What Is a Speaker Spider?

The spider is the flexible suspension component located between the voice coil and the speaker basket.

Its primary job is to support the moving assembly while allowing it to move forward and backward.

The spider also helps keep the voice coil centered inside the magnetic gap.

                 Cone
                   │
                   │
              Voice coil
                   │
             ┌─────┴─────┐
             │   Spider  │
             └─────┬─────┘
                   │
                Basket

The spider works together with the surround to form the mechanical suspension of the loudspeaker.

Why Is It Called a Spider?

The component is traditionally called a spider because of its circular shape and suspension structure.

A typical spider has a central opening through which the voice-coil former passes, with the outer portion attached to the speaker basket or another supporting structure.

The Main Functions of the Spider

A speaker spider performs several important functions:

• Centers the voice coil.
• Supports the moving assembly.
• Provides controlled mechanical compliance.
• Controls the cone's movement.
• Contributes to mechanical damping.
• Helps maintain alignment during large excursions.

The spider therefore has a direct influence on the mechanical behaviour of the loudspeaker.

The Spider and Voice-Coil Alignment

The voice coil operates inside a narrow magnetic gap.

The clearance can be very small, so the coil must remain accurately centered.

The spider provides an important part of this centering force.

Correct alignment:

        ┌─────────┐
        │   Gap   │
        │ ┌─────┐ │
        │ │Coil │ │
        │ └─────┘ │
        └─────────┘


Poor alignment:

        ┌─────────┐
        │   Gap   │
        │ ┌─────┐ │
        │   ╲Coil│
        │     ╲  │
        └─────────┘

If the voice coil becomes misaligned, it may rub against the pole piece or top plate.

Spider and Surround

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

Both components must work together to provide the required mechanical compliance and alignment.

Spider Compliance

The spider must be flexible enough to allow the required cone excursion.

Its mechanical compliance determines how much force is required to move the voice coil and cone.

Mechanical compliance is represented by Cms in Thiele-Small parameters.

The spider is one of the major contributors to Cms, together with the surround and other suspension elements.

Soft Spider vs Stiff Spider

The correct stiffness depends on the complete driver design.

Spider and Free-Air Resonance

The spider contributes to the mechanical suspension and therefore affects the driver's free-air resonance.

A simplified relationship is:

Fs = 1 / (2π√(Mms × Cms))

where:

• Fs = free-air resonance frequency
• Mms = total moving mass
• Cms = mechanical compliance

Increasing suspension compliance generally lowers Fs, while making the suspension stiffer generally raises Fs, assuming the other parameters remain unchanged.

Spider Materials

Traditional speaker spiders are commonly manufactured from treated fabric materials.

Depending on the application, different fabrics, coatings and construction methods can be used to obtain the required mechanical properties.

Modern drivers may also use engineered materials or specialized suspension constructions.

Fabric Spiders

Fabric is widely used because it can provide a useful combination of flexibility, strength and durability.

The fabric can be treated with suitable compounds to control its mechanical properties.

The final behaviour depends on:

• Fabric type
• Thickness
• Weave
• Resin or coating
• Shape
• Number of corrugations

Spider Corrugations

Most conventional spiders have a series of concentric corrugations or waves.

        __________________
      /                    \
     /  ~~~~~~~~~~~~~~~~    \
    │  ~~~~~~~~~~~~~~~~~~    │
     \  ~~~~~~~~~~~~~~~~    /
      \____________________/

These corrugations allow the spider to flex while maintaining its structural integrity.

The geometry of the corrugations strongly influences compliance and mechanical behaviour.

Why Does the Spider Have Waves?

A flat piece of material would have limited controlled flexibility in the required direction.

The corrugated shape allows the spider to deform axially while maintaining lateral stability.

The corrugations therefore provide a controlled mechanical spring.

Spider Profile

The profile of the corrugations can be designed in different ways.

Common factors include:

• Number of rolls
• Roll height
• Spacing
• Material thickness
• Outer diameter
• Inner diameter
• Attachment geometry

Changing these parameters changes the mechanical characteristics of the suspension.

Spider Diameter

The diameter of the spider depends on the speaker design.

A larger spider can provide a larger suspension structure, but diameter alone does not determine compliance.

Material, geometry, thickness and corrugation profile are equally important.

Spider Thickness

Increasing the thickness of the spider material generally increases its stiffness.

However, it can also affect:

• Moving mass
• Damping
• Mechanical compliance
• Durability

The thickness is therefore selected as part of the complete suspension design.

Spider and Xmax

The spider must allow the voice coil to move through its intended excursion range.

At very large excursions, the spider may become increasingly nonlinear.

