# Cree XM-L vs. Luminus SST-90?



## EvilJack

Can someone give a brief explanation in the difference in these two emitters? I am a novice and have searched both this site and Google and can't really find a simple answer. I'm considering two similar lights with these two emitters and wondered the difference in throw / flood, etc. Thanks.


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## MikeAusC

The XM-L can be run up to 3 amps and is a smaller chip

The SST-90 can be run at up to 11 amps, so it will put out more total light, but it's a larger chip and older generation so it will be dimmer for a sharply focussed image, even when drawing a lot more power.

Go to the Cree and Phlatlight sites to download the datasheets.


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## Vortus

XML is good to about 1000 lumens if sinked well. SST-90 is good to about 3000 lumens. But compared to each other, the SST90 is huge next to a XML. Maybe 7-8X bigger, maybe more. The SST90 needs to be in a big flashlight to make it throw due to its size. In smaller lights it makes a great flood though.


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## Jekyll & Hyde

J: Which lights are you looking at?

H: BTW, welcome. I'm pretty new too.

J&H


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## Bronco

The SST-90 has an emitter surface area of 9 square millimeters. The XM-L's emitter is 4 square millimeters. Thus if you're looking for a light that can project a tight beam a long distance, the SST will require a much larger reflector. The SST also requires much more amperage to reach its maximum output. That means more and/or bigger batteries unless you're willing to settle for significantly decreased runtimes. This increased amperage also creates lots of heat rather quickly. Figure on seeing 1800 to 2200 actual "out the front" lumens from the SST-90 in most lights. Conversely, the XM-L is more efficient but only capable of around 750 to 1000 lumens in most lights. Still it will provide very good throw with a relatively smaller reflector.


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## peterharvey73

The Luminus SST-90 is a 3mm x 3mm square for a total of 9 mm square die size.
The Cree XM-L is 2mm x 2mm for a total of 4mm square die size.
The Cree is newer in design, so it is more efficient.
The Cree XM-L can be driven up to 3 amps within recommended specifications to produce 1000 emitter lumens.
However old, the SST-90 is still much larger in size, so it can withstand more heat build-up, thus it can be driven to 9 amps in recommended specifications to produce some 2200 emitter lumens.

Because the SST-90 is larger in size, and produces more lumen output, it will tend to have a larger hot spot, and have a brighter spill, and more overall flood.

I am not exactly sure of the surface brightness of the SST-90 versus the XM-L, however from my memory, the SST-90 is no slouch in surface brightness at all - in fact it's surface brightness is better than the old XPG-R5, and only slightly inferior to the very old XR-E R2.
Thus, throw will be mostly dictated by the diameter of the reflector, not the surface brightness of the emitter.

Btw, just because the surface area of an emitter is large, it doesn't necessarily mean that it's surface brightness will automatically be low.
Also, just because the emitter is larger, it doesn't mean that it must have a proportionately larger reflector to throw as well as the smaller emitter.
These are common mistakes I use to make myself in the understanding of throw etc.

Don't focus too much on paper specifications, and generalisations about emitters.
At the end of the day, the best way to compare the two flashlights is to switch them on, and test them side by side.
If not possible, look for youtube videos of their beam performance to help.
Or if worse gets to worse, start a new thread on cpf like this one, for help...


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## Bronco

peterharvey73 said:


> Thus, throw will be mostly dictated by the diameter of the reflector...
> 
> Also, just because the emitter is larger, it doesn't mean that it must have a proportionately larger reflector to throw as well as the smaller emitter.



I appreciate your attention to detail, but two such seemingly contradictory statements might be confusing to someone like the OP who's relatively new to the high performance flashlight game. If we control for the most important variables (i.e. limit ourselves to discussing reflectored lights, assume that the manufacturers have selected reflector shapes that are reasonably well suited to the respective emitter sizes and allow for similar surface brightnesses) then it's generally the case that the larger emitter will require a larger reflector to match the throw of a smaller emitter.


