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robertbartsch
01-06-2009, 12:28 PM
I'm considering having the mags recharged in a pair of 075 tweets.

I was told by my JBL re-coner (Erik Wayne from Pomptom Plains NJ) that it requires a de-mag and re-mag and that he does not provide this service.

Who does this and how much should I expect to pay?

Robh3606
01-06-2009, 12:57 PM
Have a read

http://www.audioheritage.org/vbulletin/showthread.php?t=4031

Rob:)

robertbartsch
01-06-2009, 01:47 PM
Ok - thanks I have read the magnet info here a few times already.

My drivers were purchased from Fleabay and are +30 years old. The frams are blown and I would like everything to be OK before I install the new units.

JoMoCo
01-06-2009, 02:34 PM
GPA (Great Plains Audio) are the only ones I am aware of at this time, but I would also like to know if any other reputable speaker outfit closer to home (the Northwest) does a good job of recharging. Anyone?...

toddalin
01-06-2009, 03:09 PM
Have a read

http://www.audioheritage.org/vbulletin/showthread.php?t=4031

Rob:)


There is one simple difference between the Alnico and ferrous drivers that has the potential to affect the sound that is never discussed/disclosed in those papers.

The Alnico magnet is located inside of the voice coil whereas the ferrous magnet lies to the outside. This has other ramifications. For example, on the ferrous woofer, the magnet is located directly adjacent to the voice coil, whereas with the alnico woofer, it is next to the bobbin.

http://www.lansingheritage.org/images/jbl/reference/general/1975-sum/page03.jpg

edgewound
01-06-2009, 06:14 PM
There is one simple difference between the Alnico and ferrous drivers that has the potential to affect the sound that is never discussed/disclosed in those papers.

The Alnico magnet is located inside of the voice coil whereas the ferrous magnet lies to the outside. This has other ramifications. For example, on the ferrous woofer, the magnet is located directly adjacent to the voice coil, whereas with the alnico woofer, it is next to the bobbin.



What ramifications does this detail have?

The difference in sound between the alnico and ferrite JBL's has everything to do with the refinements of the flux field symmetry that was researched by the necessity of changing over to ferrite due to cobalt scarcity at the time.

In other words....the ferrite drivers were not only cheaper to manufacture, they were more accurate too....and heavier, by a quite a bit. An advantage of the alnico pot structure with the magnet in the center is it's self-shielding with much less stray field for CRT's, and magnetic media. The added weight can actually be a plus for home speakers due to the increased mass that the cone assembly pushes against....less re-coil.

The only effect the bobbin would have is if it is made of metal....like aluminum. This creates eddy currents in the gap that can cancel out high frequencies and add distortion.

edgewound
01-06-2009, 06:16 PM
I'm considering having the mags recharged in a pair of 075 tweets.

I was told by my JBL re-coner (Erik Wayne from Pomptom Plains NJ) that it requires a de-mag and re-mag and that he does not provide this service.

Who does this and how much should I expect to pay?


If he has a gauss meter, he can check the flux density in the gap and determine if it really needs a recharge or not.

Robh3606
01-06-2009, 06:23 PM
If he has a gauss meter, he can check the flux density in the gap and determine if it really needs a recharge or not.

Yes and there is an excellent good chance they are fine as is.

Rob:)

toddalin
01-06-2009, 06:26 PM
What ramifications does this detail have?

The difference in sound between the alnico and ferrite JBL's has everything to do with the refinements of the flux field symmetry that was researched by the necessity of changing over to ferrite due to cobalt scarcity at the time.

In other words....the ferrite drivers were not only cheaper to manufacture, they were more accurate too....and heavier, by a quite a bit. An advantage of the alnico pot structure with the magnet in the center is it's self-shielding with much less stray field for CRT's, and magnetic media. The added weight can actually be a plus for home speakers due to the increased mass that the cone assembly pushes against....less re-coil.

The only effect the bobbin would have is if it is made of metal....like aluminum. This creates eddy currents in the gap that can cancel out high frequencies and add distortion.

So then, why weren't they made like this in the first place, and why did JBL go to so much trouble to do it as they did in the first place instead of how the competition did it?

Are you saying that the competition was ahead of the curve at the time and JBL was full of beans?

Could be a world of minute details associated with the rearrangement of the magnet structure, some of which may not be measureable using test equipment.

Show me the "white papers."

Robh3606
01-06-2009, 06:32 PM
So then, why weren't they made like this in the first place, and why did JBL go to so much trouble to do it as they did in the first place instead of how the competition did it?


You have been on this site for how many years?? You don't understand why JBL originally made them using Alnico?? Your joking right just breaking Edges chops??


Rob:)

hjames
01-06-2009, 06:42 PM
Circa 2004, with a 2007 followup ...

The Great Alnico / Ferrite Debate

http://audioheritage.org/vbulletin/showthread.php?t=4031

toddalin
01-06-2009, 06:49 PM
You have been on this site for how many years?? You don't understand why JBL originally made them using Alnico?? Your joking right just breaking Edges chops??

Rob:)


;)

I'm not saying the Alnico (or ferrite) sounds "better" or "worse," but only that it can sound different and that the geometry of the magnet structure can contribute to that difference.

In other words there is more to it than just the amount of gauss in the gap, which seemed to be goal and focus of the noted articles.

And we are just talking about the magnetic assembly. More recent cone materials, suspension, compliance, etc. are irrelevent to this discussion as they can easily be updated, retaining the original magnetic structure.

And if it sounds different, that can contribute to one's enjoyment/displeasure.

Ian Mackenzie
01-06-2009, 07:02 PM
I think we have had several rants on Alnico versus ferrite and here is another point of view below. (no alliance with AE)

A motor is only as good as you wanna make it and there are good and bad examples of both varieties. In general you get what you pay for.

It would seem that in certain designs the Alnico is more prone to de magnetisation from high power use and I have heard this from Pro Shops about the Alnic Tad woofers. If you pull apart an Alinico driver the wrong way it will need re gaussing.

http://www.aespeakers.com/Lambda001-1.php



Lower the electrical conductivity of the pole piece. This typically means using extremely expensive materials or sacrificing more Bl. One group of materials of interest would be the iron/cobalt alloys such as Hiperco 27 from Carpenter (http://cartech.ides.com/datasheet.aspx?i=103&e=197&c=TechArt). The problem is the extremely high expense where the raw material for a single pole piece would be upwards of $500 on a large driver. Another option would be a powdered iron. While this is electrically non-conductive, it is also not highly magnetically permeable. You could expect to lose 20% of the flux in the gap due to the lower permeability.
(2) Permanently mount a highly conductive layer that is not magnetic between the VC and the pole. This cannot be a moving piece like an aluminum VC former. It needs to be a rigidly mounted layer, much thicker than the typical VC former.

edgewound
01-06-2009, 07:14 PM
Show me the "white papers."