Its restoring force may no longer increase proportionally with displacement.

This can contribute to distortion.

Spider Nonlinearity

An ideal suspension would have a nearly linear relationship between displacement and restoring force.

Linear suspension:

Force
  │
  │       /
  │      /
  │     /
  │    /
  │   /
  └──────────── Displacement


Nonlinear suspension:

Force
  │
  │          __/
  │       __/
  │    __/
  │ __/
  │/
  └──────────── Displacement

Real spiders become increasingly nonlinear as their excursion limits are approached.

Spider and Distortion

Nonlinear suspension forces can produce harmonic distortion.

If the restoring force is not proportional to displacement, a sinusoidal electrical signal may produce a non-sinusoidal mechanical motion.

This can introduce additional frequency components into the acoustic output.

Spider Damping

The spider also contributes to mechanical damping.

Damping affects how mechanical energy is dissipated within the suspension.

Mechanical damping is represented partly by Qms.

The spider's damping characteristics depend on its material, construction and treatment.

Spider and Moving Mass

The spider contributes some mass to the moving assembly.

The total moving mass is represented by Mms.

Mms can include:

• Voice coil
• Former
• Cone
• Dust cap
• Spider's moving portion
• Other moving components

Adding unnecessary suspension mass can influence the driver's frequency response and efficiency.

Spider Attachment to the Voice-Coil Former

The inner portion of the spider is normally attached to the voice-coil former or another part of the moving assembly.

This attachment must be strong enough to transfer the suspension force during continuous movement.

A weak joint can cause the spider to separate from the former.

Spider Attachment to the Basket

The outer portion of the spider is attached to a stationary part of the speaker assembly.

This may be the basket or a dedicated suspension support.

The attachment must remain rigid relative to the moving assembly.

Spider Adhesives

Adhesives are used to attach the spider to the voice-coil former and basket.

The adhesive must withstand:

• Repeated vibration
• Mechanical stress
• Temperature changes
• Long-term fatigue

The adhesive should also be compatible with the materials being joined.

Spider and Voice-Coil Centering

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

The surround also contributes to centering, but the spider is particularly important because it is directly connected to the voice-coil former.

             Cone
               │
               │
        ───────┼───────
               │
          Voice coil
               │
          ┌────┴────┐
          │ Magnetic│
          │   gap   │
          └─────────┘
               │
             Spider

What Happens if the Spider Is Damaged?

A damaged spider can cause serious problems.

Possible symptoms include:

• Voice-coil rubbing
• Distortion
• Abnormal cone movement
• Reduced bass performance
• Changed resonance
• Buzzing or mechanical noise
• Permanent voice-coil damage

Common Spider Failures

Spider Fatigue

A speaker spider moves repeatedly during normal operation.

After millions of cycles, the material can experience mechanical fatigue.

High excursion, excessive temperature and poor material selection can accelerate fatigue.

A fatigued spider may change its compliance or develop cracks and deformation.

Spider Sag

In some large loudspeakers, the weight of the moving assembly can cause the suspension to settle over time.

This can be referred to as suspension sag.

The effect depends on the speaker's orientation, suspension design, moving mass and material properties.

In severe cases, the voice coil can become displaced from its ideal resting position in the magnetic gap.

Speaker Orientation and Spider Stress

A loudspeaker can be installed vertically, horizontally or in another orientation depending on its design.

The direction of gravity can place different static loads on the suspension.

For most modern speakers this is not a major problem under normal conditions, but very large or specialized drivers may be more sensitive to orientation.

Spider and High-Power Speakers

High-power drivers require spiders capable of handling substantial mechanical forces.

The spider must remain stable during large excursions without becoming excessively nonlinear.

Professional drivers may therefore use specialized spider materials, multiple suspension elements or carefully optimized geometries.

Multiple Spiders

Some high-excursion or high-power drivers use multiple spiders.

Using more than one suspension element can provide additional mechanical support and help control the moving assembly.

Multiple-spider designs are particularly useful when a large voice coil and heavy moving assembly must remain accurately centered.

Progressive-Rate Spiders

Some suspensions are designed so that their stiffness increases as excursion becomes larger.

This can help limit excessive movement near the mechanical limits.

Small excursion
      │
      ▼
Relatively soft suspension
      │
      ▼
Large excursion
      │
      ▼
Increasing restoring force

The exact suspension characteristic depends on the driver design.

Flat Spiders and Corrugated Spiders

Spider geometry can vary significantly.

Corrugated spiders are common because their shape provides controlled flexibility.

Specialized drivers may use different suspension geometries to achieve particular compliance and excursion characteristics.

