Klipsch Epic CF-3 v1 crossovers and rattling dust cap. Almost done

[OO1]

On 9/27/2021 at 10:31 AM, avguytx said:

 The caps look to be in good shape and I would imagine measure close to spec.

The caps in these CF-3 seem to be very good quality , leave as is -

 

,as far as the Charred resistor , measure before replacing / plus make sure that the circuit board is not damaged  /does the black residue clean up ?  , and while you're at it check the 2 caps  next to the resistor for any signs of bulging /leakage  - 

[captainbeefheart]

Ideally when you have a resistor application where it will be getting hot you want to lift the resistor above the circuit board with extra lead length so air can get all around the resistor and reduce heat damage to the board. I doubt the ceramic resistor is bad, you shouldn't have to replace it just remove, increase lead length, and reinstall with a space between it and the board. Another option is to replace the resistor with one that is meant to be mounted to small heatsink that way it can dissipate a lot of heat and never get hot. Typical 50 watt heat sink versions are very affordable and so are the heatsinks.

 

As for the capacitors I doubt you will benefit from replacing them. People have a fear of electrolytics but in this application there is no benefit to going with film unless you want them to last forever. The electrolytic can become high ESR for high frequencies which you do not want here, you want a low impedance for high frequencies to filter them out of the woofer circuit. If you crunch the numbers though even slightly high ESR is nothing to lose sleep over unless the capacitor has gone completely belly up then you will benefit from a fresh capacitor. The ESR in these caps is much less critical vs the ones in series with horn and tweeter where you will begin to get losses across the cap with too high an ESR. I have been engineering electronics for critical application almost my entire adult life and am in the camp where there is no benefit from changing to film, the high value capacitance in small package is great for this application, if you do end up replacing just choose a high quality Nichicon, or Panasonic that is rated for long life, typically 10,000 hours @ 105°C.

[KT88]

3 hours ago, captainbeefheart said:

Ideally when you have a resistor application where it will be getting hot you want to lift the resistor above the circuit board with extra lead length so air can get all around the resistor and reduce heat damage to the board. I doubt the ceramic resistor is bad, you shouldn't have to replace it just remove, increase lead length, and reinstall with a space between it and the board. Another option is to replace the resistor with one that is meant to be mounted to small heatsink that way it can dissipate a lot of heat and never get hot. Typical 50 watt heat sink versions are very affordable and so are the heatsinks.

 

As for the capacitors I doubt you will benefit from replacing them. People have a fear of electrolytics but in this application there is no benefit to going with film unless you want them to last forever. The electrolytic can become high ESR for high frequencies which you do not want here, you want a low impedance for high frequencies to filter them out of the woofer circuit. If you crunch the numbers though even slightly high ESR is nothing to lose sleep over unless the capacitor has gone completely belly up then you will benefit from a fresh capacitor. The ESR in these caps is much less critical vs the ones in series with horn and tweeter where you will begin to get losses across the cap with too high an ESR. I have been engineering electronics for critical application almost my entire adult life and am in the camp where there is no benefit from changing to film, the high value capacitance in small package is great for this application, if you do end up replacing just choose a high quality Nichicon, or Panasonic that is rated for long life, typically 10,000 hours @ 105°C.

A question about the voltage values of capacitors when used in crossovers. If I take the same type e.g. a polyester type from the same company, once with 200 volts and once with 450 volts dielectric strength, is there a sonic difference? Assuming the dielectric is thicker in the 450 volt type, is it a sonic advantage or disadvantage for frequencies as low as audio to 20 Khz? Or does it not matter?

[captainbeefheart]

3 hours ago, KT88 said:

A question about the voltage values of capacitors when used in crossovers. If I take the same type e.g. a polyester type from the same company, once with 200 volts and once with 450 volts dielectric strength, is there a sonic difference? Assuming the dielectric is thicker in the 450 volt type, is it a sonic advantage or disadvantage for frequencies as low as audio to 20 Khz? Or does it not matter?

 

Voltage rating will not have any sonic attributes.

 

 

[Maxwell_E]

I won't say that I can hear the difference between the electrolytic caps and the film caps I put in there, but I'm glad to be rid of 25+ year old electrolytics. Also, the tweeter caps were all film with black bodies and yellow ends. I think they look like the Bennic XPP line. These appear to be original based on the solder joints and the installation.

[Deang]

Yes, those are rebranded Bennics. 

[avguytx]

Just to update. The crossovers are back in place and sound outstanding now.  The electrolytics in the woofer circuit were replaced along with the faulty resistor.  The remaining capacitors stayed in place as they all tested fine.  I know they are good to go now.

 

I did, however, have a rattling dust cap and thankfully that's all it was.  I removed it last night and cleaned up the old glue this morning with the "new" MEK. which works like a champ on removing contact cements and various glues without damaging cones.  At lunch, I'll re-glue it back in place with some M-3035 black rubber cement and it will be good for another 27+ years. 

 

[avguytx]

Dust cap fixed and back in bi'ness.  Now it's just other stuff on the wall rattling....