Why Speaker Diagnosis Is Important

Before repairing a loudspeaker, it is important to determine exactly what has failed.

Replacing a surround will not fix a burned voice coil, and replacing a voice coil will not solve a damaged magnetic motor.

A proper diagnosis helps determine:

• Whether the problem is electrical or mechanical.
• Which component has failed.
• Whether the speaker is repairable.
• Which replacement parts are required.
• Whether a complete recone is necessary.

The Three Main Types of Speaker Faults

Most loudspeaker problems can be grouped into three broad categories.

A speaker can also have more than one fault at the same time.

Start With a Visual Inspection

The first diagnostic step should normally be a careful visual inspection.

Look at:

• Cone
• Surround
• Spider
• Dust cap
• Voice-coil area
• Tinsel leads
• Terminals
• Basket
• Magnet assembly

Do not immediately connect a suspected faulty speaker to a powerful amplifier.

Inspect the Cone

Look for:

• Tears
• Cracks
• Holes
• Water damage
• Deformation
• Loose sections
• Separated joints

A damaged cone can create distortion, buzzing and air leakage.

Inspect the Surround

Check the complete circumference of the surround.

Look for:

• Cracks
• Tears
• Holes
• Detached edges
• Foam deterioration
• Uneven deformation

A foam surround that has become brittle or powdery generally requires replacement rather than a simple patch.

Inspect the Spider

The spider controls the position of the moving assembly.

Look for:

• Tears
• Cracks
• Detached edges
• Deformation
• Loose adhesive joints

A damaged spider can cause the voice coil to become misaligned.

Inspect the Dust Cap

A damaged dust cap does not necessarily mean that the speaker's voice coil is damaged.

However, a missing or badly damaged dust cap can allow contamination to enter the voice-coil area.

Check whether foreign material has entered the magnetic gap.

Inspect the Tinsel Leads

Tinsel leads connect the moving voice coil to the speaker terminals.

Look for:

• Broken wires
• Loose connections
• Frayed conductors
• Detached solder joints
• Incorrect routing

A broken tinsel lead can make a perfectly good voice coil appear to be open.

Inspect the Basket

The basket should be checked for:

• Cracks
• Bends
• Corrosion
• Loose motor assembly
• Damaged mounting points

A severely deformed basket can prevent accurate voice-coil alignment.

Inspect the Magnet Assembly

Check the magnet and magnetic structure for signs of physical damage.

Possible problems include:

• Shifted magnet
• Cracked magnetic components
• Loose motor assembly
• Rust or contamination
• Evidence of mechanical impact

A damaged magnetic motor can make reconing impractical.

The Cone Movement Test

One of the simplest speaker diagnostic tests is a gentle mechanical movement test.

The speaker must be disconnected from the amplifier.

Apply even pressure to the cone and move it gently inward.

Listen carefully.

A healthy assembly should normally move smoothly without obvious scraping.

What Does a Scraping Sound Mean?

A scraping sound during cone movement is a strong indication that the voice coil is contacting the magnetic structure or that contamination is present in the magnetic gap.

Possible causes include:

• Off-center voice coil
• Deformed voice-coil former
• Damaged spider
• Damaged surround
• Shifted magnet
• Foreign material in the gap

What If the Cone Moves Smoothly?

Smooth mechanical movement does not necessarily prove that the speaker is electrically healthy.

The voice coil may still be open, partially damaged or have an electrical connection problem.

An electrical test should therefore follow the mechanical inspection.

Checking the Speaker With a Multimeter

A digital multimeter can be used to measure the DC resistance of the voice coil.

Set the meter to an appropriate resistance range and measure across the speaker terminals.

The result should be compared with the expected resistance of the driver.

Open Voice Coil

If the multimeter indicates an open circuit, there is a break somewhere in the electrical path.

Possible causes include:

• Broken voice-coil winding
• Broken tinsel lead
• Failed connection between coil and lead
• Broken terminal connection

The voice coil itself should not automatically be blamed until the tinsel leads and terminals have been inspected.

Very Low Resistance

An unusually low resistance can indicate an electrical problem, but the expected value depends on the speaker design.

Do not diagnose a voice coil solely from the nominal impedance printed on the speaker.

Nominal impedance and DC resistance are different quantities.

Nominal Impedance vs Measured Resistance

A speaker labelled 8 Ω will normally measure less than 8 Ω when its DC resistance is measured with a multimeter.

This is normal because speaker impedance changes with frequency and includes inductive and mechanical effects.

The DC resistance is only one part of the speaker's electrical behaviour.

Testing for Intermittent Connections

A speaker may have a connection that works when stationary but opens when the cone moves.

Possible locations include:

• Tinsel leads
• Voice-coil lead connections
• Terminals
• Broken winding sections

If the resistance changes significantly during gentle mechanical movement, investigate the moving electrical connections.

