Have you ever wondered what speaker sensitivity is? This term gets thrown around a lot in the audio world, but not everyone knows what it means.
Speaker sensitivity refers to a speaker’s ability to convert power into sound and, as a result, how loud a speaker will be for a given input level, which is typically 1 watt of power supplied by the amplifier.
In this article, we will cover the basics of speaker sensitivity, including:
- What does speaker sensitivity tell us?
- How is speaker sensitivity measured?
- How does speaker sensitivity work? (An example)
- How to use speaker sensitivity to compare speakers
- How to use speaker sensitivity to pick an amp
- How to interpret speaker sensitivity from different manufacturers
- What is a good speaker sensitivity?
- Do higher sensitivity speakers sound better?
- Why don’t active speakers have sensitivity ratings?
What Does Speaker Sensitivity Tell Us?
Speaker sensitivity is another factor in the range of speaker parameters. It can be useful for the following reasons.
- Speaker sensitivity can help us compare multiple speakers.
- Speaker sensitivity gives us an indication of how powerful our amp needs to be.
- Speaker sensitivity gives us an indication of how loud a speaker will be.
How Is Speaker Sensitivity Measured?
Speaker manufacturers use a standard measurement process to determine speaker sensitivity.
- A speaker is mounted in a baffle, in a 2π anechoic environment.
- A measurement microphone (i.e. a calibrated sound level meter) is placed at a distance of 1m away from the centre of the speaker.
- 1 watt of power is fed to the speaker through the amplifier.
- The measured output that the microphone records is your speaker’s sensitivity.
How Does Speaker Sensitivity Work? (An example)
In the world of speakers and speaker design, speaker sensitivity refers to how loud a speaker will be given a specified signal input of 1Watt.
Let’s assume you have three speakers lined up with the following sensitivity rating:
- Speaker A: 85dB
- Speaker B: 88dB
- Speaker C: 91dB.
Let’s connect one speaker at a time and play a test tone through the speaker. We want 1 watt of power from our amp to be supplied to the speaker.
Next, if we measure the sound level (SPL) of each driver by placing a measurement microphone at a distance of 1m from the speaker, we will not get the same loudness from each speaker.
Speaker C will be the loudness in this example. In theory, Speaker C will need less power to reach the higher volume.
Using speaker sensitivity, our input signal, amp power, and listening distance are the same, so it is a very reliable way to compare the loudness of a speaker.
This becomes useful when selecting an amplifier for your speaker, as for a higher sensitivity speaker, you can use a less powerful amp.
In the given example, there is a 3dB difference between each of our three speaker sensitivity ratings.
In order to increase a speaker’s SPL by 3dB, an amplifier must double its power.
So Speaker A will need 1 watt of power to produce 85dB, 2 watts of power to produce 88dB and 4 watts to produce 91dB.
Whereas Speaker C can produce 91dB with just 1 Watt of power.
How To Use Speaker Sensitivity To Compare Speakers
Based on our previous example, we can see how speaker sensitivity affects the loudness of a speaker.
Here is another simple example, following the same principle as the previous example.
Let’s assume we have three speakers with the following sensitivity ratings:
|Speaker Label||Sensitivity Rating (1w/1m)||Audio Level|
|Speaker A||84dB||Quietest per unit power of input|
|Speaker C||90dB||Loudest per unit power of input|
The first thing to check when comparing speakers is to ensure that the sensitivity specification is consistent, so we are comparing truly similar sensitivity ratings.
This is implied by the specification of 1w/1m. It tells us that each of these speakers is measured at a distance of 1 meter from the speaker, with an input of 1 watt.
Using the same amplifier on each of these speakers, and playing the same signal through each one separately, we find that Speaker A is the quietest and Speaker C is the loudest.
Speaker C is the loudest, as it has the highest sensitivity rating.
In this simple example, we can say that Speaker C is the loudest per unit power of input to the speakers.
