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What can go wrong with your speakers?

 

What can go wrong with your speaker and why --

by Toby Dean Guynn

Lots of things can go wrong with your speaker, some things major, some things minor; some things the manufacturer's fault, some the user's. The most important thing is that the speaker should fit the purpose. Only an expert, hopefully your dealer, can plan that. When a problem arises, it should be solved permanently. For example, if the user gets a bad speaker, it should be replaced, and he should not have to worry about it any more. If the user damages good speakers by poor baffling, the baffling should be improved. If the user over-powers good speakers, he should replace them with heavier duty speakers, or more of them. Another option is to cut back the power.

 

A speaker can fail for three major reasons:
1. The manufacturer makes an error in production.
2. Poor baffling by the user can cause the speaker to be worn out or ripped apart.
3. Overpowering by the user can burn or char the voice coil.


MANUFACTURING ERRORS THAT SHOULD ALWAYS BE COVERED UNDER WARRANTY

First, speakers can fail due to poor design. Second, speakers can fail because they are not well made. Speakers contain about a dozen parts that are assembled by riveting, screwing, gluing, and soldering. Each speaker has a basket, a cone, a surround, a gasket, a suspension (spider), a voice coil, a voice coil former, a pole piece, a magnet, a dust cap, two plates, flex leads, and terminals. If these parts don't stay together, the speaker should be repaired or replaced under warranty, assuming the speaker has not been over powered or badly baffled. With this many parts and a great number of joints required to assemble them, a lot of things can go wrong:

A. The flex leads can fail due to incorrect length, gauge, or soldering technique.
B. The surround can come unglued in two places.
C. The spider can come unglued in two places.
D. A chip from the magnet may get in the magnetic gap.
E. The magnet structure can come apart in four places or lose concentricity.
F. The glue joint between the cone and the voice coil former can fail.
G. The cone can fracture (especially paper ones ), or melt (plastic ones).
H. The voice coil can de-laminate or become open prior to charring.

Some of these errors may cause buzzing or other noises and can be easily repaired. Other errors require that the speaker be re-built -- replacing everything but the basket and the magnet structure. Still others require a total speaker replacement.


USER ERRORS NOT NECESSARILY COVERED UNDER WARRANTY

 

A. POOR BAFFLING

Speakers in well designed baffles in homes can have an amazingly long life--ten years or more. Speakers in poor baffles in cars can have an amazingly short life--months. This is often due to mechanical failure, not thermal failure. Thermal failure comes from overheating the voice coil at any frequency. Mechanical failure happens when a speaker cone travels too far in the BASS range. This can happen easily at power levels far below the thermal (wattage) rating of the speaker in bad baffles. (Some manufacturers use a surround and a spider with a limited throw to make long excursions impossible, but that causes two more problems. Limited throw means an increase in bass distortion and a decrease in bass volume.)

 

  • What is a GOOD BAFFLE? A solid box the right size and type for the speaker in it.
  • 1. NO BOX. Yes, people will lay a speaker down with no box or baffle and play it. Sometimes they hang them up by a wire or string and play them. Then they wonder why they don't get any bass and why the speaker tears apart.

    2. A good box, but one with a port or passive radiator tuned TOO HIGH in frequency. On low notes the speaker doesn't know it's in a box. It makes a long throw, but not much audible bass.
    3. An OPEN baffle board. This means one board, not a solid box with six sides. These open boards are found in many place--behind the seat of a truck, laying over the well in the rear of a hatchback, covering the trunk area of a hatchback, fastened in place of the rear seat in a sedan, or behind the back seat in the trunk of a sedan.
    4. The REAR DECK. (usually for six by nines or four by tens) Not a good baffle for powerful bass.
    5. The PANELS in cars, trucks and vans.
    6. Any baffle that aims heavy speakers (tens, twelves, or fifteens) UP or DOWN. DOWN is not as bad as UP, but a heavy cone will sag from the pull of gravity and come to rest out of the magnetic gap. This will cause distortion, loss of power, and a possible mechanical failure of the speaker.

