Ferrite vs Neodymium
Ferrite vs neodymium is a trade between mass and money. Neodymium stores far more magnetic energy per kilo, so the motor can be much lighter for the same flux; ferrite costs less as a raw material and is what most loudspeaker motors use. The magnet does not set the sound: motor design does.
The materials
| Ferrite (Sr/Ba hexaferrite) | Neodymium (Nd₂Fe₁₄B) | |
|---|---|---|
| Energy product (BHmax) | 10 to 40 kJ/m³ | 200 to 440 kJ/m³ (sintered) |
| Energy per kg | 1× | About 12× ferrite |
| Raw material cost | Low; the most common loudspeaker magnet | Higher |
| Temperature | Loses some flux as it warms, recovered on cooling within its range | Standard grade rated to 80 °C; high-temperature grades up to 230 °C. Remanence falls 0.09 to 0.12% per °C |
What it means in a real 18"
Published weights for 8 Ω 18s with similar coils show the effect:
- B&C 18TBW100, ferrite, 100 mm coil: 15.4 kg
- RCF LF18X451, ferrite, 114 mm coil: 15.2 kg
- B&C 18SW115, neodymium, 116 mm coil: 11.9 kg
- B&C 18DS115, neodymium, 116 mm coil: 12.55 kg
- Wavemark WM1850/8, ferrite, 125 mm coil: 20 kg
On a double-18 cab the difference between ferrite and neo drivers is several kilos of the total, most of which is still plywood. For a ground-stacked system that travels in a van, that matters less than for a flown or touring rig. See moving a sound system.
Heat
All permanent magnets lose some flux as they warm, and recover it as they cool, within their rated range. Neodymium has a defined maximum operating temperature by grade, and beyond it the loss is not fully recovered. In a sub driver the heat source is the voice coil sitting in the gap, so neo motors rely on grade choice and on getting heat out of the gap. Either way, keeping the coil cool is the job of the limiter and the motor's venting. See voice coils and heat.
Does neodymium sound better?
No. Output and control come from the motor as a whole: Bl, gap geometry, flux stability and the suspension. A well-designed ferrite motor and a well-designed neo motor of equal Bl drive the cone the same way. Neo buys you lower weight; you pay for it.
Wavemark: ferrite by design
Both Wavemark 18s use ferrite motors. The WM1850/8 puts a 125 mm coil in a vented ferrite motor, rated 1800 W AES, for £275 (15.3p per rated watt). The WM18X451 uses a 115 mm copper coil, ferrite motor and double spider, rated 1800 W RMS, for £345 (19.2p per watt). The weight goes into the van; the saving stays in your pocket.
Sources: material data from Neodymium magnet and Ferrite (magnet), Wikipedia; driver weights from B&C Speakers (18TBW100, 18SW115, 18DS115) and RCF LF18X451, checked October 2026; Wavemark product data.
Questions
Is neodymium better than ferrite for speakers?
Not for sound. Neodymium stores about 12 times more magnetic energy per kilo, so the motor is lighter, but output depends on the motor design. Ferrite costs less and adds weight.
How much lighter is a neodymium 18 inch driver?
In B&C's range, the ferrite 18TBW100 weighs 15.4 kg and the neodymium 18SW115 11.9 kg, both 8 ohm.
Do neodymium magnets lose strength when hot?
All magnets lose some flux when warm. Standard neodymium grades are rated to 80 °C and higher grades to 230 °C; above a grade's rating, the loss is not fully recovered.