What Is a Tweeter?

A tweeter is a loudspeaker driver designed primarily to reproduce high audio frequencies.

In a multi-way loudspeaker system, the tweeter normally receives the high-frequency portion of the signal through a crossover network.

             Audio signal
                  │
                  ▼
             ┌─────────┐
             │ Crossover│
             └────┬────┘
                  │
          High-frequency signal
                  │
                  ▼
              Tweeter
                  │
                  ▼
              High-frequency
                 sound

The exact frequency at which a tweeter begins operating depends on the design of the loudspeaker and its crossover.

Why Do Speakers Need Tweeters?

A single loudspeaker driver can reproduce a wide frequency range, but it becomes increasingly difficult for one driver to reproduce the entire audio spectrum efficiently.

High frequencies benefit from a small, lightweight diaphragm that can move rapidly.

A multi-way system therefore divides the audio spectrum between different drivers.

• Woofer — low frequencies
• Midrange — middle frequencies
• Tweeter — high frequencies

The crossover determines which frequencies are sent to each driver.

What Frequencies Does a Tweeter Reproduce?

There is no single frequency range that applies to every tweeter.

Many tweeters operate from a few kilohertz upward and can extend well beyond the upper range of human hearing, depending on their design.

The useful frequency range depends on:

• Diaphragm material
• Diaphragm size
• Voice-coil design
• Magnetic motor
• Horn or waveguide design
• Mechanical construction
• Crossover frequency

Why Tweeter Diaphragms Are Small

High frequencies have short wavelengths.

A small diaphragm can respond rapidly to these changes in the audio signal.

A large diaphragm is more difficult to control at very high frequencies and can develop unwanted breakup modes.

Tweeters therefore generally use smaller diaphragms than woofers.

Why Tweeter Diaphragms Are Lightweight

A lighter moving assembly can respond more easily to high-frequency signals.

The moving mass of a tweeter can include:

• Diaphragm
• Voice coil
• Former
• Adhesive
• Other attached moving components

Reducing unnecessary moving mass can improve high-frequency response, although the overall performance depends on the complete driver design.

Basic Tweeter Construction

A conventional dynamic tweeter can contain many of the same basic components found in a larger loudspeaker.

• Diaphragm
• Voice coil
• Magnet
• Top plate
• Pole piece
• Basket or mounting structure
• Suspension
• Terminals

The major difference is the size and optimization of the moving assembly.

How a Dynamic Tweeter Works

A dynamic tweeter operates using the same basic electromagnetic principle as a conventional moving-coil loudspeaker.

An audio current flows through the voice coil.

The voice coil is located within a magnetic field.

The interaction between the electrical current and magnetic field produces a mechanical force.

The force moves the diaphragm and creates pressure variations in the air.

The Tweeter Voice Coil

The voice coil converts electrical energy into mechanical movement.

Because tweeters are small, their voice coils are usually much smaller than those used in woofers.

The coil must be lightweight while still being capable of handling the required electrical and thermal load.

Tweeter Magnets

The magnet provides the magnetic field required for the voice coil.

Tweeters can use different magnetic materials and motor structures.

The magnetic circuit is designed to produce an appropriate field in the voice-coil gap while keeping the driver compact.

Tweeter Diaphragms

The diaphragm is the component that moves the air and produces sound.

Common diaphragm materials include:

• Paper
• Fabric
• Silk
• Polymer films
• Polyester
• Aluminium
• Titanium
• Other metal alloys
• Specialized composite materials

Each material has different mechanical properties and acoustic behaviour.

Dome Tweeters

The dome tweeter is one of the most common tweeter designs.

The diaphragm has a dome-shaped profile and is driven around its perimeter or through a voice-coil arrangement depending on the design.

             Dome
           _______
        .-'       '-.
      .'             '.
     /                 \
    /___________________\
            │
         Voice coil

Dome tweeters are available in many different materials and sizes.

Soft-Dome Tweeters

Soft-dome tweeters use a flexible material such as treated fabric.

Silk and other fabric materials are commonly used in soft-dome designs.

Soft domes can provide smooth response characteristics when properly designed.

Metal-Dome Tweeters

Metal-dome tweeters use materials such as aluminium or titanium.

Metal diaphragms can provide high stiffness-to-mass ratios.

Their breakup behaviour and resonance characteristics must be controlled through the diaphragm geometry and the overall acoustic design.

Cone Tweeters

Cone tweeters use a small conical diaphragm.

They were widely used in older loudspeaker systems and remain useful in some applications.

Cone tweeters can be relatively inexpensive and efficient.

Horn Tweeters

A horn can be used to acoustically load and control the radiation from a tweeter.

       Compression driver
              │
              ▼
           Throat
              │
              ▼
          /-------\
        /           \
       /             \
      /               \
     /_________________\
             Horn

Horn loading can increase efficiency and provide controlled directivity.