Spider Colour

The colour of a spider is not normally an indication of its performance.

Different colours can result from:

• Fabric material
• Resin or coating
• Manufacturing process
• Manufacturer preference

Mechanical specifications are much more important than colour.

Spider and Speaker Repair

A damaged spider can sometimes be replaced, but this is generally more difficult than replacing a foam surround.

The spider is directly involved in voice-coil alignment, so the replacement must be installed very accurately.

Incorrect centering can cause permanent voice-coil rubbing.

Replacing a Spider

A typical spider replacement involves:

1. Removing the damaged spider.
2. Removing old adhesive carefully.
3. Cleaning the attachment surfaces.
4. Installing the replacement spider.
5. Centering the voice coil in the magnetic gap.
6. Bonding the spider to the voice-coil former.
7. Bonding the outer edge to the basket.
8. Allowing the adhesive to cure.
9. Checking the cone for smooth movement.

The exact procedure depends on the speaker construction.

Why Spider Replacement Requires Accurate Centering

The voice coil may have only a small clearance inside the magnetic gap.

If the replacement spider is installed off-center, the coil can rub.

Therefore, spider replacement is not simply a matter of gluing a new part into the same location.

The moving assembly must be accurately aligned.

Spider and Recone Kits

Some speaker recone kits include:

• New cone
• Voice coil
• Spider
• Surround
• Dust cap
• Adhesives

Replacing these components as a matched set can restore the original mechanical characteristics more reliably than mixing unrelated parts.

Spider and Thiele-Small Parameters

The spider influences several important loudspeaker parameters.

Spider and Enclosure Design

The spider establishes part of the driver's mechanical behaviour before the speaker is installed in an enclosure.

Once the driver is installed, the enclosure adds acoustic loading that changes the overall system behaviour.

Therefore, the spider and enclosure must be considered together when designing a low-frequency system.

Spider vs Surround: Which Is More Important?

Neither component can be considered independently.

The spider and surround perform different but complementary functions.

            Moving assembly

                  │
        ┌─────────┴─────────┐
        │                   │
    Surround             Spider
        │                   │
        ▼                   ▼
   Outer support      Coil centering
        │                   │
        └─────────┬─────────┘
                  │
              Cone + Coil

A well-designed speaker requires both suspension components to work together correctly.

Spider and Suspension Stiffness

The total suspension stiffness is determined by the combined behaviour of the spider and surround.

A simplified way of thinking about the system is that the two suspension elements contribute restoring forces to the moving assembly.

The actual mechanical system is more complex because the stiffness can change with displacement.

Spider and Low-Frequency Performance

The spider influences low-frequency behaviour primarily through suspension compliance and mechanical resonance.

A suitably compliant suspension can allow significant cone movement at low frequencies.

However, excessive compliance can create other mechanical limitations.

The correct design is therefore a balance between low-frequency capability, control and mechanical stability.

Spider and High-Frequency Performance

The spider is less directly associated with high-frequency acoustic output than the cone and voice coil, but its mass, damping and mechanical behaviour can still influence the overall driver response.

The moving system must remain mechanically stable across the intended frequency range.

Diagnosing a Spider Problem

Possible indicators of a spider problem include:

• Scraping voice coil
• Uneven cone movement
• Reduced output
• Unexpected resonance
• Buzzing
• Rattling
• Visible separation
• Visible deformation

A complete diagnosis should also inspect the surround, voice coil, spider attachment, cone and magnetic structure.

Do Not Confuse the Spider With the Surround

The two components are sometimes confused because both are flexible suspension elements.

The important distinction is their position.

Speaker front

      Surround
         ↓
   ┌───────────┐
   │   Cone    │
   └─────┬─────┘
         │
         │ Voice coil
         │
         ▼
       Spider
         ↓
      Basket

The surround is located at the outer edge of the cone, while the spider is located closer to the voice coil.

Key Takeaways

• The spider is an important part of a loudspeaker's mechanical suspension.
• It helps center the voice coil inside the magnetic gap.
• It allows controlled forward and backward cone movement.
• The spider works together with the surround.
• Spider compliance contributes to Cms.
• The spider influences the driver's free-air resonance.
• Corrugations allow the spider to flex while maintaining mechanical support.
• Spider geometry, material and thickness affect its stiffness and damping.
• Nonlinear spider behaviour can contribute to distortion.
• High-excursion and high-power drivers require carefully designed spiders.
• A damaged spider can cause voice-coil rubbing and distortion.
• Spider replacement requires accurate voice-coil centering.
• The spider should always be considered together with the surround, cone, voice coil and magnetic motor.