What Is a Speaker Spider?

The spider is the suspension component located behind the cone and around the voice-coil former.

Its main functions are to:

• Center the voice coil.
• Control cone movement.
• Provide restoring force.
• Allow controlled excursion.
• Prevent the voice coil from rubbing against the magnetic gap.
• Help maintain the mechanical stability of the moving assembly.

        Cone
       /    \
      /      \
     /        \
    /          \
   ─────────────
       │    │
       │    │ ← Voice coil
       │    │
     ╱════════╲
    ╱  Spider  ╲
   ╱════════════╲

The spider works together with the surround to control the movement of the complete moving assembly.

Why the Spider Is Important

A loudspeaker cone must move in a controlled manner.

Without a suitable suspension, the voice coil would not remain centered in the magnetic gap.

The spider therefore affects:

• Resonant frequency
• Compliance
• Excursion
• Centering
• Linearity
• Mechanical stability
• Distortion
• Power handling

Spider Compliance

Compliance describes how easily the suspension moves when a force is applied.

A more compliant spider provides less restoring force, while a stiffer spider provides greater restoring force.

Spider compliance is normally considered together with the compliance of the surround.

Spider Stiffness

The stiffness of the spider determines how much force is required to move the voice coil and cone.

A spider that is too stiff can restrict excursion and increase the driver's resonant frequency.

A spider that is too soft may not provide sufficient centering force or mechanical control.

Spider and Resonant Frequency

The spider and surround form the suspension of the loudspeaker.

The suspension compliance contributes directly to the driver's resonant frequency.

A simplified relationship is:

Fs = 1 / (2π√(Mms × Cms))

where:

• Fs = resonant frequency
• Mms = moving mass
• Cms = mechanical compliance

Changing the spider can therefore change the T/S parameters of the finished driver.

Common Spider Materials

Traditional spiders are commonly made from treated woven fabrics.

Materials can include:

• Cotton-based fabric
• Polyester fabric
• Other woven synthetic fabrics
• Specialized composite materials

The fabric is normally impregnated or treated to obtain the desired mechanical properties.

Why Fabric Is Used

A woven fabric can provide a useful combination of:

• Flexibility
• Strength
• Fatigue resistance
• Controlled compliance
• Low mass

The woven structure also allows the material to be formed into corrugations.

Spider Corrugations

The characteristic ridges in a spider are called corrugations.

      /\/\    /\/\
_____/    \__/    \_____

Corrugations allow the spider to move axially while maintaining controlled radial stiffness.

Without corrugations, a flat disc of fabric would generally not provide the same useful combination of flexibility and centering force.

Why Spider Corrugations Matter

The corrugation geometry strongly affects the mechanical properties of the spider.

Important variables include:

• Number of corrugations
• Corrugation height
• Corrugation spacing
• Corrugation shape
• Material thickness
• Material stiffness
• Spider diameter

Spider Diameter

The diameter of the spider must match the mechanical design of the speaker.

Important dimensions include:

• Inner diameter
• Outer diameter
• Corrugated region
• Voice-coil attachment diameter
• Frame attachment diameter

A replacement spider should be dimensionally compatible with the original driver.

Inner Diameter

The inner opening of the spider surrounds the voice-coil former.

The inner diameter must allow the former to move freely while providing a reliable attachment point.

Incorrect dimensions can make assembly difficult or alter the mechanical behaviour of the suspension.

Outer Diameter

The outer portion of the spider attaches to the speaker frame.

The outer diameter therefore depends on the frame and suspension design.

The attachment area must provide sufficient mechanical strength.

Spider Shape

Spiders are available in different geometries.

Examples include:

• Flat-profile corrugated spiders
• Progressive-roll spiders
• Special high-excursion geometries
• Different corrugation profiles for different compliance requirements

The exact geometry is selected according to the driver's mechanical requirements.

Progressive Spiders

A progressive spider is designed so that its restoring force increases as excursion increases.

This can help control the moving assembly at large excursions.

Progressive behaviour can be useful in high-excursion loudspeakers.

Spider Linearity

Ideally, the spider should provide predictable restoring force over the intended operating range.

Strong nonlinear behaviour can contribute to distortion.

For high-performance loudspeakers, suspension design is therefore an important part of distortion control.

Spider Manufacturing Process

A simplified industrial spider manufacturing process can involve:

1. Select the fabric.
2. Apply the required treatment or resin.
3. Dry or partially cure the material.
4. Place the material over the forming mould.
5. Apply heat and pressure.
6. Form the corrugations.
7. Cure or stabilize the material.
8. Remove the formed spider.
9. Trim the inner and outer diameters.
10. Inspect the finished part.

