Copyright 2024 Troels Gravesen


Please read response here from people up-grading from standard PP caps to super-caps:

When I first had Superior-Z caps.

First of all this is not an attempt to evaluate the sonic differences between super caps, merely to find out what super caps are and why we pay an indecent amount of money for them. I use the term "super-cap" for caps costing in the range of 5-10 times the cost of a standard polypropylene capacitor. We're used to paying in the range of 4-6 USD for a 4.7 uF standard PP, where a similar super-cap is around 20-40 USD. Quite a difference.
Caps, like coils and resistors, are necessary evils in making our speaker crossovers work in dividing the frequency band into the sections meant for our drivers. Capacitors in series with our drivers will prevent low frequences from reaching our drivers and form a high-pass filter. Good coils and resistors can be made for very little money, but capacitors are another story. Depending on materials used and winding technique they will pass the signal with more or less fidelity and the quest for better sound transmission really started already in the Sixties and in the Seventies where we saw speaker crossovers fitted with film capacitors, usually made from metallized polyester in replacement of the common bi-polar electrolytic capacitors. Metallised polyester was certainly not the final word in this quest and metallised polypropylene became standard if we wanted something better. Solen polypropylene soon became standard for many speaker manufacturers launching high-end speakers.
Now, there are people who question the sonic value of super caps claim them to be all hype and woodoo. To my experience the sonic benefits of good caps can be heard from even modest equipment; the question is at what time point we may start investing in good crossover components compared to up-grading other parts of our system. Maybe money would be better spent on a new phono cartridge or a better amplifier. Identifying bottlenecks in out system is a never ending journey - and part of our hobby.
I've had mails from people missing the "detail" and - most surprisingly - "transparency" of e.g. Bennic caps once they changed to super-caps. Bennic is to my experience at the bottom of the quality ladder. To my thinking these people have gotten so used to the sonic distortion of the Bennics, that this - to my ears - harshness is perceived as detail and transparency. Whenever things get darker from changing standard caps to super-caps, we're - to my experience - on the right track. For the same values, uF, of the capacitors, the frequency response will not change. The e.g. treble level will be exactly the same as before, yet the hizz and distortion poor caps add may be missed - and generally perceived as detail and transparency. How our brain process the information from our ears is an overlooked parametre - and one that cannot be quantified. It's called taste and habit. Two very strong players.  

In most marketing material we will read that super caps are made from two series-coupled, inter-wound capacitors, thus four times the normal size of a capacitor of same value as two e.g. 10 uF in series will measure only 5 uF. A standard cap looks like this (illustration from Wikipedia): 

To find out what we're buying there's really no alternative to simply un-wind the caps and see how they are made.
I've taken apart two well-known brands of super caps and this is what I found: 

Un-winding a super cap takes time! Usually super caps are sealed in a metal tube made from aluminum or brass, both non-magnetic materials.
Next we find various layers of extremely had ceramic-like material and plastic fillings. I never thought plastic could be this hard.

Maybe 30-50 meters of foil can be unwound from this 4.7 uF super cap! I only made a rough estimate.

Please view image above. This is where things become interesting as we at the end of the foil can identify two foils, one foil consisting of a full width metallised polypropylene with plastic foil edges, thus does not connect to anything. Laminated with this foil is another foil having two lanes of metallised foil. What we have is this:

As a matter of category, super caps are "standard" high-voltage capacitors and well, can be characterised as two series connected capacitors, in patent terms "metalised film series section capacitors", and there are quite a few patents in this field.

