Speaker Sensitivity 101: Simple Guide + SPL Calculator

Speaker sensitivity refers to how loud a speaker plays when given a certain amount of electrical power. When given the same power, a more sensitive speaker will play louder than a less sensitive model.

It’s one of the first things I learned as a sound engineer. If it’s a new concept for you, you will be surprised by the difference it makes.

This article teaches you the relationship between sensitivity, loudness and sound quality. You’ll also learn how sensitivity is measured and why it’s crucial to a home audio system.

Why is Sensitivity Important?

Sensitivity in speakers plays a crucial role in determining the amount of power needed to produce a certain level of sound. To see the difference it makes, play around with this SPL calculator.

This is a very simple calculator for SPL. I’ve removed some of the more complex factors so you can easily understand the basics of how speaker sensitivity affects loudness. You may be surprised by the results.

I’ve set the default settings like my home system – speakers with an 87 dB sensitivity (2.83V/1m) and an amplifier with a 100-watt RMS rating. The result is an SPL of 107 dB at a distance of one meter (which is how a speaker’s sensitivity is measured). Try this.

1. Move the sensitivity up by 3 dB to 90 dB. The result is 110 dB at 1 meter. It has increased by the same amount as the increase in sensitivity. That makes sense.
2. Reset the calculator and increase the amplifier power slider until the SPL result reaches 110 dB.

Wow. That’s right. You need 200 watts to reach 110 dB – twice as much power. That’s quite some amplifier upgrade. Now you can see why you should pay more attention to speaker sensitivity if you want more volume in your room.

Here’s a table showing more comparisons.

Here’s another thing to try.

1. Reset the calculator so the current settings are 87 dB (sensitivity), 100 watts (RMS power) and an SPL of 107 dB.
2. Move the sensitivity slider up 3 dB to 90 dB. The SPL goes to 110 dB.
3. Decrease the RMS power slider to 50 watts. The result is 107 dB, back where we started.

This experiment tells us if you increase your speaker sensitivity by only 3 DB, you can halve the power of your amplifier and keep the same volume in your room. So, you don’t need to buy a super powerful amp after all!

Not only do more sensitive speakers provide louder sound with less power, but they often boast better design and construction. The improved design reduces distortion, allowing for a more transparent and accurate listening experience.

Speaker Efficiency vs. Sensitivity

While related, speaker efficiency and sensitivity are different.

Efficiency measures the percentage of electrical energy speakers convert into acoustic or sound energy. Sensitivity refers to the loudness in decibels that speakers produce when given a specific electrical input.

• More sensitive speakers also tend to be more efficient.
• Speakers are typically highly inefficient, converting most input power into heat rather than sound. Typical home audio speakers have efficiencies between 0.2% and 2%.

Manufacturers commonly provide sensitivity ratings when specifying speakers to allow comparison between models. It gives helpful information about potential loudness when selecting speakers.

While efficiency provides insight into power handling and heat dissipation, they appear less often.

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

To test speaker sensitivity, an anechoic chamber or other non-reflective space is used to prevent the interference of room reverberations. Here’s an outline of the measurement process:

• The standard power measurement is one watt into 8 ohms
• The resulting SPL is measured one meter from the speaker

You might see a sensitivity specification of 2.83 volts at a distance of 1 meter rather than 1 watt. However, this measurement is the same because 2.83 volts is 1 watt of power into an 8-ohm impedance.

You can verify this using Ohms Law:

1. Power = Voltage² / Impedance
2. Therefore: 2.83² = 8 (Voltage) and Impedance = 8 ohms
3. Therefore: 8 / 8 = 1 (watt of power)

If you halve the impedance to 4 ohms, the input power doubles to 2 watts. So, when comparing the sensitivity of two speakers, it’s crucial to compare models measured using the same method. 

Some manufacturers use different power levels, distances, and impedance, making an accurate comparison difficult. 

As with all specifications provided by manufacturers, you must be careful they provide accurate sensitivity ratings. Check they aren’t artificially inflating them using different measurement specifications and room conditions.

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

Understanding the Numbers

Home audio speakers typically have sensitivity ratings ranging from 82-92 dB. A 10 dB difference in sensitivity can significantly impact perceived volume. 

Humans perceive 10 dB as twice as loud, which is quite a contrast, considering you aren’t changing your amplifier.

When interpreting sensitivity measurements:

• A higher rating means the speaker will be louder with the same power input as a lower-rated speaker.
• A difference of 3 dB, though smaller, still results in a 25% increase in loudness.

The logarithmic nature of decibels can make interpreting differences difficult.

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. Human hearing is not linear, and perceived changes in loudness differ depending on the sound’s frequency and intensity.