Compression Drivers

A compression driver is designed to generate sound through a small throat that feeds a horn or waveguide.

Compression drivers are widely used in professional sound systems because they can achieve high acoustic output.

Their diaphragms and voice coils are designed specifically for high-frequency operation.

Compression Driver Diaphragms

Compression drivers can use specialised diaphragm structures.

The diaphragm may be made from materials such as polymer films, aluminium, titanium or other engineered materials.

The diaphragm geometry and phase-plug design have a major influence on the driver's performance.

Phase Plugs

Many compression drivers use a phase plug between the diaphragm and horn throat.

The phase plug helps control the acoustic path from different parts of the diaphragm.

Its geometry can influence high-frequency response and efficiency.

Ribbon Tweeters

A ribbon tweeter uses a very thin conductive ribbon suspended in a magnetic field.

The ribbon acts as both the moving conductor and the radiating element.

Because the moving element can be extremely light, ribbon tweeters can have excellent high-frequency response.

Planar-Magnetic Tweeters

Planar-magnetic tweeters use a thin diaphragm with conductive traces or a conductor arranged within a magnetic field.

The force is distributed across a large portion of the diaphragm.

This differs from the conventional small voice-coil arrangement used in many dynamic tweeters.

Piezoelectric Tweeters

Piezoelectric tweeters use a piezoelectric element rather than a conventional moving voice coil.

An applied voltage causes the piezoelectric material to deform.

This movement produces sound.

Piezoelectric tweeters are known for their relatively high electrical impedance and can be useful in applications where high efficiency and ruggedness are important.

Electrostatic Tweeters

Electrostatic tweeters operate using electrostatic forces rather than the conventional voice-coil motor.

A lightweight diaphragm is positioned between electrically charged structures.

Changes in the electrical signal produce forces that move the diaphragm.

Electrostatic designs are relatively specialized compared with conventional dynamic tweeters.

Air-Motion Transformer Tweeters

An air-motion transformer uses a folded diaphragm structure.

The diaphragm moves air through its folds rather than operating like a conventional piston.

This design can achieve high efficiency and fast transient response.

Super Tweeters

A super tweeter is designed primarily for the upper portion of the high-frequency range.

It is commonly used in systems where an additional high-frequency driver is required above the operating range of the main tweeter.

Super tweeters are particularly common in some professional and specialized loudspeaker systems.

Horn Tweeters for Professional Audio

Professional sound systems often use horn-loaded compression drivers because of their high efficiency and ability to produce high acoustic output.

The horn can also control the horizontal and vertical dispersion of sound.

This is especially useful in large venues where controlled coverage is important.

Tweeter Directivity

Tweeter directivity describes how widely sound is radiated.

As frequency increases, the wavelength becomes shorter compared with the physical dimensions of the radiating structure.

The result can be increasingly narrow radiation at high frequencies.

Tweeter design therefore involves not only frequency response but also dispersion.

Why Tweeters Become More Directional

A radiating surface becomes increasingly directional when its physical dimensions become large relative to the wavelength.

This is one reason why tweeter geometry and diaphragm size are important.

Waveguides and horns can be used to control this behaviour.

Tweeter Waveguides

A waveguide controls the way sound leaves the tweeter.

It can improve directivity control and can also increase acoustic loading.

Waveguides are widely used with compression drivers and are also used with some dome tweeters.

Tweeter Efficiency

Tweeter efficiency describes how effectively electrical input is converted into acoustic output.

Horn-loaded compression drivers can achieve particularly high efficiency compared with many conventional dome tweeters.

Efficiency is normally expressed as sound pressure level for a given input condition.

Tweeter Sensitivity

Sensitivity is normally specified as sound pressure level produced from a defined electrical input at a defined measurement distance.

When designing a multi-way speaker, the tweeter sensitivity should be compatible with the other drivers.

A crossover or attenuation network can be used to balance the levels.

Tweeter Impedance

Tweeters are available with different nominal impedance ratings.

Common values include:

• 4 Ω
• 6 Ω
• 8 Ω
• 16 Ω

The actual impedance varies with frequency.

The crossover must therefore be designed for the electrical behaviour of the particular tweeter.

Tweeter Power Handling

Tweeter power ratings should be interpreted carefully.

A tweeter may have a relatively low continuous power rating compared with a woofer but can still operate effectively in a complete loudspeaker system.

The crossover prevents large amounts of low-frequency energy from reaching the tweeter.

Why Tweeters Are Easily Damaged

The voice coil and other components in a tweeter are small.

Excessive electrical power can cause rapid heating.

A clipped amplifier signal can also contain significant high-frequency energy that may increase the thermal stress on a tweeter.

Clipping and Tweeter Damage

Amplifier clipping produces a waveform with increased high-frequency harmonic content.

