# Cree XM-L2 Finally announced



## mds82

http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/xlamp-xml2 

"Delivering breakthrough lumen output and efficacy in the XM package, the XLamp XM-L2 LED is the highest-performing, commercially available, single-die LED. Built on the SC³ Technology Platform, the XLamp XM-L2 LED delivers up to 20% more lumens and lumens-per-watt and double the lumens-per-dollar of the original XM-L. The XM-L2 LED offers the unique combination of high efficacy and high lumen output at high drive currents, delivering an unprecedented 1198 lumens at 116 lumens-per-watt efficacy at 3 A, 25°C."


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## easilyled

Oh no ..... won't be easy to upgrade so many XM-L lights.

Sounds like its an improvement worth making though.


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## jmpaul320

Epic.


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## Gunner12

Yay! I've been waiting for this.


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## jmpaul320

1198 lumens @ 3a

Right now xmlu3 is [email protected]

I wonder if that 1198 is the top of the xml2 u2 bin?? I am not seeing a u3 bin on the new data sheet.

Wonder how long before they "hit the streets" maybe 3 months?


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## Overclocker

hmmm same viewing angle

i suppose we won't see substantial gains in throw as we did with XPG to XPG2


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## tstartrekdude

125º viewing angle, same as the old xm-l. I'm a little disappointed.


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## BenChiew

Exciting times are coming.


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## hellokitty[hk]

When would it likely be available for purchase in 4000k?


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## bshanahan14rulz

beam angle? why you care about beam angle? how do you think it will not increase throw having more light coming from same sized (?) die?

Are these gains possibly from flipping them upside down? Or is the reason for the "lack" of current spreaders perhaps because of a more complicated conversion layer? Anybody care to hazard some guesses (educated or not)?

Interesting to note the two bond wires too, while no change in 3A spec.


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## Glock 22

Awesome!


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## BIGLOU




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## Tiresius

That is awsome. I'm also interested in their high cri versions.


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## Fresh Light

How about a version with flat antireflective glass. Any one know when XML-2s will be for sale?


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## chanjyj

Time to wait for Nailbender to stock em up.


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## BenChiew

Someone said availability is a few months from now?


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## psychbeat

Hmm .. My next drop is going to be a direct to copper dedomed XM-L2 @4a in a smooth reflector I think....

Thought I was done for a while but the beat goes on!!


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## netprince

psychbeat said:


> Hmm .. My next drop is going to be a direct to copper dedomed XM-L2 @4a in a smooth reflector I think....



That sounds good to me too!


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## RoGuE_StreaK

I'm rather disappointed that the Vf/current graph is virtually identical to the XM-L; was hoping like the XP-G2 that it had dropped significantly. Hell, even dropped a _little_.

On the plus side, it's a nice silvery colour rather than the old green.


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## ergotelis

And the thermal path is the same, was expecting a bit less, still good enough though!


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## uk_caver

It's certainly interesting that that curve is essentially the same for both devices, while the XP-G/G2 equivalents did have meaningfully different slopes.


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## spencer

OP says at 25*C. Aren't current XM-L's binned at 85*C? If the below is also true (too lazy to check) and U3 bin is available then this seems like a downgrade rather than an upgrade.


jmpaul320 said:


> 1198 lumens @ 3a
> Right now xmlu3 is [email protected]


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## hellokitty[hk]

Current is binned at 25C and XM-L2 is binned at 85C.


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## ergotelis

Generally, top bin Cree xm-l2 U2 is like a Cree xm-l U4.


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## BenChiew

Question for the tech gurus. At 1amp drive, how many lumens will I get out of XML2? How about 1amp on XML?


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## Gunner12

Benchiew said:


> Question for the tech gurus. At 1amp drive, how many lumens will I get out of XML2? How about 1amp on XML?


Read the data sheet, the lumen output at 700 mA, 1 A, 1.5A, and 2A are all on there. Both data sheets too.


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## och

Awesome news!


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## StudFreeman

No solder pads on the top corners like the original. It probably saves money/time in the fab process. Cree made the same choice for the XP-E/G2.
I reckon the XM-L2 will be tricky to solder directly to copper, as if that was easy to do with the XM-L


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## Overclocker

ergotelis said:


> Generally, top bin Cree xm-l2 U2 is like a Cree xm-l U4.



seems it's not gonna be as awesome as G-to-G2 (which had a big jump in throw)

so i guess XML2 U2 is just one bin higher than XML U3 with no jump in throw. nothing to write home about but still a welcome improvement 

and the upside is we could very soon be modding existing T6 cool white flashlights into 5000K XML2 probably with little or no loss in brightness


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## Flea Bag

Humph... There were significant improvements in their warm or hi-CRI bins going from XP-G to XP-G2, but I don't see the same with the XM-L2s... Are there any updated datasheets around the net showing better?