How To Use Speaker Sensitivity To Pick An Amp
Knowing the speaker’s sensitivity can help us pick a suitable amp for our speaker.
At the end of the day, speaker sensitivity tells us how loud a speaker will be when supplied with 1 watt of power from the amp, measured by a microphone at a distance of 1m.
As a general rule, a speaker with a higher sensitivity rating will require less power input from the amp. Less powerful amps tend to be more affordable.
How To Interpret Speaker Sensitivity From Different Manufacturers
Let’s assume we have the following 8inch speakers from two different speaker manufacturers:
|Speaker Label||Speaker Name||Sensitivity||Manufacturer Website|
|Speaker A||Celestion TF0818||94dB||Specifications|
|Speaker B||B&C Speakers||97dB||Specifications|
I just picked these speakers at random from the manufacturer’s website, and both suppliers clearly list the speaker sensitivity.
- Speaker A sensitivity is measured on axis at 1W, 1m in 2π anechoic environment.
- Speaker B sensitivity is measured with an applied RMS Voltage, set to 2.83 V for 8 ohms nominal impedance
Can We Compare Both Of These Speakers On Sensitivity?
Speaker A is clearly specified as 1W at 1m, but what about Speaker B, whose sensitivity is specified as applying an rms voltage set to 2.83 V for 8 ohms?
Really, both speakers have the same standard sensitivity measurement of 1W/1m (1 watt of power measured at a distance of 1m)
Looking at Speaker B, and using the following formula for power, we can see that a voltage of 2.83V, with an 8ohm impedance, gives a power of 1 watt.
- P = V^2/I
- P = ((2.83)^2)/8
- P = 1 watt
In this case, the impedance is 8 ohms and must be 8ohms to supply the 1 watt we need.
If Speaker B had an impedance of 4 ohms, then this would not be a direct comparison between these speakers, as this would give a power supply of 2 watts.
Different Signal Inputs
Different manufacturers also use different input signals.
To my knowledge, there is not a standard input signal to be used. For example, some manufacturers may input one frequency tone, while others might do a frequency sweep, while others might just use pink nose.
As a user, we can mostly ignore this and still use the speaker sensitivity rating as a good general guide to tell us how loud a speaker will be.
What Is A Good Speaker Sensitivity?
As a general rule, a speaker sensitivity of 88dB is about average, below 84dB is considered poor. Any speaker with a sensitivity of above 90dB is considered excellent.
Do Higher Sensitivity Speakers Sound Better?
Speaker sensitivity is not an indication of the quality of sound, therefore, speakers with a higher sensitivity do not sound better by default.
There are some psychoacoustic enthusiasts out there that tell us humans associate loudness with good sound, hence the loudness wars in the 90s where songs were heavily compressed to make them sound loud on the radio in comparison to their competitors.
As a result, I can appreciate that something sounding loud could give a perception of sounding better, but this is subjective.
In theory, speaker sensitivity is just an indication of how loud a speaker will be with a given signal input. It is not related to audio quality.
Why Don’t Active Speakers Have Sensitivity Ratings?
A sensitivity rating will only be applied to a passive speaker, this is because an external amplifier is required to supply power to a passive speaker.
Active speakers have their own inbuilt amplifier and power supply, therefore they are not sold with sensitivity ratings.
Speaker sensitivity is a measure of how loudly a speaker will play relative to other speakers when an input of 1 watt is played into the speaker and listened to on-axis at a distance of 1m from the speaker.
A good general guide is that a speaker with a sensitivity of 88dB is about average, below 84dB is considered poor, and any speaker with a sensitivity of above 90dB is considered excellent.
Higher sensitivity speakers do not inherently sound better than lower ones, but they may be louder. Active speakers, which have their own amplifiers, are not given sensitivity ratings.
When shopping for new speakers, it is important to keep speaker sensitivity in mind and compare ratings between models to ensure you are getting the right level of loudness for your needs and budget.