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Thread: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamshots)

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    Default Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamshots)


    The mighty war hammer Mjölnir (myol-neer), for those of you who have not caught this summer's blockbuster or are not versed in Marvel Comics' version of Norse mythology, was commissioned by Odin (ruler of the Norse gods) and crafted from Asgardian metal by dwarven blacksmiths using the core of a star as a mold. Although it was a formidable weapon already, Odin further enhanced it with spells that bolstered its powers significantly. Odin eventually passed it on to his son, Thor after he proved himself worthy of wielding it through various trials.

    So why might you ask am I mentioning Mjölnir in a flashlight review?

    Because it was what came to my mind when I first saw pics of the XT20. Albeit the one I envisioned was not the historical one of yore that bears a passing resemblance to a boat anchor but rather the version popularized by Marvel in Journey into Mystery Issue #83 where Thor and Mjölnir were first introduced. Quite simply, the name translates into "crusher" no doubt due to its intended use. The XT20 could arguably be called as such given the girth in its dual-head which bears two "stars" of its own in the form of XM-L U2's. Let's see how well the XT20 doles out its respective "crushing".



    MANUFACTURER SPECS
    • Two CREE XM-L U2 LEDs, each with a lifespan of up to 50,000 hours.
    • Three lighting modes and one flashing mode:
    o High brightness: 1200 lumens (2 hr)
    o Medium brightness: 370 lumens (5.3 hrs)
    o Low brightness: 10 lumens (205 hrs)
    • Working voltage: 7.0V - 14.0V
    • Battery: 2x 18650/ 4x CR123A
    • Body color: Military grey
    • Reflector: Textured orange peel reflector
    • Entire length: 218.8 mm
    • Head dimensions: 68.8mm (length) x 67.3mm (width) x 33.5mm (height)
    • Body dimensions: 170mm (length) x 28mm (diameter)
    • Net weight: 270g (excluding battery)
    • Material: Aerospace-grade aluminum. Hard-anodized anti-abrasive finish
    • Waterproof to IPX-8 Standard (underwater to 2 meters)
    • Lens: Toughened ultra-clear, durable glass
    • Anti-roll and anti-slip body design
    • Accessories: Heavy duty holster, removable metal tactical ring, two spare O-rings and spare rubber boot



    PACKAGING
    While the packaging is the typical cardboard w/plastic window and inner shell, I really liked how compact it is. It is not much bigger than the packaging for a single cell light:


    Klarus made efficient use of the space available by fitting the head perpendicular to the tube and then using the remaining empty space for the holster and accessories:


    Accessories included w/the light:
    - Holster
    - User manual
    - Tactical ring
    - 2 large red O-rings
    - 1 smaller red O-ring
    - 1 black O-ring
    - 1 rubber tailcap cover
    - Lanyard
    - Mini-keychain ring



    DESIGN / FEATURES
    The Klarus XT20 is not the first light with dual heads as other manufacturers have released various iterations thereof (spotlight, flashlight, bike lights, etc). However, it is to the best of my knowledge, the first handheld flashlight featuring dual XM-L U2's which combine to generate 1200 lumens:


    The lens features AR coating (the purplish hue):


    The XT20 features dual SS bezels that are perfectly flat, so you won't be able to note if the light is on when placed on its head (I tipped light in right pic so you can see it was on):


    My sample came with two smooth reflectors although the manual states textured. There are others who have mentioned receiving one smooth and one textured reflector so best to check with your retailer in case there is a specific setup you'd like:


    Just aft of the head are these initial set of cooling fins (there are more around the throat area):

    They seem to be reasonably functional and not just for aesthetics. In a test with only an intermittent mild breeze from a nearby windows and ambient temp @ 77.6F, the head was 79F at start. The fins reached 97F after three minutes.

    While Mjölnir bears an inscription on the side: "Whosoever holds this hammer, if he be worthy, shall possess the power of Thor.", we are now in the 21st century where laser engravings are commonplace and was employed to carve precisely the manufacturer's name, model and serial number on the flat surface below the cooling fins:


    The light respects design symmetries for the most part. The logo on the battery tube is an exception since it's not centered with the head:

    Regardless of the position I place the logo when I start threading, it'll always end up on the side opposite the main logo below the fins:


    Likewise, aligning the tailcap is the same affair, although in this case, it'll ultimately affect how you can grip the light (more on this later):

    Again, symmetrephobes would feel right at home but this will bug those who have perfect symmetry OCD.