    As you can see, many people have no choice but to use BAD baffles in their vehicles. Nevertheless, they need to be aware that when they do, they are placing their speakers in mechanical jeopardy. Many people think that a trunk or a door panel is equivalent to a solid box. It's not, and the price to be paid is in poor transient response, failure to generate good low frequencies, and increased risk of premature mechanical speaker failure. Extended usage in bad baffles at high power levels in the bass range can lead to these mechanical failures:

    1. The spider can be torn.
    2. The surround can be torn or worn out.
    3. The voice coil can be thrown out of the magnetic gap, permanently, or temporarily, the latter deforming it and making it useless. (Sometimes this is caused by a VERY large transient.)
    4. The voice coil can also be deformed by hitting the bottom of the magnetic structure. This could be a speaker design problem, but good compliant speakers should be able to travel almost one tenth of their cone diameter safely.

    It should be mentioned that excessive speaker excursion is not a problem in small sealed boxes. It can be a problem in very large sealed boxes.


    B. OVERPOWERING THE SPEAKER LEADING TO A CHARRED VOICE COIL

    This type failure can happen at any frequency, not just the bass range. When people talk about blowing a speaker up they usually mean that excessive wattage caused a thermal failure of the voice coil. That type failure means that part of the voice coil became short circuited, or open, or deformed so that continued movement is impossible or very noisy. EVERY speaker voice coil can be burned up.

    What does a burned (charred) coil look like? You can't tell until the cone and spider are cut out and the coil pulled out of the gap for inspection. However, sometimes the dust cap can be removed and you can see a melted Kapton voice coil former (It goes at 750 degrees.), or bubbles in a paper or aluminum former, or even charred wire. A new voice coil is a neat little cylinder of bright copper colored wire. When operated at its rated power it turns brown. When operated above its rated power it turns black. The coil could delaminate (come unglued from itself) before it turns black. THIS SHOULD BE COVERED BY THE MANUFACTURER'S WARRANTY. But once it turns black, it s ABUSE. Excessive heat can expand the voice coil wire and the little cylinder will not be neat anymore. Eventually the wire may become unbonded and create a short or open circuit.

    Thermal overload cannot be fixed in watts. A speaker takes in heat (watts), and it can dissipate heat into the air. If the air is HOT the speaker can't handle as many watts. Power handling goes way down in the summer with a speaker in the trunk. Don't put a hot amp under a speaker or in the enclosure with it.


    TIPS TO EXTEND SPEAKER LIFE

    Don't let your speakers get wet. We pay extra money to have our parts made "water resistant," but almost any speaker will fail when it is repeatedly damp or wet. Most speakers that fail from being wet cannot be re-coned. Keep those speakers DRY!

    Keep metal filings and chips away from your speaker. (The people who cut holes in metal to do your car installation tend to leave these around.) If they get near the magnetic gap they can cause noises. If chips get in the gap, they can lead to speaker failure.

    The user may create problems while installing the speaker. He may warp the basket by screwing it to a baffle that is not flat, or by dropping it. He can stick a screwdriver through the surround or even the cone; or he may accidentally dent the dust cap. More often than not we can straighten a bent basket; mend a punctured surround with a special flexible glue; mend a hole or fracture in a cone; or replace a damaged dust cap.

    PLEASE DON'T TRY TO MAKE THESE REPAIRS YOURSELF. HOME REPAIR JOBS USUALLY ARE NOT SUCCESSFUL AND MAKE FACTORY REPAIR JOBS IMPOSSIBLE! We are happy to make small repairs on your TOBY speakers, usually at no charge


    In conclusion, we want you to understand more about how your speakers work, how they can work their best, and how they can stop working. If you have any questions about your speakers or your warranty, ask us or your dealer. Also, tell us about your application and we will make recommendations that will get you the best performance from your available space, and relate it to your amplifier power and your budget.

    • What is a BAD BAFFLE? There are lots of possibilities...
     

    6522 Midway Rd. Haltom City, TX 76117   -   682-231-2099   -     HOURS (Monday-Friday 11-6) (Saturday 11-3)