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Old 23rd February 2015, 07:06 PM   #1
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Default Passive Crossover Caps

I am replacing some capacitors in some old Klipsch Heresy's. I would like to use Polypropylene type caps without spending an arm and a leg. I have to place an order from mouser anyway so I would like to order the caps from them. I came across some caps I think might work. The datasheet says they are for active crossover networks so I am hoping they will suit my application.

Datasheet: http://www.mouser.com/ds/2/315/Capac...%29-215017.pdf

Anybody use these caps in crossovers? Will they work for my application? If not what caps are you using and why?

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-bird
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Old 23rd February 2015, 07:17 PM   #2
AndrewT is offline AndrewT  Scotland
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motor run capacitors work well as crossover capacitors.
values from 10uF to 100uF are available in 250Vac rating at reasonable prices.

But by adopting a low esr plastic film capacitor you will probably have to change other components to bring back the frequency response engineered in by the speaker designer.
Adding a resistor in series with the low esr cap may be any easy way to make the crossover perform as intended.
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Old 23rd February 2015, 07:41 PM   #3
infinia is offline infinia  United States
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how about this series
> specified dV/dt with more usable values and voltages http://www.mouser.com/ds/2/315/ABD0000CE47-63820.pdf
2.2uF 5% ~ $1.40 ea
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Old 23rd February 2015, 07:52 PM   #4
infinia is offline infinia  United States
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Quote:
Originally Posted by AndrewT View Post
motor run capacitors work well as crossover capacitors.
values from 10uF to 100uF are available in 250Vac rating at reasonable prices.

But by adopting a low esr plastic film capacitor you will probably have to change other components to bring back the frequency response engineered in by the speaker designer.
Adding a resistor in series with the low esr cap may be any easy way to make the crossover perform as intended.

even if he used modern day non polarized electro's to replace like for like, that issue might remain due to improvements in those.

I would NOT do a global replacement to film types, just the series elements
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Old 23rd February 2015, 07:54 PM   #5
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Quote:
Originally Posted by infinia View Post
even if he used modern day non polarized electro's to replace like for like, that issue might remain due to improvements in those.

I would NOT do a global replacement to film types, just the series elements
Why only series? Parallel caps are part of the circuit as well.
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Old 23rd February 2015, 08:44 PM   #6
infinia is offline infinia  United States
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shunt caps are bypassing the signal and they usually benefit from some extra esr damping, the series caps provide the actual current through the voice coils so they are more critical, but hey if you got the funds go wild.

it's madness putting 100 uF of expensive film caps on a woofers LPF and then adding a couple of ohms in series with it. I see these web sites that make their money from crossover components eg Jensen.
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Last edited by infinia; 23rd February 2015 at 08:55 PM.
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Old 23rd February 2015, 08:52 PM   #7
Face is offline Face  United States
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Bypassing AC current, interesting.
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Old 23rd February 2015, 10:50 PM   #8
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I will attach a schematic but I don't see any parallel caps, only series.

I didn't think about the esr in the original caps being part of the design and going with lower esr film caps could be a bad thing. I have some Nichicon VP series 2.2uF on hand that I will try out first, probably better than the original which is in there now.

Nichicon VP: http://www.mouser.com/ds/2/293/e-vp-23529.pdf
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Old 24th February 2015, 12:34 AM   #9
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Looking at that schematic I hardly think you should worry about ESR.

The crossover is hardly exotic. If anything should be replaced it would be the woofer's series iron cored inductance with a low resistance air cored inductor of the same value.

The poorest performing component used in any passive crossover has to be the inductor. Modern capacitors are generally of close tolerance and are well made to suit the purpose. Inductors on the other hand introduce power loss and irregular frequency response if iron cored, an 'air cored' inductor of low resistance would give a smoother performance.
I notice the schematic provides no impedance correction at all to any of the drivers which would mean a less than optimized performance from the crossover network.
So any concern about ESR with regards to what capacitors to use is neither here nor there.

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Old 24th February 2015, 12:41 AM   #10
Face is offline Face  United States
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A lower ESR inductor would change the transfer function and the driver level.
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