    The XT20 comes with a tactical ring that is not installed when shipped. It's not the typical screw-on type so I was confounded as to the proper installation given the manual wasn't very clear either. To clarify, the ring can be installed in either direction; flatside towards head (FTH) which is usually the normal way, or reversed with flatside towards tail (FTT):

    In either case, the original red battery tube o-ring must first be removed and an additional o-ring installed to fill the gap between the tube and the rim of the tailcap, but the question was which o-ring to use?

    Given the red ones seem to be replacements for the originals on the battery tube, I rationalized it had to be the single black one. The problem is if you install it FTH, there is very little room left to install the original red battery tube o-ring:


    While installing it FTT allows much easier reinstallation of the red battery tube o-ring, but leaves just a slight gap and also causes it to be free spinning, of which I'd be concerned with the anodizing over the long run:


    The rubber tailcap cover protrudes just slightly beyond the tailcap rendering the light non-tailstandable. However, even if it didn't, there is little material to make it stable anyways. I also noticed that it is not perfectly parallel to the edge of the tailcap which might be due to the way it's installed (more later):


    The XT20 does not feature squared threads, however the threads are machined precisely and well greased so I had no problems when screwing on the head or tailcap nor did I encounter any grittiness. NEW 9/10: They are also anodized so you can lock it out by unscrewing either end at least 1/4 of a turn. Two AW2600's will sit just flush with the end of the tube while a pair of AW IMR's are a little shorter and sit a bit recessed:


    The XT20 features springs in both the head and tail (in which case it's covered by a cap):


    Disassembling the tailcap reveals the buttons and electronics (left shot is the side facing the negative side of battery and right is the side facing towards tailcap cover):
    NEW 9/10:


    Given the two metal prongs that extend out of either end of the tailcap, the cover must be precisely installed to align w/them as well as the underlying buttons:


    The switch and its baseplate has a hump that aligns with the groove on the ID of the tailcap:


    Here's what it looks like installed without the tailcap cover:


    Likewise the rubber cover also has a little hump that is supposed to slot into its own groove within the tailcap:

    However I found it was a little tricky getting it perfectly aligned given it is rubber and malleable after all.

    Once you have the rubber cover on, when installing the metal baseplate for it, ensure that it slots within the rubber cover and that the rubber extends out all around it, otherwise it may compromise the waterproofness of the light:


    When first installing the batteries, I noticed a very brief flash indicating that the light goes into standby (no doubt necessary in order to access instant strobe mode) leading me to speculate that the XT20 will draw some current even when off. EDIT 9/10: I isolated the tailcap and measured a draw of 1.13 µA with a single cell and about 1.25 µA with two (EDIT: Klarus confirmed draw of 4µA but didn't specify how many cells). This is so minute as to be inconsequential, however, if you really wanted to calculate the impact; leaving the self-discharge of the battery out of the equation and taking the highest draw of 4µA (.004 mA) and then dividing it by the typical 2600 mA battery, it'd take 74.2 years to drain the battery in standby (2600/.004 and then divided by 24 and then divided by 365). I don't know about you but I'd be long gone by the time that happens...



    BALANCE & HANDLING
    Given this is a 2x18650 sized light along with the requisite length and weight, the type of grip you can use and still be able to easily access the switches may be an important purchase decision for some. The XT20 w/tactical ring installed (and no batteries) weighs 8.74oz (247.9g) of which the head alone accounts for 5.16oz (146.4g). Slotting in two AW2600 batteries brings the total weight to 12.03oz (341.1g) just about the weight of your average can of soda (at least here in the states).

    The placement of the mode button on the tailcap would necessitate that one hold the light in an overhand grip if they are to be able to change modes. Given the bulk of the weight resides in the head, this leads to a little awkardness and unbalance.
    [PICS TO COME]

    I'll lend this out to people with larger hands to see if they experience the same thing and will report back later as drawing comparisons to Mjölnir would be a little unfair since Thor didn't have any modes to change and thus I bet never had to use the overhand grip.

