ESR compensation

[Clay Wright]

Quick question:

but first, I've read about how one can add a small series resistor to compensate for ESR when replacing electrolytic caps with film caps, but it seems most of the talk is with tweeters that I could find clear explanations for.

It's obvious that when compensating for the ESR with a tweeter you'd add, say 1/4-1/2 ohm unless the electros were super old then possibly up to even an ohm of series resistance, but how would you go about adding the resistor to a parallel woofer cap? Does it go somewhere in series with the woofer or do you simply add it before or after the paralleled cap in the circuit (as in series with the cap but still parallel in relativity to the actual circuit)?
It's late and this very well may be a stupid question I'm overthinking, but I've never tried using a compensation small value resistor. Anyway, any help on this mental block of mine would be much appreciated

*And yes I know ESR is frequency dependent but this is simply an experiment and either way it seems well agreed upon that this can be a positive fix even when considering it's given flaws*

 

[Doug G.]

The resistance is always added in series with the capacitor. It doesn't matter how the capacitor is connected in the circuit. So, if you had a capacitor connected in parallel with a woofer, you would disconnect one end of the capacitor and put a resistor in that gap.

Doug

 

[DEFTECHY]

Why are you wanting to replace a woofer lytic cap with a film cap? I dont know what speaker you are working on but most woofer caps arent in the signal path like mid/high freq caps, woofer caps are just a "dump" so to speak for the woofer. Most guys just replace the woofer cap with teh same kind, and since they are usually a higher value, a film cap will usually be very large physically and may not fit on the original board or PCB.

A good brand modern electrolytic cap is better than 30-40 year old caps and should last for a very long time, the size/cost of a high value film cap for the woofer is probably not worth it IMO.

 

[Clay Wright]

The resistance is always added in series with the capacitor. It doesn't matter how the capacitor is connected in the circuit. So, if you had a capacitor connected in parallel with a woofer, you would disconnect one end of the capacitor and put a resistor in that gap.

Doug

Thanks Doug. This is what I assumed and I'm glad I did. I knew that it always is suppose to be in series with the capacitor but it was late and I was overthinking the series aspect of it. I took a step back and thought logically and said to myself - well that wouldn't make much sense to have a random resistor in series adding to amplifier load while a cap is shunting to ground haha classic example of GO TO BED!

 

[Clay Wright]

Why are you wanting to replace a woofer lytic cap with a film cap? I dont know what speaker you are working on but most woofer caps arent in the signal path like mid/high freq caps, woofer caps are just a "dump" so to speak for the woofer. Most guys just replace the woofer cap with teh same kind, and since they are usually a higher value, a film cap will usually be very large physically and may not fit on the original board or PCB.

A good brand modern electrolytic cap is better than 30-40 year old caps and should last for a very long time, the size/cost of a high value film cap for the woofer is probably not worth it IMO.[/QUOTE

Because it does make a major improvement on sound, believe it or not. You'd think that since the cap is shunting to ground that it wouldn't, but believe me when I say it does. Btw the speakers are the Klipsch RP600M stand mounts.

Confirmed with back and forth AB testing from one speaker to the other, side by side, all things equal other than the woofer cap. Even my tone deaf girlfriend was able to discern that without hesitation- and that was without me saying which one I had changed when switching back and forth by remote. It's really quite crazy how much that capacitor makes a difference. More than anything, it gives the "pitch black" background and totally aligns all the "smeared" macro details from the midrange of the woofer. I don't want to get all figurative with audiophile descriptions for what it does to the signal, but that's the easiest way to put it.
I will say that the electrolytic capacitors give a bit of a hump to the lower midrange, but this is a bloated hump and very undefined in the sound it recreates for listening.

It's a shame, too, because there actually is something kind of pleasant the electros do to the sound of the presentation as a whole, but the amount of clarity that gets robbed in no way outweighs the benefit of being a bit more smooth. Note: This is only a benefit with bright or horn speakers btw.

I suspect this has something to do with the degree of 2nd harmonic coloration they add as well as the ESR increase with frequency.

Just my 2 cents
- Clay

 

[DEFTECHY]

Ok. I dont doubt what you hear since each person hears different, if you like it thats all that matters.

If you are familiar with Bob Crites, he has said that woofer cap doesnt have much if any effect on the sound since its just a dump and not in the main signal path... all Crites capacitor kits and complete crossovers use an electrolytic cap there just like the original design. Since these are klipsch speakers, you might get more specific replies in the klipsch korner sub section here?

Do you have an ESR meter to measure the original cap or the new film cap? Without a tester its kind of a guess as to what the final ESR will be. From the testing Ive done recently, some film caps can have higher ESR than others, and some film caps are close to a good electrolytic, So if youre trying to match the original, a ESR tester is a good idea.

 

[gadget73]

its critical only in the sense that it should be on value. If its significantly off, it shifts the crossover point. That was the only bad cap in my Klipsch speakers, the other two were film and perfectly fine.

 

[Clay Wright]

Ok. I dont doubt what you hear since each person hears different, if you like it thats all that matters.

If you are familiar with Bob Crites, he has said that woofer cap doesnt have much if any effect on the sound since its just a dump and not in the main signal path... all Crites capacitor kits and complete crossovers use an electrolytic cap there just like the original design. Since these are klipsch speakers, you might get more specific replies in the klipsch korner sub section here?

Do you have an ESR meter to measure the original cap or the new film cap? Without a tester its kind of a guess as to what the final ESR will be. From the testing I've done recently, some film caps can have higher ESR than others, and some film caps are close to a good electrolytic, So if you're trying to match the original, a ESR tester is a good idea.

I actually don't have the ESR meter I was using. It was just one of the cheapo MK-328 (I think that's what they're called) Chinese meters but it is gave a fairly consistent ballpark range for ESR. I need to grab another one. Plus I need to get an inductance meter while I'm at it. I've actually never had one of those.

In regards to the comment about Crites crossovers, keep in mind that what he is referring to is an actual woofer in the 3 way heritage series Klipsch classics. My situation is different because, by "woofer" , I'm actually really referencing what is essentially a midrange driver that covers some upper low end duties but also is playing clear up to 1500 hz or so (a bit more if you count the cut off slope frequencies). In other words, his comments only pertain so much to what I'm working with because, for the most part, he was correct about how the cap is essentially only shunting low end to ground + the fact that electrolytic caps handle low end duties just fine since this is what they are designed for, but even though my cap is still acting as a shunt, it REALLY shows itself with its ESR and other parasitic effects throughout the midband. It really does make a world of difference using a film cap of any sort. I'd go as far as saying I'd bet my life that you would easily identify the difference in a simple A-B listening test.
Always good to share personal as well as listen to other's knowledge and philosophy in this hobby
- Clay