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## BenChiew

Gunner12 said:


> Read the data sheet, the lumen output at 700 mA, 1 A, 1.5A, and 2A are all on there. Both data sheets too.



Thanks. Looks like nearly similar to one another.


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## RoGuE_StreaK

If they claim it's double the lumens per dollar compared to the XM-L, and the lumens haven't increased all that much, I guess that can be interpreted as meaning there'll be a significant price drop?

That said, the XP-G2 seemed to initially be cheaper at Cutter than the XP-G, but it's now definitely more expensive.


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## bshanahan14rulz

Is the die larger? Why are people saying it will put out more light but not throw as well?


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## uk_caver

RoGuE_StreaK said:


> If they claim it's double the lumens per dollar compared to the XM-L, and the lumens haven't increased all that much, I guess that can be interpreted as meaning there'll be a significant price drop?



I think it's a maybe historic comparison.

".._and double the lumens-per-dollar of the *original* XM-L_"

How much was the XM-L when it first came out?


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## easilyled

bshanahan14rulz said:


> Is the die larger? Why are people saying it will put out more light but not throw as well?



Which people?


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## twl

Data sheets say the "old" XML does 1040 lumens at 10w.
And the "new" XML2 does 1052 lumens at 10w.

That doesn't seem so revolutionary to me.


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## Gunner12

I think the XM-L's ratings were at 25°C while the XM-L2s are at 85°C, so if you tested the XM-L2 at 25°C like the original XM-L, there should be a larger improvement.


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## BenChiew

Cree should do their spec sheet based on some standard parameters. At
least it will be easy to compare between emitters.


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## Hooked on Fenix

186 lumens per watt is a decent jump. After getting my first Quark light with a 165 lumen per watt XP-G2 l.e.d., I think I'll wait awhile before getting another high end light. I'd like to see a light at least in the 200 lumen/watt range before I blow more money on another big purchase. Cree has lab tested l.e.d.s in the 250+ lumen range now and with their lower cost SiC l.e.d.s, production is going to skyrocket, costs are going to decrease, and research and development are going to produce better products at an excellerated rate to keep ahead of the competition. I don't think I'll have to wait more than a year to get 200+ lumen/watt l.e.d.s (probably 3-6 months).


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## jtr1962

Hooked on Fenix said:


> I don't think I'll have to wait more than a year to get 200+ lumen/watt l.e.d.s (probably 3-6 months).


I fully agree. 2013 should be the year we finally see production 200 lm/W LEDs. It seems Cree's production usually lags their lab results by 3 years or so. That should mean 250+ lm/W by 2015.


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## Sinjz

Could someone please help me understand how the XM-L2 is an improvement on the XM-L? I'm not great at reading these spec sheets, but from what I can tell it looks like the XM-L2 Forward voltage is a hair less at any given current, but it also seems to give up a few lumens in exchange. Everything else seems to be pretty much the same. I don't get it.  what am I missing?


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## uk_caver

Look at the datasheet (linked earlier)
A T6 XM-L produces >[email protected] at 25°C
A T6 XM-L2 produces >[email protected] at _85°C_ and >[email protected] at 25°C, so ~13% more light for the same bin and temperature.


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## moozooh

Sinjz said:


> what am I missing?



You're missing the discussion that happens virtually on every page of these XP-G2/XP-E2/XM-L2 announcements.

The new generation Cree LEDs are rated at 85C junction temperature, while the previous generation is rated at 25C. When a LED gets hotter its performance drops. Cree has changed its rating policy to better account for real-world usage scenarios, since running a LED at 85 degrees is much more common than at room temperature. Cree did not retroactively re-rate its 1st gen LEDs, so you get the disparity.

To correct for the difference in temperature you should decrease the output of 1st gen LEDs by some 13..16%. The rule of thumb is that a 2nd gen LED of the aforementioned families is roughly two flux bins ahead of the 1st gen; i.e. an XM-L2 T6's output and efficiency is roughly identical to XM-L U3 (bins go T6 -> U2 -> U3). The average performance improvement is around 15%, to give a rough estimate.


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## Sinjz

uk_caver said:


> Look at the datasheet (linked earlier)
> A T6 XM-L produces >[email protected] at 25°C
> A T6 XM-L2 produces >[email protected] at _85°C_ and >[email protected] at 25°C, so ~13% more light for the same bin and temperature.