Todd....

JBL Tech Notes Volume 1, Number 9.

"Distortion and Power Compression in Low Frequency Transducers".

I have it, but don't have time to copy it and upload it.

The Alnico-Ferrite story is there.

toddalin
01-06-2009, 07:17 PM
The only effect the bobbin would have is if it is made of metal....like aluminum. This creates eddy currents in the gap that can cancel out high frequencies and add distortion.


Not the only effect if you really think about it. For example, as the voice coil heats up, the heat is transfered to the magnetic assembly. Put that bobbin in the way between the coil and magnet and you have an effective insulator to that heat transfer.

Like I said, many small details that may or may not be measureable.

Robh3606
01-06-2009, 07:24 PM
Edge it's already loaded on the site.

http://www.audioheritage.org/vbulletin/showthread.php?t=4746

Rob:)

Ducatista47
01-06-2009, 08:29 PM
I think we have had several rants on Alnico versus ferrite and here is another point of view below. (no alliance with AE)

A motor is only as good as you wanna make it and there are good and bad examples of both varieties. In general you get what you pay for.

It would seem that in certain designs the Alnico is more prone to de magnetisation from high power use and I have heard this from Pro Shops about the Alnic Tad woofers. If you pull apart an Alinico driver the wrong way it will need re gaussing.

http://www.aespeakers.com/Lambda001-1.php


Lower the electrical conductivity of the pole piece. This typically means using extremely expensive materials or sacrificing more Bl. One group of materials of interest would be the iron/cobalt alloys such as Hiperco 27 from Carpenter (http://cartech.ides.com/datasheet.aspx?i=103&e=197&c=TechArt). The problem is the extremely high expense where the raw material for a single pole piece would be upwards of $500 on a large driver. Another option would be a powdered iron. While this is electrically non-conductive, it is also not highly magnetically permeable. You could expect to lose 20% of the flux in the gap due to the lower permeability.
(2) Permanently mount a highly conductive layer that is not magnetic between the VC and the pole. This cannot be a moving piece like an aluminum VC former. It needs to be a rigidly mounted layer, much thicker than the typical VC former.Good stuff, Ian. A friend has visited AE and I should do the same next time I am up there. I have read in more than one place that soft iron is one of the best materials for pole pieces. We both own drivers with such pole pieces, the Hammer Dynamics Super 12. Some might find John's rundown of the modifications he made to the Eminence Beta-12LT interesting. It is a ferrite driver. From the Single Driver website ( http://web.archive.org/web/20070609103840/melhuish.org/audio/super12.html )


John Wyckoff's description of the Super 12 (compared to the Eminence Beta-12LT)

Cone composition: Beta-12LT is conventional Kraft type. Super 12 is slightly heavier (different mix of fibers).

Voice coil: Super 12 has smaller gauge wire with a Nomex former. (I dropped the Kapton former after the first ten samples.) Beta-12LT uses Kapton former which is not quite as neutral in the mids. Super 12 coil is slightly lighter bringing moving mass to about the same. Super 12 uses one shorted voice coil turn to reduce inductance and improve high frequency response.

Motor: Super 12 has a soft-iron polepiece to improve BL. Beta-12LT has low carbon steel. Super 12 has shorting ring at the base of the polepiece and is capped with an aluminum shorting ring (also called Faraday ring).

Spider and suspension: Super 12 spider is woven Kapton fiber and is slightly softer. The suspension on the Super 12 is doped to be slightly stiffer.

Glue: Super 12 uses a lower-mass, harder formulation, and less of it. Improves high frequency response.
Clark

edgewound
01-06-2009, 09:44 PM
Not the only effect if you really think about it. For example, as the voice coil heats up, the heat is transfered to the magnetic assembly. Put that bobbin in the way between the coil and magnet and you have an effective insulator to that heat transfer.

Like I said, many small details that may or may not be measureable.

Sorry to call you out as wrong ,Todd...but the examples you just cited would be measureable...in both frequency response and power compression.

As an environmental scientist....you should know that these kinds of variables are measureable...and don't just happen by chance.

robertbartsch
01-07-2009, 04:05 AM
My JBL re-coner Erik Wyne does have a gauss meter but it has a broken needle and, therefor, it is currently not functioning.

toddalin
01-07-2009, 10:28 AM
Sorry to call you out as wrong ,Todd...but the examples you just cited would be measureable...in both frequency response and power compression.

As an environmental scientist....you should know that these kinds of variables are measureable...and don't just happen by chance.

If you think all of the affected parameters are measureable, you are naive. Everything in the world affects (to some extent) everything else in the world (the butterfly effect).

From the great debate:

To be able to continue production of the speaker systems in their catalogs, the ferrite bass drivers had to be the exact sonic equivalents of the Alnico drivers they replaced. Otherwise, the entire systems would have to be re-engineered and there was no time to do this. To give you an example, the L300 Summit, both before and after the ferrite bass driver conversion, used the exact same Alnico tweeter, Alnico compression driver, enclosure and network. The only change was that the 136A driver had its Alnico motor replaced with a ferrite motor to become the 136H. The basket, cone and suspension remained identical. The only way this could work was if the ferrite motor had the exact same magnetic energy as the Alnico motor.

Note that the focus is on magnetic energy in the gap. But what of the near infinite other variables that are not being assessed?

The alnico and ferrite woofers have different weights. This in itself has ramifications:

The heavier speaker "couples" better to the floor. Think that an L300 weighing 1 pound would couple the same as one that weighs in at 1,000 pounds? I certainly don't and it is naive to think it would. Can you measure this if the weight difference were just 1 gram? It's still there but probably not measureable using current insturments so it's just a matter of degree.

The heavier speaker puts a different torque on the baffleboard changing its resonance. It's there, but can you measure it?

As the magnet "hangs" on the basket, it puts a torque on the basket deforming the shape of the gap relative to the basket. Different weight equals different torque and different deformation of the gap. (Think at the molecular level.)

Every body with mass has an effect on every other body. The "gravity" of the ferrite magnet has a "pull" on the other components. I'd like to see you measure that.

Consider shape:

The Alnico drivers have much more of the rear cone exposed. The ferrite magnet speakers show little cone to the rear. This has an obvious effect of the emination of the rear wave both in terms of reflection and refraction. Sound off the back of the cone impinges differently on the front of the cone when the cone is partially obscured. Is this measureable and has it been?