When a clipped signal is sent to a loudspeaker system, the tweeter can receive more high-frequency energy than expected.

Severe or prolonged clipping can therefore contribute to tweeter failure.

Tweeter Crossover

A crossover separates the audio signal into appropriate frequency bands.

For a tweeter, the crossover normally acts as a high-pass filter.

Amplifier
   │
   ▼
 ┌─────────────┐
 │ High-pass   │
 │  crossover  │
 └──────┬──────┘
        │
        ▼
     Tweeter

The crossover frequency and slope must be appropriate for the tweeter.

Tweeter Crossover Frequency

The crossover frequency determines approximately where the tweeter begins contributing to the system response.

The correct crossover frequency depends on the tweeter's capabilities, the desired acoustic response and the characteristics of the other drivers.

The manufacturer's recommendations should be considered when available.

Crossover Slope

Crossover slope determines how rapidly frequencies outside the tweeter's intended range are attenuated.

Common filter slopes include:

• 6 dB/octave
• 12 dB/octave
• 18 dB/octave
• 24 dB/octave

The appropriate slope depends on the driver and system design.

Why Tweeter Protection Matters

A crossover can reduce the amount of low-frequency energy reaching the tweeter.

Some systems also use additional protection components such as resistors, lamps, fuses or other protection circuits.

The objective is to reduce the likelihood of thermal or mechanical damage.

Tweeter and Capacitor Protection

A simple capacitor in series with a tweeter forms a basic first-order high-pass filter.

Amplifier
   │
   │
  ─||─
  Capacitor
   │
   ▼
 Tweeter

This is a simple arrangement, but a real loudspeaker crossover may contain additional components to achieve the required acoustic response.

Tweeter Polarity

Tweeter polarity is important when integrating the driver with the woofer or midrange driver.

Incorrect polarity can create cancellation around the crossover region.

The correct electrical polarity depends on the crossover topology and the acoustic phase relationships of the drivers.

Tweeter Phase

The phase response of a tweeter is affected by its acoustic and electrical characteristics.

The crossover also changes the phase of the signal.

Successful loudspeaker design therefore requires the tweeter and other drivers to work together acoustically, not simply electrically.

Tweeter Resonant Frequency

Like other loudspeaker drivers, a tweeter has a mechanical resonance.

The resonance is determined by the moving mass and suspension properties of the driver.

The crossover is normally selected so that the tweeter operates in a suitable region above its fundamental resonance.

Tweeter Dome Resonance

A dome can develop resonances at higher frequencies.

The exact behaviour depends on the dome material, geometry, damping and construction.

Good tweeter design attempts to control unwanted resonances so that they do not produce objectionable response irregularities.

Soft Dome vs Metal Dome

Neither type is automatically better. The complete design determines the final performance.

Horn Tweeter vs Dome Tweeter

Tweeter Distortion

Tweeter distortion can result from several mechanisms.

• Voice-coil nonlinearity
• Diaphragm breakup
• Mechanical rubbing
• Magnetic nonlinearity
• Excessive excursion
• Thermal compression
• Crossover problems

The particular distortion mechanism depends on the tweeter design.

Tweeter Thermal Compression

As the voice coil heats up, its electrical resistance increases.

This changes the electrical behaviour of the driver and can reduce the acoustic output produced for a given amplifier voltage.

This phenomenon is known as thermal compression.

Tweeter Cooling

Some tweeter designs incorporate methods to improve heat dissipation.

The motor structure, voice-coil former, magnetic assembly and surrounding materials can all influence thermal behaviour.

Professional compression drivers may use specialised motor and cooling arrangements.

Tweeter Voice-Coil Diameter

Tweeter voice coils are available in different diameters.

A larger voice coil can provide greater thermal capacity and may allow higher power handling.

A smaller coil can provide low moving mass.

The optimal size depends on the complete driver design.

Tweeter Diaphragm Materials

Different materials offer different combinations of stiffness, mass, damping and thermal characteristics.

These are general characteristics; actual performance depends on the specific diaphragm construction.

Tweeter Horn Materials

Tweeter horns can be manufactured from materials such as:

• ABS plastic
• Other polymers
• Aluminium
• Fiberglass
• Wood or composite materials

The material affects rigidity, resonance, weight and manufacturing cost.

Tweeter Horn Shape

The shape of a horn determines how acoustic energy expands from the throat to the mouth.

Different profiles can produce different loading and dispersion characteristics.

Horn geometry is therefore an important part of compression-driver design.

Tweeter Placement

The physical position of the tweeter affects the acoustic integration of the loudspeaker.

In many systems the tweeter is positioned close to the midrange or woofer to reduce excessive path-length differences.

The front baffle and enclosure geometry can also influence the tweeter response.

