Understanding Speaker Sensitivity & Efficiency

Have you ever wondered why some speakers sound louder than others? Or maybe you’re trying to upgrade your home audio system and want to know how to choose the best speakers for your setup.

One important factor to consider is speaker sensitivity.

In this article, I’ll explore what speaker sensitivity is, how it’s measured and why it’s important.

You’ll also learn how to understand the numbers and the relationship between sensitivity and sound quality.

So, whether you’re a seasoned audiophile or just starting to build your home audio setup, let’s dive in and learn more about this vital aspect of speaker performance.

What is Speaker Sensitivity?

Speaker sensitivity refers to the amount of sound a speaker produces when fed a certain amount of electrical energy.

The more power a speaker receives, the louder the sound.

The critical point about sensitivity is that a more sensitive speaker will produce more volume than a less sensitive speaker when fed the same amount of electrical energy.

You should bear in mind that increasing the volume doesn’t necessarily mean better sound quality.

In fact, increasing the power beyond the speaker’s capability can cause distortion and damage to the speaker, so it can make things worse!

So, while sensitivity is crucial in determining a speaker’s overall performance, it’s not the only thing to consider. It’s only part of the equation of what makes a good speaker.

The sensitivity rating is often included in the speaker’s specifications, and it’s one factor to consider when comparing different models.

Speaker Efficiency vs. Sensitivity

Sensitivity is often used interchangeably with the term speaker efficiency.

Although related, this isn’t entirely accurate as efficiency tells you how much electrical energy is converted into sound (given as a percentage), while sensitivity means how much sound is made from a given input (in decibels).

They are often confused because they have a direct relationship.

As the sensitivity increases, so does efficiency – because more sound is produced from the same amount of power.

In fact, speakers are highly inefficient. Most of the power is lost as heat, and very little turns into sound.

The efficiency of typical home audio speakers ranges from 0.2% and 2%. So, not very efficient.

Anyway, you won’t see the efficiency of a speaker in the specifications, just the sensitivity.

How Is the Sensitivity of a Speaker Measured?

Speaker sensitivity is typically measured in decibels (dB) using a standard called sound pressure level (SPL).

It is the loudness of a speaker when given a certain amount of power into a specific impedance.

The speaker should be tested in an anechoic chamber or other non-reflective space to avoid coloring the result with room reverberation.

This is because the noise going into the microphone would increase due to sound waves reflecting off the walls.

The standard power measurement used for measuring sensitivity is one watt into 8 ohms, and the resulting SPL is measured at a distance of one meter from the speaker.

Don’t be confused if you see a sensitivity specification of 2.83 volts at a distance of 1 meter rather than 1 watt.

This is actually the same, as 2.83 volts is 1 watt of power into an 8-ohm impedance.

You can work this out using the principles of Ohms Law:

Power = Voltage² / Impedance

Voltage: 2.83² = 8 volts and Impedance = 8 ohms

Therefore: 8 / 8 = 1 (watt of power)

Using the same equation, if you halve the impedance to 4 ohms, the input power doubles to 2 watts.

Therefore if you want to compare the sensitivity of two speakers, it’s essential to compare models that have been measured in the same way. Because different variables will result in different readings.

So be careful, as some manufacturers may use different power levels, distances and impedance, making it difficult to accurately compare speakers.

Understanding the Numbers

You now understand sensitivity, so what numbers can you expect to see in the real world?

The sensitivity range for home audio speakers can range from 80 dB up to about 100 dB, although it typically falls between 82 dB and 92 dB.

Remember that the difference in volume between speakers with a sensitivity of 82dB and 92dB is significant, with the 92 dB speaker being much louder.

A 10 dB difference results in a rough doubling of perceived volume (twice as loud), which is quite a difference considering you aren’t changing your amplifier.

However, as with all specifications provided by manufacturers, you need to be careful they offer accurate numbers for sensitivity and aren’t artificially inflating the numbers by using different measurement specifications and room conditions.

Audio Science Review had an interesting comparison of measured and advertised speaker sensitivity ratings for a range of different brands.