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## yellow

to make it short:

the XM-L is the newer one and can give _really MUCH _light.
the SST is older, can give double than that _really MUCH _light but needs 4 times the power for it.

when both are inside a housing that can move the heat away from the led - that is necessary!!! - 
the one with the XM-L will get really hot,
the one with the SST will get burning hot, coocing the led to death.

the XM-L (which is floody in itself) will give a "tighter" beam, while the SST will be some kind of a flood beam.
Like double (?) the diameter.


PS: I con not think of any battery source that might be able to power up the SST, when it really can be driven with 11 Amps.
Even the 2.8 A for the XM-L is hard for most setups (at least for some useable time)


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## MikeAusC

Both the XM-L and SST90 have Lambertian angular distribution - i.e. beamwidth of about 120 deg at 50% brightness.


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## jorn

peterharvey73 said:


> Thus, throw will be mostly dictated by the diameter of the reflector, not the surface brightness of the emitter.


The surface brightness + the size of the reflector is the key to throw. Take two leds and put them in a reflector, the one with the highest surface brightness will have the best throw in any reflector. The reflector shapes the beam, but it focuses on a "point source". If that point on the led is brighter, the hotspot will be brighter. All lights have better throw in hi mode than lo mode because surface brightness is better in hi mode.


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## HB021

peterharvey73 said:


> The Luminus SST-90 is a 3mm x 3mm square for a total of 9 mm square die size.
> The Cree XM-L is 2mm x 2mm for a total of 4mm square die size.


The die of SST-90 is 8mm diameter and the base is 10x11mm, this should be 50mm square die size?;
http://www.luminus.com/products/SST-90_2_3543760270.pdf


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## MikeAusC

When talking about the image size etc all that matters is the silicon die size, which is 3 x3 mm for the SST-90 - the yellow square you can see through the lens. See page 9 of the Rev 7 Datasheet.

No, it doesn't look 3x3mm, but that's because it gets magnified by the lens.


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## MikeAusC

peterharvey73 said:


> . . . . . The Cree XM-L can be driven up to 3 amps within recommended specifications to produce 1000 emitter lumens. . . . . .



According to the SST-90 datasheet, the N3 bin delivers 950 to 1000 lumen at 3.15 amp.


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## yliu

the SST-90 has a much bigger die than the XML, so it will require a bigger reflector to get it to throw. The SST-90 can be driven at much higher currents, and can achieve higher output than the XML. 

There aren't many flashlights using the SST-90, you are only gonna find SST-90 "searchlights" that are much bigger and bulkier. On the other hand XML are available on much smaller form factors such as 2xCR123.

I'm guessing that are considering the Olight SR90 vs SR92 or RRT-3 or TK70, since they are more or less in the same size category. Not that the XML models use 3 XML chips and will give you more output than a single SST-90.


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## MikeAusC

yliu said:


> the SST-90 has a much bigger die than the XML, so it will require a bigger reflector to get it to throw. . . . .



The XM-L is 2x2mm, the SST-90 is 3x3mm - so does the reflector need to be 1.4mm wider ????

Please explain why, and by how much, the reflector needs to be bigger.


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## HB021

MikeAusC said:


> The XM-L is 2x2mm, the SST-90 is 3x3mm - so does the reflector need to be 1.4mm wider ????
> 
> Please explain why, and by how much, the reflector needs to be bigger.



I don't really know how to calculate it but perhaps some expert could say, but it's not 1,4mm bigger it's more likely 30mm bigger (my guess is based on YouTube video looking at beampattern and size of the reflector). U'll need to take footprint size, die size, beamangle and surface brightness into consideration....


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## MikeAusC

If you take an XM-L out of a Reflector/Aspheric that shows a focussed image of the die, and replace it with an SST-90 with the same surface brightness, you will end up with - 

- A hotspot that's 50% wider (3/2)
- A hotspot that has 2.2 times the area (9/4)
- A hotspot that's the same brightness.

It's simple geometry and physics.


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## yliu

MikeAusC said:


> The XM-L is 2x2mm, the SST-90 is 3x3mm - so does the reflector need to be 1.4mm wider ????
> 
> Please explain why, and by how much, the reflector needs to be bigger.



I think you'll need a much more wider reflector to compensate for the bigger die size.


