Before and After Capacitor Replacement Measurements

[SamIAmSam]

Hey folks.

I've done a bit of digging around on this forum with the Search utility, but I've not been able to find an article that features a Before & After set of test results on swapping new capacitors into an old pair of otherwise functional speakers... I am just about to hit the "Buy" button for a UNIK-1 microphone so that I can use it to do this kind of evaluation on an old pair of KEF Cantatas that I have a replacement kit from Falcon Acoustics for.

However, if this kind of thing has been done before on this site, and the results were repeatable and settled, perhaps I'll give this process a pass.

Appreciate your input.

Andrew D.

 

[solderdude]

Best to measure the electrical signal directly at the driver instead of using a microphone.
Also you will always find some differences near the crossover frequency for the simple reason that components have a tolerance.

And yes, capacitor swap in speaker XO has been done on ASR.

Audible difference in high-end capacitors? - ABX samples

As announced long ago the last part on the subject of audibility of capacitor upgrade in crossovers. The comparison ranges from a very cheap, decades-old film capacitor to an expensive high-end capacitor. As promised, this time there are short audio samples of each capacitor (in a simple...

www.audiosciencereview.com

Capacitor upgrade in crossover - Is it audible? - Part 2

Here is the second part on the topic "Capacitor upgrade in crossover - Is it audible? This time it is exclusively about the measurable differences of electrolytic capacitors with film capacitors in crossovers of loudspeakers. The first part about film capacitors can be found here and who likes...

www.audiosciencereview.com

 

[Old_School_Brad]

You can anticipate the result if you measure your old capacitors beforehand -they’ve likely lost some capacitance. Also, make sure to measure the new capacitors before installing them.

Any perceived differences people hear are more likely due to the loss of capacitance in the old capacitors, rather than the new capacitors providing any inherent audible benefit.

 

[YSDR]

You can anticipate the result if you measure your old capacitors beforehand -they’ve likely lost some capacitance.

Or it has gained some capacitance, as is often seen with electrolytic capacitors (not with films), and the ESR value usually changes. In addition, replacing an electrolytic capacitor with a film capacitor (or vice versa) inherently involves a change in ESR value, which usually affects the acoustic response of the speaker.

 

[Old_School_Brad]

Or it has gained some capacitance, as is often seen with electrolytic capacitors (not with films),

I appreciate your perspective, but I must respectfully disagree.
Based on my experience and understanding of the component, an electrolytic capacitor loses capacitance primarily due to the drying out of the electrolyte, chemical changes over time, or the damage and thinning of the oxide layer.

 

[thewas]

Here are some comparative measurements I had done:

Capacitor upgrade in crossover - Is it audible?

If you wonder why the phase of the measured capacitors (which should be at -90°) suddenly becomes "inductive" (phase at +90°) from a certain frequency on, this is due to my laziness. The correct calibration of Arta-LIMP is time consuming and was not necessary for these measurements (up to...

www.audiosciencereview.com

Here is also a bonus photo of the crossover with the original vs the replaced foil caps:

 

[Mnyb]

Yes @ctrl has a wonderful series of articles about capacitors , he unravels the biggest issues especially in crossovers the tolerances are large in capacitors and the some parasitic values as resistance etc. can bee different So you're actually changing the circuit ! of course its different .

In the articles solderdude linked ctrl makes efforts to tigthly match most factors that can confuse the results .

Kef has done some if this in thier whitepapers on some of thier speakermodels

 

[AnalogSteph]

Or it has gained some capacitance, as is often seen with electrolytic capacitors (not with films)

They actually don't. This is a measurement artifact related to the way multimeters typically measure capacitance, and it actually indicates excessive leakage current as a result of dielectric layer breakdown. A proper (not entirely cheap) RLC meter should be more reliable in this respect. Either way, if you see that, odds are the capacitor either is in serious need of careful reforming or can be filed next to the average dodo.

 

[YSDR]

They actually don't.

Thanks for clarifying!

 

[AnalogSteph]

On a side note, I'd think speaker capacitors would be prime candidates for gentle reforming, assuming the chemistry cooperates (some 'lytics just Will Not Reform whatever you do, e.g. ordinary '80s/'90s Philips polar caps come to mind - my guess is that electrolytic pH is so far off that the oxide layer is being attacked again right away). The classic smooth foil bipolar variant tends to be relatively big so evaporation losses should be less significant, with substantial voltage handling = dielectric thickness to begin with, and they obviously never see any DC for years and years in their intended application.

The main hurdle for most would be getting ahold of a relatively high voltage DC source (potentially 250-300 V) with high output impedance. Oldschool capacitor testers (think 1950s-1960s era) aren't exactly super common. There's always the DIY option with cascaded transformers, but obviously due care has to be applied due to the health hazards posed by voltages like that.