    The holster does an admirable job of holding the light in place. I ran around a bit and didn't feel that the light will come out.

    NEW 9/11: I enlisted two friends to help model the light in the holster. The guy on the left is 5' 7" and the one on the right is 6':


    Given the placement of the button on the tailcap, one would need to use both hands to withdraw and turn on the light in an emergency:
    [PICS TO COME]

    When installed, the tactical ring will likely get caught on the bottom rim of the holster which makes it nearly impossible to perform quick, one-handed draws. EDIT: 9/11 If easier withdrawl is desired then installing it FTT would make more sense given the taper as it meets the bottom of the holster edges:


    The supplied lanyard feels robust enough and should easily support the weight of the light in case you lose your grip.
    [PIC TO COME]



    SIZE
    Based solely on the pics, I had expected the light to be just as big as Mjölnir so imagine my surprise when I finally received it and lo and behold, it's roughly about the size of my M3LT:

    From L to R: AW 18650, Xeno G10v2 (here's your sneak preview of the next light I'll be reviewing), Klarus XT20, Surefire M3LT

    The light is actually relatively compact for a dual-head 2x18650 light.



    FIT & FINISH
    The anodizing is pretty good but I was able to detect minute areas in the grooves on the tailcap where it seems the anodizing didn't fully "seep in". You may or may not be able to discern this in the pic as you really need to be looking for it to notice it:


    NEW 9/10:
    The textured finish is not aggresive and only mildly contributes to additional grip, in which case if you're holding the light in an overhand grip with your thumb over the button, it'll be largely irrelevant anyway:


    The anodizing is even and matched across the head, tube and tailcap as evidenced in the following pic in which case I compared it to two lights. The top has a mismatched tailcap and the bottom is what I consider to be flawless:


    If there is one minor concern to be had, it would be the gap between the tube and the head which really is more attributable to the design rather than any flaw in fit/finish:
    NEW 9/10:

    I stuck a piece of folded paper in the gap to give you an idea of how much space there is. I estimate the gap to be roughly 4-5 sheets thickness of paper.

    As you can see, the gap is large enough for sand and other crud to be caught in there, however, unlike most recent lights I've reviewed, the head is removable from the battery tube so should be easily cleaned in case that happens.

    Overall, it's a very solid light but given this is my first exposure to Klarus and I've only had the light for less than a week, I'll report back on how this light holds up in the long term.



    UI
    The UI is fairly straightforward and is controlled via the dedicated mode button. The main forward clicky only serves to turn the light on and off or be used for momentary on and does not change the modes. There is no memory so the light will always come on in High and then cycle to Medium and then Low in that order.

    Strobe can be accessed instantaeneously with the light off by depressing the mode button in which case it will act as a momentary button in short bursts of less than two seconds; if held longer than that, the strobe will stay on. The rate of the strobe will stay constant for as long as you keep the mode button depressed, once you let go, it will cycle between fast and slow. This was not mentioned in the instructions.

    To deactivate it, you can either depress the mode button again (to shut the light off) or simply turn on the light via the main clicky. Strobe can also be accessed when the light is on in any mode by holding and depressing the mode button for at least two seconds.



    RUNTIME
    I used various rechargeable battery combo's to provide an idea of what you can expect with similar batteries that you might own. The relevant battery stats are provided above each runtime graph along with:
    - Voltage of the battery at the start and end of the test
    - Current draw as taken right before the test
    - Actual runtime until the battery first starts to cut out (first in HR and then in M so in the case of the RL3100, read this as 2.1 Hrs OR 124 Min)
    - For testing on High and Medium (in which case a fan was used), temperature: ambient, the head at start and the max it reached

    Axis: X = Time in Min and Y = Relative Output



    I speculate the XT20 uses PWM on all levels (I am confirming with Klarus engineering) based on what I'm capturing on my light meter as well as a faint high pitched whine emitted from the tailcap on all modes. However, an interesting thing I picked up after testing all my bat's on H mode was that the light seems to step down roughly 10% in output after 2 minutes and 46 seconds (this is also visible to my eyes).