I assumed the XM-L was tested at 85°C straight across, so everything looked so similar. Why did they change?


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## Sinjz

moozooh said:


> You're missing the discussion that happens virtually on every page of these XP-G2/XP-E2/XM-L2 announcements.
> 
> The new generation Cree LEDs are rated at 85C junction temperature, while the previous generation is rated at 25C. When a LED gets hotter its performance drops. Cree has changed its rating policy to better account for real-world usage scenarios, since running a LED at 85 degrees is much more common than at room temperature. Cree did not retroactively re-rate its 1st gen LEDs, so you get the disparity.
> 
> To correct for the difference in temperature you should decrease the output of 1st gen LEDs by some 13..16%. The rule of thumb is that a 2nd gen LED of the aforementioned families is roughly two flux bins ahead of the 1st gen; i.e. an XM-L2 T6's output and efficiency is roughly identical to XM-L U3 (bins go T6 -> U2 -> U3). The average performance improvement is around 15%, to give a rough estimate.



I haven't read any of those other threads, so thanks for the info! :thumbsup:


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## hellokitty[hk]

Sinjz said:


> I assumed the XM-L was tested at 85°C straight across, so everything looked so similar. Why did they change?


Because 85C is much more realistic.


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## uk_caver

I do wonder if it might have been clearer if they'd switched to a new output binning description at the same time - presumably they're not planning on repeatedly changing the temperatures they bin at, so it would likely have been a one-off change.


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## BenChiew

From now forth, I hope CREE will report their future emitters using the 85C standards. Makes it easier and more apparent for us.


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## tstartrekdude

bshanahan14rulz said:


> Is the die larger? Why are people saying it will put out more light but not throw as well?



Nobody is saying that. How are you getting that from what is being said?

The XM-L2 is going to throw 20% better (barely noticeable) because it is 20% brighter in the same optical package as before. The reason some here including myself are talking of viewing angles and being disappointed with them is because is because the XP-G2 got a bigger optic with a narrower viewing angle, thus leading to a 50% bump in lux, something that was sadly not repeated.




Benchiew said:


> From now forth, I hope CREE will report their future emitters using the 85C standards. Makes it easier and more apparent for us.




Why do you hope that? There is nothing to have to hope for, Cree said they were moving to the 85C being standard and that is what they have done.


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## BenChiew

And where did you see CREE saying that?


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## uk_caver

tstartrekdude said:


> he XM-L2 is going to throw 20% better (barely noticeable) because it is 20% brighter in the same optical package as before. The reason some here including myself are talking of viewing angles and being disappointed with them is because is because the XP-G2 got a bigger optic with a narrower viewing angle, thus leading to a 50% bump in lux, something that was sadly not repeated.



I hadn't realised the XP-G/XP-G2 beam shape difference had effects _that_ large (presumably ~25-30% lux boost to add to 15~20% efficiency gains?)
What kind of optic was that with (reflector, TIR or aspheric)?

Scaling/overlaying the spatial distribution curves on the same scale shows what looks like a small difference - XP-G maybe being 2 or 3% brighter over much of the off-axis viewing angles - it's surprising that such a seemingly small change has such an effect.


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## langham

So do any of you have any predictions for improvements that this led would give to the more high end lights that use the U2 bin led? If what is said here is true then you would be able to see an approximately uniform 15% increase (I got closer to 12), and that means that the OSTS TN31 would be able to put out up to 316250cd and at a low 256000cd. I don't think that Saabluster would go for that, but being able to have a 300kcd+ hand held light :naughty:. The construction is slightly different as well, I have heard discussion of possibly flipping the die upside down and that eliminated the tracks as well as dropping to 2 leads to the active area. This seems like it would make the new led easier to de-dome, which I am interested in. The anode seems to have a slightly different construction, and there doesn't seem to be any topside pads for connecting to power source (though after looking at the diagram at the bottom of the data sheet it does seem to be separated down the middle for one side positive and the other negative).


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## uk_caver

It does seem odd, if the light used a reflector, that a more centre-biased LED would give greater lux.

Assuming accurate measurements and not some mundane thing like better positioning with the XP-G2, it would make me wonder if it was a larger dome refracting the 'somewhat sideways' light less and making the effective die size smaller, rather than being some function of a slightly different nominal viewing angle.


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## RoGuE_StreaK

uk_caver said:


> Scaling/overlaying the spatial distribution curves on the same scale shows what looks like a small difference


I did the same thing today with the XM-L and XM-L2 sheets, appears to be a very slight narrowing on the XM-L2. Or it could just be that the graphs aren't _that_ accurate.

