Choosing Loudest Speaker: Sensitivity and Power Wattage Is What Counts

Choosing the loudest speaker is easy.

Isn’t it?

It’s a matter of finding the speaker with the highest power output.


Well, sort of.

Choosing Loudest Speaker Sensitivity And Power Wattage

Yes, power output or wattage is an essential factor, but it’s not the most critical.

It’s speaker sensitivity that counts the most.

What the heck is that you ask? Sounds too complicated to me, you say.

But, it doesn’t have to be.

I’ll provide easy-to-understand definitions of what determines loudness. And I’ll present examples to increase your understanding and guide your choice.

Let’s get started first with those definitions.

There are two definitions to wrap your head around:

  1. Speaker power rating (wattage).
  2. Speaker sensitivity.

What is Speaker Power Rating (Wattage)?

A speaker’s power rating expressed in wattage refers to the power output of the amplifier in that speaker.

What is Speaker Sensitivity?

Speaker sensitivity is a measure of how efficiently a speaker converts amplifier power to acoustic energy.

Note this is a measure of the efficiency of converting power to energy. That’s why sometimes you’ll find people referring to this measure as “speaker efficiency.” But there is a caution to using this term which I’ll come back to later.

In other words, it tells us how loud the volume will be for power output from the amplifier.

To understand sensitivity better, I found I had to look at the measuring process.

How is Speaker Sensitivity Measured?

With a speaker, we are talking about the acoustic output, or the volume, resulting from a given amount of power.

The amount of volume produced is called the sound pressure level or SPL.

SPL is expressed in terms of decibels (dB).

Measuring the decibel (dB) output of a speaker when applying 1 watt of power provides the degree of sensitivity. The measurement is taken at 1 meter from the speaker and is usually performed in an anechoic chamber (non-reflective, soundproof room).

So, what does it mean if a speaker has a sensitivity of 89 dB SPL?

It means that the speaker with 1 watt of power measured 1 meter from the speaker can create a sound pressure level of 89 decibels.

In shorthand, “89 dB SPL 1W/1M”.

Right, you now understand what sensitivity is.

To increase that understanding from a practical viewpoint, we’ll look at comparing the sensitivity of speakers without regard for power output.

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Comparing Speaker Sensitivity

When considering only the sensitivity rating of different speakers, the comparison is straightforward.

If you’re looking to choose between the following three speakers, it’s an easy choice:

  1. Speaker 1 is 81dB (1w/1m)
  2. Speaker 2 is 84dB (1w/1m)
  3. Speaker 3 is 87dB (1w/1m)

Speaker 3 with a sensitivity rating of 87dB (1w/1m), is the loudest because at 1w/1m it produces a greater volume than the other two. The higher the dB number, the louder the speaker.

As mentioned earlier, SPL is expressed in terms of decibels (dB). Often SPL and dB, are used interchangeably, which is confusing.

Whether it’s a higher SPL or a higher dB, you know you have the louder speaker.

Next, we need to look at what happens when you consider the power rating of the speaker because the combination is not quite so straightforward.

Looking at the Combination of Power and Sensitivity

No matter what sensitivity your speaker has, there’s a general rule that applies if you want to increase decibel output by increasing the power of your amplifier.

The general rule is:

Increasing speaker sound output by 3 decibels, requires you to double the power of the amplifier.

I had to write down some examples before I understood the implications of the rule.

First, let’s look at one speaker.

Consider a speaker rated at 87 dB (always remember that decibels are measured based on 1 watt of power and 1 meter from the speaker).

The rule is that to increase by 3 dB’s; you must double the power wattage.

To produce an extra 3 dBs to reach 90 dB’s the power of the amplifier must increase to 2 watts.

But to increase by another 3 dBs to 93 dB’s the power must double from 2 watts to 4 watts.

And an increase to 96 dB’s requires the wattage to double again to 8 watts.

Second, we’ll compare two speakers.

Both speakers use 10 watts of power to output their sound.

Speaker 1 has an output of 81 dB’s, and Speaker 2’s produces 93 dBs.