    NEW 10/13: Runtime w/RL3100's added. Due to my revised testing procedures, I stopped the tests when avg. output was below 50% from start. I suspect I probably could've squeezed 20 more min or so before the PCB kicked-in.

    Normally I display my graphs in 1 minute intervals (above), which would not have clearly shown this as it looks like the light is just gradually decreasing in output.

    This chart below is the same data as above but just unfiltered and is displayed at 1 second intervals to help highlight the very distinct step down which was consistent across all 18650's I used:


    Here is the same chart blown up to further highlight this phenomenon:


    I have an inquiry to Klarus re: this.




    For the Medium test, I forgot to capture the ending voltage for IMR's but suffice to say, one cell in particular was VERY low.

    Now here is where I'd like you to pay attention!

    I have enjoyed this hobby for nearly four years now and in this time, I have never had a single incident with LiIon cells. I generally take pretty good care of them and charge them in a fireproof container as well as removing them immediately after charge. However, while conducting these run time tests, I am not always around to monitor when the testing finishes. In the event of the IMR's I think one cell got down to around 2.3V. I immediately soft charged it and then stored it away and thought nothing of it. The next morning, I installed that cell along with another IMR and gave it a quick test then put the XT20 on my shelf and left for work. When I got back I turned the light on but it only flashed briefly and then nothing. When I removed the cells to check the voltage, the one cell that was over-discharged was giving all sorts of weird readings. It would start around 2.5v and then start climbing until it was over 4.5V! There was also some weird smell so I quickly dumped it in my fireproof container and then ran out the house with it. I then removed the battery and dumped it into a flower pot full of soil and it's sitting in a corner where it's unlikely to do any damage even if it goes nuclear. I have a feeling the cell vented but given I've never experienced it before, I don't know that for a fact. However, my senses just told me something was very wrong here.

    Bottom line is to use sound judgement and to use matched protected cells in multi-cell high-powered lights like this one.

    I'm sure there will be the usual pundits who will weigh in and claim their years of experience with unprotected cells and not a single event. But think of it this way, it takes just one event to potentially alter your life forever, why risk it? Don't get me wrong, I'm not trying to drum up the hype machine and become the poster boy for safety advocacy, all I'm saying is use your noggin and play it safe.

    Whew, with that said, on with the rest of the review.



    TINT& BEAM PROFILE
    The tint is very good with green really only noticeable only on L mode (and even then only when the beam is projected closer to an object). I do notice a purplish halo around the permiter of the beam which I think may be contributed by the AR coating. I'll do some more testing and report back on this.
    [PICS TO COME]

    NEW: 9/10
    Before we get to the beam profile, I just wanted to highlight an interesting thing I noted with the LED's and that is that each look to be just slightly-off centered which I believe this was intentional and by design. This is the left head when looking at the light head on, notice how the LED is shifted just slighlty towards the left and there is more of the black gap on the right side:


    Now take a look at the right LED and note how it's just the opposite in that the LED is now shifted just slightly towards the right:


    I believe this slight adjustment is what allows the beam to point towards the center of the light so that they eventually converge to create a nice giant beam.

    Given the compact dual-head set up there isn't room for a deep reflector and as such the beam is more floody in nature but w/decent throw aided by the dual smooth reflectors. I'm confirming with Klarus whether they will eventually offer the other reflectors for sale.

    NEW: 9/9 11PM
    As for the beam, it starts off as two distinct beams that eventually meld into one after two feet or so (sequential shots were taken roughly in 6" increments):




    INDOOR BEAMSHOTS
    All shots on Canon S3 IS using WB that yields the closest to what my eyes see (left = 1/13" @ f2.7 | right = 1/80" @ f2.7).

    Please refer to this post for beamshots and comparo to 17 other lights.

    New 12/12: Here are new indoor shots on all modes I took on a Panny FZ150 w/wider angle lens to give you a better idea of the beam profile:
    High


    Med


    Low




    OUTDOOR BEAMSHOTS
    All shots on Canon S3 IS, ISO 80 @ f2.7 using Daylight WB. Distance to the white wall is 21.3 ft (6.5m) and to the steps (at the forefront of the bottom of the pic is 12ft).

