Do Bigger Magnets Make For Better Loudspeakers?


Everybody who listens to audio, whether music, podcasts, movies or other media, depends on speakers. From standalone loudspeakers and monitors to headphones and earphones to built-in laptop and cell phone speakers, it’s clear that speakers vary significantly in size. With most speakers being electromagnetic, it begs the question: do bigger magnets make better speakers?

Do bigger magnets make for better speakers? Bigger magnets are required for bigger speakers, but they do not necessarily make them “better.” Larger magnets (and stronger audio signals/voltages) are necessary to move large speaker cones and subwoofers. However, the overall quality of a loudspeaker depends on more than the size of its magnets.

In this article, we’ll discuss the role of magnets in electromagnetic/dynamic loudspeaker drivers, focusing on the factors related to magnet size.


A Primer On Electromagnetic Speakers

Loudspeakers are transducers that convert audio signals (electrical energy) into sound waves (mechanical wave energy). The transducer units are specifically referred to as speaker drivers. The vast majority of these drivers are considered “moving-coil” or “electrodynamic”, working primarily on the principle of electromagnetic induction.

Of course, there are alternative driver designs, which I discuss in my article What Are Speaker Drivers? (How All Driver Types Work) but in this article, we’ll focus on the most prevalent type.

Here is an illustration of the cross-section of a typical speaker driver.

The audio signal (AC) passes through the conductive voice coil, and an alternating magnetic field is produced. This magnetic field interacts (causes attraction and repulsion) with the permanent field of the magnetic structure. Suspended within the magnet and attached to the diaphragm, the voice coil pushes in and out, propagating sound waves into the medium as it does so.

So magnets are required for [this popular type of] a speaker to work effectively as a transducer. Now let’s move on to how magnet size affects these speaker drivers as transducers.

Related articles:
How Do Speakers Produce Sound? (A Helpful Beginner’s Guide)
Why And How Do Speakers Use Magnets & Electromagnetism?
How Do Speakers & Headphones Work As Transducers?


Do Bigger Magnets Make For Better Loudspeakers?

Magnets play a significant role in driving loudspeakers. The bigger the magnet, the stronger the potential driving force of the speaker (assuming the magnetic strength of the magnet is constant). Small magnets are for small speakers and produce, by nature, “weaker sound”, while bigger magnets make bigger speakers capable of producing louder sound.

Stronger/bigger magnets will allow for louder sound production. Other factors necessary for louder volume include stronger (more amplified) speaker level audio signals, more heat-resistant voice coils, larger cone/diaphragms, greater room for diaphragm excursion, more optimal speaker enclosure and more. In short, a bigger magnet is one of the factors that allows a loudspeaker to sound louder.

But does this constitute the oft subjective term “better”?

Yes, bigger magnets make for better loudspeakers if we’re only concerned with loudness. They make for louder speakers, which are especially important for sound quality in large rooms.

For example, a large 2-way PA speaker will fill a room much better than the built-in speakers of a laptop or tablet. However, it’s not only the fact that the PA speakers contain bigger magnets; they also feature the factors I’ve listed above.

All else being equal, a bigger permanent magnet will increase the reactivity of the speaker to the pulses of electricity running through the electromagnetic voice coil.

However, you’ve likely noticed on high-end speakers that there are often multiple driver sizes. That is because, when it comes to frequency response, larger speakers are typically better at producing low-end/bass frequencies, and smaller speakers are generally better at producing high-end/treble frequencies.

To reproduce the entire audible frequency spectrum (20 Hz – 20,000 Hz), we tend to rely on a variety of speaker driver sizes, each optimized to produce its own frequency band within the audible range. This is a drawback of electrodynamic speakers, though it is one that we’ve understood and incorporated into loudspeaker design for quite some time.

Subwoofers, for example, will have very large magnets (along with robust voice coils and great diaphragms). Their purpose is to produce low-end frequencies with long wavelengths, which require them to push and pull a lot of air. Note that, as humans, we tend to feel these sub-bass and bass frequencies more than we hear them.

Tweeters, conversely, will have small magnets (along with thinner voice coils and small diaphragms). Their purpose is to produce the high-end frequencies, which have shorter wavelengths and are more easily perceived by our hearing. There’s a great benefit of keeping these drivers smaller and allowing them to vibrate very quickly to recreate the high-frequencies.

So a bigger magnet is certainly “better” for subwoofers, woofers and even some midrange speakers (depending on the frequency bands they’re designed to produce). However, this is not the case with tweeters, super-tweeters or some other midrange speakers.

Related articles:
What Is A Good Driver Size For Loudspeakers?
How Do Small Speakers Produce Bass Frequencies?
How Fast Do Loudspeakers & Headphones Vibrate?

Before we move on, it’s important to note that the size of the magnet in any given speaker driver is subject to constraints. The overall size and weight of the drivers are factors to consider. How the magnet will interfere with other audio devices (other drivers, crossovers, amplifiers and other components) must be taken into consideration.

