What are car tweeter speakers & what do they do?

Your car's tweeter speakers are one of a handful of things that take your car's audio system from adequate to outstanding. Moreover, they enhance the overall listening experience and enjoyability associated with driving your car. 

If you're looking to upgrade the sound system of your BMW or any other vehicle, don't forget about the tweeters. 

This article will take a deep dive into the world of tweeters in the car audio realm. 

You'll learn:

• What are tweeters?
• Tweeter speaker powers, impedance, and other specs
• The benefits of using tweets in your car audio system
• Are tweeters worth it?
• Is it worth upgrading speakers for your car?

It's worth noting that a lot of the information in this guide is pertinent to all types of tweeters — home hi-fi systems, studio monitors, headphones, as well as car audio. 

What are tweeters in a car?

Car door tweeter speakers are the smallest type of speaker used to emit the highest frequencies of the audio spectrum. 

Tweeters create sounds that are often described as crisp or sharp. Technically speaking, tweeters usually produce frequencies between about 3 kHz and 20 kHz. For reference, human hearing goes up to and not beyond 20 kHz.

Fun fact: 20kHz is that sound you can't hear super well, or likely not at all once you hit 30. Especially if you frequented more than a handful of loud concerts as high frequencies at high volumes can cause irreversible damage to your ears. If you remember hearing quieter and ringing in your ears after leaving an event — your hearing probably suffered some damage that day.

You would think that all BMW’s these days would leave the factory with a decent audio system that is equipped with at least a pair of tweeters in the front but that is not the case. We don’t know why but in 2022 BMW’s most basic audio system is still not equipped with even a pair of tweeters and the base audio system is not even that rare. 

For example the current 3-Series BMWs even in the M340i version were occasionally made with the base audio system. It would have been understandable to see the base level audio system installed in a no frills manual 318d used in a fleet in Europe but in a M340i? Come on BMW.

If you have the most basic audio system in your BMW/MINI it will comprise of only four mid-range speakers in the doors and two small under-seat woofers to cover the whole audio spectrum. No tweeters to be seen on the horizon. Such an audio system is easily beat with a $200 Bluetooth speaker and you could take the latter to the beach too.

On the other side of the spectrum of BMW audio systems, you have the fairly decent Harman Kardon audio system in BMWs which has a total of seven tweeters to create a significant audio experience. Perhaps that’s where all the tweeters went ;) The HK system has been fairly difficult to come by in 2021-2022 due to chip shortages. 

Why should I install tweeters?

Can you imagine a chocolate chip cookie without chocolate chips? That’s exactly what an audio system without tweeters is. Tweeters are required for any audio system to produce high frequencies all the way to the limit of our human hearing range. Without them any audio system is simply deficient and limited. By installing tweeters you’ll get better sound quality overall and they will help give the music a sense of space and presence.

Female voices, cymbals, synthesizers, and distorted guitars will sound much better but also be heard how they were intended to sound which is what you should be aiming for with any audio system.

Tweeter speaker build/construction

You can say tweeters are built just like any other standard speaker. As you read earlier, tweeters emit sounds generally between 3 kHz to 20 kHz. 20 kHz translates to 20,000 cycles per second. Frequency, after all, is a measurement of cycles (or vibrations) per second. 

In other words, to recreate very high-frequency sounds, tweeter cones must vibrate insanely fast. This is also why tweeter speakers are small, to move more quickly!

There will of course be differences between how a specific tweeter from a specific manufacturer is built but many elements of a tweeter are universal.

The biggest difference, aside from the size, is that tweeter cones usually point outwards, toward the listener, compared to falling inward, away from the viewer, like a ‘normal’ speaker. As a result, most tweeter cones are called ‘domes’. At the end of the day a speaker cone or dome regardless of the exact shape is intended to move like a piston.

Attached to the dome is a cylinder called a former which is wrapped around with a wire called a voice coil. The tweeter dome also has a suspension around the outer edge. These elements are what moves in a tweeter making the sound and are joined into one assembly. 