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## jimmy1970

A closer comparison would be the Cree XML and the SST-50.


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## MikeAusC

yliu said:


> I think you'll need a much more wider reflector to compensate for the bigger die size.



Please explain why a 1.4mm increase in Die diagonal requires a "much more wider " reflector.


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## Bronco

MikeAusC said:


> If you take an XM-L out of a Reflector/Aspheric that shows a focussed image of the die, and replace it with an SST-90 with the same surface brightness, you will end up with -
> 
> - A hotspot that's 50% wider (3/2)
> - A hotspot that has 2.2 times the area (9/4)
> - A hotspot that's the same brightness.
> 
> 
> It's simple geometry and physics.



Exactly. Or put another way, if you want the two emitters to project a hotspot of a similar diameter, the SST-90 will require a larger diameter reflector.


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## MikeAusC

Bronco said:


> Exactly. Or put another way, if you want the two emitters to project a hotspot of a similar diameter, the SST-90 will require a larger diameter reflector.



No, the diameter of the reflector is not what determines the size of the focussed image.


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## yellow

but its 99 % of what determines the size of the image,

and constantly typing something else only raises additional questions of the ppl who dont know the whole thing


short:
with the SAME focusing device, a
XP-G makes a small dot, 
XM-L makes a dot double the diameter (4 times the surface)
SST 90 makes a dot of again (almost) double the diameter (to the XM-L)

so when the goal is a focused, bright beam, a XP-G with 1/3 lumen less will still be brighter, while the other 2 will be floody.
The "higher" brightness of the latter must be "purchased" with a considerably higher power consumed.

... or with a MUCH bigger (wider + deeper) reflector


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## MikeAusC

peterharvey73 said:


> . . . .
> We should never say that "the emitter is larger, so it needs a larger reflector to maintain the throw".
> I used to mistakenly think like this myself...



Thankyou. And to answer the question about what affects hotspot size . . . . it's the focal length of the reflector/aspheric. And that's most visible in the curvature of the reflector/aspheric. 

Big reflectors/aspherics can have long or short focal lengths. Small reflectors/aspherics can have long or short focal lengths.

Now if only Dr Jones were still around . . .


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## Jekyll & Hyde

Jekyll & Hyde said:


> J: Which lights are you looking at?


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## Bronco

MikeAusC said:


> Now if only Dr Jones were still around . . .



Good grief.  

Yes, that's exactly what a new member with one post who's just now being introduced to the hobby needs, a post graduate equivalency lecture on the esoterica of focal length and voltage sag from Dr. Jones. While we're at it, why don't we bring in a few M-Theory physicists to discuss the finer points of phosphor excitation at the sub-atomic particle level. 

All I'm trying to do is help the OP figure out whether he wants his light to throw well, flood well or do something in-between and then explain to him *in very general terms* what the likely real world consequences of that decision will be with respect to the emitters he's mentioned based on the current offerings of most flashlight manufacturers. Like it or not, *because of the way manufacturers produce torches these days* an XM-L based flashlight advertised as being primarily a flooder (think 4Sevens Quark MiNiX 123), is likely to look very much different from an SST-90 based flashlight advertised as being optimized for throw (think Olight SR-90). It may be helpful to the OP to understand how these differences are likely to manifest themselves in terms of length, diameter, weight, run time, etc. 

I think the kind of discussion you and Peter are trying to have can be very interesting and informative. I'm just questioning the appropriateness of such a focus in this particular thread.


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## peterharvey73

Bronco said:


> Like it or not, *because of the way manufacturers produce torches these days* an XM-L light advertised as being optimized for flood, is likely to look very much different from an SST-90 light advertised as being optimized for throw.



Yes, you're right - we're getting too technical for the new cpf member; we'll keep it simple.

Just another very important point.
We have three factors at play here:
1) Emitter die size, eg 
- small XP-G @ 1.38x1.38=1.92 mm sq, 
- midsize XM-L @ 2x2=4mm sq, and 
- large SST-90 @ 3x3=9 mm sq.
2) Surface brightness in lumens per mm square.
3) Total output of light in lumens.

