Curious about tweeters, compression drivers, and the differences? It’s just a little bit more complicated that you might first guess, but not much.
Read on to learn more!
Contents
What is the difference between a tweeter and a compression driver?
A compression driver, also called a horn driver or horn loaded compression driver, uses a voice coil and diaphragm to pass sound wave variations through a small diameter opening attached to an acoustic horn body. Compression drivers offer higher efficiency (higher sound pressure) and a more controlled sound output called dispersion.
Many use a central shape connected to the diaphragm called a phase plug to create the compression effect before the output.
Standard dome tweeter speakers are different from compression driver speakers in that most directly create sound from the tweeter dome attached to the diaphragm and do not use a horn body. Both can produce high frequency musical audio but use different designs.
Additionally, some compression horn speakers can produce musical content down into midrange frequencies which ordinary tweeters cannot. In both cases, they’re used in a speaker system with the correct crossover frequency to work with the woofer speaker or midrange speaker used depending on the design.
Just like with other tweeters a crossover is needed to block low frequency sounds.
Which horn tweeters are not compression drivers?
It’s important to understand these names are sometimes used interchangeably so it makes a big difference which particular type we’re referring to:
- Dome tweeter types are one of the most common and don’t use a horn body.
- A ribbon tweeter may resemble a horn loudspeaker due to a flared acoustical horn body but use a very different speaker design.
When is a tweeter a compression driver?
The answer is that it depends on the type. If the tweeter uses a compression driver speaker assembly with a small output attached to a horn body then it’s a compression tweeter as they’re often called.
Bullet tweeters for example are a type of compression driver speaker. Other tweeters may have a type of horn body attached but that doesn’t make them compression tweeters.
For example, piezo tweeters are a type of horn speaker that often use a piezo driver instead of a compression driver.
Compression horn vs tweeter pros and cons
Compression horns have pros and cons just like tweeters do. Here’s a list of the main ones to be aware of.
1. Efficiency
One of the main advantages of compression tweeters is a high sensitivity which is the sound pressure level (SPL) produced at 1 watt/1 meter distance. Unlike standard soft dome tweeter types, for example, they’re capable of much higher output at the same power.
Compression horn tweeter models commonly offer from about 105 to 110dB at 1W/1M. By contrast, typical soft dome tweeter and hard dome tweeter options range from about 90 to 94dB. Because of how speaker volume is non-linear (measured in Decibels) that’s as much as 100x more volume at the same power level in some cases!
2. Frequency response and sound quality
This is a bit of a more complicated one. You can in many cases get better clarity, realism, and sound accuracy using horn speaker design but as it’s not a guarantee. It depends on the particular speaker.
A poor or mediocre horn loudspeaker may lower sound quality but higher efficiency than a well-designed dome tweeter. An example would be a high-end metal dome tweeter with very good higher frequency performance beating the horn driver with poor response.
Generally speaking, however, horns are regarded as being capable of impressive, room-filling sound quality but may need some attenuation using an L-pad as they can sound “harsh” due to their higher output. Matching them with a mid range speaker or woofer speaker can be a problem otherwise.
High fidelity studio monitors often use them along with a cone speaker to produce the bass and midrange music portion. Some horn drivers also may have these additional frequency range features:
- Produce audio down to the midrange region (as low as 500 to 400 Hz in some cases).
- Capable of frequencies higher than 20kHz.
3. Cost
The cost advantage here goes to regular tweeters and that’s one reason they’re so popular for bookshelf speakers, for example. They make it possible to create an inexpensive speaker set at a low price.
Compression speakers on the other hand, for a quality set, cost more. A good compression driver and horn for example may average about $30 to $100 EACH. Home or car speaker tweeters can cost as little as $9 each for silk dome home stereo models and about $25 and up for car tweeters.
4. Ease of use/installation
Horn loudspeakers are a bit harder to install in a speaker enclosure as they require:
- A lot more depth installation depth
- A larger cutout to allow the acoustic horn body to fit.
They’re very rare for car audio use but some types exist, although they’re very expensive (usually a few hundred dollars) and require custom installation work. In this case, they’re used like component speakers along with mids and woofers as desired for the portion of sound they can’t produce. That’s often below 400 to 500Hz or so.
5. Power handling
Another advantage to compression loudspeakers is their power handling. Ranges starting from 50W RMS are fairly standard with limits up to 75W or even 100W each being standard. That’s a bit different from standard tweeters which tend to range from as low as 15 to 25W to upwards of 50 to 65W on the high end.
This makes them great choices for high volume application speaker systems because not only will they produce more sound (decibels) with less power but they hand be driven with more power than a lot of other types.
How do compression tweeters work?
Compression tweeters are compression horn loudspeakers that produce sound in the same upper frequency range as other tweeters. As the speaker plays, the musical sound pressure created is compressed in the small area around the throat passageway by the phase plug connected to the diaphragm.
As sounds pass through the throat and into the acoustic horn the body, also called a waveguide, guides the sound wave output in a wide fashion for better outward projection and improved efficiency.
Just like regular speakers using a voice coil and magnet assembly the musical signal applied changes the motion of the coil, producing sound as it works. During the positive voltage portion of the electrical signal, the diaphragm is moved in one direction.
During the negative portion, where the voltage changes polarity, the diaphragm moves in the opposite direction, creating a natural back-and-forth air movement to create the sound you hear.
What type of diaphragm do compression horn tweeters use?
A typical horn high frequency driver uses aluminum or titanium dome materials although lower-cost models may use a budget material like Mylar. Typical models aren’t necessarily more expensive, though, as many are still fairly affordable (under $40 each).
Phenolic is another material sometimes used as well as piezo drivers although those aren’t usually what you’d buy for the best results.
Is a bullet super tweeter a compression driver?
A bullet super tweeter is a type of compression driver design but slightly different. There are a few differences to know:
- Bullet tweeters do not have the same small throat that connects to a separate horn body. The phase plug is directly exposed at the bottom of the horn shape.
- The horn is usually permanently attached which usually isn’t the case for compression drivers.
- A bullet tweeter is smaller and requires less installation space. They also often use a general square shape versus the rectangular shape of most compression horn waveguides.
- Bullet tweeters have higher sensitivity than other tweeters but lower than that of compression drivers. Whereas horn loudspeakers tend to range around 104 to 110dB bullet tweeters are generally lower at about 104 to 108dB at 1W/1M.
- The sound dispersion and output characteristics are different than larger horn speakers as you might expect. It’s a result of the compromise required when using such a small horn body.
The design is very similar in that there’s a similar compression driver with a bullet plug attached to the smaller horn. Bullet tweeters are easier to install than larger horn speakers but don’t have the flexibility of you being able to change drivers if you like.
They’re available in both 8 ohm and 4 ohm versions along with pretty good power handling options, too.
