What Is a Speaker Cone?

A speaker cone is the diaphragm that moves air to create sound.

In a typical dynamic loudspeaker, the voice coil is attached to the cone. When current flows through the voice coil, the magnetic motor moves the coil and therefore moves the cone.

Audio signal
     ↓
Voice coil
     ↓
Mechanical movement
     ↓
Speaker cone
     ↓
Air movement
     ↓
Sound

The cone must be light enough to accelerate rapidly while being stiff enough to maintain controlled motion.

Why Cone Design Matters

The cone is not simply a surface that moves backwards and forwards. Its physical properties have a major influence on loudspeaker performance.

Important characteristics include:

• Moving mass
• Stiffness
• Internal damping
• Effective radiating area
• Shape
• Thickness
• Strength
• Frequency response
• Breakup behaviour

Ideal Cone Behaviour

At lower frequencies, a well-designed cone can move approximately as a single rigid piston.

        CONE
     __________
    /          \
   /            \
  /              \
 /________________\
        ↑
     Voice coil

This is desirable because the acoustic output is easier to predict.

At higher frequencies, however, the cone may begin to flex.

Cone Breakup

When different areas of the cone begin moving independently, the cone enters a condition known as breakup.

Rigid piston:

────────────────
────────────────
────────────────

Breakup:

──────╱╲────────
─────╱  ╲───────
────╱    ╲──────

Cone breakup can produce peaks, dips and irregularities in the frequency response.

The material, geometry, thickness and damping of the cone influence where these modes occur.

Common Cone Materials

Speaker cones can be manufactured from many different materials.

Common examples include:

• Paper
• Pressed pulp
• Polypropylene
• Polyester
• Kevlar and aramid fibres
• Carbon fibre composites
• Fiberglass composites
• Aluminium
• Magnesium
• Other engineered composites

Each material involves different compromises between mass, stiffness, damping, cost and manufacturing complexity.

Paper Cones

Paper is one of the oldest and most widely used loudspeaker cone materials.

Paper cones can provide a useful combination of:

• Low mass
• Good damping
• Good stiffness-to-weight ratio
• Low cost
• Easy forming

Paper cones can also be treated with coatings or impregnations to modify their mechanical properties.

Pressed Paper Pulp

Many speaker cones are made from a mixture of cellulose fibres formed into a shaped diaphragm.

The fibre structure can be controlled during manufacturing to obtain the required stiffness, density and damping.

Different pulp formulations can produce very different cone characteristics.

Advantages of Paper Cones

• Relatively inexpensive
• Low mass
• Good internal damping
• Easy to form
• Suitable for many woofer and midrange applications
• Can be treated to modify mechanical properties

Disadvantages of Paper Cones

• Moisture sensitivity
• Mechanical properties vary with formulation
• Can require protective treatment
• Manufacturing consistency can be more difficult

These limitations can be managed through appropriate materials, coatings and manufacturing processes.

Polypropylene Cones

Polypropylene is a thermoplastic material used in many loudspeaker cones.

It provides good resistance to moisture and can be manufactured with consistent dimensions.

Its relatively high internal damping can also be useful for certain applications.

Composite Cones

Composite cones combine different materials to obtain a desired combination of properties.

For example, a composite can be designed to provide:

• High stiffness
• Low mass
• Controlled damping
• High strength
• Good environmental stability

Composite construction is common in high-performance loudspeakers.

Metal Cones

Aluminium and other metals can be used to create very stiff diaphragms.

The high stiffness can push major breakup modes to higher frequencies.

However, metal cones can exhibit strong resonances if the breakup behaviour is not properly controlled.

Damping and crossover design are therefore important.

Cone Geometry

The shape of the cone affects its stiffness and acoustic behaviour.

Important dimensions include:

• Cone diameter
• Depth
• Angle
• Thickness
• Voice-coil attachment diameter
• Surround attachment diameter

Shallow Cone

A shallow cone has a relatively small depth compared with its diameter.

Its mechanical behaviour and directivity differ from those of a deeper cone.

Shallow cones are commonly found in certain wideband and midrange drivers.

Deep Cone

A deeper cone can provide greater structural depth and can influence the stiffness of the diaphragm.

The geometry also affects the radiation pattern and high-frequency behaviour.

Cone Angle

The cone angle influences both mechanical stiffness and acoustic directivity.

A steeper cone and a shallow cone can therefore produce different frequency-response and dispersion characteristics even when their diameters are similar.

Cone Thickness

Increasing cone thickness generally increases stiffness but also adds mass.

The designer must therefore find an appropriate balance.

More thickness
     ↓
More stiffness
     +
More mass

A heavier cone can require more motor force to achieve the same acceleration.

Cone Mass

The moving mass of a loudspeaker includes the cone and several other moving components.