Firstly, die size and surface brightness.
We note that the size of the emitter or die, doesn't necessarily determine the surface brightness at all.
The surface brightness, and hence the throw, can be whatever the engineers squeeze out.
Note how the biggest emitter, the SST-90 can still pump out a whopping 300 lumens per square millimeter in surface brightness - better than the small XP-G, and the medium sized SST-50 @ 5mm sq.
_Thus, a big emitter doesn't necessarily have less surface brightness - a big emitter can have high surface brightness if the engineers wish so._
Eg, if Saabluster or Ra Ma Sha uses active fan cooling or liquid cooling etc, they could overdrive the emitters even more, to produce more lumens, and hence more surface brightness within any particular die dimensions.
We shouldn't be embarrassed by the term "overdrive", since overdrive only means driven harder than the manufacturer's maximum specs, but who is the manufacturer to set the maximum specifications in the first place? 
Only God knows what the maximum specifications really are.

Secondly, die size and the total volume output in lumens.
The big emitters certainly have more total volume output in lumens.


Therefore, unfortunately we can't say that an XM-L is optimised for flood, while the SST-90 is optimised for throw.
- *Both *the XM-L and the SST-90 can throw, depending on their surface brightness, [which I don't know exactly, but does not vary greatly].
- However, when it comes to _total volume output in lumens_, the bigger emitters like the SST-90 wins hands down, over the midsize and smaller emitters like the XM-L etc!


Effect of Reflector Diameter
Note that both the midsize XM-L and the large SST-90, in a *small *25 or 30 mm bezel diameter, are relatively *floody;* an excellent example is the Zebralight SC600.
However, when both emitters are in say a *large *60mm bezel diameter like a 2x18650 like M3X/Catapult V3/M3C4 etc, then both emitters become _*very throwy*_!
When both emitters are in an oversized 100 mm bezel diameter like an SR90 etc, then both emitters become _*super-throwy!*_

In fact, with a *large *bezel diameter of 60mm, or an oversized bezel diameter of 100mm, the only way to get *flood *here, is to use a _*"Triple* *Emitter"*_ eg a triple XM-L which draws 3x 3 amps.
A Triple SST-90 would draw 3x 9 amps = 27 amps; thus we don't see any triple SST-90's around.

In short, the bigger SST-90 emitter etc is floodier than midsize XM-L.
Meanwhile, both XM-L & SST-90 emitters are relatively floody in small reflectors.
Both XM-L & SST-90 are throwy in large reflectors.
One can be slightly moreso than the other depending on it's surface brightness.


Surface Brightness vs Reflector Size
We know both surface brightness & reflector diameter are important.
Notice how surface brightness varies by *only 20%*, eg 250 lumens/mm sq versus 300 lumens/mm sq.
However, notice how reflector diameter can vary *four-fold *or more! Four times larger!
Eg a 23mm bezel diameter of a V10R versus the 106mm bezel diameter of the TK70!
Thus, although we should pay attention to the emitter type and the surface brightness, we should pay a lot lot more attention to the bezel hence reflector diameter...


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## WmArnold1

Very nice post, @peterharvey73!.. - Responding to the Op;

Per CPF here; the XM-L (T6 bin) emitter can survive being driven at up to 10 Watts and, similarly, the SST-90 can survive being driven at up to 32 Watts! Respectively, that's 910 and 2250 emitter lumens; _*assuming that those emitters are dissipating all the waste heat they generate properly*_. That's why hot lights [pun intended] have to throttle themselves down to sustainable power levels after a few minutes.

Fyi, 70% or more of said power must be dissipated as heat when operating at mid to max levels. Subsequently, the thermodynamics of a given flashlight body limits the maximum sustainable output more than anything else. Got fins? Size matters! Further, although the SST-90 can become almost 2.5 times as bright as the XM-L, the SST-90 requires more input power to generate the same number of lumens. But, the XM-L can't compete above 910 lumens without teaming up.. This is why triple-XM-L's are competing with single SST-90's for raw output numbers in the marketplace today; three XM-L @ 3A > one SST-90 @ 9A..

