Subwoofer Not Working – Diagnosis and Repair (Full Guide)


Even the highest-quality subwoofers are not immune to breakdowns. A variety of reasons can cause this.

Whether in your living room, home theater, or vehicle, sometimes the subwoofer will suddenly stop producing sound.

If it becomes clear during the diagnostics that this is caused by some kind of internal damage to the subwoofer, it’s unnecessary to go to the service center and buy new equipment.

Nowadays, it is very simple to repair the subwoofer – all the spare parts are available online. You only need to find the right tools and carefully study the methodology of repairing subwoofers. 

To get everything right, read this article and follow the steps.

Also, if you have difficulties with the disassembly of subwoofers, we got you covered.

BEFORE WE BEGIN, THIS ROCKVILLE SUBWOOFER IS ON A HUGE DISCOUNT ($480 to $189) on Amazon from 10/04/2022!

Types of subwoofer faults

subwoofer not working how to repair subwoofer

The main part of any subwoofer is the dynamic radiator, which is involved in converting the electrical signal into sound waves. It is also the most common part that breaks down.

What are the most common malfunctions of subwoofers?

There are generally three main causes of subwoofer failure:

  • Improper usage
  • Factory defects – the use of substandard parts or errors during the assembly of the device
  • Natural wear and tear of the acoustic equipment.

Attributing the breakdown to one of the causes is quite simple.

In the case of a manufacturing defect, the subwoofers usually break within a short time after purchase. Natural wear and tear, on the contrary, takes a very long time.

Even cheap quality subwoofers can last at least a dozen years with proper use.

Thus, the sudden breakdown most often refers to errors in the usage of the subwoofers.

Improper usage

The main cause of breakdowns when operating subwoofers is failure to comply with the permissible power limit of the signal being supplied to the transmitter.

Most often, this is because the user makes a mistake when determining the power of the subwoofer and the amplifier.

It’s very easy to do, as several methods can be used to calculate the power.

The values of effective, sinusoidal, and amplitude power can be drastically different from each other – the excess, if the wrong type of power is taken into account, can exceed 200%. Of course, the subwoofer burns out the first time it is plugged in.

Dynamic overloading is very common in subwoofers with multiple drivers. In such a subwoofer, the power of the electrical signal can be incorrectly distributed between the tweeter, the midrange subwoofer, and the subwoofer.

Typically, the victim of such a malfunction is the tweeter, which requires significantly less power than its counterparts. The power of the tweeter is usually no more than 1/10 of the total power of the subwoofer.

The fragile treble driver can break instantly if the user tries to supply more current to a tweeter by over-amplifying the treble with EQ.

In addition to electrical faults, there can also be mechanical damage to any part of the subwoofer. It is usually protected by a fabric or metal grille, but damage to the transducer is nevertheless fairly straightforward.

The dust cap that protects the unit from dust, the cone surround, and the diaphragm itself – a thin film, often made of paper, which is easily punctured or torn – can all be damaged.

The consequences of such damage can be quite serious: the coil or casing can become misaligned, making it physically impossible to play the sound.

The same result is caused by the core moving out of the center of the subwoofer, in which case the most important parts of the device get stuck in the magnetic trap.

Such damage is usually caused by very careless handling of the subwoofer, most often by dropping the device.

This can damage fragile portable subwoofers, made from not the most durable materials, and the massive floor-standing subwoofers with high power. Although the latter, of course, are better protected from mechanical damage.

Factory defects

All subwoofer parts are usually glued together, and improper gluing can cause fixed parts to move out of their intended locations.

Even the cone may peel off, making it impossible to vibrate and thus receive sound waves. 

Poor fixing of moving parts and wires markedly reduces the life of the subwoofer, and natural wear and tear occur too quickly.

Natural wear

When properly assembled, the most affected by wear and tear are the most fragile parts of the device – the suspension and flexible cables – that is, the cone holder and the wire that cables the signal to the coil.

Diagnosis

subwoofer not working how to repair subwoofer

It seems very easy to distinguish between mechanical and electrical damage – just remove the protective panel and inspect the subwoofer for damage.

If there is nothing wrong with the integrity of the parts, then the failure is related to the electrical part. 

However, it is difficult to distinguish certain types of breakdowns by eye and ear – for example, a malfunction of the flexible coil cable. In this case, more often than not, the sound is not completely gone – the subwoofer may make strange noises and stop sounding from time to time.

An ohmmeter connected to the subwoofer terminals with the diaphragm static can be used to determine if the flexible cable is broken and coil faults.

If the arrow begins to twitch, this is where the problem is. To fix the breakage, you will have to disassemble the subwoofer, separate the broken parts and put new ones – you can buy them at any radio equipment store.

