponsor SonicCraft. The 100uF Mundorf E-Cap Plain is $8.64 and the 82uF is $7.56 for a total of $16.20 per crossover.

While you're there, you can also place a couple 8uF Sonicap Gen1 caps ($18.73 each) in your shopping cart for your PSB speakers. You didn't provide a schematic, but it sounds like those may be tweeter caps that are in the signal path. The Gen 1 Sonicaps are my favorite film caps for that usage.

 

[datafone]

If you are referring to the capacitors in the second case, yes those are the values of the capacitors used in the original crossover but the builder has wired them in parallel so it's the total capacitance that counts. I looked again and the big capacitor states 124 - 138 uFD on the case. The other is 50uF. That makes the total capacitance 174 - 188. Go for the average and that's 181. I can get a 130 uF capacitor from Parts Express but it's a Solen and it's $55. Parts Express only offers one 50 uF cap and that's by Dayton at $15 each. That brings my total cost to $140 USD because there are two of these crossovers in the bass unit.

Alternatively, PE offers a Dayton 90 uF 5% cap at just shy of $25 each. I would need 4 of them then so that's about $100 even.

If I went for 175 uF, I would have to use a Dayton and an Audyn whichever combination I go for (i.e. 100 + 75 or 90 + 82)

The only way I could do it using all Audyn Caps would be to go 82 + 82+ 15. The total cost of that would be $45.25 per crossover or $90.50 total.

So I can save $9.50 by going with Audyn vs Dayton. I've heard good things about both brands. I would like to hear some feedback from folks who've tried both.

As long as different caps (brands/model) are not used in a single parallel group.

 

[elnaldo]

I agree, in values larger than 20 or 25uF , I usually prefer non polarized electrolytics, due to size-price. And they are usually shunts to ground in the woofer network.

8.2uF is OK to replace a 8uF .