Similarly, that rear wave eminates into a cabinet volume. The ferrite magnet squeezes the wave around the magnet to a greater extent changing the flow of air thoughout the cabinet.

Also, the larger magnet creates a different "Fresnel number" as the sound is forced to bend around it. Was this measured?

Consider volume of the speaker basket. It takes up cabinet space and we know this has a direct impact on tuning frequency. Different size basket equals a different internal volume.

Then there is the stray magnet field:

Every magnet has an effect on every other magnet in proximity. It would be naive to think that the stray magnetic field of the woofer has no effect on the adjacent drivers slightly distorting the shapes of their magnetic fields.

Similarly, the magnetic field has an effect on the chokes in the crossover.

Every magnet is to some extent influenced by the earth's magnetic field. (Ever seen a compass?) This obviously varies with the stay magnetism around the magnet.

What of the materials and their thermal expansion coefficients as they relate to the arrangement:

Remember 8th grade science class? The teacher had a rod with a metal ball and a rod with metal ring. They were machined such that at room temperature the ball would not pass through the ring. The teacher put the ring in a bunsen burner, it expanded and low and behold, the ball passed right though. The teacher then heated the ball and it would no longer pass through the hot ring.

Now think of the ferrite arrangement as the ring and the alnico arrangement as the ball. As the ring expands with heat, it pushes further away from the voice coil whereas the alnico magnet pushes closer toward the coil. This has got to have some effect on the sound.

I could go on with many, many more minute differences that no one has mentioned in any of the "white papers." I'm sure that if you gave it some thought, you could come up with many of your own. ;)

ratitifb
01-07-2009, 10:43 AM
Every magnet has an effect on every other magnet in proximity. It would be naive to think that the stray magnetic field of the woofer has no effect on the adjacent drivers slightly distorting the shapes of their magnetic fields.compared to the flux density inside the magnet gap and considering the distance, the strenght of magnet leaks are probably negligible :dont-know

robertbartsch
01-07-2009, 11:55 AM
As a broad generalization, would it be true that a loss in an alnico V magnet strength would be more likely in a woofer than an UHF tweeter since passive crossovers direct most of the current in a musical signal to the woofer?

Does your answer change if the tweeter diaphragms have been blown out?

Does your answer change if the tweeter was droped from a hieght of 10 inches?

Does your answer change if the tweeter were used in a traffic application?

edgewound
01-07-2009, 12:02 PM
If you think all of the affected parameters are measureable, you are naive. Everything in the world affects (to some extent) everything else in the world (the butterfly effect).

From our discussion, I said the things you pointed out would be measureable. I didn't lead you into the world of innerspace.



From the great debate:

To be able to continue production of the speaker systems in their catalogs, the ferrite bass drivers had to be the exact sonic equivalents of the Alnico drivers they replaced. Otherwise, the entire systems would have to be re-engineered and there was no time to do this. To give you an example, the L300 Summit, both before and after the ferrite bass driver conversion, used the exact same Alnico tweeter, Alnico compression driver, enclosure and network. The only change was that the 136A driver had its Alnico motor replaced with a ferrite motor to become the 136H. The basket, cone and suspension remained identical. The only way this could work was if the ferrite motor had the exact same magnetic energy as the Alnico motor.

Note that the focus is on magnetic energy in the gap. But what of the near infinite other variables that are not being assessed?

Yes...but the part you are leaving out is the reduced SFG stray field adjacent to the gap, that results in better linearity and lower distortion...Measureable.



The alnico and ferrite woofers have different weights. This in itself has ramifications:

The heavier speaker "couples" better to the floor. Think that an L300 weighing 1 pound would couple the same as one that weighs in at 1,000 pounds? I certainly don't and it is naive to think it would. Can you measure this if the weight difference were just 1 gram? It's still there but probably not measureable using current insturments so it's just a matter of degree.

The heavier speaker puts a different torque on the baffleboard changing its resonance. It's there, but can you measure it?

As the magnet "hangs" on the basket, it puts a torque on the basket deforming the shape of the gap relative to the basket. Different weight equals different torque and different deformation of the gap. (Think at the molecular level.)

I betcha that science lab out in Pasadena has instruments that can measure all of the above. Does it fall into the realm of acoustic reality? Doubtful.




Every body with mass has an effect on every other body. The "gravity" of the ferrite magnet has a "pull" on the other components. I'd like to see you measure that.


Gravity and ambient air pressure do a nice job of equalizing each other on this rock called earth...isn't nature neato? No ambient air pressure and we'd all explode. No gravity and we'd all just float away. It's called equilibrium. The outside magnetic attraction probably has nil effect on the the huge flux field in the gap.

The gap deformation you describe can be measured with the right precision instruments by virtue of mounting the frame/motor on a baffle and checking the concentricity. Is that effort worth more than Laser Interferometry that JBL uses in the lab to measure pistonic movement of the cone? That...I don't know. But Greg Timbers, Doug Button, and Jerry Mora might be able to answer that.



Consider shape:

The Alnico drivers have much more of the rear cone exposed. The ferrite magnet speakers show little cone to the rear. This has an obvious effect of the emination of the rear wave both in terms of reflection and refraction. Sound off the back of the cone impinges differently on the front of the cone when the cone is partially obscured. Is this measureable and has it been?

If you read the Tech Note that we are addressing here, the engineers were under tight time constraints to redesign a critical component due to the skyrocketing cost/lack of available cobalt for alnico magnets. Through their research, they learned alot on how to do more with less through refined engineering. Otherwise, JBL might have gone out of business. Nothing like a calamity to motivate innovation, huh?



Similarly, that rear wave eminates into a cabinet volume. The ferrite magnet squeezes the wave around the magnet to a greater extent changing the flow of air thoughout the cabinet.

Also, the larger magnet creates a different "Fresnel number" as the sound is forced to bend around it. Was this measured?

Consider volume of the speaker basket. It takes up cabinet space and we know this has a direct impact on tuning frequency. Different size basket equals a different internal volume.

Thermodynamics/vectors. Critical for the Stealth Fighter. Easy to address in a speaker box.



Then there is the stray magnet field:

Every magnet has an effect on every other magnet in proximity. It would be naive to think that the stray magnetic field of the woofer has no effect on the adjacent drivers slightly distorting the shapes of their magnetic fields.

Can you prove this? Or is this more "innerspace" speculation? I'm sure it can be measured, and I'm confident that the effect would have no effect on the sound. A glass of wine has more effect on the sound....Usually makes it better.