Looks like all physical dimensions are exactly the same, I found an updated XM-L sheet that showed it has the same dome radius as the XM-L2.


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## M79

Hi,

I`ve spotted xm-l2 emitters on digikey; min. order quantity is 250 and at the moment there are only t5 (4.62$/[email protected] reels) and t6 (whooping 7.16$/[email protected] reels) cool white bins available (in stock!). 



cheers


PS There are also prices given for many other bins (incl warm white) in 1000 or 1 piece quantities. 

full list:
http://www.digikey.com/scripts/dkse...tock=0&pbfree=0&rohs=0&quantity=0&ptm=0&fid=0


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## moozooh

There are U2s available in single pieces, too. CCT 6650 K, though.


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## hellokitty[hk]

They're available at mouser too.


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## M79

@moozooh: only t5 and t6 cool white are immediately available at digikey
@hellokitty: brilliant, my favourite 2700k`s in stock. Guys please note: xm-l2 2700k (h*t2*e8) 1 piece, 4.82 euro`s and xm-l 2700k (h*t2*e8) 1 piece - 7.0. If it is not only introduction price, then we indeed have some nice price drop here


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## psychbeat

moozooh said:


> There are U2s available in single pieces, too. CCT 6650 K, though.



Get warmer with the top dropped 
DUMDUMDEDOOMEDEDOME


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## monkeyboy

5700k u2 bins are on order at mouser and available to preorder. E2 grouping.


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## bose301s

I really want to get some 3C and 5x tints of the XM-L2, should easily be able to get 3C that are as bright as U2 CW XM-L, if not a bit brighter, should also be able to get 5x tints as bright as T6 CW XM-L.


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## hellokitty[hk]

I think I'll pick up a T5E5 when they are available.
I think it says there will be a batch delivered on the 31st.


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## JB01245

Now at Cutter's 


http://www.cutter.com.au/products.php?cat=Cree+XML-2


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## M79

Did anyone notice the difference (between xm-l vs xm-l2) in spectral power distribution? 
xm-l2 warm white has significantly lower blue part and much more red.
xm-l2 normal white seems to have not that much of orange and amber.
xm-l2 cool white and normal white do not have a shift in peak blue.


btw in both documentations ranges of kelvin 2600-3700, 3700-5000 and 5000-8300 are given. No idea which function is applicable for 3700. A mix betweend normal white and warm white?


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## moozooh

That shouldn't matter. You should remember that "3700" et al. are _nominal_ CCT values. In actuality, every LED produced has CCT such as 3720 or 3698, so the amount of LEDs that hit _precisely_ 3700 or 5000 is negligible. You'll never see those in real life.


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## M79

My question is rather if the warm white curve, which is somehow theoretical too, stands for theretical 2600 or 3700 or the mean of both. If its the mean then Id be interested how the 2600/2700 curve looks like (how much red)


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## langham

Just buy a few and tell us I am sure everyone would like to know.


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## M79

If I only could lay my hands on a spectrometer


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## moozooh

M79 said:


> My question is rather if the warm white curve, which is somehow theoretical too, stands for theretical 2600 or 3700 or the mean of both. If its the mean then Id be interested how the 2600/2700 curve looks like (how much red)



Ah, in that case it's most definitely the mean value. Reporting value from one end of the rather broad spectrum wouldn't make much sense.


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## psychbeat

Looks like the VF might ramp up a bit higher than the 1st gen @ high currents. 

Vinh's been testing em and they only pull ~5a direct drive off 26650. 

Maybe burning them in like the SSTs will help?


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## jayrob

Check this 'brightness bins' list:
http://flashlightwiki.com/Brightness_Bins

Not really a big difference between XM-L U3 vs XML2 U2

But it's great that they keep getting better and better!


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## jtr1962

jayrob said:


> Check this 'brightness bins' list:
> http://flashlightwiki.com/Brightness_Bins


Very useful chart! Thanks for the link!



> Not really a big difference between XM-L U3 vs XML2 U2
> 
> But it's great that they keep getting better and better!


At this stage with the best binned LEDs already more than 50% efficient all we're going to see are incremental improvements of maybe a bin or two a year.


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## psychbeat

jayrob said:


> Check this 'brightness bins' list:
> http://flashlightwiki.com/Brightness_Bins
> 
> Not really a big difference between XM-L U3 vs XML2 U2
> 
> But it's great that they keep getting better and better!