There is a 12 dB difference in output between the two speakers or 4 lots of 3 Db’s. So, with four lots of wattage doubling required, that means the doubling factor moves from 2 to 4 to 8 to 16 times.

Therefore, the wattage of Speaker 1 needs boosting from 10 watts to 160 watts (i.e., ten times 16) to produce 93 dB and equal the output of Speaker 2.

Putting this in table form helped my level of understanding.

Based on Speaker 1’s rating of 81 dB’s here’s the power output required to increase the sound to the same level as Speaker 2:

Increase in Power of Speaker 1Output of Speaker 1
10 watts81 dB’s
20 watts84 dB’s
40 watts87 dB’s
80 watts90 dB’s
160 watts needed93 dB’s = the output of Speaker 2

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What’s best if you want to increase power output?

It’s always better to start with a speaker that has a higher sensitivity rating as it doesn’t take as much power to increase your SPL.

And starting with a higher sensitivity rating also means your amplifier won’t use as much power as a boosted lower sensitivity speaker. Power usage is vital for portable speakers as it means the battery drain will be much less. Moreover, your playtime will be much longer.

But our focus is on choosing the loudest speaker, and the bottom line is that increasing the sensitivity rating of a speaker increases loudness with a certain amount of wattage. So, it’s always best to go for the highest sensitivity rating given comparable wattage output.

What then if we increase the power or wattage output of the amplifier?

Let’s find out.

What’s the Impact of Increasing Power Output?

We already know the general rule: doubling amplifier power increases speaker output by 3 dB.

In your reading on the subject you’ll find this basic rule expands to the following general rules of thumb:

Amplifier Power OutputSpeaker Output Level Increase
10 watts10 dB
100 watts20 dB
1000 watts30 dB

When I saw these figures, my immediate thought was, “is this another rule on top of the basic 3 dB rule?”

After some thinking, I realized there’s no new rule.

It’s just the actual conversion result that occurs when you increase the power output by precisely 10, 100 or 1000 watts.

Consider an increase of 10 watts in power output.

Remember that 8 watts are three lots of wattage doubling from 1 watt, which results in an increased output of 3 times 3 dB’s = 9 dBs. A power increase to 10 watts means that 10 watts are a part of the doubling of 8 watts to 16 watts, but at the lower end of that doubling, so it only results in an extra 1 dB of sound output.

These assessments of sound output are all based on being 1 meter from the speaker. What happens if you move away from the speaker?

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How Does Increasing Your Distance from a Speaker Impact Loudness?

We’ve all had the experience of sound fading as we’ve moved away from the source of a sound. And again, like sensitivity, a general rule applies:

“The sound level decreases by a quarter every time you double your distance from a sound source. In terms of SPL, there is a decrease of 6 dBs for each doubling of distance.”

Let’s look at an example:

A speaker that has a sensitivity rating of 84 dB (1W/1M) with a 100-watt amplifier produces a sound level of 104 dB (if you recall in the previous section, we found that 100 watts produce 20 dB, so the calculation is 84 + 20 = 104 dB).

For this speaker, the sound loss is as follows:

Distance from SourceSound Level
Base Measure – 1 Meter104 dB
2 Meters98 dB
3 Meters92 dB
4 Meters86 dB

The loss of 6 dB per 1 meter applies to an ideal acoustic environment like outdoors where there are no walls or ceilings for the sound to bounce off. Indoors the loss will be less but by how much depends on the sound absorbency of the wall, floor and ceiling materials and the presence of furniture or other objects.

So sound volume fades as we move away from a speaker. To be heard further away, all we need to do is increase the output of the speaker, right?

That’s correct, but like with all things, there is an outer limit.

We’ll now consider the calculation needed to determine the maximum amount of sound a speaker can output.

What Does Maximum SPL Mean?

A speaker’s specification may quote both a sensitivity rating and a power rating. To determine the maximum loudness that such a speaker can reach we need to perform a calculation.