With the help of a bass generator and infrasound, you can find out if the coil, some of its turns, and the cone is detached from the suspension. In this case, there will be extraneous sounds.

They will be heard at a certain frequency when the damaged part of the subwoofer enters resonance with the sound.

As for the more serious breakdowns, they are much easier to spot – you don’t even need special tools:

  1. Shake the subwoofer gently.

If anything is rolling around inside, the coil has come off the cylinder.

  1. Look at the cone.

If it is reluctant to move, the coil’s influence on it has decreased. The cartridge is likely stuck between the magnets due to the displacement of the coil.

The coil may be stuck together with the sleeve if the diaphragm does not move due to core displacement.

In the latter two cases, the repair consists of releasing the cartridge case, then disassembling the unit and correcting the cause of the problem.

Do not disassemble the subwoofer while the core is between the magnets, as this could also damage the diaphragm.

Replacing flexible cables

Repairs can be made in two situations – with free access to the cables, in which case it is not necessary to disassemble the subwoofer, and with the device closed. 

In the first case, of course, the repair is much easier. Because of the presence of magnets inside the subwoofer, it is advisable to use a tool not made of steel, if found, as magnetizing can cause damage to the diaphragm or the cap.

The flexible cable is bonded to the solenoid coil’s wiring. To separate these parts, you need to heat the bonding area with a soldering iron and carefully tear off the old pigtail from the coil. Be careful not to damage the working parts.

Your best place to buy a new cable is Amazon. But you can also make it yourself; you can use any stranded copper wire with the same cross-section as the original part.

Its twist should be made the same as that of the flexible cable to be replaced.

All wires are glued together with special glue and tinned. The spare part should then be glued to the coil cable and securely fastened to the cone’s inner surface.

How to Disassemble a Subwoofer

Subwoofers of any type, like any technique, need careful handling and proper care. This applies to proper connection and usage and the careful treatment of the device during use.

For example, subwoofers should be regularly cleaned of dust and dirt – especially the outer part of them.

The subwoofer’s enclosure is usually sealed – this is important because, inside the enclosure, special conditions must be maintained to allow sound waves to propagate correctly in space and be directed towards the listener.

There are just two holes in the cabinet in a standard subwoofer design: one containing the driver and the other a phase inverter, which usually points downwards, which means that very little dust enters the cabinet. 

But to a certain extent, it still happens, and everybody knows the effect of dust on electronics – the microcircuits that control the subwoofer overheats and can fail.

So how do you disassemble a subwoofer for cleaning or repair?

Disassembling the cabinet

If the subwoofers are broken and need repair, or it seems that it is time to clean the inside of the subwoofer from accumulations of dust and dirt, you need to get access to the inside of the cabinet.

So how to do it? Should you disassemble a well-built enclosure at all?

In the manufacture of the subwoofer cabinet can be assembled using one of three techniques:

  • Bonding the walls of the enclosure
  • Fastening of the parts using metal fasteners (link to Amazon) – screws or self-tapping screws
  • Placing the electrical elements of the device inside the case made of a single piece of plastic or wood.

The last option, of course, is rarely used. In addition, such cases are often plastic – if you can cast a solid piece of polystyrene.

Plywood or medium-density chipboard, of which wooden cases are made, will have to be fastened separately in any case.

The first two options are usually combined – for example, the sides, top, and bottom walls are permanently glued with glue or epoxy resin, and the front and back panels are screwed together. 

This allows the user to access the internal parts of the subwoofer without much trouble for repair and cleaning. So how do you disassemble such an enclosure?

Glued Enclosures

If all the enclosure parts have been glued together and there is no easy access to the insides, you will have to destroy the glue compound.

To do this, you will need a certain set of materials:

  • Solvent

It can be different, depending on the glue used. I recommend this one. Since you can not determine the type of glue by eye, you will have to experiment – stock up on the most powerful solvent: acetone, alcohol, ethyl acetate.

The latter, however, is not recommended, as it is toxic and can cable to health problems.

However, if the glue is especially strong and nothing else will take it, there is no other way out – you will have to use ethyl acetate.

In this case, you need to protect yourself – wear a respirator mask to protect the respiratory tract gloves on the hands, as contact with the concentrated liquid on the exposed skin can cable to chemical burns.

  • A sharp knife 

It will help divide the parts, especially if the body is made of pressed wood.

  • Matches or toothpicks

They will be used as a prop. You will not be able to dissolve all the glue at once. In addition, you need to put a constant load on the parts that came off, so in the places where the glue was dissolved, you need to place these stanchions between the surfaces of the parts to be separated.

  • A glass pipette

With its help, the glue will be poured precisely into the gap between the walls of the subwoofer housing. Instead of a pipette (Amazon link), you can use a thin medical syringe.

  • Any flat metal tool

– a wide screwdriver or spatula. Will be used as a lever to separate the body parts from each other.