Yeah but are not the xml2 and all other second gen Cree emitters measured @ a higher temp?
Or does this list take that into account ?


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## IMSabbel

jayrob said:


> Check this 'brightness bins' list:
> http://flashlightwiki.com/Brightness_Bins
> 
> Not really a big difference between XM-L U3 vs XML2 U2
> 
> But it's great that they keep getting better and better!



Maaaaybe they changed that page, but what I see is that an XML U3 has about the same flux as a XML2 T6, maybe a little better.

So a solid 2 bin advantage.


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## brted

psychbeat said:


> Yeah but are not the xml2 and all other second gen Cree emitters measured @ a higher temp?
> Or does this list take that into account ?



It takes the temperature into account, using 25 degrees for the newer LED's so they can be compared to older LED's.

It's explained on the Cree page here: http://flashlightwiki.com/Cree


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## langham

Does anyone know where I can see a light that was built with these? Maybe a thread that has mention of the improvements in a direct swap? I don't have mine yet, but I understand that some people have already received them.


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## easilyled

langham said:


> Does anyone know where I can see a light that was built with these? Maybe a thread that has mention of the improvements in a direct swap? I don't have mine yet, but I understand that some people have already received them.



I don't know of one yet, but its only a matter of time before the majority of powerful LED lights will be using them.

I'm expecting that the XM-L2 will be almost indisguishable from the XM-L in real-life terms, just slightly more output when driven at the same current. In practical terms, its like going up a bin from an XM-L U3.

In fact, it seems like its more a marketing exercise in the case of the XM-L to change the terminology to XM-L2 to keep in line with the more real improvement of XP-Gs to XP-G2s and XP-Es to XP-E2s.


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## twl

Malkoff has just released a new Hound Dog XML2 model. The first batch has already been sold out, and I wasn't quick enough to get one.
Anyway, it has 1100 Lumens OTF at turn-on, and sustained 950 OTF.
It draws 1.5 amps from the batteries at 9v, such as 3 CR123 primaries, or 2 x 18500.
The previous Hound Dog XML produced 750 Lumens at turn-on, with sustained 700 Lumens, with 1.25 amp draw from the 9v supply.
So, a quarter-amp more draw, and almost 1.5db increase.
No, lux figures released yet.


So, the first XML2 light is on the market now!


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## langham

easilyled said:


> I don't know of one yet, but its only a matter of time before the majority of powerful LED lights will be using them.
> 
> I'm expecting that the XM-L2 will be almost indisguishable from the XM-L in real-life terms, just slightly more output when driven at the same current. In practical terms, its like going up a bin from an XM-L U3.
> 
> In fact, it seems like its more a marketing exercise in the case of the XM-L to change the terminology to XM-L2 to keep in line with the more real improvement of XP-Gs to XP-G2s and XP-Es to XP-E2s.


They are significantly more bright at the same size and they use all of the same mounting, they have a smooth surface for use in aspherical applications and they are about the same price.


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## TMCGLASSON36

I got some bare emitters coming should be here saturday. Got some good host for them.


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## easilyled

langham said:


> They are significantly more bright at the same size and they use all of the same mounting, they have a smooth surface for use in aspherical applications and they are about the same price.



The figures in the *Wiki link* with both at 25 degrees C show that an XM-L2 (U2) bin is brighter than an XM-L (U3) bin by almost exactly the same amount as an XM-L (U3) bin is brighter than an XM-L (U2) bin.

In other words the new XM-L2 (U2 bin) is about one bin code brighter than the highest XM-L available.

So they could have just have easily called it an XM-L(U4), except that this doesn't sound as good from a marketing perspective.


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## langham

It is a completely different emitter they did some major changes in the design, they just made it with same mounts so that we could replace our old emitters with it.


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## easilyled

langham said:


> It is a completely different emitter they did some major changes in the design, they just made it with same mounts so that we could replace our old emitters with it.



My main point is that its not any brighter than an increase in one bin over the existing latest XM-L (U3)

I'm quite happy to admit that I don't know much else about the XM-L2.

Please feel free to enlighten me about these major design changes. I'm always interested to learn.


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## brted

easilyled said:


> My main point is that its not any brighter than an increase in one bin over the existing latest XM-L (U3)
> 
> I'm quite happy to admit that I don't know much else about the XM-L2.
> 
> Please feel free to enlighten me about these major design changes. I'm always interested to learn.



Looking at the XM-L U3 at 3000mA, output is 1040-1105. That compares with the XM-L2 T6 output of 1044-1119, so that's 2 bins.