Sensitivity is a rating that describes the base loudness of a speaker given 1 watt of power.

The power rating is the number of watts available to produce a loud sound.

Combine the two, and you get the maximum loudness of a speaker known as Maximum SPL.

Let’s explain with an example.

A speaker has 87 dB sensitivity and a power rating of 250 watts. We apply the familiar formula of doubling the power to boost loudness by 3 dB.

1 watt87 dB’s
2 watts90 dB’s
4 watts93 dB’s
8 watts96 dB’s
16 watts99 dB’s
32 watts102 dB’s
64 watts105 dB’s
128 watts108 dB’s
256 watts111 dB’s

So, the Maximum SPL for this speaker is 111 dBs.

Knowing the maximum SPL is useful because that can help determine if the speaker will be loud enough for where you want to use it.

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How Loud Do You Want Your Speaker to Be?

Loudness is not only about where you want to use a speaker.

It’s personal too.

One person’s loud is another person’s quiet.

Although we’ve been talking about objective measures of sound by way of decibels, loudness is subjective and personal to the listener.

Let’s look at different ranges of decibels and see what that means in a practical sense:

dB RangeEveryday Sound
0 dBThreshold of Hearing
15-25 dBA Whisper
40-60 dBHome or Office Background Noise
65-70 dBNormal Speaking Voice
85 dBIdling Bulldozer
105 dBOrchestral Climax
120+ dBRock Concert
130 dBPain Threshold
140-180 dBJet Aircraft

At this point, it’s worthwhile issuing a health warning.

If a sound reaches 85 dB or stronger, it can cause permanent damage to your hearing. Moreover, damage also happens if exposure is over an extended period.

It follows then that any speaker with a dB rating over 85 is loud.

It then becomes a matter of your music taste and where you’re going to use a speaker as to how much above 85 dB you want your speaker to deliver.

For inside listening, you probably don’t want to go too much over 105 dBs, which is a loud sound. Any level above is likely to be deafening even if you’re a rock fan and like your music loud.

Going outdoors means going higher up to around 120 dBs so that your sound can spread over a larger area. Just make sure you’re not standing too close.

No matter what sound level you choose, you do need to keep in mind whether the sound quality continues at peak volume.

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What You Shouldn’t Sacrifice in the Pursuit of Loudness

There is no point buying a speaker that makes a dreadful sound when you ramp up the volume.

Yes, you want a speaker that’s loud, but the whole point is you’re listening to music, you want the sound to be clean and distinct, so the musicality comes through and is not ruined by distortion.

You should make sure that distortion (technically called THD or Total Harmonic Distortion) is less than 1%. If the speaker specifications don’t quote this figure, make sure you test run the speaker first before buying (you should do this regardless).

Moreover, you don’t want a speaker that sacrifices quality at the lower volumes either. You want there to be a balance between the highs, mids, and lows. And perhaps some equalizer capability to tweak up the bass sound to suit the music.

Along with checking for quality, remember that choosing loudness is about speaker sensitivity. So, we need to distinguish sensitivity from efficiency.

A Caution About Speaker Sensitivity versus Speaker Efficiency

Earlier I warned about using the terms “speaker sensitivity” and “speaker efficiency” interchangeably. Often marketing people will do so, suggesting that “sensitivity” and “efficiency” are the same thing.

The trouble is, though related, they are not the same.

Technically the term “sensitivity” describes in more precise terms how loud a speaker will play when it receives an input signal at a given voltage level. It is measured in terms of decibels.

“Efficiency” refers to the amount of power going into an amplifier and the acoustic power coming out of the speaker expressed as a percentage.

It is possible to convert efficiency to sensitivity and vice versa, but that is way beyond my basic arithmetic.

It’s worthwhile noting that the “efficiency” percentage for all speakers usually is around 2% or less, which means that the bulk of the input power converts to heat rather than sound.

Knowing the difference in meaning, it makes sense we use “speaker sensitivity” as the means of determining loudness.

And being a standard calculation, it offers a basis for comparing the loudness of different speakers.

