# XML-T6 Vs. XML-U2



## madecov (Jan 22, 2012)

I own lights with both emitters. I can't tell any difference.
Can anyone explain in plain non technical english what the differences are?


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## phantom23 (Jan 22, 2012)

U2 is 7% brighter at the same current. Unless you bought it from some chinese vendor, in that case genuine T6 can be even brighter...


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## madecov (Jan 22, 2012)

I have a Klarus and Fenix lights that came with U2 emitters.
I was just wondering since I also have several T6 and R5 lights also.


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## Mike S (Jan 23, 2012)

Has Cree not updated their datasheet for the XM-L? They continue to show the T6 as being their top flux bin.


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## egrep (Jan 23, 2012)

What does this mean? If you bought an XML U2 from a chinese vendor (manufacturer or vendor?) then it's probably a fake? Or a second? At any rate, it's probably dimmer than a T6? Is there some widespread counterfeiting of the U2 going on? Is the T6 not being counterfeited? Thanks for the clarification. Overall I prefer the T5 for it's more neutral tint.


phantom23 said:


> U2 is 7% brighter at the same current. Unless you bought it from some chinese vendor, in that case genuine T6 can be even brighter...


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## Th232 (Jan 23, 2012)

Excluding the actual output, all XM-Ls are physically identical, there's no size difference, no stamp or other marking with the flux bin or anything else. As such I wouldn't say fake or counterfeit, as that (to me) implies that they've manufactured something that isn't a real XM-L as made by Cree. If they say it's a U2 and it turns out to have less output than spec'd then I'd just call it lying.

As for the question about T6 not being counterfeited, similar to the above I'd say LEDs aren't being counterfeited, but why lie and say a specific output bin is a T6 when you can lie and say it's a U2?

Speaking of T5s, you do know that T5 only refers to the output bin and has nothing to do with tint, right?


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## egrep (Jan 23, 2012)

Thanks for the explanation. Totally makes sense. It's about misrepresentation at a finer level. Asfor T5 referring to the output bin, I do know that but confusingly people speak of them in terms of tint. Saying the T5 is 'neutral'. I've asked people about this and didn't get a satisfactory answer. I suspect you can clear it up for me. I'd appreciate it if you would. Nonetheless, the T5 is noticeably 'warmer' tint than the T6. At least in my experience. I'm sure there's a good explanation for that and I sincerely thank you in advance 



phantom23 said:


> U2 is 7% brighter at the same current. Unless you bought it from some chinese vendor, in that case genuine T6 can be even brighter...





Th232 said:


> Excluding the actual output, all XM-Ls are physically identical, there's no size difference, no stamp or other marking with the flux bin or anything else. As such I wouldn't say fake or counterfeit, as that (to me) implies that they've manufactured something that isn't a real XM-L as made by Cree. If they say it's a U2 and it turns out to have less output than spec'd then I'd just call it lying.
> 
> As for the question about T6 not being counterfeited, similar to the above I'd say LEDs aren't being counterfeited, but why lie and say a specific output bin is a T6 when you can lie and say it's a U2?
> 
> Speaking of T5s, you do know that T5 only refers to the output bin and has nothing to do with tint, right?


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## Th232 (Jan 23, 2012)

egrep said:


> Thanks for the explanation. Totally makes sense. It's about misrepresentation at a finer level. Asfor T5 referring to the output bin, I do know that but confusingly people speak of them in terms of tint. Saying the T5 is 'neutral'. I've asked people about this and didn't get a satisfactory answer. I suspect you can clear it up for me. I'd appreciate it if you would. Nonetheless, the T5 is noticeably 'warmer' tint than the T6. At least in my experience. I'm sure there's a good explanation for that and I sincerely thank you in advance



When LEDs are made, while the processes allow the manufacturer to get within a certain ballpark, factors like flux, tint and Vf still have an element of chance involved. So after a batch of LEDs are made, the manufacturer tests all of them for those qualities and then sorts them appropriately. Sometimes the process will be more skewed in one direction, especially in the early stages. I remember the earliest of the R5 and S2 XP-Gs were all in a relatively green tint bin. As they refine the process and so on, they're able to get better control and we get "better" tint bins. I expect a similar thing happened with the tint of the T5 and T6 XM-Ls you've described.

