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Speaker Magnet Re-charge service in India

Castle Knight 2 Speakers

Hari Iyer

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Do you have any company in India who does old vintage speakers magnet re-charge. I have done some work in this area and the speakers benefit a lot with the magnet re-charge. Agreed speakers dont loose their magnetic property but they for sure loose their strength over age. Having a speaker magnet recharge service will allow the old vintage speaker to gain their lost strength. Even some speakers purchased in the 90's can benefit with their magnet recharge if they are not being used currently due to loss of juice in them.

Its similar to a completely discharged car battery being charged at a battery vendor.
 

Danieljohn

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Apr 29, 2014
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Hyderabad
I have done some work in this area and the speakers benefit a lot with the magnet re-charge. Agreed speakers dont loose their magnetic property but they for sure loose their strength over age. Having a speaker magnet recharge service will allow the old vintage speaker to gain their lost strength. Even some speakers purchased in the 90's can benefit with their magnet recharge if they are not being used currently due to loss of juice in them.

Its similar to a completely discharged car battery being charged at a battery vendor.

Hi Hari,
If original speaker is charged 1 Tesla/10,000 Gauss.
1.Then to what extent we can re-charge it to?
2.re-charging to 2-Tesla/20,000 Gauss possible?
3.how many decibels will be increased by this ? I for sure believe powerful motors are sensitive.
4. What are the limitations or restrictions for re-charging speaker magnets?
5. I meant is ther a re-charge limitation for specific magnet types Eg : Alnico, Neodymium, Ferrite, Ceramic etc. I know both Alnico & Neodymium can go upto 2.4 Tesla and Ferrite & Ceramic can go upto 2.0 Tesla.
6. Can we re-charge the speaker which still have original cones or need to be re-charged before reconing?

Thanks in Advance !

Regards
IRONICAL
 
Last edited:

Hari Iyer

Well-Known Member
Joined
Feb 8, 2010
Messages
3,166
Points
113
Location
Mumbai
Hi Hari,
If original speaker is charged 1 Tesla/10,000 Gauss.
1.Then to what extent we can re-charge it to?
2.re-charging to 2-Tesla/20,000 Gauss possible?
3.how many decibels will be increased by this ? I for sure believe powerful motors are sensitive.
4. What are the limitations or restrictions for re-charging speaker magnets?
5. I meant is ther a re-charge limitation for specific magnet types Eg : Alnico, Neodymium, Ferrite, Ceramic etc. I know both Alnico & Neodymium can go upto 2.4 Tesla and Ferrite & Ceramic can go upto 2.0 Tesla.
6. Can we re-charge the speaker which still have original cones or need to be re-charged before reconing?

Thanks in Advance !

Regards
IRONICAL
I am not much aware of the technicalities involved. I just tried magnetising some vintage speakers lying with me. You can try feeding around 5 Hz to 10 Hz to a driver and measure before and after. I think that will be safer than feeding DC.
 

Danieljohn

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Messages
195
Points
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Location
Hyderabad
I am not much aware of the technicalities involved. I just tried magnetising some vintage speakers lying with me. You can try feeding around 5 Hz to 10 Hz to a driver and measure before and after. I think that will be safer than feeding DC.
1.It seems first you must have tried feeding DC.
2.By feeding 5 hz to 10 hz what we going to derive?
3. I wanted to re-charge vintage ceramic motor speakers without cones to maximum possible charge like may be 2-2.4 Tesla if it can be done !
 

Hari Iyer

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1.It seems first you must have tried feeding DC.
2.By feeding 5 hz to 10 hz what we going to derive?
3. I wanted to re-charge vintage ceramic motor speakers without cones to maximum possible charge like may be 2-2.4 Tesla if it can be done !
Feeding DC needs to be monitored for current else the coil can burn. You can water-cooling the magnet by dipping the magnet in a water bowl when doing so. The power supply used for doing this needs to be regulated PS. also do not feed more than 5v DC.
Do not exceed DC power more than 5 watt to your driver.
 

Danieljohn

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I won't be doing this by myself !
I would be giving my drivers to a friend who does this job.
I never discussed anything regarding these things in detail but I wanted to know little bit about the process before handing my drivers.
Kindly answer whether we can re-charge beyond (2.4 Tesla) to what the original charge (1 Tesla) was ?
 

Hari Iyer

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I won't be doing this by myself !
I would be giving my drivers to a friend who does this job.
I never discussed anything regarding these things in detail but I wanted to know little bit about the process before handing my drivers.
Kindly answer whether we can re-charge beyond (2.4 Tesla) to what the original charge (1 Tesla) was ?
Don't know, it will require higher voltage/ current to do that. The driver should be able to withstand high current through the voice coil. The voice coil can short if it can't handle high temperature. You can try if you have nothing to loose.
 

yogibear

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You cannot recharge a speaker magnet beyond its actual specs. Trying to do so may demagnetize it permanently. And increasing its field beyond the original / actual specs will vary more parameters than just the dB.
 

yogibear

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1.Have you tried?
2.Which Parameters?

All TS parameters. Never tried magnetising as I presume the magnet motor has to be disassembled which may require reconing.