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## easilyled

brted said:


> Looking at the XM-L U3 at 3000mA, output is 1040-1105. That compares with the XM-L2 T6 output of 1044-1119, so that's 2 bins.



The bin code after the emitter is arbitrarily assigned.

The most powerful XM-L2 available at present (assigned U2) is one bin code more powerful than the last available XM-L (assigned U3). That is the salient factor.


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## uk_caver

Surely, the most relevant thing is what bins the new LED will be readily available in compared to the old one (allowing for the increased output for a given bin code compared to the old LED).

That may be something that will take a little time to become clear.


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## twl

Let's not forget the new temperature(85*C) for the rating of the XML2, compared to the old XML(25*C).
The XML2 is rated at operating temp, and the old XML is rated at cold turn-on.
Big difference.

The same was true of the XPG2, and we are seeing the XPG2 kicking the butt of the XPG in the real world now.


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## easilyled

twl said:


> Let's not forget the new temperature(85*C) for the rating of the XML2, compared to the old XML(25*C).
> The XML2 is rated at operating temp, and the old XML is rated at cold turn-on.
> Big difference.
> 
> The same was true of the XPG2, and we are seeing the XPG2 kicking the butt of the XPG in the real world now.



The figures in the Wiki link have both XM-L and XM-L2 rated at 25*C


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## WmArnold1

uk_caver said:


> Surely, the most relevant thing is what bins the new LED will be readily available in compared to the old one (allowing for the increased output for a given bin code compared to the old LED).
> 
> That may be something that will take a little time to become clear.



Don't call me Shirley  I think I also read that the XM-L2 reel-prices are about 60% of what the "old" XM-L cost. So, I'm sure that the purchasing folks will push the XM-L2 into production forthwith.


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## Kevin1322

So, for the modders or other ones in the know, how hard can this XM-L be driven and what could be the lumen output at turn on? Anyone know yet?


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## WmArnold1

Kevin1322 said:


> So, for the modders or other ones in the know, how hard can this XM-L be driven and what could be the lumen output at turn on? Anyone know yet?



Cree says that the XM-L2 (U2) will produce 1198 Lu when driven at 3A for as long as your heat-sink can hold the LED junction down to 25 deg-C. (and that's the true challenge)

Otoh, if your heat-sink allows the LED to rise to 85 deg-C (which is easier to maintain, imho) it should still emit 1054 Lu or so. YMMV.


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## Kevin1322

WmArnold1 said:


> Cree says that the XM-L2 (U2) will produce 1198 Lu when driven at 3A for as long as your heat-sink can hold the LED junction down to 25 deg-C. (and that's the true challenge)
> 
> Otoh, if your heat-sink allows the LED to rise to 85 deg-C (which is easier to maintain, imho) it should still emit 1054 Lu or so. YMMV.


Right, but I know modders have pushed other XM-Ls to 5, even 6 amps. So I'm curious (and excited) of predictions for the L2 U2.


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## WmArnold1

Kevin1322 said:


> Right, but I know modders have pushed other XM-Ls to 5, even 6 amps. So I'm curious (and excited) of predictions for the L2 U2.



Hmm.. I wonder how that would affect the 100,000 hour lifetime expectation? Do they let the LED go over 150 deg-C too?


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## ergotelis

So, am i going to be again (as in xp-g2) the first that will make a massive xm-l2 flashlight update? I will try to keep a track of the difference in performance in many flashlights, ordered already some of them.


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## Kevin1322

WmArnold1 said:


> Hmm.. I wonder how that would affect the 100,000 hour lifetime expectation? Do they let the LED go over 150 deg-C too?


Well, I'll never use an LED 100,000 hours haha. As far as modders running them over 150 degrees? I don't know what they do, but I have a couple XM-Ls pushed at 4.42 amps when on high and they are awesome! When I think they are getting too hot, I go down to medium mode. Haven't had a problem so far.


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## psychbeat

It seems that Vinh's initial testing of the XML2 shows a higher VF @ high currents. 
So the first gen might still be best if overdriving above ~3.5amps


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## Epsilon

Kevin1322 said:


> Right, but I know modders have pushed other XM-Ls to 5, even 6 amps. So I'm curious (and excited) of predictions for the L2 U2.



Very dependant on the PCB. Standard alu stars can't handle 5A on the XM-L either. The LED-tech.DE PCB's however, see gains up to 6.5A (50% increase vs 3A, and a 40% increase on 5A).


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## Kevin1322

Epsilon said:


> Very dependant on the PCB. Standard alu stars can't handle 5A on the XM-L either. The LED-tech.DE PCB's however, see gains up to 6.5A (50% increase vs 3A, and a 40% increase on 5A).