Spider Impregnation

The raw fabric normally does not provide the final mechanical characteristics required for a loudspeaker spider.

A resin or coating can be used to modify:

• Stiffness
• Compliance
• Strength
• Damping
• Environmental resistance

The amount and type of treatment can significantly affect the finished spider.

Spider Resin

The treatment resin must be compatible with the fabric and the intended manufacturing process.

Important properties include:

• Flexibility after curing
• Adhesion
• Temperature resistance
• Fatigue resistance
• Dimensional stability

A resin that cures excessively hard can make the spider too stiff.

Why Ordinary Epoxy Can Be Problematic

A rigid epoxy can produce a very stiff composite structure.

This may be unsuitable when the objective is a flexible suspension.

The spider must flex repeatedly over its operating life, so the material system must be selected for repeated flexing rather than only for static strength.

Spider Forming Mould

A forming mould determines the final corrugation geometry.

          PRESS
            ↓
     ┌───────────────┐
     │   FORMING     │
     │     TOOL      │
     └───────┬───────┘
             ↓
       /\/\ /\/\ /\/\
      /               \
     ───────────────────

The mould should accurately reproduce the required corrugation profile.

Male and Female Moulds

A production forming system can use matching male and female mould surfaces.

The fabric is placed between the moulds and compressed into the corrugated shape.

The moulds can be designed from the desired spider cross-section.

Heat Forming

Heat can be used to soften or activate the binder or resin during forming.

The material is pressed into the mould while the temperature and pressure are controlled.

After forming, the spider is cooled or cured while maintaining its shape.

Pressure Forming

Pressure must be sufficiently uniform to reproduce the corrugations consistently.

Uneven pressure can produce:

• Uneven corrugation depth
• Asymmetrical stiffness
• Warping
• Dimensional variation

DIY Spider Making

Making replacement spiders in a small workshop is possible for experimental and repair applications, but achieving exactly the same mechanical properties as a factory-made spider can be difficult.

A practical DIY process can use:

• Suitable woven fabric
• Forming mould
• Appropriate flexible resin or treatment
• Heat source
• Clamping or pressing system
• Cutting template
• Caliper
• Precision scale

DIY Spider Mould

A mould can be made from:

• MDF
• Hardwood
• Machined aluminium
• Engineering plastic
• Composite materials

For repeated production, a rigid and dimensionally stable mould is preferable.

A CNC machine can be useful for producing accurate corrugation profiles.

Designing the Corrugation Profile

The corrugation profile should be defined before manufacturing the mould.

Important dimensions include:

• Peak height
• Valley depth
• Pitch
• Number of corrugations
• Inner radius
• Outer radius

Small changes to these dimensions can alter compliance significantly.

Number of Corrugations

The number of corrugations influences the mechanical response of the spider.

More corrugations can allow a different combination of axial flexibility and radial stiffness.

There is no single corrugation count that is correct for every speaker.

Spider Thickness

Material thickness has a strong influence on stiffness.

A thicker material generally produces a stiffer spider, while a thinner material generally produces greater flexibility.

The correct value depends on the driver design and desired compliance.

Spider Fabric Weave

The weave of the fabric influences its mechanical properties.

Important characteristics include:

• Thread thickness
• Thread density
• Weave pattern
• Material type
• Fabric weight

The final behaviour is determined by the fabric together with its treatment and corrugated geometry.

Spider Fabric Weight

The fabric's mass affects the moving mass of the driver.

Excessively heavy suspension material can increase Mms.

For this reason, the spider should be strong enough for the intended application without unnecessary mass.

Spider Damping

Internal damping helps control mechanical resonances.

The damping characteristics depend on:

• Fabric
• Resin
• Corrugation geometry
• Thickness
• Adhesive

The objective is not simply maximum damping, but appropriate damping for the intended driver.

Spider and Voice-Coil Centering

One of the most important functions of the spider is maintaining the voice coil in the magnetic gap.

      Magnetic gap
   ┌───────────────┐
   │   │       │   │
   │   │ COIL  │   │
   │   │       │   │
   └───────────────┘
        ↑
      Centered

If the spider does not provide sufficient centering force, the voice coil can move sideways and contact the pole structure.

Spider and Voice-Coil Rubbing

Voice-coil rubbing can be caused by:

• Incorrect centering
• Damaged spider
• Incorrect spider dimensions
• Uneven spider stiffness
• Damaged former
• Frame deformation
• Incorrect assembly

A correctly manufactured and installed spider helps prevent these problems.