However, have experimented by adding extra magnet assembly at the rear of the drivers and have made permanent ferrite magnets back in college out of iron poles using coils. Beyond saturation point of a particular pole, you actually end up destroying the magnetism.
 

yogibear

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No Doubt about that !



Did it had any effect on Sound?
If so in what way?
I mean the sensitivity increased or certain frequencies?

I attached a ferrite ring magnet behind the original magnet assembly and noted more SPL and better weight to lows. It was a slight increment to magnetic field to a 12” vintage woofer.

I have seen DIYers attach an assembly of Neo
Magnets to the original motor at the rear with good benefits. No need to recharge but this has to be done well planned wrt magnetic field lines else it may do more harm than good. Gaussmeter needed as well. I would like to experiment tracing original magnetic lines of field by the old fashion way. Iron dust on white paper.
 

Hari Iyer

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When I added additional magnets on my OB driver, it ruined the mids and highs making it very shrill. Needless to say, I removed them immediately.
 

yogibear

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When I added additional magnets on my OB driver, it ruined the mids and highs making it very shrill. Needless to say, I removed them immediately.

Yep, you may mess up with mids and highs in case of a midrange or extended range driver. I will only try that with a bass driver or if a mid is surely not up to its mark.
 

SIDEWINDER18X

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Folk's over here are discussing topics which are way beyond to their limits. This is all assumptions which are nowhere near to the reality. You cannot assume things out of the theory. Cannot change the law of physics with your own assumptions.
If you have a point ... Prove it with some theoretical
aspect supportive with some illustrated diagrams please.....
 

Danieljohn

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Dear Sidewinder,
I'm sure you can Prove it with some theoretical aspects supporting with some illustrated diagrams as you felt the discussed topics here are way beyond to their (whose?) limits & with full of assumptions which are no where near to the reality.
I believe whatever you said are True !

Regards
IRONICAL
 

yogibear

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Well, I have played a lot with rare earth Neo magnets, grade 52 was maximum that was available at that time back in early 2000. The objective was similar, to make very high magnetic field assemblies, way above the ferrite counter parts. To my amusement, I recently found, what I did back then, It was very very similar to guys making their own long ribbon planar tweeters for their line arrays today. It’s was done manually by me, was my own idea, out of hunch and was not an easy job but dangerous one as the magnets cubes would fly off like a bullet or crush your fingers to a slice.

Long story short: I ended up developing strongest magnetic sputtering guns defying industry standards for use in PVD machines (high vacuum deposition) for deposition of high purity (99.99% and more) magnetic materials. And developed at unimaginable cost versus $3-$10k off shelf prices. Got a US Patent later for the application process.
 

SIDEWINDER18X

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Dear Sidewinder,
I'm sure you can Prove it with some theoretical aspects supporting with some illustrated diagrams as you felt the discussed topics here are way beyond to their (whose?) limits & with full of assumptions which are no where near to the reality.
I believe whatever you said are True !
Regards
IRONICAL

To understand a Loudspeaker magnetic circuit (motor structure) you will first got to know how this circuit is working.
(A) There are 2 types of magnetic field paying into action in a loudspeaker magnet....
1. DC or (static field).
2 AC field (generated)... when the coil is moving.

(B) The entire magnet assembly's main focusing point is the gap geometry. The advance engineering in a Loudspeaker is to get a linear or radial semmetrical feild between the T-yoke and Top plate.
And to focus the fringe feild up and below the gap more and more into the radial gap.
Several patented design had been implemented to achieve the highest and efficient gap strength with a semmetrical flux lines.
To know more and more about this one has to explore the unlimited datasheet and white papers on Loudspeaker magnet modeling and design.
The T-yoke or the return structure of a magnet assembly with the ring magnet in between and the top washer on the top is a cyclic path of magnetic field which flows from Noth to South or South to North .... between the gap width at the edge of the top washer and pole piece upper circumstance of the T-yoke.
The thickness of the top plate is the so called... "Gap-Height". This thickness is the main area of the entire magnetic assembly which has the strongest magnet energy.
Adding an extra magnet to the rear of the T-yoke will not do any better to the cyclic flow of the existing magnet circuit bringing any change to the actual gap geometry.
Apart from this many design had been implemented by adding an extra magnet on top of the pole piece for achieving linearity and suppressing flux modulations.
Generally rear attached magnets charged with an opposite polarity are used sometimes to sheild the entire magnet structure to prevent any leaking flux which can effect nearby electronics such as cathode ray tubes ... etc
The motor structure faces some real challenges in regards to eddy currents, inductance stabilization, flux stabilization, Fringe or leakage feild (around the gap), generation of 2 & 3rd harmonics, and many other issus related to temperature, offset DC, over excursion and bottoming.
Designer and engineers all around the globe are developing and bringing out new ideas and technology to overcome these serious issues and problems.
If only adding an extra magnet at the rear would increase the efficiency of the Loudspeaker then the designer would have simply used an oversized magnet intially. It is not that simple. Selection of a magnet size is a part of a particular loudspeaker design intended for a specific use with a specific parameters.
This discussion is endless ... it will further get complicated and can get offtrack.
I guess there a several books and information out there online to know more and more on this.
Thank you
Vivek
 
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