Marshall Origin 5: Swapping the Speaker Driver

I’m not personally familiar with the sound of AlNico. How does it compare with ceramic?
This tells me you want to switch because of something you read, not what you heard :)

Leave the Celestion 8-15 , the best driver there.

To boot, it´s 16 ohm, it will be VERY HARD to get a Guitar 16 ohm Alnico driver.

Want to improve sound?
Plug amp out into a full size 1/2/4 x 12" speakers.
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> Plug amp out into a full size 1/2/4 x 12" speakers.

Yes. An Eight is small for guitar. Magnet material is subtle. One Twelve (any good type) is better. A Four-Twelve stack will kick your guts, even with just a few Watts. (True, it won't fit in the closet, or a small car.)
 

Gnobuddy

Member
2016-03-01 4:10 pm
I’m not personally familiar with the sound of AlNico. How does it compare with ceramic?
Interesting fact: outside of the wonderful (and frequently confused) world of guitar, loudspeaker designers and manufacturers never ask this question.

The reason for this is that the actual material in the magnet doesn't matter! When it comes to speaker magnets, the thing that actually matters is the magnetic field strength in the loudspeaker's voice coil gap.

In the guitar world, though, when someone compares a guitar speaker with an Alnico magnet with a different speaker with a ceramic magnet, they are likely to be comparing two speakers that are built very differently, because they originally came from two different engineering eras.

In other words, the magnet material isn't the only thing that's different - and it's likely that the other changes are the ones actually responsible for changing the sound of the speaker.

It's a little like racing a red car with wide, sticky race-compound tires on it, against an identical-model blue car with skinny, super-hard-compound, extra long life road tires on it, and then concluding that red cars run faster than blue cars. :)


-Gnobuddy
 
Gnobuddy hit the nail on the head there except; I fitted a pair of Celestion 12" neodymium speakers and that makes the Fender Twin Reverb handleable again. The ceramic/ferrite magnets added 6kG to the overall weight!
It still sounds as good as ever and can be moved without taking your back out as it is 6kG lighter. The only reason to replace them.
 

thoglette

Member
2008-12-20 5:59 am
Interesting fact: outside of the wonderful (and frequently confused) world of guitar, loudspeaker designers and manufacturers never ask this question.
Yup. Ceramic is far too cheap!:D
The reason for this is that the actual material in the magnet doesn't matter!
Well, it does. The physics is different (but at a second order, relating to field "stiffness") but as you say...
In other words, the magnet material isn't the only thing that's different - and it's likely that the other changes are the ones actually responsible for changing the sound of the speaker.
 

Gnobuddy

Member
2016-03-01 4:10 pm
Yup. Ceramic is far too cheap!:D
...and so took over the industry decades ago, being used in virtually every Hi-Fi speaker made. In some countries the term ferrite is more commonly used than ceramic, but they are the same thing.

I think you're exactly right, though: the reason guitarists think AlNiCo is better is because it's costlier, nothing else. It's the same effect as pulling a guitar off the production line, applying a fifty-cent decal that carries the image of Eric Clapton's or David Gilmour's signature, and selling it for a couple of thousand bucks more than otherwise-identical guitars without the decal. If it costs more, it must be better. :rolleyes:
The physics is different
There's less eddy current damping at high frequencies in a ceramic magnet, but this is completely swamped by the damping in the metal parts of the magnetic structure - the pole-piece inside the voice coil, and the back-plate that completes the magnetic circuit.

Those metal parts are made of the same materials whether the magnet itself is ferrite, neodymium, or Alnico, so the magnet material itself has very little effect.