Spider Attachment to the Frame

The outer spider edge is normally bonded to the speaker frame.

The attachment must withstand repeated movement and vibration.

The frame surface should be clean and properly prepared before bonding.

Spider Attachment to the Voice-Coil Former

The inner spider opening is bonded to the voice-coil former.

The connection must be accurately centered.

Excess adhesive should be avoided because it increases moving mass.

Spider Adhesive

The adhesive must provide a durable bond while surviving repeated mechanical movement.

Important characteristics include:

• Good adhesion
• Flexibility where required
• Temperature resistance
• Fatigue resistance
• Controlled curing

The adhesive should be compatible with both the spider material and the speaker frame or former.

Spider Installation

A typical installation sequence is:

1. Remove the damaged spider.
2. Clean the frame and former.
3. Check the voice-coil dimensions.
4. Prepare the replacement spider.
5. Position the spider on the former.
6. Center the voice coil.
7. Attach the spider to the frame.
8. Allow the adhesive to cure.
9. Install the cone.
10. Recheck centering.
11. Install the surround.
12. Allow the assembly to cure completely.

Spider and Cone Alignment

The spider, voice coil and cone must form one correctly aligned assembly.

The voice coil should remain centered throughout the intended excursion.

Even a small alignment error can cause rubbing in a narrow magnetic gap.

Spider and Surround Working Together

The spider and surround form the two main suspension elements in many dynamic loudspeakers.

The spider primarily controls the inner portion of the moving assembly, while the surround controls the outer cone edge.

Their combined compliance determines the mechanical behaviour of the driver.

Spider vs Surround

Spider Types by Application

Different speakers require different suspension designs.

• Small full-range drivers
• Midrange drivers
• Woofers
• Subwoofers
• Professional PA drivers
• High-excursion drivers

A spider designed for a small midrange driver should not automatically be used as a replacement for a high-excursion subwoofer spider.

High-Excursion Spiders

High-excursion loudspeakers require suspension systems capable of supporting large movement.

The spider must maintain centering while allowing the required excursion.

Its geometry and compliance must therefore be selected carefully.

Double Spiders

Some high-power loudspeakers use multiple spiders.

Using more than one suspension element can provide greater mechanical control and improve centering.

However, the combined stiffness must be considered during driver design.

Progressive Suspension

A progressive suspension becomes increasingly resistant as excursion increases.

This can help prevent excessive mechanical travel and improve large-signal control.

The exact force-versus-displacement curve depends on the spider, surround and overall suspension geometry.

Spider Fatigue

The spider flexes repeatedly during normal speaker operation.

Over time, excessive mechanical stress can cause:

• Material fatigue
• Cracking
• Permanent deformation
• Loss of compliance
• Separation of the adhesive joint

Material selection and correct operating limits are therefore important for long-term reliability.

Spider Heat Resistance

In high-power loudspeakers, heat from the voice coil can reach the spider.

The material and adhesive must therefore tolerate the expected temperature.

A material that works perfectly in a low-power speaker may not be appropriate for a high-power professional driver.

Spider Making for Speaker Repair

When replacing a damaged spider, the objective is to reproduce the mechanical characteristics of the original as closely as practical.

Important measurements include:

• Inner diameter
• Outer diameter
• Number of corrugations
• Corrugation height
• Spider thickness
• Spider weight
• Attachment dimensions
• Approximate compliance

Do Not Choose a Spider by Diameter Alone

Two spiders can have the same inner and outer diameter while having very different mechanical properties.

They may differ in:

• Thickness
• Material
• Fabric weave
• Corrugation profile
• Number of corrugations
• Resin treatment
• Compliance

For speaker repair, dimensional matching alone is therefore not sufficient.

Measuring Spider Compliance

For advanced repair work, the compliance of the spider can be estimated experimentally by measuring force and displacement.

A controlled test can determine the relationship between applied force and cone movement.

Force
  ↑
  │       /
  │      /
  │     /
  │____/____________→ Displacement

The slope of the resulting force-displacement relationship provides information about the mechanical stiffness.

Spider Making and Thiele-Small Parameters

Changing the spider changes the mechanical suspension and can therefore change the driver's Thiele-Small parameters.

Important parameters affected by suspension changes can include:

• Fs
• Qms
• Qts
• Cms
• Vas

After a major suspension replacement, the finished driver should ideally be measured again.

Spider Making and Speaker Testing

A newly manufactured or installed spider should be tested carefully.

Useful tests include:

• Mechanical centering
• Free movement
• DC resistance
• Impedance sweep
• Resonant frequency
• Frequency response
• Distortion
• Large-signal excursion

Spider Break-In

Some suspension materials can change slightly after repeated movement.

