How To Add A Capacitor To A Car Tweeter

Norvan Martin
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Car tweeters produce a high-frequency sound from the sound wave coming into the speaker. These sounds are delivered as high-range treble that makes it possible to hear each lyric and tune properly. However, these tweeters are incapable of delivering those bass frequencies due to bass blockers without which your tweeter can blow.

Discover how you can add a new capacitor to your car tweeter to keep enjoying the highs and bass from your music while also protecting your tweeter.

Tweeters are delicate sound producers and as a result of their inability to produce a strong sound like the low-frequency bass, they get blown easily when they receive such low-frequency sounds.

How To Add Capacitor To A Car Tweeter Step-By-Step

A capacitor is used in tweeters to block any signal frequency that is lower than what it can process.

Step 1: Identify the Positive Terminal

The first rule when dealing with wires as a nonprofessional is to be careful. The wires can’t shock you, however, you might damage the wire from its source. Therefore, gently disengage the wires to connect the capacitor to it.

Next, identify the positive and negative terminal of the tweeter to connect. Join the leg-positive terminal of the tweeter to the capacitor. Solder a dot to the connection with an iron using the soldering iron to ensure that the connection does not move soon. It is only necessary to connect one cap to the positive terminal of the tweeter.

Step 2: Solder the Capacitor to the Tweeter

The capacitor has two legs on which wires are to be connected. However, only one of these legs is connected to the tweeter directly. The other leg is to be connected to the positive wire from the speaker itself. Connecting the two legs to the tweeter will cancel out all the sound from the tweeter completely.

Do the following:

  • Connect one leg of the capacitor to the tweeter’s positive terminal.
  • Secure the connection by applying solder with a soldering iron to prevent future movement.

Note: Only one capacitor is needed on the positive terminal. if you add a capacitor to both terminals, this will filter out all the sound, rendering the tweeter silent.

Step 3: Connect Speaker Wires

Now that both legs of the capacitor have been connected, leave out the negative wires from the tweeter and the speaker. Connect the two wires i.e. the negative wire from the tweeter and the negative from the speaker. Strengthen the connections together by soldering them together.

Step 4: Complete the following

    1. Attach the positive speaker wire to the other leg of the capacitor.
    2. Connect the negative speaker wire directly to the tweeter’s – (negative) terminal.
    3. Solder these connections for stability and reliability.

Step 5: Reinstall the Tweeter

Return the tweeter to its box and repack the speaker packet the way it was before disassembling it. Once the connections are secure, refit the tweeter to its original position in your vehicle.

Best Capacitor For Tweeter Crossover

Choosing the best capacitor to use for your tweeter is mostly dependent on the value of its capacitance and many other factors including how well it controls the frequency flow; dielectric type; the capacitor wire material; how high or low its voltage; and other factors that are determined by its compatibility specifications.

However, the best kinds of capacitors that deliver quality sound for tweeters are basically:

  1. Electrolytic capacitor; and
  2. Film capacitor

Although, most of the time it depends on your choice as long as you want the best for your tweeter, you might most likely have to choose between these two.

Why? This is because these two are the most stable forms of capacitors for audio use.

For instance, capacitors such as ceramic ones have a vibrating effect which might often lead to change in the current. Another factor that influences the reason for selecting the two capacitors is the fact that they are budget-friendly.

Tweeter Capacitor Value

Capacitor value refers to the size compatible for use with your tweeter. Generally, the average capacitor value for a 4-ohms tweeter is 500uf for a bass frequency of around 100hz. However, the capacitor value is measured by the resistance.

Bass Blocker Capacitor Chart

The bass blocker capacitor chart will be presented using the 4-ohms and 8-ohm resistance tweeter:

Frequency in Hz Capacitor Value for 4-ohms Capacitor Value for 8-ohms
800 70uf 35uf
1000 50uf 25uf
1500 40uf 20uf
2000 25uf 13uf
5000 20uf 10uf
8000 8uf 4uf
10000 5uf 2.5uf


What Size Bass Blockers Are Needed For Tweeters?

Generalizing won’t work here! Before deciding what size bass blocker to choose, the first thing to consider is the frequency capacity of your tweeter.

This varies from brand to brand, which means that you might have two different cars with entirely different frequencies for their tweeter.

After checking the frequency of the tweeter, use the chart above to select the most suitable bass blocker for your tweeter.

Should Your Tweeter Capacitor Be Positive Or Negative?

Most capacitors are not polarized i.e.they are not distinctively divided into positive and negative. The audiophile electrolytic capacitor is polarized.

Which means that it has to be connected in the right pattern to function properly.

Therefore, determining the positive or the negative on a polarized tweeter capacitor requires careful examination. Below are some of the things to watch out for to differentiate positive from negative:

  • Red for positive; black for negative
  • A black stripe or arrow to indicate the negative side
  • Plus sign (+) for positive; minus sign (-) for negative

However, in some, there will be no form of marking. Simply check for an indented ring that represents the positive side.

How To Know If Your Car Tweeter Has A Bass Blocker?

Tweeters – either the one in your car or home stereo – can’t process low-frequency sound hence the need for capacitors to help them redirect those low frequencies coming into them.

How To Know If Your Car Tweeter Has A Bass Blocker

However, most speakers come with a crossover that efficiently distributes low frequencies to the woofers and the high frequency to the tweeter.

While thinking of changing or adding a capacitor to your tweeter, here is how you can confirm if there is one in your tweeter or not.

  • Separate the tweeter from the speaker box. Separate both the positive and the negative wires from the speaker.
  • Get a 9V battery. This battery has just the right amount of power to test the speaker’s response.
  • To know if there is a bass blocker in the tweeter, hold the positive wire on any one of the battery terminals and scratch the other terminal with the negative wire repeatedly. If there is a repeated distortion sound from the tweeter, then it’s an indication that there is no bass blocker built into the tweeter.
  • Repeat this process by changing the terminal where the positive wire is placed initially. If the distortion sound persists, know that the tweeter has no ready-made bass blocker in it and you might need to add a capacitor to block the low-frequency sounds. However, if there is just a one-time click sound instead of the repeated distortion sound from the tweeter on both sides, know that the tweeter has a built-in bass blocker working in it.

Built-in bass blockers naturally perform the function of the capacitors in blocking out the frequencies that might damage the tweeter.


Capacitors are essential in tweeters without ready-made capacitors to protect them from damage. However, it might be hard at times to say if a tweeter has a bass blocker built into it or not. Therefore you might need to check first to confirm if it has or not before fixing a capacitor in it. Finally, before adding your capacitor to your car tweeter, you may want to charge the capacitor first.

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Norvan Martin is the founder of He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin