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Reading all those numbers from the speaker’s specifications list can be a real nightmare if you don’t know what to look for and what all the numbers mean. Even if you have some basic understanding of these specifications, you might get confused by different measurement methods and different units. One of the characteristics that can be really tricky is speaker sensitivity and there are numerous reasons for that – some manufacturers call it efficiency (sensitivity and efficiency are not the same things), some manufacturers use dB at 1m per 1W, others use dB at 1m per 2.83V, different manufacturers use different measurement methods, etc. The main problem with sensitivity is that there is no industry standard when it comes to measuring and unit of measurement that would be the same for all the manufacturers. In this article, we will be focusing on all the important things related to sensitivity ratings. We will try to clarify all the ambiguities, make a difference between sensitivity and efficiency, explain different measurement methods and measurement units, and offer you a few pieces of advice on how to compare sensitivity ratings.
Before we go any deeper into the matter, it’s important to define all the important terms.
Speaker sensitivity – it tells us how loud noise a speaker will make for some given input. To simplify, it should tell us how loud a speaker can be (but it’s not the only rating that determines the loudness of a speaker). It’s often measured in dB of SPL (SPL stands for Sound Pressure Level) measured at 1m distance for 1W input or in dB SPL at 1m distance per 2.83V for a given frequency or a range of frequencies (we will explain different units of measurement later).
Speaker efficiency – efficiency rating tells us how efficient a certain speaker is at converting electrical power into acoustic power and it’s given as a percentage. In order to calculate the efficiency, you have to divide the acoustic power output by the electrical power input. The speakers, in general, are highly inefficient when it comes to converting the electrical input into acoustic power output and even the most efficient speakers have efficiency rated at 2%. The most of the electrical power input is actually converted into heat.
Sensitivity and efficiency are often used interchangeably but they are not the same thing. Still, they are closely related and you can calculate the sensitivity if you know the efficiency and vice versa.
Based on these two equations, if the speaker sensitivity is 85dB (1W/1m), the efficiency is 0.2%, and if the sensitivity is 95dB (1W/1m), the efficiency is 2%. So, if the efficiency increases, the sensitivity increases, too.
Speaker impedance – impedance rating tells us how hard it is to drive the speaker. Speakers with low impedance rating offer lower resistance to the current supplied from an amplifier and they draw more current and cause the amp to work harder. Speakers with high impedance are actually easier to drive because they draw less power. The impedance is measured in Ohms (Ω). We will explain the relationship between impedance and sensitivity later.
Power ratings – these ratings tell us how much power the speaker can handle continuously (RMS power) and how much power it can handle for short periods of time (Peak or Maximum Power Input). The maximum loudness of a speaker depends on the power rating and its sensitivity.
Measuring Speaker Sensitivity
The most common explanation of the measurement method that you will find online is that the sensitivity is measured with a calibrated SPL meter at 1m distance (from the speaker) for 1W of given power input. You might find a sensitivity rating written like 89dB (1W/1m). This rating means that the speaker will make 89dB noise when 1W of power is supplied from an amplifier and when SPL is measured at 1m distance.
This method seems quite simple and unbiased but there are some flaws. The manufacturers don’t always state the frequencies they used to test the speaker (is it only one frequency (usually the most sensitive one) or a set of frequencies, is it pink noise, etc.). Placement of the microphone can also make a difference. The microphone with SPL meter has to be 1m away from the speaker but is it one meter away from the center of the most sensitive speaker in the cabinet or 1m along the cabinet’s center axis. Some manufacturers choose to place the microphone even further away and then convert their results back to 1m distance. The environment in which the measurement is performed can make a difference, too. The manufacturers can perform their measurements in a non-reflective environment (in order to avoid sound reflecting from the walls) or in a real room with all the walls and everything. All these parameters can affect the results and make them hard to compare.
Still, it’s not that bad since the most of the renowned manufacturers perform their measuring in the same way. They use calibrated SPL meter, it’s placed 1m away from the speaker along the center axis of the cabinet, and the measuring is done in the non-reverberant environment because they prefer controlled conditions (in controlled conditions they get more accurate results and can repeat tests multiple times). The majority of the renowned manufacturers measure sensitivity for multiple frequencies ranging from 300Hz to 3kHz and then calculate the average sensitivity. The speaker sensitivity should be given along with the info on the nominal impedance of that specific speaker and we will explain why in the next section.
Sensitivity (2.83V/1m) VS Sensitivity (1W/1m)
Some speaker manufacturers (especially those renowned manufacturers like Klipsch, ELAC, KEF Yamaha, Pioneer) state the sensitivity for certain voltage (2.83V to be more specific) measured at 1m distance. So, you might see the sensitivity rating written like this:
SENSITIVITY: 96dB at 2.83V/1m
and not like this
SENSITIVITY: 96dB at 1W/1m
The reason for using voltage instead of power is really simple. The speaker is actually driven by the voltage and not by the power. You might wonder why 2.83V and not some other voltage and the explanation follows.
The electrical power can be calculated with this formula:
Where P stands for electrical power (expressed in watts), V stands for voltage (expressed in volts), and R stands for nominal impedance or resistance (expressed in ohms).
If the speaker’s impedance is 8Ω, and if it’s driven by 2.83V voltage, you will get the electrical power of 1W. So, for the 8Ω speaker from our example, you can express the sensitivity in dB as 96dB at 1W/1m or 96dB 2.83V/1m. Both forms are equally correct (but the one with 2.83V/1m is more accurate from the technical point of view).
