“These headphones use special neodymium magnets so they sound better,” said a salesman to me once long ago.
You see this kind of marketing all over audio equipment, and even on sites that compare various models of equipment. When researching headphones before I’ve come upon sites that list pros and cons of two models — which is useful — but it always lists a set with neodymium as a “clear win” over ones with ferrite magnets.
Those sites go on to explain that neodymium “produces deeper bass and clearer detail.”
Neodymium magnets tend to be more expensive, so a great way to sell them is to call them special.
But is there really a big difference or is this one of those things that is mostly marketing?
The Biggest Differences Between Neodymium and Ferrite Magnets
It is true that neodymium magnets have a greater magnetic force to size ratio. That is to say that a smaller neodymium magnet can produce a given amount of attractive force than would be needed with a ferrite magnet. That means that any speaker or headphone that uses neodymium will be lighter, which is part of the draw in headphone manufacture.
Lighter is better, right? Well actually in subwoofers the extra weight can be useful to keep the cabinet from rattling/moving when the woofer gets moving. For those that travel a lot with speakers however, such as musicians, the weight savings of neodymium can be very useful.
Ferrite magnets resist corrosion better, which makes them ideal for outdoor speakers.
Neodymium is also a much more expensive magnet, so the choice between that and ferrite often comes down to production costs and retail price of the finished product.
(Good discussion about differences here.)
Some have pointed out that neodymium magnets also conduct a tighter band of force rather than a wider radiation of magnetic force (like ferrite), so in cases with speakers and voice coils can more tightly control the voice coil since it’s concentrating a lot of energy right into that space rather than a wider band for which some energy is not focused on the coil.
But when it comes to actual sound quality, is there a difference?
To answer this we need to understand the basics of how speakers work. Without getting too technical, a speaker is basically a cone attached to a voice coil that carries electrical current at alternating polarity (+/-). Since magnets attract opposite polarity and repel same polarity, the speaker’s magnet basically pushes and pulls the cone back and forth very rapidly to the frequency of the sound signal.
What we may call “sound quality” refers to how accurately the speaker can reverberate to the signal given to it. A magnet’s ability to “control” the cone is only really determined by it producing the proper amount of force, depending on the size of the cone.
There’s a good discussion about this in the Sound on Sound forums, in particular.
Let’s say that for a given driver/cone size we need a magnet that can generate X amount of magnetic flux, given the driver’s size and density. As long as the magnet can generate that flux, it will be able properly control the driver.
(There are other considerations like the design of the voice coil/spider, cone suspension, cone material, etc.)
Since neodymium magnets generate more magnetic force than ferrite at the same weight, a neodymium magnet matched for this particular speaker driver’s size will be smaller. However, outside of the above mentioned reported differences in how each type of magnet generates waves of force (and how the shape of those differ) in terms of actual magnetic force theoretically both could achieve the same figure. The ferrite magnet would be larger.
Other factors will affect sound quality, such as the construction of the voice coil and the cone itself, the design of the enclosure of the speaker, etc. In as much effect as the magnet can have, though, two magnets of the same amount of magnetic flux will be the same. Ferrite will just have to be bigger to do that.
Sure, a lot of high end headphones use neodymium magnets, but a great example of a ferrite-driven headphone that still sounds great is the V-Moda M100. They’re heavier than other headphones of similar size, partly because of the magnets and partially the rugged steel construction, but are still widely lauded as great-sounding headphones.
Whether or not those headphones are your cup of tea or not, they serve as an example of the following concept:
Simply noting a magnet type in itself doesn’t automatically tell you about a speaker’s (or a pair of headphones) sound quality. In my opinion the V-Moda M100’s sound better with ferrite magnets than quite a few neodymium-based headphones I’ve used, likely due to the other factors in build quality. Yet there are other headphones I’ve used that sound better than the M100’s and have neodymium magnets.
It’s a spec that can tell you something, but doesn’t tell you everything. You might think of it like looking at a speaker’s sensitivity rating. It can give you some insight into how loud it might play or how easy it would be to drive it (from an amp standpoint) but it doesn’t tell you much about how good it will sound.
Don’t the Lowther speakers have a choice of ceramic or neodymium magnets with otherwise identical drivers. They’re said to sound different by comparison although I believe only the magnets are different.
Some woofers do use neodymium magnets instead of earth magnets. It’s hard to say; some people swear it makes a difference in sound, and others say magnetic pull is magnetic pull and the main difference between the two types of magnets is the weight to magnetic force ratio. Each has its own potential advantages or disadvantages for a subwoofer.
For instance, sometimes a lighter speaker is far better for a PA system where you’ll be carrying it around, but other times the extra weight helps a subwoofer stay put when driven hard without the box moving around.
The acceleration of the voice coil depends on the flux density in the magnetic gap. A neo magnet and a larger, heavier ceramic magnet will be designed to generate the same flux density within the gap. With everything else equal, performance is identical.
However, in high power systems, neo magnet systems better dissipate heat. This improves power handling and sound quality. As a voice coil gets hot, it’s electrical resistance increases and therefore the impedance at any given frequency increases. This decreases efficiency and requires the amplifier to do more work, if it can. When amplifiers are pushed above optimal levels they produce more distortion. This advantage of neo magnets applies to high power drivers that are expected to get hot, such as compression drivers.
Hi everyone, I seem to remember reading about and also observing the differences between common ceramic and neodymium magnets. In a mechanical aparatus like a speaker I believe that these differing properties actually WOULD make a significant difference in performance. That said it would be a tradeoff as usual and i doubt that one or the other could really be declared “better”
What im referring to is the density, and ultimately the size of the magnetic field in question.
Take two magnets, one ceramic one neo. Each is capable of suspending a one pound object and they are thus said to be of equal strength. They differ greatly in size and weight.
But now get out some iron filings and paint a picture of the field surrounding each magnet.
What you will find is that the size of the field around each is roughly proportional to its size and mass.
The neo has a compact and strong field that acts at short distances with great strength
The ceramic has a wider field that acts at a longer range with less strength
I could be wrong here this is just dredged up from memory… But if true it would certainly affect acceleration of moving parts of a speaker.
to some degree the design of the speaker could override these differences id guess.
A side by side test would be revealing. Two duplicate speakers equipped with different magnets and some fancy measuring equipment 🙂
Sorry ! Don‘t agree. It‘s also about the reaction time with neodymium driven cones.
Interesting. Have you found that its lower weight allows for tighter control of the driver?
…which was covered in the article when it said that if the magnet can create enough force it can properly control the driver. That sounds to me like it includes response time. Since there’s no moving parts in the neodymium magnet itself, ‘response time’ is irrelevant. If you’re talking about how fast the magnet moves the cone, see above.
Magnetic force, like all electromagnetic waves, travel at the speed of light.
Very true and have neodymium speaker headphone not even perfoming equivalent to old one heaphone having ferrite magnet
Very interesting article. Thanks.
Dennis agrees with you 100%, in his 30+ years working with sound reproduction, it was frustrating how many times speakers were sold on hype rather than sound quality.It amazes me how many people make purchases based on advertising hype rather than their own ears. Fortunately for marketers, many people equate high dollars with high quality.