The other essential parts of any tweeter get combined into a second assembly consisting of a magnet sandwiched between two metal plates (called a top plate and a back plate). These plates create a cylindrical magnetic gap in which the tweeter's voice coil will move according to the audio signal being fed to it. 

These two assemblies then get precisely glued to each other and voila — you have a tweeter. Of course it’s not as simple as that. In the process of putting the two together you have to attach the tiny voice coil wires to a set of terminals and maybe even fill up the magnetic gap with a special fluid. Our Alpha One Tweeters have the voice coil gap filled with a ferrofluid to enhance and maximize their performance. The presence of a ferrofluid increases power handling via enhanced heat dissipation from the voice coil and also reduces resonances so why not. 

Tweeter domes can be made out of many different types of materials, each having its own influence on the sound. There are often commonalities in the way aluminum domes from different manufacturers sound like, but the fact that the dome is made from a certain material doesn’t determine what a specific tweeter sounds like.

Alpha One vs. Harman Kardon Tweeters 

For example if you look at an Alpha One tweeter from the front next to a Harman Kardon tweeter taken from a BMW — you might think they’re actually one and the same. Furthermore you will find the Harman Kardon tweeter has all of the negative acoustic characteristics stereotypically assigned to tweeters with aluminum domes. They’re harsh, screamy and just over the top compared to our Alpha One tweeters that have a detailed yet smooth response without any such harshness. Just clean and precise sound. Why is that?

To use another culinary analogy — a cook and a chef can be tasked with sourcing the same ingredients to make the same kind of salad. The cook will get run of the mill industrial farmed and processed ingredients from the nearest supermarket and toss them together in a flurry. The chef on the other hand will visit his local farmers market to get produce straight from the farmer he knows doesn’t use any pesticides or herbicides on his lovingly grown produce. Once in the kitchen the chef will proceed to masterfully put together a salad with just the right amount of fresh and tasty ingredients to make a mouth watering feast. The saying “don’t judge a book by its cover” applies to tweeters too.

What do car tweeters do?

As you read earlier, car tweeter speakers create the high frequencies of the audio spectrum. High frequencies have a short wavelength, so they're crucial for creating clarity and stereo imaging.  

Tweeters in sound reproduction — stereo imaging

Tweeters are very directional, especially in the highest frequencies compared to lets say a subwoofer. If you listen to a tweeter off axis (from the side) — you’ll observe a significant drop in output when you're standing next to it compared to directly in front of it. Furthermore high frequencies are easily damped with curtains at your house or the carpet and headliner in your car.

On the other hand low frequencies can travel through concrete walls and can’t be damped out as easily nor can you tell exactly where they are coming from. When you compare these two behaviors you’ll understand why tweeters are essential for stereo imaging: that is, creating the perception of space and three dimensionality in music. Tweeters are vital for building the stereo separation in your car's audio system. An audio system with good stereo separation will make a well recorded female vocal seem as if the artist is in a specific location on the dash or windshield (if you can imagine that with closed eyes) rather than coming directly from the car doors next to you. 

Tweeters and sound balancing 

Believe it or not, aside from the size and power required, there's not a lot of difference between a giant subwoofer and the smallest car door tweeter. They're speakers dedicated to recreating a specific part of the audio spectrum. 

And because they're each dedicated speakers they're essential for sound balancing. 

When you compare a compromised base stereo system in a BMW (only 4 midrange speakers and two small woofers) with a 676 HiFi system consisting of 5 mids, 3 tweeters and two decent sized underseat woofers — in both cases the designers tried to balance the sound as best as possible. It’s much easier to do when you have a set of 3 different types of speakers compared to just a midrange and woofer.

That’s why for base stereo equipped BMW’s we recommend replacing the mids, adding tweeters and replacing the woofers all with Alpha Ones. You just can’t add tweeters and expect them to blend well with the existing mids and woofers as the balance will be off. The lack of tweeters is just the tip of the iceberg.