In general, the technology of disassembly of the case, assembled with glue, is very simple.

1. You need to carefully examine all the adhesives to examine the joints under a magnifying glass – you need to find the weakest place, which will begin the process of dissolving the glue.

2. The joint is poured into the solvent – pour it a lot until the glue begins to dissolve.

If the subwoofers are old, the glue could become as strong as cement, and a very large amount of solvent will be needed.

3. Slowly, a spatula or knife is inserted into the joint, and the gap is widened with careful movements. When the parts are wide enough, you can put a match through the hole between them to maintain a constant width of the seam.

Move along the entire length of each glued face until all the body walls are separated from each other.

After cleaning or repair, the joints will need to be cleaned of old glue and solvent residue to reassemble the case. 

The latter, however, may evaporate on its own. After the edges of the walls are cleaned and sanded, they have glued together again with any plastic glue.

To ensure that the attachment turns out to be strong enough, you need to follow the instructions from the manufacturer of the adhesive compound exactly.

Enclosures on screws

subwoofer not working how to repair subwoofer

If the walls of the subwoofer housing are fastened to each other with fasteners – screws, bolts, or self-tapping screws, it is much easier to separate them.

If only part of the walls are fastened with screws, and the other part is glued, you should remove only the former – there is no point in fiddling with the glue in this case.

The back wall is the easiest to remove – usually, the screws are visible there and can be easily unscrewed.

There can be a situation when only a part of the wall is screwed down and when you remove it, a small hole is revealed through which you can get access to the inside of the acoustic device.

Usually, the engineers had a good enough reason for that, and there is no need to argue with them – leave everything as it is and remove only what can be removed without extra effort.

When removing the back wall, the most important thing is not to damage the power elements and wires connecting the connectors on the back panel to the chip inside the subwoofer. 

Therefore, after unscrewing the screws, you should not pull strongly on the detached panel – you should carefully remove it from its place and put it aside as far as the stroke and length of the wires allow.

As for the front panel, you won’t be able to remove it completely. It is also dangerous – having completely removed the front wall, it is easy to damage the subwoofer controls – volume control, power button, power supply indicator, and possible headphone or microphone jacks.

The easiest way to remove the subwoofers is the large enough holes to penetrate the cabinet. 

To do this, remove the protective fabric shields from the drivers. Under them, you will find an easily recognizable diaphragm of the cone with a protective cap in the middle – all this is held on the metal body of the subwoofer.

It is screwed to the body of the subwoofer. Take a screwdriver and safely unscrew everything that can be unscrewed.

At the same time, you must be careful not to bring the metal tool too close to the center of the subwoofer because there are permanent and electrical magnets.

Having disassembled the cabinet or at least removed enough of the external elements that protect the inside of the subwoofer, you can shine a flashlight in there and see if the subwoofer needs to be cleaned of dust other contaminants. 

If a lot of dust has accumulated, you need to clean the microchips very carefully.

The bulk of the dust can be removed with a vacuum cleaner, taking care not to touch the tube to the electrical circuit boards not to damage them. The fine dust is removed with a brush, after which the subwoofer is blown out to remove all residual dirt from the housing.

If the subwoofer has been disassembled for repair, you can remove those parts that you believe cause the subwoofer’s malfunctioning.

If it is a control chip, then, in principle, there is not much point in repairing it. It is easier to buy a new subwoofer. 

The built-in audio amplifier can be replaced by buying a similar one at a radio parts store or from a spare parts supplier for music subwoofers.

If the subwoofer is broken, you will also have to disassemble it.

Disassembling a subwoofer shell

Many parts in a subwoofer can break – these include the flexible cables, the magnetic coil, and the cone itself.

More often than not, all of the driver components are hidden between the paper or polymer diaphragm and the metal base of the subwoofer.

How do you get inside without damaging the thin film of the diaphragm?

The diaphragm is fixed in two places – at the outer perimeter with a cardboard or rubber hanger and in the center, where it is attached to the sleeve.

You will have to tear it off from the outside. Under no circumstances should you just cut it off – gluing it back, in this case, will not work. You will have to buy a new cone.

The process for removing the surround is the same as taking apart a glued box – gradually, the solvent is poured away, the material is gently lifted away from the substrate and propped up with toothpicks. 

You must be as careful with the cardboard hanger as possible so that it does not collapse.

When the diffuser is removed from its place, the only thing left is to peel off the centering washer. This gives you full access to the inside of the subwoofer. Dust doesn’t get in here, so you won’t need to clean the sub.

Tray Fiddy

Tray has come to terms with the fact he will probably never be a famous DJ.... but that hasn't stopped him from mixing and throwing parties around the town. Tray has over 10 years experience of DJing at home and events.

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