Wow, how sweet would that be! Makes me want to switch out the SST-90 in my modded mag.


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## Kevin1322

psychbeat said:


> It seems that Vinh's initial testing of the XML2 shows a higher VF @ high currents.
> So the first gen might still be best if overdriving above ~3.5amps


He will be the one to mod a light or two for me, so I guess I will let him tell me if he thinks it's worth it.


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## bshanahan14rulz

So, kinda surprised not more talk about the guts of the LED?

Nice to see philips flip chip at work.

Interesting to see that they still use bond wires (although, for the cathode instead)

Wonder if they will have a version with that build-up for reducing internal reflection like on the DA series chips?


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## langham

They talked about it briefly a little earlier, but it seems that most want to get a sample prior to talking technical and that hasn't happened for most.


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## bose301s

bshanahan14rulz said:


> So, kinda surprised not more talk about the guts of the LED?
> 
> Nice to see philips flip chip at work.
> 
> Interesting to see that they still use bond wires (although, for the cathode instead)
> 
> Wonder if they will have a version with that build-up for reducing internal reflection like on the DA series chips?



EZ chips have their own light extraction optimizations.


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## bshanahan14rulz

I know I'm pushing your boundaries, but I remember the microstructure on the EZ chips, that's about the only thing observable without getting some sort of inside knowledge or something. I haven't seen a teardown, but based on how the phosphor looks, it wouldn't be much of a stretch of the imagination to think that the same roughened surface is present in the XM-L2. So perhaps all EZ chips will be getting the flip upgrade, and they're just starting with their more used products?

Did you see the article from LEDProfessional that slebans linked to, about how texturing the surface of the LED like the cuticle of the emitting surface of the firefly resulted in a 50% gain in extraction (compared to what, I don't know)? It was interesting that they noted that scaling down the structure actually decreased efficiency and that the relatively macro structure at the same scale as the firefly's abdomen's structure was the best performing size. 

I think the benefit was more about the angles and points, and less about the shingle design, so maybe a roughened surface could be roughened in such a way as to create steep peaks and valleys that terminate in flat or rounded tips. Kind of like a bunch of microscopic funnels that either let light pass out, or reflect it internally up to the tip and out.

After thinking about it, yeah, basically a bunch of microscopic things like the thing on DA chips. `cept more needle-like.


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## bose301s

Well, I can't say too much, but what we are dealing with is Snell's law for TIR based on Critical angles. What you need to do is make sure the light has a better chance at striking at less than the critical angle than it does at an angle greater than the critical angle, there are many was to accomplish this.


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## psychbeat

I'm curious how the new gen will perform when dedomed 
i have A dedomed XML2 module on the way and will report back tho I don't have a dedomed first gen to compare to.


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## bshanahan14rulz

Heh, here's my smart-*** reply: It will probably put out fewer lumens, but will increase the apparent surface brightness.

Dedoming actually plays into our conversation quite well. You see, the reason for the dome isn't to magnify the LED, or to make it bigger. It is to cut down on light being reflected by the inside of the package. Make the dome big enough and you can ensure that light extracted from any point on the LED die will not hit the dome at a shallow enough angle to be internally reflected. Even better, you can ensure that light is incident upon the dome surface at close to a 90 degree angle for maximum transmission.

When you dedome, it ideally creates a flat, smooth surface, which lets most light out, but imagine light coming from a far corner of the die, traveling diagonally across the die, at a very shallow angle that is just enough that it would hit that flat surface. Well, instead of going through it, it will just reflect back into the dome remnants, becoming wasted light that would otherwise have made it out of the package. 

I think it'd be neat to have a progressively index-matched potting material that slowly brings the index of the LED potting material to match that of air. Lot of work, probably not cost effective, but I bet it would get some good gains in extraction in the lab for non-domed LEDs.


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## psychbeat

^^yep 
I'm curious as to how the new surface texture on the 2nd gen behaves dedomed compared with the first gen.


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## RoGuE_StreaK

bshanahan14rulz said:


> it will just reflect back into the dome remnants, becoming wasted light


Just to throw a feline amongst the avians, would this reflected light not further excite the phosphor, increasing it's output ala light recycling?

[EDIT] 2xTrinity mentions the same thing in his reply in the phosphor thread, I'd guess from the reply that the effect is insignificant?


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## 2xTrinity

RoGuE_StreaK said:


> Just to throw a feline amongst the avians, would this reflected light not further excite the phosphor, increasing it's output ala light recycling?
> 
> [EDIT] 2xTrinity mentions the same thing in his reply in the phosphor thread, I'd guess from the reply that the effect is insignificant?