Ultimately, 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.
• The length of time you hear something.
• Even how well your ears work!

Finally, remember sensitivity measurements are not the only factor that affects a speaker’s performance. Other factors like frequency response and distortion also have a significant impact.

What Factors Determine Sensitivity?

Speaker design plays a crucial role in determining a speaker’s sensitivity. Several features will have an impact:

• Driver size: Larger driver cones can move more air and be louder for a given power input. Speakers with larger woofers and tweeters tend to be more sensitive.
• Driver material: The material used for the woofer and tweeter affects efficiency. Ceramic and titanium dome tweeters tend to be more sensitive than fabric domes. Rigid and lightweight woofer materials like polypropylene and aluminum are more efficient.
• Magnet strength: Stronger magnets in the driver motor assemblies make it easier for the voice coil to move the cone, increasing sensitivity. Higher-end drivers tend to use large, powerful magnets.
• Enclosure type: Bass reflex ported enclosures can boost sensitivity compared to sealed boxes but may sacrifice some accuracy. Horn-loaded and transmission line enclosures are extremely sensitive but have a distinctive sound.
• Crossover design: The crossover frequency, slope, and components impact how efficiently the drivers integrate and use power. Simple crossovers allow for higher sensitivity.
• Impedance: Speakers with lower nominal impedance (4 ohms vs 8 ohms) often have higher sensitivity. The tradeoff is they also place higher current demands on the amplifier.

With all these factors, there are always tradeoffs with other design goals like accuracy and amplifier compatibility.

Do You Need More Sensitive Loudspeakers?

After all this dull technical discussion, we come to the main point. Should you consider upgrading to more efficient speakers? There are several points you should think about before deciding what to do.

Here are the main issues you should consider.

1. Cost Differences

Sensitive speakers usually cost more than less efficient ones. 

For example, Bowers & Wilkins produces excellent speakers with various sensitivities and prices. Here are some examples from their range.

1. Bowers & Wilkins 607 S2 bookshelf speakers: 84 dB – $799 per pair.
2. Bowers & Wilkins 707 S3 series: 84 dB – $1799 per pair.
3. Bowers & Wilkins 805 D4: 88 dB – $4250 each!

Of course, if your primary goal is to increase loudness in the room, you may not need a more powerful amplifier, which may justify the increased cost of more sensitive speakers. And not all speakers that are more sensitive cost as much as that.

While higher sensitivity isn’t the only reason for a higher price, it’s something to consider if you want improved performance without breaking the bank.

2. Speaker Size

In general, larger speakers have higher sensitivity. When upgrading, 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 following:

• The size of your listening room.
• The type of audio content you listen to.
• Your personal preferences.

You won’t get the best from big 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? Then, you might not appreciate the improved speaker performance as much. Movie audio is more compressed than classical music, with a high dynamic range and detail.

3. Your Existing System

Before upgrading your speakers, evaluate your current system’s overall performance. New speakers may not make a significant difference if other components, like your amplifier or source material, are low quality.

For example, you wouldn’t get the best from highly efficient speakers if you had a low-powered amplifier that couldn’t drive them adequately.

In that case, upgrading the amplifier rather than the speakers may yield more improvement in sound quality. Carefully consider each part of your system to determine the best upgrade path.

Do you need more volume? Or better sound quality? These are different.

Of course, if you have plenty of money, then why not? More sensitive speakers will usually be an upgrade in speaker quality, which is always a good thing to do.

4. Sound Quality

A speaker’s sensitivity is only part of the story for sound quality. Even though more efficient models tend to be pricier and sound better, it’s only one piece of the puzzle.

A more sensitive speaker will be louder with less power, but that doesn’t guarantee it’ll sound superior. Other factors also shape sound quality, like:

1. Frequency response
2. Distortion levels
3. Phase response

You’ve got to look at the complete signal chain, too – amplifier, cables, everything. One weak link can drag down the entire setup’s performance. That’s why having quality components across the board is ideal, or one thing can drag everything down.

Given all these variables, listening tests are crucial when buying speakers if you want to feel confident about your purchase. They reveal nuances of sound quality and flaws that spec sheets might not highlight.

Try playing various tunes you know very well, and listen for distortion, harshness, or lack of detail. Well-engineered speakers should deliver balanced sound without coloring it too much. But again, room acoustics, amps, and cables can all dramatically influence what you ultimately hear.

So, if you can, listen in your own space with your equipment first. It’s the best way to gauge speakers for yourself before committing.

About The Author

Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has been a sound, lighting and audio-visual engineer for around 20 years. At home, he has spent more time than is probably healthy installing, configuring, testing, de-rigging, fixing, tweaking, re-installing again (and sometimes using) various pieces of hi-fi and home cinema equipment. You can find out more here.