JBL 2445_46 frq.response

You missed a couple of things in this thread Robert,

The knock off driver doesn't work well, that's the reason for this thread. And the fact it does not perform well delights me! The fact that someone (ivica) bought them unknowingly and in reality has been cheated sorrows me.

Also it was not difficult to identify it as a knock off, at all, when I saw a picture of it I knew what it was right off as did others, and I am no expert.

You're right, it's cheaper to make them in Asia, but, as Warren Buffet rightly said, "Price is what you pay, value is what you get." So, are they of any value? They would not be to me. How inexpensive would they have to be for you to say, "Yeah, they suck, but they were cheap!

If they could not even duplicate the performance of an obsolete driver they had in their hands as a model, how do you think they will surpass JBL? And if they do surpass JBL in quality, who's fault would that be?

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5. The participants in today's world economy do not always play fair.

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No they don't, and I don't know if they ever did.

You missed a couple of things in this thread ...

The knock off driver doesn't work well, that's the reason for this thread. And the fact it does not perform well delights me! The fact that someone (ivica) bought them unknowingly and in reality has been cheated sorrows me.

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I don't think I missed the fact that the "knock-off drivers" do not perform to JBL specs - surprise, surprise.

To me, the fact that the buyer was ripped-off is sad, however, some here might have missed the BIG picture. Someone went to the trouble to make a fairly exact copy of one of the best compression drivers on the market and that was done for a reason. My guess is that they did so to obtain manufacturing knowledge so they could eventually design their own drivers and compete in the marketplace with Harman.

I'm not an engineer, but I assume their shortfall in the knock-off was that they failed to copy the OEM phase plug exactly. Wow, I wonder how hard that would be to correct?

These drivers have been out of production for a while and the knock-off copies are not new either, so this indicates the "knock-off "problem" has been with us for a while. If I were Harman management, this would scare the cr@p out of me!

Most knock-offs like shoes, handbags, sports clothing, jewlery, ect. are made to undercut the seller/manufacturor of high-price luxury items. Considering these drivers are mostly used in professional installations like movie houses and sound reinforcement, I doubt that this was done to undercut JBL and that is why Harman should be very concerned.

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Originally Posted by 1audiohack

You missed a couple of things in this thread Robert,

The knock off driver doesn't work well, that's the reason for this thread. And the fact it does not perform well delights me! The fact that someone (ivica) bought them unknowingly and in reality has been cheated sorrows me.

Also it was not difficult to identify it as a knock off, at all, when I saw a picture of it I knew what it was right off as did others, and I am no expert.

You're right, it's cheaper to make them in Asia, but, as Warren Buffet rightly said, "Price is what you pay, value is what you get." So, are they of any value? They would not be to me. How inexpensive would they have to be for you to say, "Yeah, they suck, but they were cheap!

.

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Firstly to say, I was not so careful while buying mentioned "2445", because i have no idea that such thing is "attractive enough" to be copied, especially the driver were mounted on enormously large horns ( may be the horns are "fake" JBL 2360A ).
I am sure that the company making copy of the drivers has quite enough knowledge to understand what is important for audio quality compression driver. I do believe that they had made lot of measurements of their product before starting "mass" production. But after all, I can not understand two things: why they make so large 'cavity' in the voice coil 'circuits', because that it is "visible from the plain" that such construction would reduce the efficiency, and only very cheap ring made of plastic or aluminum would dramatically improve the characteristic of the driver, and the production price would increase insignificantly. and second, concerning the phasing-plug is the same story. The amount of the material is the same, and to copy the shape is very easy.

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Originally Posted by robertbartsch

...someone went to extraordinary measures to copy this driver and, from the visual inspections, it was diffucult for the experts here to identify them as fakes.

OK, so what have we learned from this?

1. Harman to Houston: "We have a problem!"

6. If I'm the CEO of Harman, I need to keep close tabs on what is happening in the marketplace and to take appropriate action to avoid being uterly CRUSHED!

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I think that Harman "couldn't care less" about JBL-pro products at all.:(

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Originally Posted by robertbartsch

...one other thing...

I'm going home tonight and I plan to check my pair of 2445Js to see if they are real. When I installed a new pair of OEM 8 ohm frames about one year ago, I remember not being able to see down the throat to the phase plug, so I should be OK.

...This blows!

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I believe that you are lucky and you have original 2445 frame,
but why you put 8 Ohms diaphragm frame instead of 16 Ohms ( yes larger current for the same voltage, but "Bl" factor less ), but that is only my curiosity.

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Originally Posted by grumpy

It is still interesting (at least to me), that your AkAbak model assumptions seem to correspond to the "problem" driver behavior.

At least one mystery was solved.

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If you have some amount of time you can see :
http://www.kozystudio.com/bu2bu2/fake/fake.htm
(of course with translation from Japanese) I can say "my diver in detail"
even on resposne there is a small notch at 3kHz, but because of the large horn
(jbl like 2380) sound at 1kHz 'mask' the rest

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Originally Posted by grumpy

It is still interesting (at least to me), that your AkAbak model assumptions seem to correspond to the "problem" driver behavior.