These can include:

• Voice coil
• Former
• Dust cap
• Part of the surround
• Part of the spider

Cone mass contributes to the driver's total moving mass, Mms.

Stiffness-to-Weight Ratio

A useful cone material should provide appropriate stiffness without adding unnecessary mass.

This is one reason composite materials can be attractive in high- performance designs.

However, maximum stiffness is not always the objective because controlled damping can also be desirable.

Internal Damping

A cone material with good internal damping can reduce the amplitude of some resonances.

This can help produce smoother acoustic behaviour.

Paper and some polymer materials naturally provide useful damping, while some very stiff materials may require additional treatment.

Paper Cone Making

Paper cones are generally produced by forming a fibre-based material into the required shape.

A simplified manufacturing process is:

1. Prepare the paper pulp or fibre mixture.
2. Form the cone shape.
3. Remove excess water.
4. Press the material into the desired geometry.
5. Dry the cone.
6. Apply any required treatment.
7. Trim the cone.
8. Inspect the finished part.

Paper Pulp Preparation

The characteristics of the finished cone depend partly on the fibre mixture.

Important variables can include:

• Fibre type
• Fibre length
• Fibre concentration
• Water content
• Binders
• Additives

Industrial cone manufacturing uses controlled formulations to obtain repeatable mechanical properties.

Forming a Paper Cone

A cone can be formed using a mould or former.

        Mould
     __________
    /          \
   /            \
  /              \
 /________________\

The wet fibre material is formed against the mould and then dried while maintaining the required geometry.

Cone Mould

A mould determines the final shape of the cone.

The mould should have:

• Correct cone angle
• Correct diameter
• Correct depth
• Smooth surface
• Accurate voice-coil opening
• Accurate surround attachment region

For repeated production, dimensional accuracy of the mould is very important.

DIY Paper Cone Forming

Small experimental cones can be made using paper or fibre materials and a custom mould.

A simple approach is to create a mould with the required cone geometry and form the material against it.

The challenge is obtaining consistent thickness and mechanical properties.

DIY cone making is therefore more suitable for experimentation and repair work than for highly consistent industrial production unless the process is carefully controlled.

Using Paper Sheets

A simple DIY cone can also be constructed from a shaped paper sheet.

The basic geometry is a sector of a circle.

       _________
     /           \
   /               \
  /                 \
 /___________________\

The sheet can be cut, formed into a cone and joined along the seam.

However, the seam introduces a discontinuity that can affect the mechanical behaviour of the cone.

Making a Cone From a Paper Sector

A conical surface can be developed from a circular sector.

The required geometry depends on:

• Outer cone diameter
• Inner diameter
• Cone depth
• Cone angle

Accurate geometric construction is important if the cone is to fit an existing speaker frame.

Seam Construction

If a paper cone is made from a flat sheet, the seam should be neat and secure.

Excess adhesive should be avoided because it adds unnecessary mass.

The seam should also be positioned consistently so that the cone remains mechanically balanced.

Thermoformed Plastic Cones

Thermoplastic materials can be shaped using heat and a mould.

A simplified process is:

1. Heat the plastic sheet.
2. Place it over or into the mould.
3. Apply pressure or vacuum.
4. Allow the material to cool.
5. Remove the formed cone.
6. Trim the edges.

The exact process depends on the plastic and equipment.

Vacuum Forming

Vacuum forming can be used to shape suitable thermoplastic sheets over a mould.

Heated sheet
──────────────
      ↓
   ┌───────┐
   │ Mould │
   └───────┘
      ↑
    Vacuum

Atmospheric pressure pushes the softened sheet against the mould.

This can produce a consistent cone shape when the process is properly controlled.

Plastic Cone Materials

Possible thermoplastic cone materials include:

• Polypropylene
• Polyester-based materials
• Other engineered thermoplastics

Material selection should consider density, stiffness, damping, temperature resistance and forming characteristics.

Composite Cone Making

Composite diaphragms can be constructed from fibre-reinforced materials.

Possible reinforcement materials include:

• Carbon fibre
• Fiberglass
• Aramid fibres
• Other high-strength fibres

The resin and fibre combination determines much of the final mechanical behaviour.

Carbon-Fibre Cones

Carbon fibre provides high stiffness at relatively low mass.

Carbon-fibre speaker diaphragms can therefore achieve high structural stiffness.

However, the manufacturing process is considerably more demanding than simple paper-cone production.

Fiberglass Cones

Fiberglass composites can provide a useful combination of stiffness, strength and durability.

The resin content should be controlled because excessive resin can add mass without providing proportional acoustic benefit.

Cone Coatings

Paper cones are sometimes treated with coatings or impregnations.