Similarly, the magnetic field has an effect on the chokes in the crossover.

Yes...I've been to Westlake Audio....they measure it...I saw it.



Every magnet is to some extent influenced by the earth's magnetic field. (Ever seen a compass?) This obviously varies with the stay magnetism around the magnet.

Our entire Universe relies on magnetism. Is it naive to think this? Ever hear of Black Holes? We wouldn't be able to use our computers without magnetism. Every magnetic field can be measured....and so can it's effects....at some cost that might not be relevent to the task at hand.



What of the materials and their thermal expansion coefficients as they relate to the arrangement:

Remember 8th grade science class? The teacher had a rod with a metal ball and a rod with metal ring. They were machined such that at room temperature the ball would not pass through the ring. The teacher put the ring in a bunsen burner, it expanded and low and behold, the ball passed right though. The teacher then heated the ball and it would no longer pass through the hot ring.

I don't recommend using a Bunsen Burner on your speakers....The sound will stop. That would be called "Extreme Power Combustion in Low Frequency Drivers".



Now think of the ferrite arrangement as the ring and the alnico arrangement as the ball. As the ring expands with heat, it pushes further away from the voice coil whereas the alnico magnet pushes closer toward the coil. This has got to have some effect on the sound.

Yes...no one said that heat doesn't effect the sound. Unless it's an eBay ad.



I could go on with many, many more minute differences that no one has mentioned in any of the "white papers." I'm sure that if you gave it some thought, you could come up with many of your own. ;)

Todd....honestly...Do you think that all of this stuff hasn't been thought of before?

There's a concept in business and manufacturing called the "Law of Diminishing Returns". Bart Locanthy decided to leave JBL by invitation of Pioneer Corp to start TAD. TAD drivers are very exclusive, expensive, and according to Mr.Widget, nearly unobtainable without extended wait times. Can you think of higher engineered drivers than that? Do they really make long term business sense without being part of a specialty division...with speakers? Good as it gets is good enough when the listeners are humans, with nondurable transducers.

JBL done much good research to attain high end performance within the constraints of the market's resources.

Let's hope it continues.

edgewound
01-07-2009, 12:15 PM
As a broad generalization, would it be true that a loss in an alnico V magnet strength would be more likely in a woofer than an UHF tweeter since passive crossovers direct most of the current in a musical signal to the woofer?

Does your answer change if the tweeter diaphragms have been blown out?

Maybe...depends on how it was blown....but doubtful.



Does your answer change if the tweeter was droped from a hieght of 10 inches?

Maybe...Onto a bed, no...concrete floor, maybe....doubtful.[/quote]




Does your answer change if the tweeter were used in a traffic application?

Probably...Harsh environment....corrosion, dirt, hot, cold .

I know what you're getting at Robert, but the only definitive way to know is to check with a gauss meter.

Otherwise, clean it up, new diaphragm...how does it sound? It can always be disassembled and recharged without damage. It can even be recharged without disassembly....it's no big deal.

toddalin
01-07-2009, 02:08 PM
From our discussion, I said the things you pointed out would be measureable. I didn't lead you into the world of innerspace.



Yes...but the part you are leaving out is the reduced SFG stray field adjacent to the gap, that results in better linearity and lower distortion...Measureable.



I betcha that science lab out in Pasadena has instruments that can measure all of the above. Does it fall into the realm of acoustic reality? Doubtful.




Gravity and ambient air pressure do a nice job of equalizing each other on this rock called earth...isn't nature neato? No ambient air pressure and we'd all explode. No gravity and we'd all just float away. It's called equilibrium. The outside magnetic attraction probably has nil effect on the the huge flux field in the gap.

The gap deformation you describe can be measured with the right precision instruments by virtue of mounting the frame/motor on a baffle and checking the concentricity. Is that effort worth more than Laser Interferometry that JBL uses in the lab to measure pistonic movement of the cone? That...I don't know. But Greg Timbers, Doug Button, and Jerry Mora might be able to answer that.



If you read the Tech Note that we are addressing here, the engineers were under tight time constraints to redesign a critical component due to the skyrocketing cost/lack of available cobalt for alnico magnets. Through their research, they learned alot on how to do more with less through refined engineering. Otherwise, JBL might have gone out of business. Nothing like a calamity to motivate innovation, huh?



Thermodynamics/vectors. Critical for the Stealth Fighter. Easy to address in a speaker box.



Can you prove this? Or is this more "innerspace" speculation? I'm sure it can be measured, and I'm confident that the effect would have no effect on the sound. A glass of wine has more effect on the sound....Usually makes it better.



Yes...I've been to Westlake Audio....they measure it...I saw it.



Our entire Universe relies on magnetism. Is it naive to think this? Ever hear of Black Holes? We wouldn't be able to use our computers without magnetism. Every magnetic field can be measured....and so can it's effects....at some cost that might not be relevent to the task at hand.



I don't recommend using a Bunsen Burner on your speakers....The sound will stop. That would be called "Extreme Power Combustion in Low Frequency Drivers".



Yes...no one said that heat doesn't effect the sound. Unless it's an eBay ad.



Todd....honestly...Do you think that all of this stuff hasn't been thought of before?

There's a concept in business and manufacturing called the "Law of Diminishing Returns". Bart Locanthy decided to leave JBL by invitation of Pioneer Corp to start TAD. TAD drivers are very exclusive, expensive, and according to Mr.Widget, nearly unobtainable without extended wait times. Can you think of higher engineered drivers than that? Do they really make long term business sense without being part of a specialty division...with speakers? Good as it gets is good enough when the listeners are humans, with nondurable transducers.

JBL done much good research to attain high end performance within the constraints of the market's resources.

Let's hope it continues.


You are missing the point.

The point is that there is more to sound than gauss in the gap and that there are differences between the alnico and ferrite drivers that has not been noted/measured so all of the data are not in.

If there are differences in the sound, than the two speakers are not exactly the same and do not perform exactly the same. While the ferrite magnet may be more linear with less distortion, it is different and that difference may be pleasureable, objectionable, or unobservable to the listener. But, they are not exactly the same. And exactly means exactly that 0.00000000000000000000... difference.

BTW, sometimes distortion can be a good thing. Why do you think they put dither (an intentional distortion) in CDs?

As to whether the differences are audible, there are some on this forum who can't even hear a difference when taking off their glasses while others of us most definitely can.

'nuff said.

edgewound
01-07-2009, 03:34 PM
You are missing the point.