It’s also essential that the magnet’s magnetic field be concentrated in the pocket where the voice coil is suspended. If you questioned the odd shape of the magnet in the illustration I provided earlier, note that the bizarre construction (complete with pole pieces) is to concentrate this magnetic field at the voice coil.


How Loud Is A Loudspeaker? Sensitivity & Power Rating

The loudness of a loudspeaker is measured in decibels (dB). It is sometimes referred to as the Sound Pressure Level (SPL), but more often/officially as its sensitivity.

Sensitivity is sometimes denoted by a number, for example, 10 dB. The notation describes the sound pressure level (related to perceived loudness) a speaker will produce at a distance of 1 meter when 1 watt of power is applied.

For example, a 10 dB speaker produces 10 decibels when 1 watt is applied, measured 1 meter away from the speaker. The specification can also be given as 10dB (1W/1m).

But here’s the thing: If you increase the sensitivity of your speaker by double (+3 dB), the loudness doesn’t necessarily double as well. Increasing the sensitivity by double only increases the speaker output by 3dB. In other words, if the output of a speaker is 81dB and the power rating is 10W, if you double the power to 20W, the loudness will reach only 84dB. If you again double the power to 40 watts, it will produce 87dB. And 80 watts will give you 90dB.

It takes an SPL increase of 10dB to double the perceived loudness of the sound coming out of a speaker.

That’s the math on power (W) and sensitivity (dB). That is how loud a loudspeaker gets if you increase its power rating.

If this is at all confusing, I have in-depth articles on decibels and speaker sensitivity. Consider reading through the following My New Microphone articles to answer any lingering questions:
What Are Decibels? The Ultimate dB Guide For Audio & Sound
Full Guide To Loudspeaker Sensitivity & Efficiency Ratings

Bigger magnets, in theory, increase speaker sensitivity. The bigger the magnet is, the more reactive and powerful the driver will be. A powerful permanent magnet also translates to a more sensitive loudspeaker.

Neodymium is a powerful natural magnet. A small piece of neodymium has stronger electromagnetic currents than an inferior magnet of the same size. This is the reason why powerful speakers have become more lightweight. So it’s less about the size and more about the magnetic strength.

Larger/stronger magnets produce stronger internal magnetic fields, which will interact with the voice coil to cause stronger diaphragm movement, increasing the speaker’s excursion and loudness.


Amplifier Output And Speaker Power Rating

The speaker’s power rating refers to the maximum signal level the speaker can experience from the amplifier. As the specification title suggests, it’s rated in watts (electrical power). This has less to do with the magnet and more to do with the burning/melting of the overloaded voice coil. Note that power rating can be given in a variety of “wattage types,” including peak, RMS, average, and more.

I go into greater detail on loudspeaker power ratings in my article The Complete Guide To Speaker Power Handling & Wattage Ratings.

The power rating (W) of a speaker is essentially concerned with the output of its amplifier. The speaker must be able to handle the power flowing from the amplifier to its drivers.

As the name suggests, power amplifiers amplify the power of the audio signal to drive the speakers adequately. Ideally, the amplifier will not affect the audio quality, though some amps include EQs and other tonal adjustments to allow users to adjust bass, mids, treble, etc.

For everything you need to know about EQ, check out my article The Complete Guide To Audio Equalization & EQ Hardware/Software.

As a general rule, your speakers should have a higher power rating than the amplifier. This ensures that your amplifier does not supply power that your speakers cannot handle because your speakers can only take as much as their power rating limits.

There are other factors to consider when matching amplifiers and speakers, such as impedance and the aforementioned speaker sensitivity.

Related articles:
Why Do Speakers Need Amplifiers? (And How To Match Them)
The Complete Guide To Speaker Impedance (2Ω, 4Ω, 8Ω & More)
What Is Amplifier Impedance? (Actual Vs. Rated Impedance)

Bigger magnets will allow a speaker to produce more volume with less signal from the amplifier.


Conclusion

Bigger magnets will, in some cases, make for better loudspeakers. However, there are numerous interrelated speaker specifications, along with the purpose of the driver in question, that must be taken into account when determining what constitutes a “better speaker”.

To learn about all of these specs, check out my article Full List: Loudspeaker & Monitor Specifications w/ Examples.


Choosing the right PA speakers for your applications and budget can be a challenging task. For this reason, I’ve created My New Microphone’s Comprehensive PA Speaker Buyer’s Guide. Check it out for help in determining your next PA speaker purchase.


This article has been approved in accordance with the My New Microphone Editorial Policy.

Arthur

Arthur is the owner of Fox Media Tech and author of My New Microphone. He's an audio engineer by trade and works on contract in his home country of Canada. When not blogging on MNM, he's likely hiking outdoors and blogging at Hikers' Movement (hikersmovement.com) or composing music for media. Check out his Pond5 and AudioJungle accounts.

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