That.
We are used to poor speaker efficiency.
But on a machine, specially a power tool, power/torque loss is brutally apparent.
A beast of a machine.
Magnet pull is very strong and focused in the gap, so if loose, polepiece will smash against gap wall pinching the voice coil.
Yes.
Speaker magnets are bought in cardboard boxes, 20 to 40 each depending on size, and they are sold UNmagnetized or not only you couldn't assemble the speaker, it would be very complicated to transport it.
Imagine the magnetic field around a 20 large magnet box.
They would also stick to each other HARD
That!
That +1000
Ring area to gap area ratio is the parameter to consider.
Car type multi stacked magnet speakers are laughable, terrible designs.
You stack 3 or 4 magnets, you may increase gap flux by 10% or so, terrible return on investment ... but it sure looks good to buyers.
Stacking two is reasonable to allow for a long coil excursion, you increase x-max by the added thickness.
Anything above is pure waste.
And as Mark mentions, it's doubtful they are properly magnetized, they are much deeper than what a magnetizer yoke expects.
If you look at car (and guitar) speaker prices, it often makes you frown anyway.
Prices there don't make any sense at all.
Yeah, but stacked magnets look COOL!
Plus they have to make them look expensive somehow. Big magnets, big surrounds and big numbers are what sell car speakers, especially subs.
Plus they have to make them look expensive somehow. Big magnets, big surrounds and big numbers are what sell car speakers, especially subs.
Sad but true. Subs that have 72 to 78 db of efficiency/watt. As JMFahey mentioned when you charge a loudspeaker there is usually a coil that the motor sits in. a very heavy wire, sometimes actually bussbar not wire transformer that you send a very high current pulse through. If any of you have done welding on large machines the cables are huge. 10mm cross section easily. And I have regularly watched them jump around each time a motor is energized. I might have video. It's not so smart to be close up I can tell you that. Credit cards, Flash drives, magically they don't work any more!
Oh magnetized magnets. I have a box of 20 or so Neodymium magnets. Eventually I will make something interesting with them. They are all energized. 75mm O.D. 35mm I.D. 6mm thick. 8 pcs. one was removed and not put back with it's hardboard spacer. I have tried to get them apart. 🤣
And I am not a small man!
Mark
I am actually used that they ship them stacked, in their own box and polarities switched each time.
Still have to be careful though.
But that also counts for big drivers.
When people used to wear mechanical watches, enough warned interns with a broken watch lol.
Still have to be careful though.
But that also counts for big drivers.
When people used to wear mechanical watches, enough warned interns with a broken watch lol.
I didn't realise they were that bad, but I guess it's a case of chasing your tail, more watts means a thick voice coil to take the heat, a thick voice coil is heavy, so it needs more power, more power means...
Then you need strong stiff suspension to hold it all, even more power. When I realised I was only using less than 3 watts, it made everything easier.
Yup. I don't design crap like this. You can buy it cheap enough from China. But mind you, there are some very talented Chinese driver engineers. Some made in the USA brands are just that. Designed by Jinleda engineers but pretended to be designed by the owner.
exactly, it's even worse, if you take power compression into consideration.
Nice exponential runaway!
They weren't that stupid in the 70s.
Just get a big cabinet with high efficient drivers. 😉 🙂 😀
(okay okay that also has its own technical disadvantages lol)
Never a free lunch. I prefer horns, including bass horns. Second problem. I like Bach, and Organ music......
Great big Mother Hooter Horns ( Best thick Scottish accent please )