Diagnosing a Burned Voice Coil

A burned voice coil may show:

• Open circuit
• Abnormally changed resistance
• Burnt smell
• Discolored winding
• Deformed former
• Scraping caused by heat deformation

Severe thermal damage generally requires voice-coil replacement or reconing.

Signs of Voice-Coil Overheating

Inspect the voice-coil area for:

• Darkened or burned wire
• Discolored former
• Damaged adhesive
• Deformed winding
• Burning smell

Overheating can damage both the winding and the materials that hold it together.

Diagnosing a Broken Tinsel Lead

A broken tinsel lead can produce complete loss of sound even when the voice coil itself is intact.

Inspect the lead from the terminal all the way to its connection with the voice coil.

Look for visible breaks and loose connections.

Diagnosing a Loose Tinsel Lead

A loose tinsel lead may cause intermittent sound or crackling when the cone moves.

The lead should be mechanically supported while still having enough flexibility for normal cone movement.

Diagnosing a Torn Cone

A torn cone can produce:

• Buzzing
• Distortion
• Reduced output
• Air leakage
• Unusual cone movement

Small tears may sometimes be repaired, while extensive cone damage may require replacement.

Diagnosing a Damaged Dust Cap

A damaged dust cap may produce buzzing or allow contaminants into the voice-coil area.

If the cap is loose, inspect it carefully before assuming that the voice coil itself has failed.

Diagnosing a Damaged Surround

A damaged surround can produce:

• Buzzing
• Reduced bass
• Uneven cone movement
• Excessive excursion
• Air leakage

A severely deteriorated foam surround should normally be replaced.

Diagnosing a Damaged Spider

A damaged spider can affect cone centering and suspension behaviour.

Possible symptoms include:

• Voice-coil rubbing
• Uneven cone movement
• Reduced mechanical stability
• Buzzing
• Incorrect cone rest position

Diagnosing Voice-Coil Misalignment

A misaligned voice coil often produces scraping when the cone is moved.

Possible causes include:

• Incorrect reconing
• Damaged suspension
• Shifted magnet
• Deformed former
• Foreign material in the magnetic gap

Voice-coil centering should be checked carefully before replacing components unnecessarily.

Diagnosing Foreign Material in the Gap

Small particles can enter the magnetic gap and cause rubbing.

Possible contaminants include:

• Metal particles
• Dust
• Old adhesive
• Voice-coil fragments

A speaker that suddenly develops scraping after mechanical damage may have contamination inside the gap.

Diagnosing a Shifted Magnet

A strong impact can sometimes disturb the alignment of the magnetic motor.

A shifted motor can cause the voice coil to rub even if the cone and suspension appear undamaged.

This type of fault can be significantly more difficult to repair than a simple surround or voice-coil problem.

Diagnosing a Bent Basket

A bent basket can move the suspension or magnetic motor away from its intended position.

Check whether the basket remains symmetrical and whether the motor assembly is securely mounted.

A severe deformation may make accurate repair impractical.

Speaker Produces No Sound

If a speaker produces no sound, follow a systematic procedure.

1. Disconnect the speaker from the amplifier.
2. Inspect the terminals.
3. Inspect the tinsel leads.
4. Measure voice-coil resistance.
5. Check for an open circuit.
6. Inspect the voice coil if accessible.

If the voice coil measures open, determine whether the break is in the coil or an external connection.

Speaker Produces Weak Sound

Weak output can have many causes.

Possible speaker-related causes include:

• Partial voice-coil damage
• Mechanical rubbing
• Damaged cone
• Damaged surround
• Loose connection
• Suspension problems

The amplifier, crossover and wiring should also be checked before concluding that the speaker itself is faulty.

Speaker Produces Distortion

Distortion can be caused by:

• Voice-coil rubbing
• Torn cone
• Loose dust cap
• Damaged surround
• Damaged spider
• Loose adhesive joint
• Overexcursion
• Voice-coil damage

Mechanical inspection is particularly useful when distortion occurs even at relatively low power.

Speaker Produces Buzzing

Buzzing is often associated with a mechanical problem.

Possible sources include:

• Torn cone
• Loose dust cap
• Loose surround
• Detached spider
• Loose tinsel lead
• Voice-coil rub
• Loose adhesive joint

Careful listening and gentle cone movement can help identify the source.

Speaker Produces Scraping

Scraping during cone movement strongly suggests a mechanical problem around the voice coil.

Check:

• Voice-coil centering
• Magnetic gap contamination
• Voice-coil former
• Spider
• Surround
• Magnetic motor alignment

Speaker Produces Rattling

Rattling can come from the speaker itself or from something attached to it.

Inspect:

• Dust cap
• Grille
• Terminals
• Tinsel leads
• Basket
• Loose adhesive joints
• Cone

Speaker Works at Low Volume but Fails at High Volume

This behaviour can indicate a problem that becomes apparent only with larger excursion or higher thermal stress.