No...No I'm not missing the point. The ferrite SFG's were an improvement...at the time...in the implementation of the magnet material to redesign the motor out of necessity. There was no constraint to make sure they didn't perform better. As a matter of fact, Peavey copied JBL's concept and called it "Focused Field Geometry" in Black Widow speakers. Flattery...well...

A speaker motor is just that....a motor that pushes/pulls on the diaphragm to move air...ideally as a piston. The material itself doesn't make a difference in how it sounds as long as the goal is linearity of voice coil/cone movement with relationship to the input waveform to accurately reproduce it. And yes...some speakers are designed to have distortion. Guitar amp speakers especially....sound producers.

Alas....some people pretend to hear a fly breathe, too. Hmmm... they tend to wheeze after landing on dog poop.

CDs have dither added to fill up the holes between samples to more replicate an analog wave form. Computing power has caught up with digital recording to better approach a discrete waveform by packing the samples so tight as to be undiscernable from analog....without the stylus or tape head noise.

Progress...

toddalin
01-07-2009, 03:49 PM
No...No I'm not missing the point. The ferrite SFG's were an improvement...at the time...in the implementation of the magnet material to redesign the motor out of necessity. There was no constraint to make sure they didn't perform better. As a matter of fact, Peavey copied JBL's concept and called it "Focused Field Geometry" in Black Widow speakers. Flattery...well...

A speaker motor is just that....a motor that pushes/pulls on the diaphragm to move air...ideally as a piston. The material itself doesn't make a difference in how it sounds as long as the goal is linearity of voice coil/cone movement with relationship to the input waveform to accurately reproduce it. And yes...some speakers are designed to have distortion. Guitar amp speakers especially....sound producers.

Alas....some people pretend to hear a fly breathe, too. Hmmm... they tend to wheeze after landing on dog poop.

CDs have dither added to fill up the holes between samples to more replicate an analog wave form. Computing power has caught up with digital recording to better approach a discrete waveform by packing the samples so tight as to be undiscernable from analog....without the stylus or tape head noise.

Progress...

Yeah you are.

To implement the ferrite magnets, other changes had to be made to the architecture. You can't simply change the magnetic material without other changes in the design.

These changes in architecture create other sonic effects, most of which, while extremely small, have probably not been thouroughly investigated. That's all.

Robh3606
01-07-2009, 03:58 PM
These changes in architecture create other sonic effects, most of which, while extremely small, have probably not been thouroughly investigated. That's all.

They were and the new ferrites were better and are better now than the original Alnico motors they replaced.

End of story, that's all, the Fat Lady is singing and Elvis left.

Rob:D

edgewound
01-07-2009, 04:07 PM
Yeah you are.

To implement the ferrite magnets, other changes had to be made to the architecture. You can't simply change the magnetic material without other changes in the design.

These changes in architecture create other sonic effects, most of which, while extremely small, have probably not been thouroughly investigated. That's all.

Where in the hell did I ever say that changes weren't made to the original architecture? I said all along that improvements were made in the implementation of ferrite to make a better performing motor.

It would help, Todd, if you would actually read what I wrote rather than try to piss back at me with a bigger stream.

I'm with Elvis.

Ian Mackenzie
01-07-2009, 04:55 PM
I recall when I bought my second set of 2231H's and they were obviously ferrite.

I am damned if I can recall if there were worse, the same or better but they lasted longer and were a drop in replacement for all intensive purposes:D. No one even knew of T/L was all about back then:blah:.

toddalin
01-07-2009, 05:13 PM
Where in the hell did I ever say that changes weren't made to the original architecture? I said all along that improvements were made in the implementation of ferrite to make a better performing motor.

It would help, Todd, if you would actually read what I wrote rather than try to piss back at me with a bigger stream.

I'm with Elvis.

I never said that you said that there were no changes to the architecture. Maybe you need to reread stuff.

What I said was that the conversion led to changes in the architecture and changes in the architecture bring about a sonic difference at some level and that any sonic difference is interpreted by the listener, good, bad, or indifferent.

I also inferred that there is no possible way to know all of these near infinite number of changes and differences using readily available equipment, nor could they all have possibly been explored.

Heck, we all know that the best test equipment available today has no way to know the way your brain interprets the sound waves, and their minute variations, and each person is different based on physiology and past experience.

I never said one technology was better or worse than the other. Only that there are differences and not all of them can have possibly been explored in every situation.

I'm with Elvis and I've been trying to leave the building, but you guys keep pulling me back inside!:uhmmmm:

mech986
01-07-2009, 05:43 PM
Wow. At the risk of getting embroiled in this, uh, discussion, could I offer this picture of what may be going on at most of the larger or OEM driver/speaker manufacturers or the well heeled corporations they work for?

They likely have well educated (either school/college engineering / technical background or a combination of that with practical/experimental experience) people working on these designs. They may call themselves engineers or scientists or maybe even enthusiasts. But they have a job to do which puts limits at times on what they can spend time, money, and resources on.

They likely have at their disposal equipment and personnel who can create from basic materials the prototypes of the designs based on ideas, theories, literature, copies, and reverse engineering of other competitor products. The prototypes are hopefully pretty precision built and measured so they conform closely to the design within an engineering tolerance (nothing is perfect).

They then also have measurement equipment and suitable environments to take those measurements. They also would have to have the mindset and knowledge of what to measure and how to measure it, and then have some idea of how to interpret that measurement and what relavence it has to the task at hand.

They probably also have design teams and meetings who set parameters on time, money, resources, and ultimate use of this research and development in some type of finished product OR regard the exercise as some type of learned knowledge, either positive or negative in result.

And then you have the project managers who answer to the marketing dept. or exec's who ultimately determine what those products are going to be that will be sold to keep the money flowing in to keep everyone in the company employed.

Ultimately, then you have to have them all get together to figure out how to build the objective (note I didn't say best) for the appropriate (didn't always say least) cost to make the project acceptable and useful for the company. This may require then the, for some, inevitable tradeoffs and compromises that lead to the finished product. In comparision to the nth degree tweaked prototype, there may be some changes of accuracy, fidelity, weight (+/-), etc. There will likely be gains in ease of production, reproducibility and consistency, field service, packaging, marketability, and sometimes even accuracy and fidelity.

I suspect that JBL Engineering (and Harmon, now through Revel, Floyd Toole and others) has conducted a TON (probably more like 100 TONS) of basic research into transducer design. Their dumpsters full of failed or discarded prototypes is probably 1000 times larger than the equipment archive of production product samples shown in the 2004 or 2005 factory tour. Quite a bit of JBL's research has been shared through the AES Journal, in lay articles (like the Audio papers on subs), and in engineering and advertising literature - some technical and some with marketing or advertising slants to them.

