CAUSES OF SPEAKER DAMAGE
A speaker will 'blow' from either the mechanical failure of its components or from electrical thermal damage, both of which can be avoided through correct use. The most important factor above all is firstly to buy a system that's capable of performing in the way you wish it to.
So if you're a working DJ for example, or you like to play loud music at gatherings, you simply cannot buy the cheapest speakers and expect them to work (not for long anyway) as they just aren't capable of those output requirements.
THERMAL FAILURE
The most common cause of 'blown' speakers comes from a poor quality signal (music from a mobile phone or laptop for example) which is then boosted at the amplifier or a mixer through a gain control or EQ, which could be a standard set of tone controls or a slider based graphic equaliser. The biggest mistake people make is to use these controls to boost the perceived volume on top of the system's actual volume control.
Budget active speakers or an amp and passive speaker system suffer this mistake the worst, as the signal gain from an EQ can be as much as +10dB (ten times the original signal) with all the controls fully up, which is a horrific amount of gain, and the amplifier's input and output stages become overwhelmed and often don't feature the intelligent circuitry required to shut the amp down automatically.
The amplifier simply cannot deal with such a huge signal properly and immediately starts to cut that signal down best it can, by cutting off the signal peaks. This is referred to as ‘clipping’ as the amplifier sends what it can to the speakers and leaves what it can't, which results in you hearing a heavy distortion to the music, with muffled mids, horrible bass, and often cracking and popping noises.
A similar effect can also happen when the amplifier itself is underpowered, even with a good quality input signal, as it will quickly reach and exceed its capabilities if you're trying to get sound levels from it that are higher than it was meant to produce and it will clip at its output stage. This will eventually destroy the amps output transformer as it overheats.
Though these are slightly different processes, the results are basically the same, as electrically these clipped signals have much larger voltage output than a normal clean audio signal, and their smooth AC signwave has pretty much become a chopped DC squarewave, which causes the voice coils in the speaker drivers to quickly overheat, eventually destroying them completely. Whilst this is happening, the excess heat can also melt the varnish on the speaker driver's suspension, causing it to tear.
COMPONENT FAILURE
Not as common, certainly not in budget systems or active speakers, is a blown speaker due to mechanical failure. This is where the actual driver has torn or ripped under stress, or the voice coil has fallen apart. There are usually two main causes for this to happen, the first being cheap or inferior components, and occasionally this does happen from time to time with mass-produced equipment and is unavoidable.
The other way this can happen is common in separate amplifier / budget passive speaker setups, where the amplifier's output rating far exceeds the speakers' capabilities. Whilst it's always good practice to have a higher power amplifier than the speakers require, this of course is reliant upon the user exercising caution and recognising the limits of their speaker units.
If for example you have a 4000-watt RMS power amplifier and you're running it into a pair of 100w budget speakers and the amp's volume is up even halfway, you can expect a fairly dramatic demise of those poor little speakers. Electrically speaking, the speaker's coil will be receiving a clean signal so will just keep going, but the physical movement will become just too much for the low-cost cone or its surround material to cope with and they will let go.
Avoiding this type of damage doesn't require technical knowledge any more than it just needs some common sense applied.
INPUT SIGNAL & GAIN
Make sure your music feed is of suitable quality, recorded at a decent level, and isn't distorted (YouTube for instance is heavily compressed and is a terrible audio source)
If using a mobile phone, portable mp3 player or laptop as a direct source, ensure the volume for the output jack/headphone socket is up at a good level, around 60-75% is good. Many people make the mistake of putting the volume full up, but this just hits the input stage of the amp or mixer too hard and introduces distortion. The same settings should also be used for a Bluetooth connection
If feeding your source to the amplifier via a mixer, or using a media controller then you have much more control over the signal level, and the VU signal level meters will give you a visual guide to get your output signal as close to its 0dB unity gain as possible, which is what the amp ideally wants to see.
BASICS OF GAIN
Gain is a useful tool in audio signal control, but it can get you in trouble fast if you're not very careful, so think of your sound system as a chain, if you feed it distorted rubbish then that's exactly what you will get out of the other end only much louder.
Using a mixer as the best example, each channel has volume and gain controls. The volume pot controls the audio level of that channels output in dB.
Say you have a record player and a CD player connected to the mixer and you want to mix between the two sources. You could set the volumes of each channel to be identical, but the CD players signal will be much louder. This is because it puts out a much larger electrical signal than the record player can. This is where you would use the gain control as it allows you to increase (or decrease) the actual signal level so you can get them to match.
The thing to understand is that a volume control only makes things louder as it's at the end of the chain. It has no effect on the tone or quality of the signal.
Gain, on the other hand, is the ratio of the input signal to the output signal. You can physically alter the amplitude of the signal, add and cut frequencies (EQ controls are also gain controls), changing the sound drastically from the original source.
Too much gain however and your signal becomes a monster, and the next part of the chain (your amplifier) simply can't process it. So, it does what it can and trims it to fit by losing the tops and bottoms from the audio wave. This chopped mess then gets amplified and sent to your speakers.
EQUIPMENT SUITABILITY
A 5000w RMS PA amp with £20 of pc speakers isn't going to do your party, and nor will a pair of £3000 passive cabs being fed from a 25w powered mixer amp. Your amplifier and speakers act as one unit and must be thought of as such. They should all be of similar quality and ratings and should be designed to cope with the specific tasks you have in mind for them. We all like to save money, and there are excellent budget systems available which are great when used correctly, though that doesn't mean they are automatically suitable for your needs.
There is often a misunderstanding at the term ‘correct use’ when it comes to audio equipment, with people confusing incorrect usage with misuse or abuse. It goes without saying that you shouldn't drop speakers, get them wet etc. When a seller or manufacturer states ‘correct use’ they are referring to the equipment being operated within its specifications and limitations.
Again, common sense prevails, and it should be fairly obvious that providing adequately loud music for a party, wedding or outdoor event will require a professional PA system not a set of home party speakers.
CONCLUSIONS
Firstly, to repeat the important opening statement;
The most important factor above all is firstly to buy a system that's capable of performing in the way you wish it to.
As with all consumer electronics, whatever the cost of the unit or its stated capabilities, it is completely in the hands of the end-user to ensure it is set up and operated correctly in order that it does not exceed those capabilities. So for instance, if you're planning a party for 500 people in a hall or large marquee, you aren't going to be able to do what you need to with a set of £89 10-inch party speakers, no matter how good you think the price is.
If you decide to go ahead anyway, and not only ruin your party but also the speakers you shouldn't have bought, that is incorrect use resulting in damage. You may have taken perfect care of them, but they simply weren't up to the task presented to them and this is not a fault of the unit or the seller.
Secondly, use the best quality audio source you can. You have the physical media options of CD and Vinyl, but most people will be using digital files these days, so make sure to use the best quality available. Don't use YouTube, and don't use MP3, as both are very low bitrates. You should be looking at FLAC, AAC, Apple Lossless, WAV, or any format that's at least equal to CD quality.
Third is understanding your equipment. You can just as easily destroy an expensive speaker as you can a budget one. Learn how to set up your mixer or amplifier properly and learn the difference between volume and gain. Direct source connections such a laptop or phone into a powered speaker or mixer should be treated no differently than any other source device, with their volume set at 60-75% to avoid any distortion being introduced to the input of the mixer or amp. This is also true for a Bluetooth connection.
Here at ElectroMarket, we offer free advice on all of our available products and their suitability to your requirements. We are happy to specify the equipment which will suit you best and will endeavour to stick to any budget constraints you have in place, or advise you that your proposed budget is either too big or too small for the performance levels you want from the system.
