In this article we hope to help you to understand the difference between line level vs speaker level.
To put it briefly, line level signals have a high impedance and low voltage, and speaker level signals have low impedance and high voltage, which result in a high current. Line-outs and speaker-outs aren’t interchangeable and you should send speaker level signals only to speakers exclusively and line level signals to devices that are intended to receive it.
Now let’s take a deeper look into it.
What is an audio signal level?
Before we begin discussing the main subject of this article, it would be rather beneficial to understand what exactly an audio signal level is.
Luckily, this will take no time at all since the signal level is a strength with which signal is carried from one audio device to the other. From a more practical point of view, this would mean that an audio device with a certain output level requires to be connected to the other device that has the input that supports the same level.
But more importantly, this also means that devices with different input and output levels don’t really get along pretty well.
In audio production, we use a different level of signal depending on its voltage and impedance, which we will discuss later. Microphone level signal is a signal that, believe it or not, is generated by a microphone and is considered to be the weakest signal level of them all, which inevitably means that microphones require some amplification in order to be brought up to the line level.
USB microphones are, of course, excluded from this general rule since they have a built-in A/D converter in order to output a digital signal. But it’s a topic for a whole other discussion.
Instrument level signal is what electric instruments such as electric guitars, basses, and keyboards output. It’s slightly stronger than the mic level signal but still much weaker than the line level, so, again, an amplifier is required. But it’s very much possible to connect any instrument straight to the line input with the help of a device which is called a DI box.
This device brings up the instrument level signal to the line level without any amplification, although it should be said that some models have a built-in preamp. And it’s also very important to remember that any external amplification affects the purity of the signal by adding noise and sometimes distortion.
Line level signal is the strongest one and doesn’t require amplification. These types of signals are what most of the audio equipment use for internal processing, which means that it can be found between preliminary amplification and the final amplifier that leads straight to the speakers.
Line levels used by consumer audio electronics are slightly less powerful and usually are rated somewhere around -10 dBV. And, on the other hand, the professional line level is much stronger and can be found on mixing desks, studio preamplifiers, and audio interfaces. After the line level signal is processed, it’s sent to the amplifier, which brings it up to the speaker level.
Speaker signal level has the highest voltage, which means that it’s the strongest of the four. Speaker level signal requires especially dedicated cables, which are usually unshielded and have very thick wires. Speaker level signal has such a high voltage that if you connect shielded instrument cables with thin wires to the speakers, the signal might actually melt the cables down.
Although smaller speakers require less voltage and, on the contrary, bigger speakers need more voltage, it still wouldn’t be very wise to use anything other than speaker cables even if you have the smallest speakers possible.
The difference between line level and speaker level signals
As we established before, line level signal is what audio equipment uses for internal processing and it flows between the preamplifier and the final amplifier that sends a signal to the speakers. And speaker level signal is the final result of signal manipulation and has a much higher voltage than the line level signal.
Knowing all of that, we can easily conclude that those signal levels aren’t interchangeable and sending speaker level output to anything other than the speakers can bring very unfortunate and damaging results.
But why is that, you may wonder? Well, to find out, we have to dig a little bit deeper into the physics on which signal processing is based.
Impedance represents the ability of a device or a certain object to resist alternating currents. Each and every given audio device output has its own output impedance and the higher is the value of the impedance, the lower would be the current, and vice versa if an output has a low impedance, the current will be high.
Line outputs usually have the impedance of 100-600 ohms and speaker outputs usually deliver 2-16 ohms, which means that if speaker output would be connected to the line input, that device will most likely be damaged because the current will be much higher than it can take.
Voltage, as we remember from our happy and careless school days, is a difference in electric potential and is measured by the amount of work needed to move a charge between two points. In order to drive speakers, a much higher voltage is needed than it’s required to carry line level signals.
A typical AA battery has a voltage of 1.5 volts and a car battery has 12 volts. Average speaker outputs have a voltage of 10 volts or even more, so it’s now should be rather obvious why you need cables with thicker wiring because instrument cables simply couldn’t withstand such high voltage.
Line-in and line-out
Line-in is an input port designed to receive a line level signal, such inputs have high impedance and low voltage. As we established before, line level signals are used for internal processing and line-in is designed to receive such a signal from another device that carries it.
Line-out is an output port that sends line level signal to another device capable of receiving it. Line-ins and line-outs by design cannot output or receive anything other than line level signals. So trying to send or receive another type of signal to the line-in or line-out will lead to the consequences that we will discuss later.
Speaker-out is an output port that is designed to send a speaker level signal to a dedicated device, usually, you can find one of those on amplifiers and guitar amp heads. It has a very low impedance and high voltage, which also means that it has a very high current that is needed in order to drive the speakers.
This means that sending a signal from a speaker-out to anything other than the speakers will most likely damage the equipment on the receiving end.
It’s a rather disturbing thought, but all of the consumer and professional audio equipment usually have all of the inputs and outputs clearly labeled so it’s very hard to mismatch anything by mistake.
Can you use line-out instead of speaker-out?
Weirdly enough, both line-out and speaker-out usually have the same type of cable connection, so technically, it would be very easy to send a line level signal to the speakers. But the problem is that nothing useful will most definitely come out from this endeavor, since line-outs have a very high impedance and a very low voltage, the current would be too weak to drive the speakers.
Your equipment with a very high probability wouldn’t be damaged, but still, there’s no reason even to try this, unless you need another elaborate way to make speakers silent apart from turning them off.
Can you use speaker-out instead of line-out?
Connecting a speaker-out to anything other than the speakers would be dangerous since, as we already know, the speaker level signal has a very high current. This means that any equipment that wasn’t designed to receive speaker level signal will be severely damaged if you decide to send such a signal to it anyway.
It also can damage the amplifier that carries the initial signal by overheating it. So it wouldn’t make any reasonable sense to do it unless you’re tired of your equipment and didn’t find any other way to get rid of it.