For that, we can be eternally grateful that they thought enough about us, the end user, enthusiast, and genuine hi-fi nut (many of whom were the same types of scientists, engineers, and curious people) to publish, share, educate, and nay, market that information to us over the last 60 years.

I'll also suggest that a ton of that research remains proprietary, for the exclusive use of JBL for its products to remain competitive, cutting edge, more practical, more reliable, or more serviceable. And, perhaps in more than a few instances, trendy or attractive to a particular niche of customers to satisfy their needs or wants. However, and this is important, at some point someone had to make a qualitative decision/choice/judgement about whether the research result or detail was big enough or useful enough to use or spend time ($$) on.

The genuine interest in wanting to know everything there is about a design and the influences of each issue or detail is very useful. However, it must, for a functioning company, be tempered by the allocation of resources and the cost/value of the research. Also, the validity of any experiment, design, or research must also be examined, interpreted, and perhaps replicated by hopefully like minded colleagues. This is not always possible in a competitive industry like audio and loudspeakers.

The standards of engineering that JBL has were set from James B. Lansing and his cohorts from the beginning. The fact that Willam Thomas and Harmon International have fostered and continued that high engineering standard is testament to why JBL maintains a high reputation in audio today.

If we had a window on the research or could tap into the minds of past and present JBL engineers and designers, I'll bet the answers to many, many detail questions would be there. But that information is not always available to us, or maybe it was already investigated and deemed with some value judgement.

We may just have to accept that for now.

Regards,

Bart

SMKSoundPro
01-08-2009, 01:05 AM
Wow! I am sure glad I didn't get into the middle of this!!!

Scotty.

robertbartsch
01-08-2009, 03:23 AM
I thought re-magnitizing Alnico Vs would be a standard procedure for re-building drivers by authorized techs...

....apparently, this is not the case...

UHG!

4313B
01-08-2009, 05:08 AM
If we had a window on the research or could tap into the minds of past and present JBL engineers and designers, I'll bet the answers to many, many detail questions would be there. But that information is not always available to us, or maybe it was already investigated and deemed with some value judgement.You do have a window, it's called attending public events. Everyone who is anyone at JBL knows all about this website and this forum. Convincing them that their time is better spent here answering questions instead of doing virtually anything else with their time is an extremely difficult thing to do.

Attend events and engage in discussions in the proper venue where the engineers and designers, should they have the time to attend, are more than happy to answer your questions.

*****

Most are aware of the dangers of participating in public Internet forums. Don and I have discussed this fact at length. Those few that are naive very quickly learn to stay away from them after one or two engagements. This thread is a classic example of the kind of discussion to avoid on the Internet.
I thought re-magnitizing Alnico Vs would be a standard procedure for re-building drivers by authorized techs...

....apparently, this is not the case...

UHG!It isn't. Having a way to remag alnico magnets is not a requirement.

*****

Old alnico woofer hardware is a known unstable platform. In the typical home environment, however, it is rarely, if ever, an issue. In the Pro arena they know what they are doing and how to handle their gear so it isn't an issue there either. JBL came up with the SFG ferrite solution. It is quite fortuitous that world events caused a shift to the SFG ferrite hardware. All that information has been painstakingly documented. It has been documented by JBL that the 1500AL is a "correct" way to implement alnico hardware to avoid the problems of the past. Read it and comprehend it?

This particular thread effectively ended with post number 4. In addition to GPA, JBL and OCS can handle remags. I know there are others but I can't find their names right now.

robertbartsch
01-08-2009, 07:49 AM
...all I want is to re-mag a pair of old tweeters before I install new OEM diaphragms.


4312:
Are you saying that an authorized JBL dealer can re-mag these but most JBL re-coners cannot? How is this different from a authorized re-coner who is trained and licensed (????) to repair JBL drivers?

So the authorized re-coners aren't required to have the necessary equipment to do this? I would assume that a licenced re-coner would have a gause tester and re-mag equipment to test all Alnico drivers that are to be rebuilt.

So I can own a screw driver and an air compressor as tools and become a JBL authorized re-coner?

Tell me this is not true!

4313B
01-08-2009, 07:53 AM
...all I want is to re-mag a pair of old tweeters before I install new OEM diaphragms.Them send them to JBL and get it done. Has JBL refused to do it? If so, we should all know about it. GPA and OCS can also do it for you.

edgewound
01-08-2009, 07:58 AM
...all I want is to re-mag a pair of old tweeters before I install new OEM diaphragms.


4312:
Are you saying that an authorized JBL dealer can re-mag these but most JBL re-coners cannot? How is this different from a authorized re-coner who is trained and licensed (????) to repair JBL drivers?

So the authorized re-coners aren't required to have the necessary equipment to do this? I would assume that a licenced re-coner would have a gause tester and re-mag equipment to test all Alnico drivers that are to be rebuilt.

So I can own a screw driver and an air compressor as tools and become a JBL authorized re-coner?

Tell me this is not true!

No, this is not true...it's not that simple. But, those that aren't JBL
authorized love to trash those that are.

Reconers are like any other professional, e.g., accountants. Some are good, some are bad, some are indifferent.

There is a list of required tools that reconers must have.

The most important tool is skill, and it must be demonstrated to the folks at JBL.

I'm off to CES for the rest of the week.

4313B
01-08-2009, 08:17 AM
Are you saying that an authorized JBL dealer can re-mag these but most JBL re-coners cannot? How is this different from a authorized re-coner who is trained and licensed (????) to repair JBL drivers?

So the authorized re-coners aren't required to have the necessary equipment to do this? I would assume that a licenced re-coner would have a gause tester and re-mag equipment to test all Alnico drivers that are to be rebuilt.Why would Authorized JBL Consumer and/or Professional Dealers be able to remagnetize magnets? :blink: I'm sure a few can that are also large Authorized JBL Service Centers but most just don't have that kind of equipment. It isn't required. It's a value added service.

If I were sinking a bunch of money into ancient alnico hardware for some inexplicable reason I would personally get the recharges done. Since that's never going to happen because there are better alternatives available today all I can tell you is send your alnico stuff to the aforementioned Centers and have it done. I'm pretty sure there is a Center near you that can do it. I vaguely remember someone being in N.Y.