A coating can change:

• Stiffness
• Mass
• Damping
• Moisture resistance
• Surface durability

The amount of coating must be controlled because excessive material can increase moving mass.

Waterproofing a Paper Cone

A paper cone can be treated to improve resistance to moisture.

However, the treatment should not significantly change the intended mechanical characteristics.

A heavy coating can increase mass and alter the driver's frequency response.

Cone Doping

The term doping is commonly used for applying a treatment to a paper cone or surround.

Depending on the formulation, doping can modify:

• Stiffness
• Damping
• Flexibility
• Moisture resistance
• Mechanical durability

The formulation should be selected according to the intended application.

Edge of the Cone

The outer edge of the cone connects to the surround.

This region must be designed carefully because the surround must allow the cone to move while maintaining centering.

Cone
───────────────╲
                ╲
                 ╲ Surround
                  ╲____

Voice-Coil Attachment

The inner part of the cone is connected to the voice-coil former.

The connection must be strong and accurately centered.

Any significant misalignment can cause the voice coil to rub inside the magnetic gap.

Cone Neck

The narrow region around the voice-coil attachment is sometimes referred to as the cone neck.

Its geometry affects the transition between the voice coil and the main cone.

This region must withstand repeated mechanical stress.

Dust Cap

The dust cap covers the central opening of many loudspeaker cones.

Its primary function is to help prevent dust and debris from entering the magnetic gap.

The dust cap can also contribute to the acoustic behaviour of the driver.

See: Dust Caps .

Dust-Cap Material

Dust caps can be made from:

• Paper
• Fabric
• Polymer materials
• Aluminium
• Composite materials

The material and shape can influence mass and high-frequency response.

Cone and Surround Attachment

The cone and surround must form a reliable mechanical connection.

The adhesive should remain flexible enough for the required movement while providing sufficient strength.

The joint should also remain reasonably lightweight.

Cone and Voice-Coil Attachment

The voice coil transfers its mechanical movement directly to the cone.

The joint therefore experiences continuous vibration.

A weak or poorly bonded joint can fail under high excursion or high power.

Cone Alignment

The cone must be centered relative to the magnetic gap.

During speaker assembly, the voice coil is normally centered before the cone and suspension adhesives are allowed to fully cure.

Accurate alignment is essential for avoiding rubbing.

See: Voice-Coil Centering .

Cone Making for Speaker Repair

For speaker repair, reproducing the original cone dimensions is often more important than simply making a visually similar cone.

Measure:

• Outer diameter
• Inner diameter
• Cone depth
• Voice-coil attachment diameter
• Surround attachment diameter
• Cone thickness
• Dust-cap diameter

Measuring an Original Cone

If the original cone is available, carefully measure it before removing damaged components.

Useful tools include:

• Digital caliper
• Steel ruler
• Depth gauge
• Micrometer
• Flexible measuring tape

Record all measurements before beginning reconstruction.

Cone Weight

The mass of the replacement cone should be considered during speaker repair.

A substantially heavier replacement cone can alter the driver's Thiele-Small parameters.

It can also reduce sensitivity and change the high-frequency response.

Cone Material and Thiele-Small Parameters

Changing the cone can change the moving mass Mms.

Because Mms is part of the driver's mechanical system, changing it can affect parameters such as:

• Fs
• Qms
• Qts
• Sensitivity
• Frequency response

A replacement cone should therefore be as close as practical to the original design when restoring a driver.

Cone Making and Speaker Efficiency

Cone mass affects the acceleration of the moving system.

A lower moving mass can be advantageous, but mass alone does not determine efficiency.

Motor strength, suspension, cone area and other parameters are also important.

Cone Area

The effective radiating area of the cone is represented by Sd.

A larger cone area can move more air for a given excursion.

This is particularly important for low-frequency reproduction.

Cone Area and Low-Frequency Output

The approximate volume displacement is:

Vd = Sd × Xmax

where:

• Vd = displacement volume
• Sd = effective cone area
• Xmax = linear excursion

This illustrates why low-frequency systems often require large cones, large excursion, multiple drivers or a combination of these.

Making a Cone Former

For DIY experimentation, a cone-forming mould can be manufactured from materials such as:

• Wood
• MDF
• Hard plastic
• Machined aluminium
• Composite materials

The mould surface should be smooth and accurately shaped.

CNC-Machined Cone Mould

A CNC router or CNC mill can be used to create an accurate cone mould.

This is particularly useful when making multiple cones with identical dimensions.

The mould geometry can be designed in CAD before machining.

DIY Cone-Making Process

A small workshop can approach cone making as a sequence of controlled operations:

1. Measure the required cone dimensions.
2. Create the cone geometry in CAD.
3. Build or machine the mould.
4. Select the cone material.
5. Form the material over the mould.
6. Allow it to stabilize or cure.
7. Trim the outer edge.
8. Cut the voice-coil opening.
9. Inspect the cone.
10. Weigh the finished cone.
11. Attach the voice coil.
12. Attach the surround.
13. Install the dust cap.
14. Center the voice coil.
15. Test the completed driver.