On HiFi and Harman Kardon equipped BMW’s on the other hand you can easily replace just the woofers with Alpha One A90’s without touching anything else and you’ll be golden as our woofers alone are a great upgrade on their own. Of course they would sound even better when paired with our mids and tweeters for a fully balanced and full sound.

Tweeters make it easier for mid-range speakers to focus on midrange frequencies; the woofers mean mid-range speakers don't have to reproduce low-end frequencies. 

As a result of having car speakers dedicated for both the high and low-end, mid-range speakers are free to create a better quality of mid-range sound rather than struggle to create high and/or low-end sounds. 

With the correct tweeters, your mid-range speakers will distort less, and the sound will be significantly better balanced. 

Tweeter speakers specifications

Not all car tweeters are created the same. Different types of magnets, cone materials, and crossover points mean that there's a lot on the market. But finding the best tweeters for your car isn't too challenging. 

What size tweeters are in my BMW or MINI? 

Most dedicated tweeters in the car audio space are approximately 1 inch or 25mm in diameter, and some are 0.75 inches (19.05mm). A slightly larger tweeter will be able to reproduce 3kHz more easily while a smaller one will have more difficulty with that. We believe 1” tweeters are the way to go for any BMW or MINI.

If you own a BMW or MINI and want to know more about your existing audio system, use our VIN lookup system.

Tweeter impedance

The impedance of car tweeters varies, but the most common tweeters have an impedance between 4-8 ohms. Tweeter impedance isn’t the most important thing to look at as they’re arguably the most efficient speakers out there and draw little current. There is simply not a whole lot of energy in high frequencies. 

Tweeter power handling

As noted several times earlier, car tweeters are small — they have a small magnet used to move a small cone via the voice coil. Small, when compared to the cones and magnets of car subwoofers. 

What this all means is that tweeters can only handle a fraction of the power that’s sent to mid-range speakers and subs. Most 1-inch tweeters have a power handling rating of around 50 watts max which would be about 25W RMS. That doesn’t sound like a whole lot but it would be enough to get you running out of a car with the right high pitched noise.

How to install tweeter speakers in BMW’s and MINI’s

Perhaps you want to install audio tweeters in your car as an upgrade over your current system. Maybe your current tweeters aren’t performing well, or you might not even have them at all. 

If you’re upgrading your existing tweeters in a BMW our Alpha One tweeters are a drop in plug and play replacement for compatible cars. We don’t offer them for your car unless they will fit — just type in your VIN. You will need to remove some trim to get to their mounting spots and you’ll be good to go. We have many installation videos for different chassis and PDF manuals if we don’t have a video.

Things get a bit more complicated if your BMW or MINI didn’t come equipped from the factory with tweeters. In this case our website will let you know what parts you’ll need to order from your local dealer to allow mounting them. It's usually a window molding or triangular grill and in some cases even a whole A-Pillar cover that needs to be replaced for an OEM counterpart which has a tweeter mounting spot and a grille.

Learn more about the Alpha One Audio Upgrade.

Where to buy tweeter speakers?

If you’re driving a BMW or MINI, you can install BimmerTech’s Alpha One audio system. You’ll take your high-end, low-end, and all frequencies in between to the next level without having to calculate impedance, power handling, and whether or not our tweeters will fit in your car. 

Using the factory mounting points, the installation is a simple swap. Easily doable by yourself in less than a day, and your entire car audio system will be miles above anything it ever was. 

Conclusion – Are tweeters worth it?

Tweeters get less talk than woofers that's for sure. The truth is that in all aspects of car audio, everything matters.

Tweeters are the kind of addition to an audio system that you don’t understand the importance of until you have them or until you experience good ones. They can make your music sound crisper, and more detailed, and simply better when set up and tuned correctly. Once you’ve enjoyed the entire audio spectrum with a set of tweeters in your car if you didn’t have them before, you’ll wonder how you ever managed without.