4313B
01-08-2009, 08:20 AM
I'm off to CES for the rest of the week.Cool! :yes:

I want to check out the latest voice recognition devices that they have for home and auto. They were talking about it on NPR this morning. Sounds very cool! Unfortunately they were also mentioning that it would be slow out of the gate due to the overall economic climate. The future is here, we just can't afford it anymore. :applaud:

Just think! If our corporations had been thinking about the future instead of merely the next quarter they could have helped keep American buying power strong and we could have leapfrogged to all this new technology. Oh well! Such is the bane of living only in the moment. :rotfl:

scott fitlin
01-08-2009, 08:32 AM
Cool! :yes:

I want to check out the latest voice recognition devices that they have for home and auto. They were talking about it on NPR this morning. Sounds very cool! Unfortunately they were also mentioning that it would be slow out of the gate due to the overall economic climate. The future is here, we just can't afford it anymore. :applaud:

Just think! If our corporations had been thinking about the future instead of merely the next quarter they could have helped keep American buying power strong and we could have leapfrogged to all this new technology. Oh well! Such is the bane of living only in the moment. :rotfl:I THINK I agree here!

BASICALLY , "MADE IN CHINA" WASNT SO CHEAP, And cost us dearly!

:D

scott fitlin
01-08-2009, 08:40 AM
Mind you 4313, IN Americaca CORPARATE POLOTICS SUCK!

YES, I SAID THIS! :applaud:

4313B
01-08-2009, 08:40 AM
I THINK I agree here!

BASICALLY , "MADE IN CHINA" WASNT SO CHEAP, And cost us dearly!

:DI'm laughing as companies learn that fact. I just can't stop laughing. If I stop laughing I'll cry, so I'll keep laughing hysterically.

subwoof
01-08-2009, 08:57 AM
Hope to see some new goodies at NAMM next weekend. Been away 9 years and miss snagging event passes from Mr gander at the last min on sat evening...:)

Anyone else attending? It would be nice to see faces attached to monikers.

sub

Oldmics
01-08-2009, 09:53 AM
I would like to address robertbartsch with the hope to clairify his perceptions on JBL.

JBL Dealers only sell product.They are NOT authorized to preform service/repair work on the product.

JBL Service centers are recognized by JBL to do factory authorized repairs on products that they are franchised allowed to do so on.
This includes both warranty submission and determination along with general "pay" repair services.

Some JBL Service centers preform the reconing service only.

Others are authorized for additional repair capacitys including Transducers, Electronics, EON, LSR, 6208, JRX, ,PRX,MPro & SoundFactor.

Some Service Centers are also JBL Dealers and vice versa.Therefore the possibility exists that a JBL Dealer can service the product,but only if they are also a JBL Service Center.

These are the JBL Pro Division criteria.

JBL Consumer Division has a different (but similiar) implimentation.

Not all JBL Service Centers service both Pro and Consumer products.

There is as Edgewound states a "Minium Loudspeaker Parts Requirement" list for JBL Pro that states minium required tools to preform repairs.

Nowhere on either the Pro or Consumer list is there a requirement for a "gaussing machine".

Now,my business as both a JBL Pro Dealer and a full line JBL Pro/Consumer Service Center has invested in many more tools than required by the minium required list.

I think that we do a good job at representing what JBL produces.

There are times when we have to educate a dissillusioned customer who cant get 142 db of bass from his Eon 15P and the unit fails for some bewildering to reason to him.

It gets submitted as a warranty inspection and promply kicked for abuse of the componet and the customer is upset because it was "sold to him with those expectations" (thanks G.C. :barf:)

The point that I am making is that even though we did not invest in a "gaussing machine" we do have a gauss meter to ascertain magnetic motors in question.

We can get to the root of the problem and advise.

Edge said it all

"Reconers are like any other professional, e.g., accountants. Some are good, some are bad, some are indifferent.

The most important tool is skill, and it must be demonstrated to the folks at JBL."

Without the desire to do better and the skill to follow thru you may not get to the root of the problem.
Tools that are availiable and are NOT on the list will be had by Service Centers that are of a better quality.

So I guess we are not at the top of the heap since we do not have a gaussing machine. :blink:

To robertbartsch"s delema,

Your service needs are not a "standard proceedure" repair.You are armed with more in depth questions to ask than the average customer and are seeking a top of the line new preformance results from old devices.

A demanding customer such as yourself needs the extra time and effort a quality Service Center would offer to you.
Find a competent JBL Service Center that you feel comfortable with and have them inspect your tweeters.

If they do need to be regaussed they can send them to the JBL factory.

Quality work is not inexpensive in any shop.

Hope this helps.

Oldmics

Doc Mark
01-08-2009, 10:23 AM
Hey, Friends,

I'd like to add my own two cents in this thread, if I may. I've done many repairs on our cars, over the years, and most of the time, it's worked out very well. But, just because I can do that, and just because I own most of the proper tools to do those jobs, does NOT mean that I can call myself a "mechanic"!!! I'm "shade-tree", all the way!! Same thing for those who recone transducers, and other such jobs. There is a huge difference between being able to do a certain job, and being a true professional at dong that same job!!

I can say that, after having played music professionally for almost 30 years, and after having seen many, many "Authorized Service Centers", all over the US, Edgewound's comments about the differences of individual dealers like that, ring absolutely true!! Furthermore, I can say, without any reservation at all, that the work that Edgewound does is top of the line, period!! I've seen lots of reconing work, and his is simply better than most everything else I've seen!! Want to know why? (Good! Glad you asked!;):)) It's because he is a truly skilled professional who takes PRIDE in his work, and he enjoys what he does!! That shows in the end results of his work, and believe me, I've seen lots of work from other "Authorized Service Centers" that can't hold a candle to what Edgewound sends out of his shop!!! So, without doubt, not all "Authorized Service Centers" are created equal, and for me, I'd recommend Edgewound over many others whose work I've seen. End of story, as far as I'm concerned.

On a second point, using China to create inexpensive products is a boondoggle for which we'll all pay, in the years to come. I think that, now, and I've ALWAYS thought that!! When everything became "bottom-line"-oriented in the US, that's when this off-shore production mentality raised it's ugly head, and that was the beginning of the end, as far as I'm concerned! I hope we can recover from all this, but sincerely doubt that such a recovery will be soon in coming, if it ever comes, at all..... Sigh.... Greedy, short-sighted, Bastiges!!!!:biting::banghead: Take care, and God Bless!

Every Good Wish,
Doc

4313B
01-08-2009, 10:32 AM
Hope this helps.

OldmicsPerfect! Thank you very much! :yes:

robertbartsch
01-08-2009, 10:59 AM
OK - thanks OldMics

Live and learn - Your explanation above is informative.

I suppose my thoughts on the capabilities of authorized JBL re-coners was, in part, based on discussions with and narratives posted on the Great Plains Audio web page.