For this reason, the measured parameters of a newly assembled driver may differ from those measured after controlled use.

For accurate characterization, measurements should be performed consistently and under known conditions.

Common Spider-Making Mistakes

• Using a spider that is too stiff.
• Using a spider that is too soft.
• Choosing only by diameter.
• Using incorrect corrugation dimensions.
• Using excessive resin.
• Using an unsuitable resin.
• Making the spider too heavy.
• Making the spider asymmetrical.
• Using excessive adhesive.
• Misaligning the inner attachment.
• Misaligning the outer attachment.
• Using a material unsuitable for the operating temperature.
• Failing to check voice-coil clearance.
• Failing to test the completed suspension.

DIY Spider-Making Workflow

1. Identify the original driver specifications.
2. Measure the original spider.
3. Measure the voice-coil former.
4. Determine the required inner diameter.
5. Determine the required outer diameter.
6. Measure the corrugation profile.
7. Select a suitable fabric.
8. Select an appropriate treatment.
9. Design the forming mould.
10. Machine or construct the mould.
11. Prepare the fabric.
12. Apply the treatment.
13. Form the corrugations.
14. Cure or stabilize the spider.
15. Trim the spider.
16. Measure its dimensions.
17. Measure its mass.
18. Install it on the voice-coil assembly.
19. Center the coil.
20. Bond the outer edge to the frame.
21. Allow the adhesive to cure.
22. Install the cone and surround.
23. Perform low-level testing.
24. Measure the finished driver.

Spider-Making Equipment for a Small Workshop

A small speaker-repair workshop can use relatively simple equipment for experimental spider production.

• Digital caliper
• Micrometer
• Precision scale
• CAD software
• CNC router or mill
• Forming mould
• Heat source
• Clamping or pressing system
• Cutting templates
• Adhesive tools
• Impedance measurement equipment

Using CNC to Make a Spider Mould

A CNC machine can be useful for manufacturing accurate spider moulds.

The corrugation profile can first be designed in CAD and then machined into the mould.

This is particularly useful if the same spider must be reproduced multiple times.

Quality Control

A finished spider should be inspected before installation.

Spider Making and Professional Speaker Production

Industrial spider production requires considerably tighter control than one-off DIY repair work.

Production processes may control:

• Fabric composition
• Fabric weight
• Resin concentration
• Forming temperature
• Forming pressure
• Curing time
• Corrugation geometry
• Dimensional tolerances
• Mechanical compliance
• Mass

These controls allow multiple spiders to have consistent mechanical characteristics.

Spider Design for a New Speaker

When designing a new loudspeaker, the spider should not be selected as an isolated component.

It should be designed together with:

• Voice coil
• Former
• Cone
• Surround
• Magnetic motor
• Frame
• Required excursion
• Target Fs
• Target Qts

The suspension is part of the complete loudspeaker system.

Spider and Maximum Excursion

The spider must permit the required excursion without excessive mechanical stress or loss of centering.

At high excursion, the geometry of the corrugations changes as the spider flexes.

This is one reason the suspension can become nonlinear at large displacements.

Spider and Distortion

Suspension nonlinearity can contribute to harmonic and intermodulation distortion.

A properly designed spider should provide predictable mechanical behaviour over the intended operating range.

See: Speaker Distortion .

Key Takeaways

• The spider is a critical suspension component in a dynamic loudspeaker.
• Its main job is to center the voice coil and control the movement of the cone.
• Spider compliance directly influences the mechanical resonance of the driver.
• Fabric, thickness, corrugation geometry and treatment determine the mechanical behaviour of the spider.
• Corrugations allow the spider to provide axial flexibility while maintaining useful radial stability.
• A spider should not be selected only by inner and outer diameter.
• Two spiders with identical dimensions can have very different compliance and stiffness.
• Resin treatment can significantly change the mechanical properties of the fabric.
• A rigid adhesive or coating may make a spider excessively stiff.
• The spider must withstand repeated flexing and the temperature generated by the loudspeaker.
• The spider works together with the surround to form the complete suspension.
• Changing the spider can change the driver's Thiele-Small parameters.
• A replacement spider should therefore reproduce the original mechanical characteristics as closely as practical.
• DIY spider production is possible, but consistency is more difficult than simply reproducing the visual shape.
• A forming mould can be produced using CNC machining for accurate and repeatable corrugations.
• The finished spider should be checked for dimensions, mass, symmetry and mechanical quality before installation.
• After installation, the completed driver should be tested for centering, impedance, resonance and mechanical noise.