Unfortunately, though, manufacturers don’t use the formula in a standard way, so this invalidates the comparison.

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Why You Can’t Always Believe Manufacturer Sensitivity Figures

Manufacturers can and do use different methods to calculate the sensitivity of their speakers.

Some manufacturers use 1 watt as the input level, while others use 2.83 volts. There’s a separate technical discussion about the use of 2.83 volts which I’ll set aside for another day.

Manufacturers also vary the frequencies they use for the calculation:

  • Some use “pink noise,” which is the combination of all frequencies.
  • Some use only one frequency (often this will be the most sensitive).
  • Some state each frequency.
  • Some measure several frequencies and average the result.

There can also be differences in performing the testing:

  • Only the best speaker in the speaker enclosure is measured.
  • All the speakers combined are measured.
  • The test may be conducted in a pure environment where there are no reflective materials,
  • Alternatively, the analysis is performed in a typical setting that is incapable of being duplicated by other testers

Using these different methods on one speaker inevitably leads to different results each time. That is a frustrating outcome because “sensitivity” as a measure is objective. It provides the basis for valid comparisons of different speakers.

Despite these concerns and in the absence of anything else, comparing the sensitivity ratings of speakers provides an idea of how loud a speaker will be.

But wait, here’s the “kicker.”

Most manufacturers don’t specify the sensitivity ratings for “closed systems.”

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The Frustration of Comparing the Loudness of “Closed Systems”

What’s a “closed system” you ask?

It’s where there’s an internally powered system like you have with:

  • Subwoofers.
  • Soundbars.
  • Bluetooth speakers.

Often manufacturers will provide wattage but as we’ve seen before this is next to useless for comparison purposes without sensitivity figures. And even more so if we don’t know:

  • How the power is measured (like maximum distortion level and load impedance).
  • Whether the speaker drivers can handle the output power of the amplifier.

In short, there’s no point in rating internally amplified products, such as soundbars, Bluetooth speakers, and subwoofers, by pure wattage or even using the wattage with a sensitivity rating.

An SPL (sensitivity) rating on its own is the closest measure for a real-world idea of what volume levels the products can achieve.

And in the absence of an SPL rating use the total output volume of the unit if it’s available.

On that note, I’ll move to a final wrap.

A Summary on How to Choose the Loudest Speakers.

When it comes to choosing the loudest speakers, the critical factor is “speaker sensitivity” often identified by the term “SPL” and measured as decibels (dB):

  • If amplifier power output is the same, choosing a speaker with higher sensitivity will get you a louder speaker.
  • If speakers have the same sensitivity, the speaker with the higher wattage will be louder.

When comparing speakers that have different sensitivity ratings, you need to look at the combination of sensitivity and power wattage to find the loudest speaker.

Power wattage can be boosted on a speaker with a lower sensitivity to reach or surpass the higher sensitivity of a smaller wattage speaker. It all depends on the number combination.

Two final examples:

  1. A 1000-Watt speaker with 85 Db sensitivity will produce 115 dB’s while a 300-Watt speaker with a higher 89 dB sensitivity will produce a lower 113.5 dBs. The 1000-Watt speaker is louder.
  2. Again a 1000-Watt speaker with 85 Db sensitivity will produce 115 dB’s but this time the 300-Watt speaker has a higher sensitivity of 93 dB’s which produces a higher 117.5 dBs. The 300-Watt speaker is louder.

Some cautions:

  • Distance from a speaker reduces its loudness.
  • Take care with the accuracy of manufacturer specifications of SPL and wattage.
  • Remember speaker sensitivity is not the same as speaker efficiency although they’re related.
  • Don’t chase loudness at the expense of sound quality.
  • Get a demo of the speaker – it’s the best test of whether it meets your requirements after you’ve narrowed down the field of speakers down to one or two using what you’ve learned in this article.

Choosing the loudest speaker is a challenge but now you can work your way through the technical jargon with ease and be better placed to make your choice.

I wish you many pleasure-filled years of listening to loud music.

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