Ultimately, speaker manufacturers have complete control over the amount of eddy current damping in the speaker magnetic structure - they can add a shorting ring to the magnet pole-piece to provide any additional damping they want, and this is done in many Hi-Fi speakers. If a manufacturer wants a ferrite magnet speaker to have the same eddy current damping as an Alnico speaker, she can achieve exactly that.
(but at a second order, relating to field "stiffness") but as you say...
The coercivity and the shape of the hysteresis loop are certainly different, but the belief that Alnico de-magnetizes and re-magnetizes itself as music is being pumped through the speaker (compressing the signal in the process) is almost certainly complete nonsense. Without any solid evidence (or a even a convincing mathematical model) for the hypothesis, it is about as believable as the Loch Ness Monster. :)


-Gnobuddy
 

PKI

Member
Paid Member
2011-08-10 10:14 pm
...and so took over the industry decades ago, being used in virtually every Hi-Fi speaker made. In some countries the term ferrite is more commonly used than ceramic, but they are the same thing.

I think you're exactly right, though: the reason guitarists think AlNiCo is better is because it's costlier, nothing else. It's the same effect as pulling a guitar off the production line, applying a fifty-cent decal that carries the image of Eric Clapton's or David Gilmour's signature, and selling it for a couple of thousand bucks more than otherwise-identical guitars without the decal. If it costs more, it must be better. :rolleyes:

There's less eddy current damping at high frequencies in a ceramic magnet, but this is completely swamped by the damping in the metal parts of the magnetic structure - the pole-piece inside the voice coil, and the back-plate that completes the magnetic circuit.

Those metal parts are made of the same materials whether the magnet itself is ferrite, neodymium, or Alnico, so the magnet material itself has very little effect.

Ultimately, speaker manufacturers have complete control over the amount of eddy current damping in the speaker magnetic structure - they can add a shorting ring to the magnet pole-piece to provide any additional damping they want, and this is done in many Hi-Fi speakers. If a manufacturer wants a ferrite magnet speaker to have the same eddy current damping as an Alnico speaker, she can achieve exactly that.

The coercivity and the shape of the hysteresis loop are certainly different, but the belief that Alnico de-magnetizes and re-magnetizes itself as music is being pumped through the speaker (compressing the signal in the process) is almost certainly complete nonsense. Without any solid evidence (or a even a convincing mathematical model) for the hypothesis, it is about as believable as the Loch Ness Monster. :)


-Gnobuddy

:nod::cheers:
 

thoglette

Member
2008-12-20 5:59 am
The coercivity and the shape of the hysteresis loop are certainly different, but the belief that Alnico de-magnetizes and re-magnetizes itself as music is being pumped through the speaker (compressing the signal in the process) is almost certainly complete nonsense. Without any solid evidence (or a even a convincing mathematical model) for the hypothesis, it is about as believable as the Loch Ness Monster. :)
Agreed. But, should the designers have a clue, (ha! ) they might get different based on Ragnar Lian's commentary from on the topic from back in 1998.
I have, just to tease, done calculations on three different magnet systems; my old Scanspeak system with 18 mm coil, 100 windings and a 120 mm ferrite magnet, but without SD (Symmetric Drive). Then an imagined system with a 40mmx40mm alnico magnet, and one system with a 40x10 neodymium magnet. These three systems have roughly the same magnetic field, statically speaking. The ferrite system has an asymmetry of 25%, the alnico system has 4% and the neodymium system at about 2% ! Mysterious? Not at all! If we picture the voice coil, 18 mm long, 100 turns, at 5 amps, this produces 500 amp-turns, or a field strength of 28000 A/m, this is a magnet "let loose" around the air gap. It is directed with or in opposition to the main field, depending on the direction of the current, and acts directly upon the field in the air gap, and also shifts the operating point of the magnet. The ferrite magnet's operating point is at about 2500 gauss, and has an incline such that it can easily be shifted 2-300 gauss, that's quite a few per cent! Both the alnico magnet and the neodymium magnet have operating points up around 10-11000 gauss, and an incline which makes them somewhat "stiffer", meaning that they can't be moved much. Both neodymium and alnico have the property of having a permeability close to 1, in other words the same as air, and they do not affect the inductivity of the voice coil! Then we can go back to the early 70's, when JBL spoke of "The Alnico Sound" - that was no lie!

This was from the old "joe list" email list, translated by Thomas Dunker saved here.