But what happens if you use that kind of form for a 4Ω speaker (or any speaker with impedance different than 8Ω). Let’s apply that power equation on a 4Ω speaker.
So, if a 4Ω speaker is driven with 2.83V, it will be driven by 2W of power instead of 1W. The same equation can be applied to 6Ω or 2Ω speakers. If a 4Ω speaker is supplied with 2.83V, it will draw more current than the 8Ω speaker (which means more power). If 8Ω and 4Ω speakers are supplied with the same amount of voltage (2.83V), and if their sensitivity ratings are the same, the 8Ω speaker is actually more sensitive (or louder) because the 4Ω is driven by more power. Look at the example below:
Impedance: 8Ω Sensitivity: 89dB at 2.83V/1m (or 89dB at 1W/1m)
Impedance: 4Ω Sensitivity 89dB at 2.83V/1m (or 89dB at 2W/1m)
Some people consider that cheating but there is nothing we can do to force all the manufacturers to be honest about their speakers. What we can do, is to be careful and check the impedance when comparing sensitivity ratings. If you are comparing 8Ω and 4Ω speakers that have the same sensitivity like in the example above (both sensitivities given for 2.83V at 1m), you will have to subtract 3dB from the sensitivity rating of the 4Ω speaker (we will explain the correlation between power and sensitivity in the next section). In the example above, the real sensitivity of the 4Ω speaker is 86dB (at 1W/1m) and the sensitivity of the 8Ω speaker is, as stated before, 89dB (at 1W/1m). So, the 8Ω speaker has greater sensitivity (it’s louder when driven by the same amount of power).
You will have to do the similar thing when comparing 6Ω and 8Ω speakers. If the sensitivity is given for 2.83V at 1m distance, you will have to subtract 1.2dB from the sensitivity rating of the 6Ω speaker in order to compare two sensitivity values.
We have prepared a few examples for you. In the pictures below, you can see how different manufacturers list their sensitivity ratings. You will notice that all of them list the nominal impedance of their speakers and that they all express the sensitivity in dB at 2.83V/1m. But not all the speakers in the pictures have 8Ω impedance. Some speakers, like ELAC B6 and Pioneer SP-BS22, have 6Ω impedance and in order to compare their sensitivity with the sensitivity of Klipsch and KEF speakers, you will have to subtract 1.2dB from the ELAC’s and Pioneer’s sensitivity ratings.
Specifications list – Klipsch RP-160M (provided by Klipsch)
Specifications list – KEF Q100 (provided by KEF)
Specifications list – ELAC B6 (provided by ELAC)
Specifications list for Pioneer SP-BS22 (provided by Pioneer)
The Correlation Between Sensitivity and Power
As you could see from the previous section, there’s a correlation between power and sensitivity (or SPL level). Let’s say you have a 65W speaker with an 8Ω impedance and with sensitivity rated at 88dB (2.83V/1m). The general rule when it comes to power/sensitivity correlation is that doubling the power increases the SPL level by 3dB. So, if the sensitivity of the speaker is rated at 88dB (when driven by 1W), you will get 91dB for 2W, 94dB for 4W, 97dB for 8W, 100dB for 16W, 103dB for 32W, 106dB for 64W. So, the maximum SPL of this speaker will be approximately 106dB (if you have the amplifier that can supply the speaker with enough power).
The Correlation Between Sensitivity and Distance
There’s a similar correlation between loudness (SPL) in dB and distance. You probably know, based on your own experience, that the loudness (volume) decreases if the distance increases and there’s a simple rule that describes this correlation – doubling the distance decreases the SPL by 6dB. Let’s take the speaker from the previous example (88dB sensitivity, 106dB max SPL). If you are standing 1m away from it and play the music at maximum volume, the SPL will be 106dB. If you are standing 2m away from it (double the distance) and measure the SPL, you’ll get 100dB. If you double the distance again (4m away) you will get another 6dB decrease to 94dB, etc.
Comparing Speaker Sensitivity Ratings – How to Avoid Comparing Apples with Oranges
Well, we have pretty much explained how to compare speakers with different impedances and sensitivity ratings but it doesn’t hurt to repeat that. The crucial thing you need to do is to check the impedance when comparing sensitivities. Also, you should pay attention to the maximum power the speaker can handle and to the maximum output power of your amp. If speakers have different impedance ratings and sensitivity ratings are given in dB at 2.83V/1m, you should subtract 1.2dB from the sensitivity rating (for 6Ω speakers), 3dB (for 4Ω) or add 3dB (for 16Ω speakers) in order to compare the real sensitivity values. That’s the only way to compare sensitivities (assuming that all the manufacturers use the same measurement methods). Comparing sensitivities and power ratings of different speakers will give you the general idea on how loud they can be.
Does Greater Sensitivity Mean Better Sound?
If you need a simple answer, it’s no. Great sensitivity rating (anything above 90dB at 1W/1m or at 2.83V/1m) doesn’t imply that the speaker can deliver excellent sound quality. If the sensitivity was the only or the decisive factor, the manufacturers would make much lighter and more sensitive drivers but that would increase the distortion and ruin the performance and sound quality. Sensitivity is just one of the things that you have to consider when buying speakers. You also have to consider their frequency response, crossover frequency, size of the woofers and tweeters and the materials they are made from, build quality of the cabinet, distortion, etc. And after all, it would be best to test them and really hear them before actually buying them. All the numbers in the specifications lists don’t mean anything if you don’t like the sound you hear.