Keep-in-mind though, if you want to focus & throw 800+ lumens within a nice beam-shot; you're probably looking for a single emitter SST-90 - as the preceding posts have excellently explained. As others have already said too; you've gotta consider the light as a complete unit - there are numerous trade-offs.


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## Bronco

Peter, I agree with WmArnold wholeheartedly. That was a very informative post presented in a way that is accessible to all. 

We may have had a very minor misunderstanding relative to your point below:



peterharvey73 said:


> Therefore, unfortunately we can't say that an XM-L is optimized for flood, while the SST-90 is optimised for throw.



I've edited my original post to make it clear that I was referring to various production flashlights being manufactured with these emitters rather than the emitters themselves.


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## EvilJack

OP here - sorry I've had a real hard time posting to CPF in the past day or so. But wow, thanks to everyone for all the super informative and educational replies in this thread. I'm fairly sure I learned as much in this thread as I have to date here at CPF. 

As fyi, I was looking at some smaller lights - the Maelstrom S12 (SST-90) and the Maelstrom X10 (XM-L). Maybe I should be considering other makes / models? I'm just not familiar enough to look elsewhere yet. I have a Quark 123 and love it so I was sticking to what I know and appreciate. Those two lights are both running on the same battery and seem to be in the same host. I'd prefer a tighter beam on throw so perhaps I should choose the X10 this time?

Thanks again to everyone.


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## peterharvey73

That's fine Bronco.
When I first got into flashlights in April, I use to post that a big emitter needed a proportionately big reflector to be able to maintain the throw etc.
Eventually, GCBryan and Big Chelis etc corrected me & showed me the correct concepts, so now I have a better understanding of the science behind emitters and throw etc.

There's a lot of things I still don't know about flashlights - like focal lengths etc; I'm glad I'm not into asphericals...


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## WmArnold1

@EvilJack - Fyi, there's plenty of *great* reviews at CPF!.. :devil:


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## hapiness

the following link is about the led emitter index. 
it contain some photos of xm-l, sst-90 or others led emitter, which can do you a favor, as far as i am concerned
[URL="http://www.thebrightsideforums.com/viewtopic.php?f=14&t=224"]http://www.thebrightsideforums.com/viewtopic.php?f=14&t=224






[/URL]*





*http://www.thebrightsideforums.com/viewtopic.php?f=14&t=224http://www.thebrightsideforums.com/viewtopic.php?f=14&t=224


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## Jekyll & Hyde

EvilJack said:


> I was looking at some smaller lights - the Maelstrom S12 (SST-90) and the Maelstrom X10 (XM-L).


J: Hi EJ. Thanks for replying.

H: I had the same decision to make a while back myself.

J: Except I was looking for a floodier light. So I chose an S12 (along with the nice 4sevens charger and batts).

H: It's a nice strong light, so there's still a fair bit of throw to go along with that bright wide spill.

J: But if you're looking for max throw, then the XM-L will be a bit better choice (in this body).

H: Or better yet, mebbe check out a different LED (or light) altogether. Check the reviews, beamshots, videos, etc.




EvilJack said:


> AI have a Quark 123 and love it so I was sticking to what I know and appreciate.


J: Yup. One light I really like is my Quark 123-2 Turbo X (Neutral White XM-L). They still stock these at both 4sevens and Going Ge&r.

H: It is a bit more compact (doesn't absolutely require a holster like the Maelstroms), it's lighter, almost as strong (in real-life usage), and has more battery options.

J: Plus I really like the tint, and (Quark Tactical) UI.

H: UI depends on what you need this light for though, since it's really a 2-mode UI (loose head/tight head). Modes are then programmed via twists and clicks.

J: With the Maelstrom, it's only High and Higher (twist the tail). With memory.


H: So which light to choose? That's a toughie.

J: I'd really recommend evaluating what you want to use this light for, and how you want to use it.

H: Since a big bright light will still be next to useless if it doesn't match your needs!

Best of luck!
J&H

ps. You might also want to check out the Maelstrom X7 (Cool or Neutral). Even more battery options.


