Speakers used in PA systems and audio systems come in various dimensions for numerous purposes. You may use active speakers, passive speakers, stage monitors, subwoofers etc. To be able to understand how a loudspeaker works and how to know if your speakers are blown, first of all, you’ll need to know what it is made of and have a little bit of an idea how they are constructed.
How do loudspeakers work?
Although it may look like one piece, the speaker is formed of several components: dust cap (dust cover), surround, cone, suspension, voice coil, chassis, front plate, magnet, yoke.
- Dust cap or dust cover is actually a part of the speaker cone and it affects on frequency response and cone function while keeping the dirt and dust out of the voice coil
- The surround is also described as the front suspension and it controls the voice cone range. It can easily be physically damaged.
- The cone is the greatest factor defining the frequency response and overall sound of the speaker. It also has the highest mechanical requirements and because of that, it has a significant influence on the power of the speaker.
- The suspension is an important part of the low-frequency response and mechanical power treatment of the loudspeaker. Its primary purpose is to keep voice coil in its place.
- The voice coil is basically wire wound around a chassis. Choices of enamel, adhesives and the method you wrap that wire can vary in its efficiency as well as in its power rating.
- The chassis produces its own acoustic field also. Low quality or just wrong chassis will vibrate and it can affect the sound of your speakers like making it distort, lose its clarity and definition.
- The front plate, with the assistance of the magnet and yoke, creates the magnetic circuit. Magnetic efficiency and stability, speaker sensitivity and power handling depend on the front plate’s diameter and thickness.
- The magnet provides the main force of the speaker and it is present in all kind of sizes and specifications. It is the heaviest part of the speaker.
- The yoke is placed on the backside of the speaker and plays a big role in the efficiency and stability of the magnet structure, as well as in keeping the voice coil temperature at optimum range.
Now you are familiar with all the parts, and it will be much easier for you to know exactly what is wrong with your faulty speaker.
What do blown speakers sound like?
The first thing you will notice if one of your speakers is blown is the noticeable change in sound quality. I’m sure that, at least once in your life, it has perhaps happened to one of the speakers in your house stereo system, car stereo, guitar amp, where the loudspeaker stops working completely or starts to produce a strange sound. The first thing to check is that you connected it up properly. If everything is ok with connections, then you perhaps need to consider that the speaker is damaged in some way?
Blown speakers in church sanctuary PA systems, or auditorium sound systems usually have been ruined by an extreme amount of power, driven through the speakers. Identifying blown or partially blown speakers is very simple. Listen to your speakers. A faulty speaker will create static buzz, fuzzy sound at loud levels if partially blown, and distortion at all levels or no sound at all if completely blown. A common problem of speakers, especially old or low-end speakers, is those made with paper cones.
With too much power applied, or with too much treble or bass, the paper cone can be ripped quite easy. Not that such things don’t happen to high-end speakers, either. Many of them can be blown also if they are played too loudly, especially with strong bass and high treble.
Completely blown speaker – no sound
If your speaker doesn’t produce sound at all, or the speaker produces distorted buzz sound on any volume, that means that the cone has separated from the coil and your speaker is completely broken. You can also indicate whether your speakers are blown or not by pressing it. If your speaker cone is working properly its suspension will allow movement. If you press gently on the speaker cone and if it is stuck in place, you have a faulty speaker. Even if you can move the speaker cone, you should listen for noises and check for loose movements of it.
Those can also be indications of bad suspension. In these cases, you can do two things, the first is to take it to an audio technician to have it repaired, and the second is to replace the entire broken speaker. Before you jump to action, make sure you’ve checked if cables are connected properly just in case you might have overlooked something. Once you have ruled out other possible causes, you can then evaluate what is the best action.
Diagnose a partially blown speaker
If you are wondering if you might have a partially blown speaker, there are some things you can check for. Listen to your speakers. They will sound relatively OK at a lower volume, however, if you turn your volume knob up, it will be distorted. The cause of a partially blown speaker is very often when the midrange or tweeter drivers have malfunctioned. So, if you can hear the sound, but it is distorted, then your speaker may be partially damaged. Check that the driver mounting screws are tight and of course, check connection cables also. If you think it might be fixable, take to a store that does speaker repair.
Ways to avoid blowing speakers
It is simple as turning the volume down! The main cause of damaged loudspeakers in audio systems is too much power, so make sure you don’t have the volume too high for the speaker rating. Also, make sure your cables and connectors are properly plugged in i.e. amplifier power cable for active speakers, speaker wires, and audio cable etc. Commonly asked questions – Will I blow my speakers if I use this amplifier with these speakers? Can I connect more than one speaker to one output, etc?
You won’t blow your speakers if you keep volume knob at a reasonable level. If you, for example, connect a couple of speakers to one output on your amplifier, it will work…but to some point. Depending on speaker impedance, if you turn the volume knob up, your amp will power off or in the worst situation, will be damaged. So, I don’t recommend that you experiment with that if you are a beginner, especially if your equipment is expensive. It is also worth checking treble and bass eq settings, as sometimes pushing too much of certain frequencies can cause damage. You might also be interested in reading my post about how to connect a microphone to a speaker.
Blown Speaker Sound – bass rattle
Anything can cause a bass rattle. Powerful low frequencies at a high level can shake some electrical and mechanical connections causing all sorts of problems. The first thing you should do in this situation is, lower the volume and listen carefully. If rattle is still present before you conclude that your speaker cone is damaged, check the nearest object around your speaker (like speaker stand if you have it). Check if the rattle is happening within both speakers. Don’t forget to check cables and connectors, amplifier wiring on active speakers and tighten screws on your speaker, these can also vibrate and making a rattling noise.
Test speakers for coil damage with a multimeter tester
If you or any of your friends have a multimeter, you can test if one of your speakers is blown. ( A multimeter should be part of any audio techs toolbox anyway!)
- Disconnect the speaker
- Connect the two probes to the multimeter tester
- Turn the multimeter on to measure ohms (Ω)
- Insert the red probe into the positive lead and the black probe into the negative lead
- The multimeter will then measure the amount of impedance
If there isn’t any impedance number on your multimeter screen, your speaker is unfortunately damaged.
How to tell when a speaker needs to be replaced or repaired
You will definitely know when is the time to replace speakers and know the blown voice coil symptoms. If you can hear crackling, distorted, buzz sound or even no sound at all from your speaker/s, or if you are noticing a lack of sound quality, it is time to spend some money on new gear. If only one speaker is causing problems, it may be difficult to find a match for the good one, as the model may have been discontinued. In this case a whole speaker system upgrade will be required.
Check out my other post on loudspeaker placement.
How to check for visible damage of speaker cone
Visual damage would usually be among the lesser problems that can happen to speakers, and it is also very easy to detect by the naked eye. Why do I say “usually”? Because in many cases, it may just be surrounding damage. You can easily see if there is any kind of crack in the surrounding area after you remove the grill from your speakers (if you have it). If just the surrounding area is damaged, you can easily repair or replace it by yourself. But, if the cone is damaged like punctured or ripped, you have a much bigger problem on your hands. You should visit a professional audio expert for further advice or for speaker repair. Alternatively, you may need to buy a new pair of speakers.
You should check out other posts I have on this blog –
Using a microphone with a djembe drum
Setting up a microphone for a cajon
Frank Edwards is the founder and owner of churchsoundtips.com and has over 10 years experience running sound in his local church.