RoGuE_StreaK said:


> Just to throw a feline amongst the avians, would this reflected light not further excite the phosphor, increasing it's output ala light recycling?
> 
> [EDIT] 2xTrinity mentions the same thing in his reply in the phosphor thread, I'd guess from the reply that the effect is insignificant?



For cool white LEDs in particular (where there's a lot of unabsorbed blue light that can drive the phosphor on a second pass through the system) you will see some increase in surface brightness but the recycling process, at least as done via de-doming is very inefficient. You might see a gain in apparent surface brightness not nearly enough to offset the ~50% loss in apparent die area. Every attempt I've made at light recycling schemes personally (where using de-doming, prism retroreflectors or other methods) has resulted in terrible tint shifts (toward pea green) and severe color non-uniformity. 

Also, if you're working with a warm or neutral white LED the tint and efficiency problems are much worse. Finally if you're working with a bare emitter (no phosphor to re-scatter light back out into usable range of angles) light recyling will be a pretty negligible effect. 


I'm not sure how the company who Saabluster is licensing light recycling technology from for the DEFT-X was able to solve these issues to be honest.


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## 2xTrinity

bshanahan14rulz said:


> Heh, here's my smart-*** reply: It will probably put out fewer lumens, but will increase the apparent surface brightness.
> 
> Dedoming actually plays into our conversation quite well. You see, the reason for the dome isn't to magnify the LED, or to make it bigger. It is to cut down on light being reflected by the inside of the package. Make the dome big enough and you can ensure that light extracted from any point on the LED die will not hit the dome at a shallow enough angle to be internally reflected. Even better, you can ensure that light is incident upon the dome surface at close to a 90 degree angle for maximum transmission.
> 
> When you dedome, it ideally creates a flat, smooth surface, which lets most light out, but imagine light coming from a far corner of the die, traveling diagonally across the die, at a very shallow angle that is just enough that it would hit that flat surface. Well, instead of going through it, it will just reflect back into the dome remnants, becoming wasted light that would otherwise have made it out of the package.
> 
> I think it'd be neat to have a progressively index-matched potting material that slowly brings the index of the LED potting material to match that of air. Lot of work, probably not cost effective, but I bet it would get some good gains in extraction in the lab for non-domed LEDs.



A flat gradient index slab going from 1.5 to 1 would act like a perfect antireflection coating and would eliminate partial reflection losses for rays at less than the critical angle, but it would not prevent total internal reflection for rays above the critical angle. Magnification of the die while it may not be the goal of the dome is a necessary consequence of extracting the otherwise trapped light.


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## bose301s

psychbeat said:


> ^^yep
> I'm curious as to how the new surface texture on the 2nd gen behaves dedomed compared with the first gen.


Hope someone does dedome one soon, will be interesting to see.


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## bshanahan14rulz

I have one, single XM-L2, so... NOT IT!


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## langham

Good to see I am not the only one in Tennessee. Have you guys seen the deal that thrunite has on the new versions of the TN31 and TN30? They just put the new XM-L2 emitter in both lights and discounted them, if anyone is interested. I personally am going to order 2 of the bare emitters and install one in my TN31.


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## argleargle

Cree XM-L2 @ $8 each. Awesome!


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## p7united

I bought a bare XM-L2, unfortunately I have terrible soldering skills. I wonder when the stars will start hitting the market.


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## langham

They are already available, are you willing to sell me the bare emitter? I tried to buy some, but have had no contact with the seller since that day.


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## psychbeat

Speaking of bare- I received my XM-L2 DE-DOMED P60 module today. 
It's running @4.2a in a SMO reflector. 

The hotspot seems to be more intense than my neutral XR-E module. 

I only have first gen XMLs with the dome intact to compare with but this seems just as bright with a smaller more intense hotspot. 

I'm pretty excited. 

The tint is 5000K-ish & vanilla w no green!
Started out as "6500k" but I'm not sure what exact tint it was.


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## Canuke

Psychbeat or others: how does XM-L2 compare to the original for color uniformity across emission angle? I've heard reports that the XP-G2 improved in this regard.


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## psychbeat

Canuke said:


> Psychbeat or others: how does XM-L2 compare to the original for color uniformity across emission angle? I've heard reports that the XP-G2 improved in this regard.



My only XML2 is dedomed & I think most of the tint shift on the previous gen was from the dome/optic. 

No tint seperation noticeable on my dedomed module


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