I will quickly point out I have not done a mathematical model of this!;) I'm biased, having had rather good experiences with Mr. Lian's speakers over the years.
 

Gnobuddy

Member
2016-03-01 4:10 pm
I will quickly point out I have not done a mathematical model of this!
I would think a simple acoustic THD measurement of the loudspeakers in question would tell the tale, no? After all, that's the thing we can hear, so it's more relevant (for this purpose, i.e. identifying any audible superiority of AlNiCo vs Ferrite speakers) than the percentage of nonlinearity in the magnetic field.

Five amperes is a lot of current to push through a guitar loudspeaker voice coil, equivalent to 100 W RMS into an 8 ohm speaker if we assume 5 A is the peak current. (If its RMS current, then we're talking an even bigger 200 W RMS to the speaker.)

I think just about any guitar speaker on the planet will distort like crazy with that much input power, so will slight changes in the shape of the hysteresis loop be audible on top of that? Dunno for sure, but I have doubts.

Ye Olde typical valve guitar amp will also generate a lot of distortion when pumping out 100 or 200 watts, once again making any distortion from the speaker magnetic system perhaps less important, as it will likely be swamped by the amp distortion.

I'm more than willing to change my opinion about things like this when presented with trustworthy engineering data - it's the unsupported claims and conflated concepts I'm skeptical about.

This particular (guitar) speaker comparison thing seems to be as difficult to pin down as the proverbial greased pig. For a fair comparison, we'd want two drivers with identical cones, surrounds, spiders, and voice coils, also identically long pole-pieces and identical BL constants as well. Only the magnet material should be different. I've never seen two speakers like this.

But the kicker, for me, usually comes back to the fact that the guitar player always seems to matter far more than the amp, speaker, or any other part of the audio chain.

Here are some good musicians performing using gear - for the entire band, i.e. four musicians - bought for a total of one thousand British pounds (we're talking "starter pack" guitars and amps): YouTube

And here is another band, with a lot of much more expensive gear: YouTube


-Gnobuddy
 

PKI

Member
Paid Member
2011-08-10 10:14 pm
But the kicker, for me, usually comes back to the fact that the guitar player always seems to matter far more than the amp, speaker, or any other part of the audio chain.

-Gnobuddy

Know why? I've been there :). Because it is way way easier to play that constant gear-modding game than actually practice and bring your playing to a different level.
As you just posted you can play and sound great on any cheap *** gear, it is mostly for a player as listeners would not care and will not tell what gear yo are using 99% of the time...

You might remember I was planing on building "the best" practice amp, but decided to save some time and got new Yamaha THR10II instead. Can not be happier, actually playing every free minute I have and let me tell you I finally cleaned some of my chops. So yep there is nothing wrong with treating guitar stuff as an RPG computer game and build up you your character as long as you understand that it has very little to do with you becoming a better player :)
 

Gnobuddy

Member
2016-03-01 4:10 pm
...new Yamaha THR10II...Can not be happier, actually playing every free minute I have...
Much the same story here, except I bought a Boss Katana 50 this summer. It's both the best bedroom guitar amp I ever had, and the best stage amp I ever had. It even works well as an acoustic guitar amp. :)

I also use a Digitech Trio+, IMO one of the best guitar practice and learning tools I've ever encountered. The drum machine keeps your timing honest, the invisible bass player just adds to the fun, and the loop you lay down gives you something to practice soloing over.

Now I can hunt through the A-major scale for the chord tones in an E7sus4 chord without driving anybody else nuts, and if I accidentally play a D# (instead of a D) the first time around, I can correct my mistake the next time through the chord progression. :)


-Gnobuddy
 

PKI

Member
Paid Member
2011-08-10 10:14 pm
Dont get me wrong I will still be making that ax84 October amp and planing on adding a separate eq for the OD channel in my slo-ish clone :). I just think we all need to draw a line when we have an itch to swap perfectly functional pickups with alnico 5 for alnico 2 :)