My recollection is that they describe the Altec re-coning process and tell you that their standard procedures include re-magnitizing all Alnico motors.

I just assumed this was standard procedure for all Alnico re-cone work. I thought the discussion on alnico Vs ceramic magnets posed on this cite alludes to the fact that alnico magnets may loose strength if exposed to massive power surges which, I assumed, are the major causes of blown diaphragms. As I indicated earlier, my 075 frams are blown.

Erik Wayne my re-coner who is currently working on a pair of 2240s for me told me he would install the 075 frams for me but he does not have a "working" gauss meter or de-mag/re-mag equipment.

robertbartsch
01-13-2009, 09:52 AM
Since these were originally installed in a traffic application and have blown diaphragms, and I acquired them used from Fleabay, I really would like to avoid any potential issues now and in the future.

Therefore, I forwarded the cores to Bill from Great Plains Audio who will recharge the magnets for $15 each.

I believe this is a very reasonable price for the satisfaction that the rebuilds will include re-charged magnets and new frams and will be correct.

Why take a chance with 30-40 year old drivers; this seems like a prudent step to me; right?

toddalin
01-13-2009, 09:57 AM
Since these were originally installed in a traffic application and have blown diaphragms, and I acquired them used from Fleabay, I really would like to avoid any potential issues now and in the future.

Therefore, I forwarded the cores to Bill from Great Plains Audio who will recharge the magnets for $15 each.

I believe this is a very reasonable price for the satisfaction that the rebuilds will include re-charged magnets and new frams and will be correct.

Why take a chance with 30-40 year old drivers; this seems like a prudent step to me; right?

That's a very good price. OCS charges $25 each if they are doing a new surround/recone and more if that is the only reason for bringing in the speaker. :applaud:

robertbartsch
01-13-2009, 11:17 AM
Yeh, I got another quote of $65 to re-charge the pair. These would have been shipped by me to a JBL re-coner and then to an authorized JBL service center and then they would be shipped back to the re-coner who would then ship them to me......

...all this shipping nonsence would have added another $65 or so, I suppose.

UHG!

toddalin
01-13-2009, 11:26 AM
Yeh, I got another quote of $65 to re-charge the pair. These would have been shipped by me to a JBL re-coner and then to an authorized JBL service center and then they would be shipped back to the re-coner who would then ship them to me......

...all this shipping nonsence would have added another $65 or so, I suppose.

UHG!

More chances for damage too.

hjames
01-13-2009, 11:30 AM
Subwoof has had some comments on repurposed Traffic tweeters ...

..."not counting the OEM variations that went to the railroad / traffic companies."

http://audioheritage.org/vbulletin/showthread.php?t=12208

And ...

http://audioheritage.org/vbulletin/showpost.php?p=24109&postcount=4

pity no one saves images to the LHS server on these weirdo ebay sales -then they'd still be here 2 years later ...

Mr. Widget
01-13-2009, 12:19 PM
...pity no one saves images to the LHS server on these weirdo ebay sales -then they'd still be here 2 years later ...Many do, but it isn't as often as I'd like.

I had completely missed this thread as I assumed it was another alnico vs. ferrite debate and I am bored with those. :banghead: Had I followed this thread I might have posted these comments here instead of creating a new thread: http://audioheritage.org/vbulletin/showthread.php?t=23594

Basically remaging can be important, but as Oldmics and edgewound have pointed out, rebuilding these vintage drivers is almost as much art as science. Almost anyone can pop a new cone or diaphragm in a driver, but only those with the proper equipment and as importantly, skill, will return your drivers in the condition you are expecting. Looking for a factory authorized repair facility is a good start, but asking folks in your area for recommendations is also a good idea...


Widget

robertbartsch
01-13-2009, 01:38 PM
I removed the nose and horn assembles but I left the old diaphragms in and then I shipped them to Bill for the re-mag work. I need to refinish the nose cone and paint the horns black. They are now pea green.

Anyway, so you think I should have my JBL re-coner install the new OEM frames?

As you know, these drivers have two alignment pins to help guide the new diaphragms in place. The old frames have a twisted face and it looks like the nose cones were over-tightened such that they destroyed the original diaphragms. Each unit had red wax seals on the body screws, so the way these diaphragms were damaged is somewhat puzzling at this point.

I assume the installation trick is to not to twist the bullet nose on re-installation such that they destroy the new diaphragms.

SMKSoundPro
01-13-2009, 02:23 PM
Yes, that appears to be the case. Someone twisted the "nose" to tighten it, just like Moe always did to Curly, or was it Larry???

Once twisted, twice ruined. Pretty simple really.

These bullets are not rocket science! When you receive them back from re-mag world, install the diaphragms in the proper polarity, install and tighten the phase plug (nose) and reattach the horn and mounting ring.

Sweep test with a tone generator GENTLY, reinstall and listen!

Mr. Lansing would be so proud, I hope.

subwoof
01-13-2009, 02:31 PM
The green paint is REALLY bonded to the aluminum - it's a military corrosion type that happens to be a great primer should you want to paint them. To get it all off will mean removing some aluminum.

I might have extra bullets and horns in the storage room that would replace yours. Give me a shout in about 10 days - after the NAMM show and the festival weekend here ( why people think winter is fun is beyond me ).

sub

robertbartsch
01-14-2009, 11:30 AM
The pea green finish is easily removed from the bullet nose with a wire wheel. I painted the horns with flat black spray paint.


...looks original now!

edgewound
01-14-2009, 12:19 PM
The pea green finish is easily removed from the bullet nose with a wire wheel. I painted the horns with flat black spray paint.


...looks original now!

I don't recall the factory finish on the 2402 horn ever to be flat black. The mounting ring, yes, was flat black.

The horn has always been the machine turned aluminum.

http://www.jblpro.com/pub/obsolete/2402.pdf

Mr. Widget
01-14-2009, 02:40 PM
The pea green finish is easily removed from the bullet nose with a wire wheel. I painted the horns with flat black spray paint.


...looks original now!A nicer finish can be obtained by chucking it in a drill press and running it against a 3M finishing pad... you'll get nice concentric swirl marks.


Widget

robertbartsch
01-21-2009, 11:37 AM
...these are older black 075s not the 2402s. I thought the older bullet nose drivers had black horns and brushed aluminum noses.... The 4-bolt mounting brackets on these units are "built into" the horns.

...anyway, the old pea green baked finish was easily removed from the noses and the units look more original now, I suppose.

I'll post some pics when I receive the cores back from re-charging at Great Plains Audio.