At least one mystery was solved.

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what is more interesting lot of expect-able problems around voice coil and cavity near
were mentioned in 1936 patent, US2037187 and later elaborated
http://www.aes.org/e-lib/browse.cfm?elib=2932
(unfortunately i can not download this document)

Ivica:
When I bought my pair of 2445Js they came with original JBL diaphragms that were dated in the late 1980s I beleive. Anyway, since the frams were many years old, I decided to replace them and the other components in my planned system were 8 ohms so that was the logical choice.

I may have missed this in the earlier threads, but how did you obtain these drivers? Can you return them to the seller and request a refund since they are obvious fakes?

Good luck!

PS - Since a significant amount of revenues of Harman International are derived from JBL Professional equipment, I would have to say that JBL cares about their products and the knock-off problem.

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Originally Posted by robertbartsch

Ivica:
When I bought my pair of 2445Js they came with original JBL diaphragms that were dated in the late 1980s I beleive. Anyway, since the frams were many years old, I decided to replace them and the other components in my planned system were 8 ohms so that was the logical choice.

I may have missed this in the earlier threads, but how did you obtain these drivers? Can you return them to the seller and request a refund since they are obvious fakes?

Good luck!

PS - Since a significant amount of revenues of Harman International are derived from JBL Professional equipment, I would have to say that JBL cares about their products and the knock-off problem.

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Unfortunately the possibility to refund my expenses is near 0.00000001%
either for the drivers or the diaphragms, so that means I can put the diaphragms in to "picture frame" and "hang them on the wall" with all JBL stickers on them.
The driver may be i can use for "door bumpers" because they have very good preserved rubber surroundings around the magnet

May be I can sand an e-mail to JBL-pro dept. so that they can suggest me how to "upgrade" my fake-drivers to reach near original. May be JBL can offer me Phasing-plugs that can help.

I dont think JBL would touch them with a ten foot pole.,,, Its not there problem...Its your loss.

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Originally Posted by Maron Horonzakz

I dont think JBL would touch them with a ten foot pole.,,, Its not there problem...Its your loss.

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they may be able to physically confirm that they are fakes/clones tho'
or tell the purchaser how to discern between the two.



:)

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Originally Posted by ivica

Unfortunately the possibility to refund my expenses is near 0.00000001%
either for the drivers or the diaphragms, so that means I can put the diaphragms in to "picture frame" and "hang them on the wall" with all JBL stickers on them.
The driver may be i can use for "door bumpers" because they have very good preserved rubber surroundings around the magnet

May be I can sand an e-mail to JBL-pro dept. so that they can suggest me how to "upgrade" my fake-drivers to reach near original. May be JBL can offer me Phasing-plugs that can help.

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On the plus side, you do seem to have real JBL diaphragms, so all you need now are blown 2445s, which are not too hard to come by.

At first I was surprised to see that the fake had a redesigned phase plug, and a really poor one at that. But of course if it's not infringing on any patents etc. and it's simpler to make then JBL can't do anything about it. But, whoever put the JBL label on the back broke the law.

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Originally Posted by tomee

On the plus side, you do seem to have real JBL diaphragms, so all you need now are blown 2445s, which are not too hard to come by.

At first I was surprised to see that the fake had a redesigned phase plug, and a really poor one at that. But of course if it's not infringing on any patents etc. and it's simpler to make then JBL can't do anything about it. But, whoever put the JBL label on the back broke the law.

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tomee:
what is 'interesting" for me is that the "phasing plug" has , say, equally distance annular input throats but with different width (smallest towards the center) and as can be seen from the picture with almost equally with of the 'mouth', what is expect-able trend concerning the rule: "percentage of area of mouth of each wave guide of total output area has to correspond to the percentage area of each input area"), on the other side mentioned "phasing plug" is 'connected to the "inverse" short conical horn while together with mentioned phase plug generate 'sound' wave front at the throat of the internally short horn. All in all it seems that someone had spent some time in calculating and projecting all this (I believe that it had been easier to copy some of JBL or others verified products).
On the other side under vice coil path there is enormously large cavity which is known as a potential 'notch generating problem' in driver response. May be at the beginning there was large amount of 'Ferrofluid', but as it is known such construction with open system would become full of dust and would block voice coil assembly after years of use.

for me it would be nice to find a pair of "blown" 2445, but where ?????:confused:

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Originally Posted by Maron Horonzakz

I dont think JBL would touch them with a ten foot pole.,,, Its not there problem...Its your loss.

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Maron:

Yes, I think so, but I am sure that (or better to say: I would expect that) in JBL someone has to "track" JBL fake products in the world market, and nowadays, with Internet "support", it would be very easy to show on, here say, www.JBLPRO.com
site one page where all potential customers can see how 'fake product" look like....:eek:

I have decided to "fill-in" the large cavity under voice coil path, and the i will make new measurements to see what would happen. I expect that the efficiency would rise, and that the notch would move towards higher frequency, may be 'out of the interest'.:(