The problem is that most companies advertise the LEDs in their torches by output and not so much by tint (and when they do it's more of a cool/neutral/warm rather than any specific tint bin), so when people see a whole batch of greenish S2 XP-Gs, they come to the conclusion that S2 = green tint. I suppose I should note that while "S2" is a designation that in no way relates to the tint bin, the manufacturing process does connect flux and tint. The catch is that when the manufacturing process improves, the association between flux and tint is separated (leading to a greater variety of tints), but by that point a stereotype may already be firmly established.

Hope this clears it up a bit!


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## romteb (Jan 24, 2012)

madecov said:


> I own lights with both emitters. I can't tell any difference.
> Can anyone explain in plain non technical english what the differences are?



T6 and U2 are contiguous flux bin, you could very well have one led from the T6 bin and one from the U2 bin that are 1 lumen apart when driven at the same current.


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## Creerules (Jan 29, 2012)

The brightness bin(T5, T6, U2 and so on) does not have any connection to the color. The color is defined in a specific color bin(see datasheet). So if you just order a T6 XM somewhere which is not specified in detail it is pure luck what color you get(in the range specified in the datasheet of course).

For usual applications the exact brightness bin is often of much lower importance, then people think. As said before, the difference between T6 and U2 for example is maximum 7%, but may be also just 1%. The price on the other hand is very different mostly. For 7% more brightness you can easily pay a 50% higher price in many cases. Just check the common traders like cutter, dealextreme or ledrise and you will see: The prices vary from 5 Euro for a T6 XML to >10Euro for a U2 XML.

If the color is important to you look for dealers who actually give the exact color Bin, thats the only way to tell what exact color you will get.


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## Swedpat (Feb 15, 2013)

I have been wondering about the XM-L T6. In some cases it's a neutral LED but in many cases the tint isn't even mentioned. So that's hard to know sometimes...


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## arek98 (Feb 15, 2013)

In theory you may have T6 in cool, neutral, warm tint.

In theory because in reality usually higher flux bins are cooler colors and lower are warmer.

Because how LED emits light it is harder to make bright LED that has warmer color using same amount of input power.

This is why brightest bins (like U2) usually come in cool only. Current technology dos not allow production of U2 in warm tint, yet. Warmer tints will have lover flux bins, like T5 or even less. You can have cool tints in lover flux bins as well (cool T4, T5, T6 whatever) but there is really no point for manufacturer to make them if at the same cost the can make brighter once. In stores that may be older stock since as said above process improves over time.


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## MikeAusC (Feb 15, 2013)

madecov said:


> I own lights with both emitters. I can't tell any difference.
> Can anyone explain in plain non technical english what the differences are?



The average U2 brightness is 7% more than the average T6 brightness.

For a brightness difference to be easily noticeable by the eye, you generally need at least 20% change in brightness.


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## madecov (Feb 15, 2013)

I have only been able to tell the difference between them when side by side on a white wall. And then it is based on tint. Out in the field a cool T6 or cool U2 can hardly bee seen.


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## Fresh Light (Feb 15, 2013)

I don't know if the Vf for U2/3 leds have come down recently, but I have been told by a builder that they typically are higher than the Vf of T6 XMLs. So, at a given current the Ubins will be brighter but also require more power to do so compared to a lower Vf T6. But if you get a low Vf T6 and only increase the current a little it will be brighter and use less energy than a U binned LED. Here is the example I was given:

U2 @ 3.9v 3A = 11.7w 320L
T6 @ 3.6v 3A = 10.8w 300L

So for another 1.8 watts you get 20 more lumens with the U2.

But if you bump up the T6 current just a bit (200mA):

T6 @ 3.6v 3.2A = 11.52w 360L

You get 40 more lumens than the U2 with less power consumed using the T6.


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