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## peterharvey73

EvilJack said:


> OP here - sorry I've had a real hard time posting to CPF in the past day or so. But wow, thanks to everyone for all the super informative and educational replies in this thread. I'm fairly sure I learned as much in this thread as I have to date here at CPF.
> 
> As fyi, I was looking at some smaller lights - the Maelstrom S12 (SST-90) and the Maelstrom X10 (XM-L). Maybe I should be considering other makes / models? I'm just not familiar enough to look elsewhere yet. I have a Quark 123 and love it so I was sticking to what I know and appreciate. Those two lights are both running on the same battery and seem to be in the same host. I'd prefer a tighter beam on throw so perhaps I should choose the X10 this time?
> 
> Thanks again to everyone.



Selfbuilt measured the *X10 XM-L *on a *1x26650 *with *46mm* bezel @ *310* meters throw.
There is no Selfbuilt measurements for the *S12 SST-90* on *1x26650* with *46mm* bezel's throw*?*
Selfbuilt measured the *S18 SST-90* on *6xCR123* with *63mm *bezel @ *361* meters throw.
Meanwhile the *S18* *SST-90* on *6x16340* with *63mm* bezel @ *377 *meters of throw.

The S12 and X10 have the same midsize 46mm bezel, but differ on emitter only - SST-90 versus XM-L.
The S12 SST-90 with 46mm bezel would _throw roughly the same _as the X10 XM-L 46 mm bezel. _Give or take._
Unfortunately, there is no Selfbuilt throw measurements for the S12 SST-90 with 46mm bezel?
It is hard to guess.
The S18 SST-90 *cheats *with a whopping *63mm* bezel to throw a whopping 377 meters, easily passing the X10 XM-L's 310 meters, thus the SST-90 is no slouch; so if the one emitter is better than the other, and if one emitter has more surface brightness than the other - it won't be by much!!
See how the reflector diameter has more influence on throw than the emitter???

When we consider that the S18's SST-90 has nearly 1.5 times more reflector diameter, but achieves only 20% more throw, we can say that the X10's XM-L has better surface brightness than the S18's SST-90.
However, just by increasing the S18's bezel diameter from 46 to 63mm, the S18 has still managed to throw 20% more than the X10 XM-L.
Again, reflector diameter plays a greater role in throw, than the emitter and it's surface brightness.

Another thing - flood, and total lumen output.
Look at Selfbuilt's table below.
Notice how the X10 XM-L 46mm bez outputs only 770 lumens?
While the S18 SST-90 63mm bez outputs roughly 1350 lumens!
Thus, even if the XM-L does match or out-perform the SST-90 for surface brightness & throw, the SST-90's 9mm sq die has totally out-flooded the XM-L's 4mm sq die!

However, remember that the SST-90 needs an inefficient V8-like 6xCR123/16340's, while the XM-L is a compact, economical & thrifty turbocharged 4 cylinder on just 1x26650.

In conclusion, the S18's SST-90 draws up to 9 amps, requires 6x16340's making the S18 very big, long, and heavy @ 700 grams!
It's SST-90 totally out-floods the XM-L on the lumen count!
Although the SST-90 may have inferior surface brightness to the XM-L emitter, it won't be by very much.
Because reflector diameter plays a bigger role in throw than surface brightness of the emitter, just by increasing the S18 SST-90's bezel diameter from 46mm to 63mm, the S18 SST-90 has still managed to out-throw the X10 XM-L by 20%, or 67 meters, from 310 to 377 meters.

The XM-L emitter is modern, efficient, with an excellent power to weight ratio.
The SST-90 is old and inefficient, but wins on sheer brute...


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## peterharvey73

OP, you wanted to know about X10 XM-L versus S12 SST-50?
I just strolled into this thread by chance:
http://www.candlepowerforums.com/vb/showthread.php?318735-The-1000-Lumen-Beamshot-Thread-SR90-SR91-SR92-Big-Bruiser-Dry-3*XML-Scor-Turbo/page2

Look at vinhnguyen54's photos below.
It seems that the X10 XM-L does indeed out-throw the bigger & cooler white hot spot of the S12 SST-50?
Meanwhile the Eagletac M3C4 XM-L with a bigger 61mm bezel - Selfbuilt has measured to throw 394 meters, throws the furthest of the three...








