Before we talk about which are the best audiophile capacitors, let’s talk about what a capacitor is in the first place. A capacitor is one of the 3 passive electrical components : resistors, capacitors and inductors. A capacitor is basically a frequency dependant resistor. A resistor blocks all frequencies, however, a capacitor only blocks low frequencies. The rating of the capacitor (in Farads) determine which frequencies pass or not.

In the actual construction of the capacitor you will find 2 pieces of material which conduct electricity (called electrodes) and sandwiched between them, an insulating layer (called dielectric). Since we got a piece of material that doesn’t conduct electricity (the dielectric), doesn’t that mean that the circuit is now open? Well, yes and no.

1. If you are passing AC current, then you will get that property that we talked about earlier. Some frequencies will pass, and some will not, depending on the size of the capacitor (cap for short).
2. If you are passing DC current, then the cap will act like an open switch. However, in this case, all the positive charge will bunch up on one side of the cap, and all the negative charge on the other side. They want to reach each other, but can’t, because there is the dielectric in the way. If you remove the cap from the source, you will still have that charge in the capacitor. That’s why a capacitor can hold a charge. If your source has too much voltage, then the dielectric cannot hold the 2 charges separated (negative and positive), and the dielectric is ripped apart. In this case, the capacitor is destroyed. That’s why the capacitor is rated in VDC.

Best audiophile capacitors – what to look for?

Besides the obvious thing, which is the capacitance value, what should you look for in a capacitor? If you want the best audiophile capacitors, you have to get the best in most of these properties :

• The type of dielectric.
• The material used for the conductor plates.
• The material used for the wires.
• The ESR (equivalent series resistance). Usually this is negligible for a capacitor (not so much for inductors).
• Rated voltage. Some capacitor types have low voltage rating so be careful.
• Tolerance (the error margin from the quoted value, in percentage).
• Other proprietary techniques : like how the capacitor is wound (for film capacitors), Oil impregnation etc.

These are all capacitor traits that you need to look out for. However, besides these properties, when it comes to audio grade capacitors you will find mainly two types : electrolytic and film capacitors. Don’t get me wrong, there are a lot more types out there, but we are talking about the best audiophile capacitors, and these 2 are the top picks. Normally,  an electrolytic cap is polarized. This means that it’s important to check the polarity when you connect it. However, in audio you will find only bipolar or non-polarized capacitors. This means that you can wire however you want. It doesn’t matter.

Electrolytic capacitor

When it comes to audio grade capacitors, the electrolytic capacitor (Amazon affiliate paid link) is the budget option. Compared to the film capacitor, the electrolytic cap is considered to be inferior, from the standpoint of sound quality. Some argue that if your loudspeaker is not super high-end, these types of caps are quite suitable and the difference is hard to tell. We will get in a minute into the strengths and weaknesses of this type of cap.

Like any other capacitor, the electrolytic cap has 2 electrodes and the dielectric. One electrode is covered in some oxidized material (which servers as the dielectric), and the other electrode is some sort of electrolyte, which is either solid or liquid. Depending on the materials used, you can reach really high capacitance levels in a small form-factor. These are the main pros for the electrolytic capacitor : the price is reasonable and it’s small in size.

The shortcomings of the electrolytic cap

On the downside, besides the fact it doesn’t match the sonic properties of the film capacitor, it has a low VDC rating. This can be an issue in some sections of the crossover. You will see film capacitors with 250, 400 VDC ratings, no problem. However, electrolytic caps usually hover around 63 VDC, which is pretty low.

To get around this issue you can wire multiple caps in parallel. For example, if you need a 100 uF cap. You can wire 2 x 50 uF caps in parallel. You get the same capacitance level, but double the power handling. Other times, people opt to wire in parallel a very low capacitance film capacitor. Some say that by doing this, not only you are increasing the power handling, but also gain improvements in the sound quality department. This is easily done, because a low capacitance film cap is small and cheap.

One other downside of the electrolytic capacitor is that it degrades with time. So if you plan to keep your speakers for 15+ years, make sure you choose film capacitors. Since the electrolytic capacitor uses chemicals, it has a limited lifespan, so take this into consideration if you want to take the budget route.

Film capacitors

One of the best audiophile capacitors out there is the film capacitor (Amazon affiliate paid link). Don’t get me wrong, these branch out into all kinds of types. Like I said in the beginning. Watch out for the materials used in different areas of the capacitor.

The main difference is in the construction process. It uses a sheet of conductive material and add a sheet of insulator on top. And you simply roll that up into a cylinder. As you keep rolling, you will get higher and higher capacitance values. So if want high capacitance values, expect to see a capacitor the size of a can of coke.

The wounding process of the capacitor and the placement of the electrodes, creates a desirable effect. It’s like placing a lot of smaller capacitors in parallel. For this reason, the capacitor issues a very low ESR. So, besides the sonic capabilities, this is why you would choose a film capacitor over an electrolytic. But also take note that as you increase the capacitance, the price can get ridiculously high and the size as well.

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Polypropylene is the material of choice for the dielectric. If your caps mentions this word, odds are favorable that it’s a good cap. Of course, there are other material choices out there for the dielectric. To mention some : polyester, polycarbonate, paper etc. While some material may excel in certain areas, polypropylene is a great all-rounder.

Some capacitors are metalized, which contain a vacuum-metalized metal layer, which gives the capacitor self healing properties. The metal coat evaporates in the damaged area of the dielectric, which insulates it. Sometimes oil is used to fill out all the hollow spaces. This is to reduce electrical and mechanical losses due to vibrations.

Conclusion

To answer which are the best audiophile capacitors? The answer is : it depends. First of all, it depends on your budget. Film capacitors can get really expensive. So, there is no need to triple the price of your project just to use the best capacitors. Maybe you need a 100 uF cap, and don’t want to place on the crossover board a capacitor the size of your fist. Go for an electrolytic.

You might be wondering why only these 2 types? These are the most suitable for audio. For example, ceramic capacitors  have a piezoelectric effect, meaning vibrations can cause voltage changes. This would be super bad for audio. On the other hand, electrolytics caps are just fine. Even though they are considered the budget option, they are widely spread and sound just fine. Some use film for the direct signal path and electrolytic for the rest. It’s all up to you. To name some brands which produce good capacitors : Mundorf, Jantzen, Clarity Cap, Bennic, Solen, Axon, Visaton, Obbligato-Cap, Audyn-Cap etc.

References

1. Mundorf components catalog.