But there are more to good caps than two-lane foils providing high voltage capability: Quality of the foil, tightness with which it is wound and not least the "wrapping", being molded into rigid materials and finally sealed in tubes to prevent any vibration from distorting the signal passing the capacitor. This is where things get tough. The actual conducting foil can be metalised polypropylene, usually aluminum, but also pure silver or silver mixed with e.g. 1% gold. On top of this pure foil (no plastic) can be used with insulation made from oiled or waxed paper. The insulation (yellow colour above = dielectric material) can also be teflon, which is particularly troublesome in winding (soft and has holes. I've seen vintage Russian teflon caps wound on two layers of teflon to overcome the problem of holes in the foil as it is highly unlikely two holes would be at the same spot). 
And we shouldn't forget tin-foil. Tin has the advantage of weight and by sheer weight reduce vibration. To my ears the most cost-efficient caps for audio are tin-foil caps, but they rarely deliver the ultimate resolution of super caps. Tin foil caps are usually "standard" caps in terms of winding technique, but are serious competitors to super caps, in particular as coupling caps in amplifiers. I never tried tin-foil caps for speaker, but would like to some day. I guess V-caps, TFTF, are not double lane super caps, but made from tin-/alu-/copper-foil and Teflon, hence the astronomical price tag, but I'm not sure and haven't taken one apart.
Some super caps are also wound in a non-oxygen atmosphere, e.g. nitrogen. This prevents the extremely thin metallised foil from being oxidised with possibly subsequent sonic degradation. Production obviously becomes more expensive from these precautions, but whether this really is an issue, we don't know. People come up with a lot of stuff meant to make us believe their product is better than others. 
Latest addition to the range of super-caps I've tested is the Jantzen Audio Alumen-Z, being a bit above double-lane super-caps, despite being a single lane foil, rather than metallised polypropylene. They provide the same resolution with a tad more neutral sound. The polypropylene foil separating the aluminium foil is very thin, thus 100 volt max can be applied. This is by far good enough for speaker crossovers. Reduced thickness of foil means less storage of electrons = reduced memory = less smear of details. Whatever is going on, these foil caps provide qualities on par with the double-lane caps and the thing is that even double-lane caps can add a certain colouration to the sound - although miniscule.
Super-caps can sometimes make music sound just a little bit better than life by adding a certain sheen/glair/brightness/radiance to particularly high frequency content. There may be psychoacoustics involved here leaving us to believe one cap delivers more transparency than another. English is not my native tongue and different words that may be used to describe the issue, so take your pick. I wouldn't use the word lush. Lush is more related to 2nd harmonic distortion to my thinking.
Currently I'm testing low-voltage copper foil capacitors (Jantzen Audio Amber-Z) for crossovers and these appear to even better the aluminium foil caps. Not much, but a little. Major problem with copper foil caps is size and not least costs. They cost a fortune.

Single lane foil, high-res, thin insulator capacitors for crossovers


Single lane foil, high-res, thin insulator capacitors for crossovers.
If you can't live with the thought of not having the most expensive. Sometimes a tad better than Alumen-Z, but it may come down to actual recording.

When I had my first Superior-Z caps

This goes all the way back to my Acapella NEXT build in 2007.

Testing standard PP caps against Superior-Z and Alumen-Z caps. The change can be done from listening seat due a double relay changing input to the caps.

This is difficult! Having set up the two speakers as described above, the fun started. One speaker with Superior Z-caps (SZC) to the mid, the other with Cross-caps (CC). All other things the same. Frequency response was checked and was the same for the two speakers within 0.5 dB. It's hard to get any closer than that. In my workshop I have a connection panel attached to the power amp so that I can switch between two pairs of speakers.

The two speakers certainly didn't sound the same. One brighter than the other. The CC version sounded brighter compared to the SZC, but at the same time, while listening to the SZC version my perception of the sound could swap - and all of a sudden I could hear the Superior Z-cap version being the brightest. Weird!!
The problem is this: With the CC the sound is somewhat more compressed compared to the SZC version. With the CC the midrange appears to be located around the speaker front panel plane, where the SZC has a significant deeper soundstage, thus less presence is perceived, yet it allows you to focus your attention on the bright (treble) parts of the instruments and voices and then - brighter. Quite simple actually. The SZC will allow you to focus on details that standard MKPs cannot resolve.

During this exercise I changed the position of the speakers from time to time - left and right. These are dipoles or rather semi-dipole speakers and highly dependent on room position. However, still what is described here followed the speakers no matter what position they had. The SZCs simply reveals details and a depth in the acoustic scenario the CCs are not capable of. The CCs certainly aren't bad, not at all. They very much sound like what we're used to hear from the majority of hifi-speakers. Even if you don't have high-quality front end gear, SZC will improve sense of depth and perspective.

I better order 6 x 22 uF SZC. Having bundled my residual stock of Superior Z-caps I now have both running with SZCs and they are in my living room right now, driven from my 20 wpc SET amps. Thank Heaven I didn't get rid of the Acapella cabs during my Autumn sale. 20 wpc do well, even up to considerable levels, but ultimately I recommend 40 wpc really high-quality watts for these 90 dB/2.8V speakers. It will provide a more firm bass and the ability to play really loud too.

What more can I say?
Well, if you have some 10-15 kilo US $ burning in your pocket for a pair of commercial speakers, ask your carpenter what he takes for a pair of Acapella cabs. You may save megabucks in doing so.
OK, OK, I know, but as one of my American colleagues always says: "It ain't bragging if it ain't lying!"