Tweeter Baffle Effects

The loudspeaker enclosure is part of the acoustic environment of the tweeter.

The shape and dimensions of the front baffle can affect diffraction and frequency response.

Rounded cabinet edges can be used in some designs to reduce certain diffraction effects.

Tweeter Protection During Repair

When testing or repairing a tweeter, avoid applying excessive power.

A tweeter can be damaged quickly if it receives a large low-frequency signal or excessive high-frequency power.

Use an appropriate crossover or test method when performing repairs.

Diagnosing a Faulty Tweeter

A systematic diagnosis can begin with:

1. Visual inspection.
2. Check the terminals and wiring.
3. Measure DC resistance.
4. Inspect the diaphragm.
5. Check for mechanical damage.
6. Check the crossover.
7. Perform a controlled low-level test.

Do not assume that a silent tweeter is necessarily defective. The crossover, wiring or amplifier may also be responsible.

Tweeter Resistance Test

A multimeter can be used to measure the DC resistance of a conventional dynamic tweeter.

An open reading can indicate a broken voice coil or connection.

However, piezoelectric and other non-conventional tweeters require different diagnostic considerations.

Tweeter Voice-Coil Failure

A failed voice coil can result in:

• No sound
• Open electrical circuit
• Abnormal resistance
• Burning smell
• Mechanical rubbing

A damaged dynamic tweeter voice coil may require replacement of the diaphragm and coil assembly.

Tweeter Diaphragm Replacement

Many compression drivers are designed so that the diaphragm and voice coil assembly can be replaced.

This can make repair considerably easier than replacing the complete driver.

The replacement diaphragm must match the driver model and motor geometry.

Tweeter Maintenance

Tweeters generally require little routine maintenance.

However:

• Keep the diaphragm free from physical impact.
• Keep foreign objects away from the acoustic opening.
• Protect the driver from excessive amplifier power.
• Keep the crossover functioning correctly.
• Inspect for loose mechanical components.

Common Tweeter Problems

Choosing a Tweeter for a DIY Speaker

When selecting a tweeter for a DIY loudspeaker, consider:

• Nominal impedance
• Sensitivity
• Frequency response
• Recommended crossover frequency
• Power handling
• Dispersion
• Diaphragm material
• Physical dimensions
• Mounting depth
• Horn or waveguide requirements

The tweeter should be selected as part of the complete loudspeaker system rather than independently.

Tweeter and Woofer Matching

The tweeter and woofer must work together around the crossover region.

Important matching factors include:

• Sensitivity
• Impedance
• Frequency response
• Directivity
• Crossover compatibility

A tweeter with very different directivity from the woofer can produce an uneven off-axis response around the crossover region.

Tweeter and Midrange Matching

In a three-way system, the tweeter must also integrate correctly with the midrange driver.

The crossover between the midrange and tweeter determines where each driver operates.

The acoustic centres, directivity and phase behaviour should all be considered.

Tweeters in Two-Way Speakers

A two-way loudspeaker normally consists of:

• Woofer
• Tweeter
• Crossover network

The woofer handles the lower frequencies while the tweeter handles the higher frequencies.

The crossover integrates the two drivers.

Tweeters in Three-Way Speakers

A three-way loudspeaker normally uses:

• Woofer
• Midrange
• Tweeter

This allows each driver to operate over a more restricted frequency range.

Why Tweeters Are Usually Mounted at the Top

Tweeters are frequently positioned near ear level because high frequencies can be more directional than lower frequencies.

The listening position can therefore have a significant influence on perceived high-frequency response.

Tweeter Height and Listening Position

In many loudspeaker systems, the tweeter is positioned approximately at the listener's ear height when seated.

This is not a universal requirement, but it can help provide the intended on-axis response.

Key Takeaways

• A tweeter is designed primarily to reproduce high audio frequencies.
• Tweeters generally use small and lightweight moving structures.
• Dynamic tweeters use a voice coil and magnetic motor.
• Dome, cone, horn, compression, ribbon, planar, piezoelectric, electrostatic and air-motion-transformer designs are different approaches to high-frequency reproduction.
• Soft-dome and metal-dome tweeters have different mechanical and acoustic characteristics.
• Horn-loaded compression drivers can provide high efficiency and controlled directivity.
• The diaphragm material strongly influences tweeter behaviour.
• Tweeter impedance varies with frequency.
• Tweeter power handling must be considered together with the crossover.
• Amplifier clipping can increase the stress placed on tweeters.
• The crossover protects the tweeter from unwanted low-frequency energy and integrates it with the other drivers.
• Tweeter directivity becomes increasingly important at high frequencies.
• Waveguides and horns can be used to control dispersion.
• A tweeter should be selected as part of the complete loudspeaker system.
• Proper diagnosis should distinguish a defective tweeter from a faulty crossover, wiring or amplifier.