Why Cone Reproduction Is Difficult

A cone can look correct while behaving very differently from the original.

Small changes in:

• Thickness
• Mass
• Stiffness
• Damping
• Geometry
• Material composition

can change the acoustic behaviour of the finished driver.

Common Cone-Making Mistakes

• Using material that is too heavy.
• Making the cone too thick.
• Using an incorrect cone angle.
• Making the cone too shallow or too deep.
• Making the voice-coil opening the wrong size.
• Making the surround attachment diameter incorrect.
• Using excessive adhesive.
• Creating an uneven seam.
• Failing to maintain symmetry.
• Using a mould with an inaccurate surface.
• Failing to control cone thickness.
• Ignoring the mass of coatings or treatments.
• Failing to check the finished cone weight.

Testing a DIY Cone

Before installing the cone permanently, inspect:

• Shape
• Symmetry
• Weight
• Thickness
• Surface defects
• Voice-coil opening
• Surround attachment area

After assembly, perform low-level electrical and mechanical tests before applying high power.

Cone Making and Distortion

A poorly designed or manufactured cone can increase distortion.

Possible causes include:

• Cone breakup
• Uneven stiffness
• Excessive mass
• Asymmetrical construction
• Loose joints
• Incorrect voice-coil attachment

See: Speaker Distortion .

Cone Making and Frequency Response

Cone geometry and material influence the frequency response of the driver.

A cone that is too flexible can begin to break up at a lower frequency.

A very stiff cone can push breakup modes higher, but the resulting resonances may require careful control.

See: Frequency Response .

Cone Making and Voice-Coil Winding

The cone and voice coil must be designed as a compatible mechanical system.

The voice coil determines the central attachment dimensions while the cone determines how the coil's movement is transferred to the surrounding air.

See: Voice-Coil Winding .

Cone Making for Woofer Repair

For woofer repair, the replacement cone should match the original driver as closely as practical.

Particular attention should be given to:

• Cone diameter
• Cone depth
• Neck diameter
• Voice-coil diameter
• Winding height
• Surround diameter
• Cone mass
• Dust-cap dimensions

Cone Making for Midrange Drivers

Midrange cones generally require good control over their behaviour at higher frequencies than a typical woofer.

Cone stiffness, damping and breakup behaviour therefore become particularly important.

Cone Making for Full-Range Drivers

Full-range drivers require the cone to operate over a very wide frequency range.

The cone must therefore provide a useful balance between:

• Low-frequency displacement
• Stiffness
• Low mass
• Damping
• Controlled breakup
• Wide-band dispersion

DIY Cone-Making Equipment

A small workshop may use:

• Digital caliper
• Micrometer
• Precision scale
• CAD software
• CNC router or mill
• Drill press
• Forming mould
• Clamps
• Adhesive applicators
• Cutting tools
• Measurement microphone
• Impedance measurement equipment

From Prototype to Production

If you intend to make cones repeatedly, consistency becomes more important than simply producing one successful part.

A repeatable process should control:

• Material quantity
• Material composition
• Forming pressure
• Drying conditions
• Cone thickness
• Cone dimensions
• Cone mass
• Coating quantity
• Final inspection

Quality Control

Each finished cone can be checked for:

Key Takeaways

• The speaker cone is the main acoustic diaphragm in a conventional dynamic loudspeaker.
• Cone mass, stiffness, damping and geometry strongly affect speaker performance.
• Paper is widely used because it combines low mass, useful damping and relatively low manufacturing cost.
• Polypropylene, metals and composite materials provide alternative mechanical characteristics.
• A cone must be stiff enough for controlled motion while remaining light enough for efficient acceleration.
• Cone breakup can create unwanted response peaks and distortion.
• Increasing cone thickness generally increases stiffness but also adds mass.
• Coatings can change stiffness, damping, moisture resistance and mass.
• The cone must be accurately connected to both the voice coil and surround.
• A replacement cone should match the original dimensions and mass as closely as practical.
• Changing cone mass can change the driver's Thiele-Small parameters.
• DIY paper cones can be formed using custom moulds, although consistent thickness and mechanical properties can be difficult to achieve.
• Thermoplastic cones can be produced using forming processes such as vacuum forming.
• Composite cones can provide high stiffness-to-weight ratios but require more advanced manufacturing techniques.
• Accurate mould construction is important when producing repeated cones.
• For professional-quality cone production, dimensional and mass control are essential.
• A newly manufactured cone should be tested at low power before high-power operation.