Capacitor upgrade in crossover - Is it audible?

[ctrl]

Replacing 20 year old caps is fairly silly. There is an enormous difference in the construction, chemistry and lifespan of a cap made in the 90s vice something of 60s/70s vintage.

This will also be tested in the next part. For my 100µF Visaton electrolytic capacitors from about 1985 it actually looks quite good.
Stay tuned...

 

[Shazb0t]

I wished you would've compared some 20+ year old electrolytic caps. Because those are the ones people are most likely to replace.

Nobody really questions replacing old caps which no longer measure the proper capacitance. This was about if there are audible changes from replacing perfectly functioning/measuring lower priced caps with "audiophile upgrade" caps.

 

[Rick Sykora]

While from quite a while ago, these "quality" component myths must be so marketable that I found one seemingly reputable high-end manufacturer claiming to use air-core inductors when they were not. While visually the inductor appeared to be air-core, found an iron-core when I was salvaging it from the board.

 

[bigx5murf]

Nobody really questions replacing old caps which no longer measure the proper capacitance. This was about if there are audible changes from replacing perfectly functioning/measuring lower priced caps with "audiophile upgrade" caps.

Thing is even 20+ year old electrolytic, despite drifting from age, are still usually in spec, especially if they're rated +/- 10% tolerance. There is an industry built around crossover "upgrades" with high end caps. Look at the Polk SDA series, custom crossover boards, with high end caps easily cost more than the market value of the speakers they're meant to upgrade.

 

[DualTriode]

Hello All,

Several days ago I also did some testing with a capacitor and tweeter as well.

One thing that I noticed is that a resistor in series with the capacitor and tweeter driver made a difference in terms of phase.

Another thought is that a tweeter will almost always have a resistor in series with it to pad the output. There will be some kind of Time Constant that will change with series resistance.

Seems to me that there may be several things that not being measured that could make an audible difference.

To name one, there may be a phase/time change between the tweeter and midrange at the crossover frequency causing a shift in the crossover lobes. In you are replacing an old dried out electrolytic cap with a film cap with lower ESR the sweet spot where you sit and listen may not be so sweet any more.

Thanks DT

If it is a very expensive cap exchanged for for a much cheaper film cap then no bets.

 

[solderdude]

That's why L-Pad (circuits) exist. These attenuate without changing the crossover frequency.
Using 1 resistor in series with a driver only works correctly when the filter is designed to work with it.
I do not recommend to simply add a resistor in series with a driver or change the value(s) without looking at the crossover.
Only using an L-Pad = a (variable) voltage divider with constant input resistance. you can change levels safely.

 

[Hiten]

This will also be tested in the next part. For my 100µF Visaton electrolytic capacitors from about 1985 it actually looks quite good.
Stay tuned...

Thanks very much for the test. How will be the electrolytic capacitors be tested ? Since you have 35 yr. old electrolytic capacitor, if it is not too much effort can you please test capacitance before putting them in any circuit. This way we may even know that old capacitor (if) dried can be reformed or not. and how much capacitance value changes before after running them for few hours.
Thanks again for the effort. These are very informative tests in audio hobby.
Regards

 

[Trouble Maker]

Thanks very much for the test. How will be the electrolytic capacitors be tested ? Since you have 35 yr. old electrolytic capacitor, if it is not too much effort can you please test capacitance before putting them in any circuit. This way we may even know that old capacitor (if) dried can be reformed or not. and how much capacitance value changes before after running them for few hours.
Thanks again for the effort. These are very informative tests in audio hobby.
Regards

Ohhh... they've just sat for too long and need broken in again.

 

[Hiten]

No I am not talking about break in or hardly I believe in it.
I said (if) they are dried wanted to see the difference in capacitance before first use and after few hours run in.
Regards.

 

[Juhazi]

Second opinion here http://www.humblehomemadehifi.com/Cap.html

An example:
"Sound: I can agree with Audience AV in that the Auricap XO is definitly more transparent than the standard Auricap. I found the XO to still have a pleasently smooth and clear presentation but gone is the slightly forward nature. The are more open and have more fine detail. These characteristics make it easy to follow the leading edge of instruments and create a greater sense of depth in the recording. Compared to the extremely neutral Jantzen Audio Superior Z-Cap there is more clarity, while maintaining a similar level of neutrality. Although there is lots of detail the XO never becomes edgy or sharp like some other "detailed" capacitors can sometimes be. Comparing the Auricap XO to the Jantzen Audio Amber Z-Cap it is obvious what you don't get with the XO: the rich and natural tone that only true copper foil capacitors can give. But that is an unfair comparsion as those type of capacitors cost a multitude of the Auricap XO. Overall I found the Auricap XO to have a nice balance between detail, transparancy and smoothness. I have added it to my favourites list. "

 

[Trouble Maker]

No I am not talking about break in or hardly I believe in it.

Sorry if my sarcasm did not translate well, it was meant as a joke.

 

[Hayabusa]

0) What does a capacitor in the crossover of the chassis do?

To put it simply, the capacitor lets the high frequencies pass and suppresses the low frequencies and in our case creates a high pass.

The example below shows an ideal driver (frequency response would be dead straight at 90dB sound power level, also ideal constant 8 Ohm impedance).
The brown curve shows the frequency response of the ideal chassis with a 2.7µF capacitor in the crossover section of the driver, the red curve shows a capacitance of 12µF.
View attachment 56197
You don't need to know more to understand the review.