Possible causes include:

• Voice-coil rubbing at higher excursion
• Loose suspension component
• Damaged spider
• Damaged surround
• Thermal voice-coil problems
• Mechanical limitation

Speaker Sounds Good at Low Frequency but Bad at High Frequency

High-frequency problems may involve:

• Dust cap
• Cone breakup
• Voice-coil inductance
• Mechanical damage
• Loose components

The exact cause depends on the speaker design and system.

Speaker Sounds Good at High Frequency but Bad at Low Frequency

Low-frequency problems can be associated with:

• Damaged surround
• Damaged spider
• Air leakage
• Excessive mechanical excursion
• Suspension deterioration

Diagnosing a Foam Surround

Pressing gently on the cone can reveal mechanical problems caused by surround deterioration.

A deteriorated foam surround may feel uneven or unusually weak.

Visual inspection should be used together with the movement test.

Diagnosing a Speaker After Overpowering

A speaker exposed to excessive amplifier power can suffer both thermal and mechanical damage.

Check:

• Voice-coil resistance
• Voice-coil movement
• Burn marks
• Former deformation
• Suspension damage
• Cone damage
• Tinsel leads

Do not assume that an apparently normal resistance measurement means the speaker has suffered no damage.

Diagnosing a Speaker After Clipping

Severe amplifier clipping can generate significant heat in a loudspeaker, particularly in some frequency ranges.

If a speaker has been exposed to a heavily clipped signal, inspect the voice coil for thermal damage.

Electrical Diagnosis vs Mechanical Diagnosis

Systematic Speaker Diagnosis

              Speaker fault
                    │
                    ▼
            Visual inspection
                    │
                    ▼
           Cone movement test
                    │
          ┌─────────┴─────────┐
          │                   │
       Smooth               Scraping
          │                   │
          ▼                   ▼
    Electrical test     Check voice coil,
          │              gap and alignment
          │
     ┌────┴────┐
     │         │
   Normal     Open
     │         │
     ▼         ▼
 Low-power   Check coil,
    test     leads and
              terminals

This approach helps prevent unnecessary replacement of components.

Do Not Diagnose From One Test Alone

A single measurement rarely provides the complete diagnosis.

For example, a normal resistance measurement does not prove that the voice coil is mechanically healthy.

Likewise, a scraping sound does not automatically prove that the voice coil itself is damaged.

Use several diagnostic methods together.

Speaker Diagnosis Checklist

• Disconnect the speaker from the amplifier.
• Inspect the cone.
• Inspect the surround.
• Inspect the spider.
• Inspect the dust cap.
• Inspect the tinsel leads.
• Inspect the basket.
• Inspect the magnet assembly.
• Gently check cone movement.
• Listen for scraping.
• Measure DC resistance.
• Check electrical connections.
• Inspect for foreign material in the magnetic gap.
• Check voice-coil alignment.
• Perform a controlled low-power test.
• Determine whether repair or replacement is appropriate.

When a Speaker Should Not Be Repaired

Some speakers are technically repairable but economically or practically unsuitable for repair.

Replacement may be preferable when:

• The basket is severely damaged.
• The magnetic motor is badly damaged.
• Replacement parts are unavailable.
• The cost of repair approaches the cost of a replacement.
• The speaker has extensive damage in several components.

When Reconing Is Appropriate

Reconing can be a practical solution when the basket and magnetic motor remain usable but the moving assembly is damaged.

A recone may replace:

• Cone
• Voice coil
• Spider
• Surround
• Dust cap
• Tinsel leads

See also: Speaker Reconing .

When Recoiling Is Appropriate

If the cone, spider and surround remain usable and only the voice coil has failed, replacing or rewinding the voice coil may be sufficient.

The replacement coil must match the original mechanical and electrical requirements.

See also: Speaker Recoiling .

Diagnosis Before Buying Parts

Always diagnose the speaker before ordering replacement components.

Knowing the actual failure can prevent buying a complete recone kit when only a tinsel lead or surround needs attention.

Conversely, it can prevent wasting time trying to repair a surround when the voice coil is already severely damaged.

Key Takeaways

• Start speaker diagnosis with a careful visual inspection.
• Check the cone, surround, spider, dust cap, tinsel leads, basket and magnetic motor.
• Gently move the cone by hand to check for rubbing.
• A scraping sound can indicate voice-coil misalignment, contamination or magnetic-motor problems.
• Measure the voice-coil DC resistance with a multimeter.
• An open circuit can be caused by the voice coil, tinsel leads or another electrical connection.
• Nominal impedance is not the same as DC resistance.
• A normal resistance reading does not prove that the speaker is mechanically healthy.
• Buzzing can originate from cones, dust caps, surrounds, spiders, tinsel leads or loose adhesive joints.
• Severely deteriorated foam normally requires surround replacement.
• A damaged magnetic motor or basket can make reconing impractical.
• Always diagnose the speaker before purchasing replacement parts.
• Use mechanical, electrical and controlled audio tests together.
• Perform low-power testing before applying significant power to a repaired speaker.
• A systematic diagnosis can save time, money and unnecessary component replacement.