I don’t have the depth of know how as some people in the UK and US and Far East but magnets are misunderstood and I don’t know why to be honest, when it’s quite simple.
Ferrite, barium, strontium magnets are ceramics, and these are lower in power then Samarium, Cobalt and Neo but used in a large stack give a very stable and powerful field, even more so than a small single plate of neodymium, the gauss reading is meaningless at times as the distance and area measured is never stated.
14,200 gauss at 1 cm is a powerful reading but what if its only 100 grams of Neodymium grade N38.
2000 gauss, at 1 cm seems weak from 3 Kg ferrite but the surface area and mass makes a difference and I hate to admit it but size matters, the earth being the ultimate magnet at only 0.5 milligauss I think, it the most powerful magnet even more so than the multi ton super magnet feed by a super silly billion watt generator, firing a pulsed magnetic field over 60 Tesla!
Round magnets, tube magnets and cylinder magnets are more expensive than square magnets as there cut from square plates and slabs, that’s why Wharefdale used square magnets in there dove tail range of speakers back in the 60s and 70s I think, they are better value.
The size of the voice coil and number of windings has a direct affect on the size of the magnet, a large voice coil is very low typically in sensitivity so a Hugh plate magnet is required and this is expensive.
Manufacturers don’t look for ways to spend money they look for ways to save it
The wider the magnet the more costly it is, the thicker the magnet the more costly it is, you want a nickel coating, the price jumps up, chrome, it jumps again and so on.
We should not fully judge a speaker by its specifications or magnet, that’s like choosing a car based on engine size, hi-fi has to be about fidelity and quality and a little bit of magic.
We would not judge a person based on there specifications alone, talking and listen yields a reality or truth that cant be measured because what we feel is not a measurement and ultimately our brains are just to strange! Well mines is anyway
Ferrite, barium, strontium magnets are ceramics, and these are lower in power then Samarium, Cobalt and Neo but used in a large stack give a very stable and powerful field, even more so than a small single plate of neodymium, the gauss reading is meaningless at times as the distance and area measured is never stated.
14,200 gauss at 1 cm is a powerful reading but what if its only 100 grams of Neodymium grade N38.
2000 gauss, at 1 cm seems weak from 3 Kg ferrite but the surface area and mass makes a difference and I hate to admit it but size matters, the earth being the ultimate magnet at only 0.5 milligauss I think, it the most powerful magnet even more so than the multi ton super magnet feed by a super silly billion watt generator, firing a pulsed magnetic field over 60 Tesla!
Round magnets, tube magnets and cylinder magnets are more expensive than square magnets as there cut from square plates and slabs, that’s why Wharefdale used square magnets in there dove tail range of speakers back in the 60s and 70s I think, they are better value.
The size of the voice coil and number of windings has a direct affect on the size of the magnet, a large voice coil is very low typically in sensitivity so a Hugh plate magnet is required and this is expensive.
Manufacturers don’t look for ways to spend money they look for ways to save it
The wider the magnet the more costly it is, the thicker the magnet the more costly it is, you want a nickel coating, the price jumps up, chrome, it jumps again and so on.
We should not fully judge a speaker by its specifications or magnet, that’s like choosing a car based on engine size, hi-fi has to be about fidelity and quality and a little bit of magic.
We would not judge a person based on there specifications alone, talking and listen yields a reality or truth that cant be measured because what we feel is not a measurement and ultimately our brains are just to strange! Well mines is anyway
Hi,
it's a long time since I read up on speaker magnets.
What are Maxwells? Is it some kind of relationship between gap height times gap length times gap flux? or am I away with the fairies?
If so Maxwells could be a measure of magnetic power, and maybe related to sensitivity.
What is B in the BL spec? This relates to sensitivty as well, doesn't it?
Finally, can you direct me to some sites that give a wide ranging background in speaker magnet attributes and/or design criteria?
it's a long time since I read up on speaker magnets.