So what kind of signal levels are we a talking about?
90dB@ 1meter, so around 2-3 volts RMS?

Could it be there will be more significant distortion at higher/extreme signals levels?

 

[solderdude]

Could it be there will be more significant distortion at higher/extreme signals levels?

But will increased measured distortion in such case from the driver or microphone rather then a series capacitor.
Of course, in a speaker there will also be plenty of low frequency voltages across the capacitor which ca easily reach 30V or more.

 

[ctrl]

So what kind of signal levels are we a talking about?
90dB@ 1meter, so around 2-3 volts RMS?

In order to keep the distortion contribution by the measuring microphone as low as possible, a level below 90dB@1m was measured. Because the microphone was <0.02m away from the tweeter during the measurement and at [email protected] there is a sound pressure of about 124dB at the microphone (Which is no problem for the used measurement microphone). The measuring voltage should have been 1.5-2V.

Could it be there will be more significant distortion at higher/extreme signals levels?

I would doubt that. A "normal" film capacitor usually has a dielectric strength of 400V. The used tweeter would deliver already more than 100dB@1m sound pressure at 10V.

 

[DualTriode]

That's why L-Pad (circuits) exist. These attenuate without changing the crossover frequency.
Using 1 resistor in series with a driver only works correctly when the filter is designed to work with it.
I do not recommend to simply add a resistor in series with a driver or change the value(s) without looking at the crossover.
Only using an L-Pad = a (variable) voltage divider with constant input resistance. you can change levels safely.

Hello All,

An “L-Pad” is a voltage divider.

Take a look at the attached, even with an “L-Pad” there is a resister, R1, in series with the driver and in this case a capacitor is also in series and the phase of the driver output will shift with the selection of the L-Pad resistors. The Time-Constant will shift as the values of the resistors in the L-Pad are varied.

Yes the crossover frequency will stay the same (mostly) however the phase of the driver output will shift and the drivers, mid and tweeter beaming or output lobes will shift to some degree. The output lobes will shift vertically if the tweeter and mid are stacked one over the other. This is easily audible.

Thanks DT

https://www.electronics-tutorials.ws/attenuators/l-pad-attenuator.html

 

[ctrl]

One thing that I noticed is that a resistor in series with the capacitor and tweeter driver made a difference in terms of phase.

Please read the whole test, there it is described under 1) that the measurement of a single driver represents a minimal phase system and therefore the phase information can be derived directly from the frequency response.
This means that if the frequency response practically does not change, as shown in the tests, the phase does not change either.

Seems to me that there may be several things that not being measured that could make an audible difference.

Not as far as the capacitor comparisons are concerned.
... one more time, please consult on minimal-phase systems.

 

[DualTriode]

Please read the whole test, there it is described under 1) that the measurement of a single driver represents a minimal phase system and therefore the phase information can be derived directly from the frequency response.
This means that if the frequency response practically does not change, as shown in the tests, the phase does not change either.


Not as far as the capacitor comparisons are concerned.
... one more time, please consult on minimal-phase systems.

So if you change out a capacitor in you speaker crossover and only listen to the tweeter you are correct.

You are the OP, you make the rules.

We will leave it at that.

 

[Hiten]

Sorry if my sarcasm did not translate well, it was meant as a joke.

No Problem.
2nd part of continuation of this thread is posted. And old capacitor is measureed and it still is holding capacitance value. So well made capacitor of yesteryears may be good and no need to replace or reform. Thats what I was curious about.
Best regards.

 

[ctrl]

Hello ctrl and friends,

Thank you for this interesting thread. Although I do not have skill and tools for full objective measurements like ctrl described, last summer I experienced great improvement of total sound quality by renovating LC-network+attenuators of my SP, YAMAHA NS-1000. I can say "it is audible for sure!". You would please refer to my post here.

At that time, all of the capacitors, coils and attenuators were replaced by new ones; with high-grade audio film capacitors, with air core thick coils and with fully overhauled/cleaned attenuators. The new alignment of the coils was carefully designed to minimize the possible electromagnetic interactions. Furthermore, I took all the LC-network+attenuators out of the SP cabinet and installed them in a outer network box. All the cabling/connections were done by careful soldering using AWG12 cables.

At that time, I used two of 47 uF (microF) electrolytic chemical capacitors (MUNDORF Ecap100v-47.0uF) for woofer, but in February this year, I changed them to film capacitors MUNDORF MCAP250-47t (white big ones), and again the improvement of woofer's sound was clearly audible.

Through my above experience of renovation of LC-network+attenuators, the total sound quality was much improved in;
- cleanliness and transparency
- speed, especially in low frequency
- sonority (so called..?)
- 3D sound perspectives (really amazingly)
and "it is audible".

I believe not only the new capacitors but also the new coils, the coil alignment in larger space, careful soldering connections with thick wire, new attenuators, and moving all of them into outer box, are all together contributing the significant improvement of the total sound quality.

When replacing the components, did you measure them with a simple LCR meter to make sure that the values are as accurate as possible?

When replacing the coils, did you make sure that the DC resistance of the coil was not changed.

If not, it's no wonder that you hear a significant difference in sound, since practically a new crossover tuning has been created.

 

[dualazmak]

When replacing the components, did you measure them with a simple LCR meter to make sure that the values are as accurate as possible?

When replacing the coils, did you make sure that the DC resistance of the coil was not changed.

If not, it's no wonder that you hear a significant difference in sound, since practically a new crossover tuning has been created.

Sorry, but I moved my post to your "part 3" thread...