S12 SST-50 46mm bezel






X10 XM-L 46 mm bezel






M3C4 XM-L 61mm bezel


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## DM51

The thread is principally concerned with emitter types rather than the flashlights that use them, so I'm moving it from LED Flashlights to LED.


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## saabluster

DM51 said:


> The thread is principally concerned with emitter types rather than the flashlights that use them, so I'm moving it from LED Flashlights to LED.



Good call. Never saw it wherever it was prior. Quite a few errors in this thread as well. I'll try and address them when I don't have a headache.


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## peterharvey73

We'd be most honoured to read your input Saabluster - hopefully that headache subsides quickly...


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## Dr.Jones

I accidentally stumbled across this thread and even found my name mentioned... 

Here's a newer version of that LED spec table:





Hm, isn't the XP-E R4 available meanwhile? Might have to update again.

I'll stick to the max specs, so the XM-L U2 @3A has 30% less 'surface brightness' than the XR-E R2 EZ900 @1A (T6:35%).
To get the same throw, it needs a 20% bigger reflector (in diameter) (T6:24%)

Regarding throw, there isn't much difference between [email protected] and [email protected]; the SST-90 will emit a clearly larger beam with more flux (lumen), but a similar intensity and throw. The larger beam will usually be more fun, but more difficult to power (30W) and heat-sink.


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## peterharvey73

Thanks for giving us the latest XM-L data Dr Jones.
I knew the XM-L's surface brightness wasn't that great, but I'm surprised the SST-50 & SST-90's surface brightness is so much better than the XM-L - because so many cpf members have been saying that the Cree XM-L has better surface brightness & throw than the Lunimus SST-50 & 90...


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## saabluster

MikeAusC said:


> The SST-90 can be run at up to 11 amps, so it will put out more total light, but it's a larger chip and older generation so it will be dimmer for a sharply focussed image, even when drawing a lot more power.


The SST-90's maximum allowed current is 9A not 11A. I believe it was at one time but Luminus learned the hard way they were not being conservative enough and throttled back.



Vortus said:


> XML is good to about 1000 lumens if sinked well. SST-90 is good to about 3000 lumens. But compared to each other, the SST90 is huge next to a XML. Maybe 7-8X bigger, maybe more. The SST90 needs to be in a big flashlight to make it throw due to its size. In smaller lights it makes a great flood though.


 XM-L tops out at about 1040lm @3A and the SST-90 [email protected]



MikeAusC said:


> According to the SST-90 datasheet, the N3 bin delivers 950 to 1000 lumen at 3.15 amp.


Now can you actually find an N3 bin in stock anywhere? I couldn't. N2 is the best I see. :shrug:




MikeAusC said:


> If you take an XM-L out of a Reflector/Aspheric that shows a focussed image of the die, and replace it with an SST-90 with the same surface brightness, you will end up with -
> 
> - A hotspot that's 50% wider (3/2)
> - A hotspot that has 2.2 times the area (9/4)
> - A hotspot that's the same brightness.
> 
> It's simple geometry and physics.


Very true. If you could manage to get an SST-90 to have the same surface brightness that is. Not likely in the real world. 




MikeAusC said:


> No, the diameter of the reflector is not what determines the size of the focussed image.


Yeah it kind of is. It is not the only thing but it is a huge component. The size of the emitter obviously sets your first potential and the second half of the equation is the distance of the reflective/refractive surfaces. In a reflector increasing the diameter moves the reflective surface away from the emitter and therefore makes a smaller projected image.



peterharvey73 said:


> The surface brightness of a die, can be whatever the engineers want it to be...


I maybe misunderstanding you here but you make it sound like surface brightness is a parameter that can be tweaked the same as they may adjust the dopants in the chip. They can't just make it whatever they want it to be. The key to surface brightness is the base performance of the chip in question. That is what puts the major functional constraint on surface brightness. And then to a lesser degree the size of the chip puts a functional constraint on it as well. By functional constraint I am not referring to the arguably arbitrary constraint put on it by the manufacturers. If Cree made the SST-90 they would not spec it at 9A for max drive. 