When interpreting sensitivity measurements, it’s important to understand that a higher sensitivity rating means the speaker is louder when given the same amount of power as a speaker with a lower rating.

But it might not make as much difference as you might think.

For example, when given the same amount of power, a speaker with a sensitivity rating of 90 dB will sound roughly 25% louder than a speaker with a rating of 87 dB.

This is because an increased output of 10 dB results in a doubling of perceived volume (measured in phons) – so an increase of 3 dB is much less.

It’s easy to get confused between the increase in measured SPL (the thing you see on an SPL meter) and the actual perceived volume (the thing you hear between your ears).

Calculating the perceived volume of a certain decibel level involves a complex mathematical formula. This is because human hearing is not linear, and perceived changes in loudness differ depending on the sound’s frequency and intensity.

Basically, your ears aren’t the best judge of audio, and what you hear will vary depending on many factors – how far away from the sound you are, the frequency and volume of the sound, how long you hear something for – even how well your ears work!

It’s also important to note that sensitivity measurements are not the only factor that affects a speaker’s performance.

Other factors like frequency response and distortion can also significantly impact sound quality.

Why is Sensitivity Important?

The important points have been covered already, but it’s a confusing subject, so let’s summarise the basics again without the mathematical formulas.

When it comes to speakers, sensitivity is important because it affects the amount of power needed to produce a certain level of sound.

Speakers with higher sensitivity ratings require less power to produce the same volume as speakers with lower sensitivity ratings.

Using more sensitive speakers means you can use a less powerful amplifier, saving you money and possibly reducing the risk of damaging your equipment (although that depends on how you operate the amplifier in your room).

So, the main takeaway regarding speaker sensitivity is that different speaker ratings will produce different volumes with the same power level from your amplifier.

This is important because increasing the output volume by only 3 dB takes double the amplifier power.

Or, to put it another way, for every 3 dB increase in sensitivity, the amount of power needed to produce the same volume is cut in half.

For example, a speaker with a sensitivity of 90 dB will require half as much power as a speaker with a sensitivity of 87 dB to produce the same volume.

This means more sensitive speakers can play louder with less power, and vice versa.

More sensitive speakers are often better designed and constructed, too, so they also tend to have less distortion, meaning the sound will be more transparent and accurate.

This is especially important for music with a lot of dynamic range, like classical or jazz, where the difference between the softest and loudest parts can be significant.

Although, in real-world listening, the difference in distortion levels can be hard to hear.

Do You Need More Sensitive Speakers?

After all this dull technical discussion, we come to the main point. Should you consider upgrading to more efficient speakers?

There a several points you should think about before deciding what to do.

Here are the main issues you might want to consider.

1. Cost Differences

Generally, more sensitive speakers tend to cost more than less efficient ones.

However, this cost difference can be offset by not having to buy a more powerful amplifier.

Here’s a quick example.

Bowers & Wilkins produce excellent speakers for hi-fi and home theater use.

The entry-level Bowers & Wilkins 607 S2 bookshelf speakers are 84 dB (2.83Vrms at 1m) and retail at $799 per pair.

The next level, Bowers & Wilkins 707 S3 series, are also 84 dB (2.83Vrms at 1m) and retail at $1799 per pair.

Up a level again, the Bowers & Wilkins 805 D4 are 88 dB (2.83Vrms at 1m) and retail at $4250 each!

That’s some price difference if your only consideration is improved sensitivity.

Of course, improved sensitivity isn’t the only reason a speaker is more expensive.

Higher-quality speakers with greater sensitivity will have better engineering across the board, all of which contribute to the increased price.

And you don’t necessarily have to pay that sort of money for a speaker with a higher rating. This is just one example from an excellent speaker brand.

Another alternative is to buy larger speakers (see the next point for more detail).

Carrying on with the same example, the entry-level Bowers & Wilkins 603 S2 floor-standing speakers are 88.5 dB sensitivity and retail at around $1150 each.

