Why Class D amp with ceramic speaker?

[Axtman]

I have worked on a few Gallien Krueger amps which I love (the sound, not so much the repair). I am puzzled that their little lightweight (MB series) combo amps have Class D amplifiers but with ceramic (not neodymium) speakers. I mean if you are going for lightweight go all the way (like Fender Rumble series).

[Enzo]

Maybe they didn't find a neo they liked the sound of or the performance of. It ain't an all or nothing world.

[tedmich]

cheapest might be ceramic and class D, the price of neodymium spiked almost 300% between July 2020 and March 2022!

[g1]

GK make 10,12, and 15 inch in both neo and ceramic. The current model MB 212 uses neos, the other MB's with 10's use ceramic. They say they are all designed specifically for those particular cabinets.

[glebert]

I've never heard anyone say "Man, these neo speakers sound GREAT!" Do all the Rumbles use them or just the big ones? I love the small Rumbles but haven't really liked the bigger ones I've tried.

[uneumann]

I've never heard anyone say "Man, these neo speakers sound GREAT!" Do all the Rumbles use them or just the big ones? I love the small Rumbles but haven't really liked the bigger ones I've tried.

Can't resist.... Man, these neo speakers sound GREAT.
I use Weber neos (for guitar). The 10 and 12" both sound good to me. Can't comment about bass spkrs.
As with any speaker, personal pref's and the amp/spkr/cab combination can matter.

[J M Fahey]

Every coin has 2 sides.

1) voice coil does not know or care about magnet materials, weight, whatever, only what magnetic flux/density it´s floating in.

So if you have 2 otherwise identical speakers (same cone, voice coil, etc.) , different magnets but same flux, say 12000 Gauss / 1.2 Tesla , they will sound the same.

2) that said, Ferrite still has a long life ahead, and I personally prefer it because it´s more robust, forgiving, not bad in a field where speakers (and everything else) is regularly abused.

A big point against Neo is their weakness under thermal abuse.

Voice coil considerable heat is mostly dissipated into the magnet structure, clearly a large heavy disk such as a ferrite system can absorb (lots of mass) and dissipate (lots of surface) WAY more than a magnetically equivalent Neo system, made out of a tiny Neo plug inside a small "cup".

To make matters worse, there is a temperature called "Curie point" above which magnets lose all magnetism for good;it´s lowest for Neos, which even start losing pull above puny 80C , go figure.
https://www.apexmagnets.com/news-how...ymium-magnets/

While Ferrites stand twice higher than Neos and to boot, it´s harder to heat them up that much ........ now with lightweight Neos? ... easy peasy.

Notice many Neo powered speakers sport built-in heatsink fins, there´s a reason for that.

So in a nutshell, light to average Ferrite speakers still have usefulness and are not *that* heavy considering other elements such as cabinets and transformers.

Of course, backbreaking monsters such as EVM, JBL, etc. are something else.

[uneumann]

A big point against Neo is their weakness under thermal abuse.

Thanks for that - it's new info to me.
I rarely run my neo spkrs at even 50% of rated power, so I assume heating is not an issue under those conditions.
But, I wonder if the published power ratings take magnet heating into consideration.
Are there cases of magnet failure before voice coil or mechanical failure?

[Helmholtz]

Above the Curie temperature permanent magnets lose all their power and stay de-magnetized when cooled down.
.
The Curie temperature Tc of Neo's is above 300°C, so little chance to be exceeded in a speaker.
But partial de-magnetizing already starts considerably below Tc.
The max. operating temperature Tmax for Neo is 80°C to 150°C, above which irreversibe effects can be expected.
From this it seems that Neo magnets are predestined for lower wattage speakers (say <30W).
Heat sinks/cooling fins might somewhat extend the range.

Ceramic magnets: Tc around 450°C, Tmax between 200°C and 250°C, but at this temperature a ceramic/ferrite magnet might already be 30% weaker than at room temperature. This is typically a reversible property, meaning that magnet strength mostly recovers at lower temperature.

Alnico magnets: Tc around 800°C, Tmax = 500°C, irreversible effects above 550°C, most temperature-stable.

[Mick Bailey]

Neo magnets suffer badly from corrosion in humid or damp environments. The nickel plating peels off, leaving a deep furry layer of powdery corrosion and a bonded magnet assembly just falls apart.

[uneumann]

Neo magnets suffer badly from corrosion in humid or damp environments. The nickel plating peels off, leaving a deep furry layer of powdery corrosion and a bonded magnet assembly just falls apart.

Yikes. I'll watch for that. Yet another corrosion problem for gear that lives on a coast.

[glebert]

To the OPs question I would also wonder about class D amps that use old school iron power transformers. I'm pretty sure the Peavey Max amps are like this..