What are Maxwells? Is it some kind of relationship between gap height times gap length times gap flux? or am I away with the fairies?
If so Maxwells could be a measure of magnetic power, and maybe related to sensitivity.
What is B in the BL spec? This relates to sensitivty as well, doesn't it?
Finally, can you direct me to some sites that give a wide ranging background in speaker magnet attributes and/or design criteria?
Paradise_Ice said:
Can you explain how size matters?
I really don't follow it, the only thing that counts as far as I understand is the flux in the magnet gap consisting of metal pole pieces, the magnet gap "don't know" what kind of "magnet" there is in the magnetic field path, it just "transport" the flux as good as possible limited by the polepiece material own saturation level... correct me if I'm wrong.
Regards Michael
Hello Ultima
you are right the flux in the gap is the be all and end all of the magnet force in a speaker, but i think reverse field modulation has a larger affect on smaller magnets over larger magnets.
I was talking more generally, how the gauss reading is not a good way to judge a magnets power.
I had to repair a magnet system from a RE MT woofer only 3 weeks ago as the plates had slipiped when someone dropped the 25Kg magnet, it used normal ferrite magnets but a triple stack 75mm tall and a width of 225mm the BL was 37 and i was surprised, it used very low carbon steel plates which where 23mm thick, if N38 was used the 20Kg of ferrite could be replaced by only 2 Kg of Neodymium but i dont think it would improve the performace which is already pretty amazing.
I know people dont believe magnets sound different and they only provide simple flux but this does not tally up in my ears esp with tweeters.
you are right the flux in the gap is the be all and end all of the magnet force in a speaker, but i think reverse field modulation has a larger affect on smaller magnets over larger magnets.
I was talking more generally, how the gauss reading is not a good way to judge a magnets power.
I had to repair a magnet system from a RE MT woofer only 3 weeks ago as the plates had slipiped when someone dropped the 25Kg magnet, it used normal ferrite magnets but a triple stack 75mm tall and a width of 225mm the BL was 37 and i was surprised, it used very low carbon steel plates which where 23mm thick, if N38 was used the 20Kg of ferrite could be replaced by only 2 Kg of Neodymium but i dont think it would improve the performace which is already pretty amazing.
I know people dont believe magnets sound different and they only provide simple flux but this does not tally up in my ears esp with tweeters.
"Reach for the Top" began life as a CBC television quiz game for high school students, modeled on the British television series "Top of the Form". First played on the local CBC outlet in Vancouver in 1961, it was produced by Dick St. John and hosted by Terry Garner. The first National Finals of Reach For The Top were played in 1965, and it became a national T.V. show in 1966, with separate local productions across the country and national finals series played by the regional winners.
davesaudio said:
In Grade 11 i was on a team (w 3 Grade 12s) that reached the provincial finals. We smoked both the other contenders in the round robin, but got beat in the final by the team we beat 650-410. The score board only went up to 590 so it looke like 50-410. The record that was set in that game for total points scored stood for some time. The guy asking the questions had to use questions from the next game becasue he ran out of the questions for our game.
The team the next year wasn't as good.
dave
Paradiseice,
so you don't have any scientific/technical explanations to your doubts regarding replacing big ferrite magnets with much smaller Neodymium magnets with the same total amount of flux in both cases?
I would really like to hear what is causing a Neodymium eventually not to be as robust as ferrite magnets against external flux modulation, what parameters is actually getting affected and changing etc.
Perhaps somebody with insight into this issue could shed some light.
Regards Michael
so you don't have any scientific/technical explanations to your doubts regarding replacing big ferrite magnets with much smaller Neodymium magnets with the same total amount of flux in both cases?
I would really like to hear what is causing a Neodymium eventually not to be as robust as ferrite magnets against external flux modulation, what parameters is actually getting affected and changing etc.
Perhaps somebody with insight into this issue could shed some light.
Regards Michael
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