Since LEDs put out just as much or more heat than light you can consider a 9mm2 die as nothing more than a 1mm2 die with a heater 8mm2 surrounding it. Adding all that extra heat depresses the output and puts more thermal strain on the die. What this means is that you cannot expect to get current densities on a large chip as high as you could on a small chip with equivalent stress levels. The base chip in the SST-90 is not as good as the XM-L so why do they spec a higher current density than the XM-L even though it is much larger and inferior? Seems quite arbitrary to me. 




peterharvey73 said:


> We shouldn't be embarrassed by the term "overdrive", since overdrive only means driven harder than the manufacturer's maximum specs, but who is the manufacturer to set the maximum specifications in the first place?


Agree wholeheartedly.  Cree seems a little conservative to me and Luminus a little too generous although they seem to be learning. 



Dr.Jones said:


> I accidentally stumbled across this thread and even found my name mentioned...
> 
> Here's a newer version of that LED spec table:
> 
> 
> 
> 
> 
> 
> Hm, isn't the XP-E R4 available meanwhile? Might have to update again.
> 
> I'll stick to the max specs, so the XM-L U2 @3A has 30% less 'surface brightness' than the XR-E R2 EZ900 @1A (T6:35%).
> To get the same throw, it needs a 20% bigger reflector (in diameter) (T6:24%)
> 
> Regarding throw, there isn't much difference between [email protected] and [email protected]; the SST-90 will emit a clearly larger beam with more flux (lumen), but a similar intensity and throw. The larger beam will usually be more fun, but more difficult to power (30W) and heat-sink.


Yes the XP-E R4 is supposed to be available. BTW love your chart! This is by no means exhaustive but here are few adjustments I would suggest. 

SST-90 N2(highest available bin) [email protected] 285mm2

XM-L U2 [email protected] 260mm2

XP-C Q4 [email protected] 285mm2 ,die size .46mm2

XR-C shows available bin of Q2 in the datasheet and Q3 shows available on the webpage for it on Cree's site.

Although I would not add it to the list I believe that it is helpful to know that the XM-L at similar current densities as the SST-90 outperforms. The XM-L at 4A which is eqivilent to the SST-90's 9A puts out 304mm2 vs the SST at 285mm2. This is with the Cree less stressed to boot. Also the XP-C at a *very* reasonable 700mA has an intensity of 356mm2. Very impressive that! That is not stressing that die at all either. Hence why I can drive it 3 times the rated max.

edit: I thought I'd add that I ran an XR-C over 3A the other day. Was working on a new method of heatsinking and was quite surprised to see the result. It held at 3A "fairly" well but 3.2 was just too much for the poor thing.


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## peterharvey73

Thanks for your lovely input Saabluster.
We'd love to ask you more questions about lights, but we don't want to waste your time..


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## saabluster

peterharvey73 said:


> Thanks for your lovely input Saabluster.
> We'd love to ask you more questions about lights, but we don't want to waste your time..


I'm glad to help. If you have any questions just ask. Although it does take a lot of time for me to put together some of these posts(that last one took about 3 hours) I don't think it is a waste of time. I don't always have the time to give but if I can I will. Ask away.


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## Pizeer

peterharvey73 said:


> Back in the 80's and 90's, would we have automatically discounted Mike Tyson as a boxer because he was only 5'11", while Larry Holmes & Trevor Berbeck etc was 6'2" to 6'4"?
> When we compare a four or six cylinder turbo with a V8, do we automatically jump to the conclusion that the V8 will out-perform the former two?
> Likewise, when we compare a SMO with a LOP reflector, do we automatically jump to the conclusion that the SMO will out-throw the LOP reflector?
> Or do we be smarter, .....
> 
> Wow thanks, this is really good learning for me.


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## deadrx7conv

I wonder what would happen to the SST if Cree came out with LEDs as big as the SST50, 80, 90.....? 5-10mm² Cree flashlight LED? add xpg2/xpe2... to that above chart?


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