Still, no matter the reason, more efficient speakers will cost more money, so is it worth it for the improved performance?

2. Speaker Size

Generally, larger speakers tend to be more sensitive than smaller ones.

If you are considering a speaker upgrade, you might get more sensitive speakers by choosing larger ones – like floor-standing speakers rather than bookshelf models.

However, it’s important to remember that bigger speakers may not always be better.

The ideal speaker size depends on the size of your listening room, the type of music you listen to, and your personal preferences.

You won’t get the best from large tower speakers if you have a small room or live in a house where close neighbors mean you must keep the volume down.

What if you mostly watch movies rather than listen to music?

You might not appreciate the improved speaker performance as much in that case.

Movie audio is more compressed and full-on than, say, classical music, with a high dynamic range and detail.

So it also depends on what you use your speakers for.

But, if you think your system will benefit from more sensitive speakers, you may get more bang for your buck by buying larger models than smaller ones.

3. Your Existing System

It’s also important to consider your current system’s performance before upgrading speakers.

Upgrading your speakers might not make a big difference if other parts of your system, like your amplifier or source material, hold you back.

If you’ve got a poor-quality, cheap amplifier, it won’t matter what speakers you have. You won’t get the best from them.

Also, more efficient speakers may not necessarily improve the overall sound quality if you use a low-powered amplifier and can’t drive the speaker harder.

In this case, upgrading to a higher-powered amplifier may be better than upgrading your speakers.

4. Amplifier Power

Finally, it’s important to consider the relationship between amplifier power and speaker sensitivity.

As mentioned earlier, more efficient speakers require less power to produce the same volume as less efficient ones.

However, if you use a low-powered amplifier with more efficient speakers, you may not be able to achieve the same volume levels as with less efficient speakers and a more powerful amplifier.

Ultimately, if money is tight, then it’s not a simple decision.

You need to consider your current setup and where you can improve performance.

You should think about the cost difference, speaker size, current system performance, and the relationship between your amplifier’s power and speaker sensitivity.

Do you need more volume? Or better sound quality? These aren’t the same things.

Or course, if you have plenty of money, then why not? More sensitive speakers will usually be an upgrade in speaker quality, which is never a bad thing to do.

Speaker Sound Quality and Sensitivity

The final point is that there is more to making a good speaker than sensitivity alone.

While more efficient speakers are generally more expensive – and therefore sound better – the sensitivity is only a part of why they are better quality speakers.

So while a more sensitive speaker can produce more volume with less amplifier power, it doesn’t necessarily mean it will have better sound quality.

Other factors like frequency response, distortion, and phase response all play a role in the quality of the sound produced by a speaker.

And you should also consider the complete signal chain, including the amplifier and cables.

This is why you should ideally have high-quality components through the complete signal path, or one part of the chain can reduce the quality of everything.

Given all these factors, listening to speakers before purchasing is important if you want to be confident in what you buy.

Listening tests can reveal how well a speaker performs regarding sound quality and any shortcomings that may not be apparent from a spec sheet.

An excellent way to test a speaker is to listen to a variety of music that you’re familiar with and listen for any distortion, harshness, or lack of detail in the sound.

Every speaker has a particular sound that you may or may not like.

Well-made speakers shouldn’t color the sound too much and should provide a good balance between the high, mid and low frequencies – which has little to do with sensitivity.

Also, remember, the amplifier, cables and, primarily, room acoustics can all dramatically affect the sound you hear from speakers, so listening in your own room with your own amplifier is best.

Conclusion

Hopefully, this article will have clarified why it can be helpful to know about speaker sensitivity.

While it is not generally your primary concern when buying a new set of speakers, it is a specification that you should consider when deciding which speakers are suitable for your system.

The bottom line is that more efficient speakers should allow you to get more from your amplifier – so try to buy speakers that are as sensitive as you can afford.

However, it may not be worth spending a significant amount extra just to get more efficient speakers.

You can always just turn the volume up on your amplifier – if you have enough power to spare – and just because they are more sensitive doesn’t mean they sound better!