    Shutter speeds: left = 1/4" | center = 1/20" | right = 1/80"

    Click on pics to load full size.


    NEW 10/12
    LONG DISTANCE OUTDOOR BEAMSHOTS

    I recently completed some long distance outdoors shots. For full details and comparo vs. other lights, see here.

    As mentioned in the thread, the massively bright floody beam profile gave me the most comfort in this creepy location.

    NEW: 9/11
    CONCLUSION
    Overall, I really like this light a lot. To echo skyfire's comments "the wtf factor is definitely there" and overall the reaction I've received from friends and family were positive and I got a lot of "Man, that thing is bright!!". However, with that said, while I like this first release, what I'd like to see from the next iteration would be:

    - current controlled vs. PWM w/better regulation
    - Turbo mode where it's driven at 3A or more for a brief period of time before auto-stepping down
    - ability to turn each individual head on/off as this would work really well if you have one smooth and one textured reflector and ability to control level for each head too

    Overall a very solid release from Klarus, and again given this is my first experience with their lights, I'll report back in a few months to see how it's holding up.



    GALLERY





    SPECIAL THANKS
    ...goes to my wife for putting up with me and helping take these shots (and the intro one) in which I was trying to emulate that cover from the Thor comic:


    This one came close but wasn't as dramatic:


    Disclosure: The XT20 was provided by the manufactuer for review. Any other items used in this review that were provided by a manufacturer/dealer have been previously disclosed in their respective review.
    Last edited by turboBB; 12-12-2011 at 08:13 PM. Reason: New wide angle indoor shots added (search 12/12)

  2. #2
    Flashaholic* skyfire's Avatar
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    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    great write up, cant wait to see the pics.

    the more i look at that light, the more im liking it!
    cant iimagine myself using a light of that size, but the wtf factor is definitely there.

  3. #3
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    DM51's Avatar
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    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Excellent work - moving it to the Reviews section!

    The incident you had with the faulty cell is interesting. Maybe you should start a thread about it in the Batteries "Smoke & Fire" section, to see what members think.
    Resistance is futile...

  4. #4
    Enlightened
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    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Excellent in depth review! Thank you!!

    Concerning the incident with the LiIon cells, is the situation you experienced only a problem with cells in parallel and would not be an issue with a flashlight with cells in series?

  5. #5
    Flashaholic* candle lamp's Avatar
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    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Excellent review. Tim!
    Thanks for your time & effort.

    According to the runtime graph, the range of relative output with time is somewhat(rather very) wide on high & med. mode to me. I think it can be noticeable while testing.

    Could you let me know what the relative output means? (Is it lux measured by lightmeter?)
    Last edited by candle lamp; 09-09-2011 at 07:37 AM. Reason: To add ( )

  6. #6

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Excellent review turboBB. Love the detailed commentary and photographs. A very enjoyable and readable evaluation.

    I'm also curious about your runtime graphs. Do I understand that the output was fluctuating by more than 100% every second (i.e. swings of more than double the lowest outut)? That would be extremely visible.

    As for PWM, I find the easiest way to detect it without an oscilloscope is by shining the light on fast-moving fan blades (computer fans should do in a pinch). Also lets you tell if the frequency shifts between levels (i.e. pattern changes on the blades).

    As for the unprotected battery, I echo concerns here. For your own safety, I recommend you do not runtimes unsupervised. But of greater concern to me is in the re-charging of potentially damaged cells. In my experience, unprotected cells will drop to unsafe voltages within seconds of the output dropping signficantly (in most lights). If I understand your medium graph correctly, your IMR cells were completely discharged and left running for well over an hour and a half? If so, I'm not surprised a cell failed - I'm just glad to hear it didn't catch fire when you put it back in the charger!

    Stay safe (I hope to see more reviews from you ).
    Full list of all my reviews: flashlightreviews.ca. Outdoor 100-yard Beamshots 2011. Latest: Fenix LD60.
    Gratefully accepting donations to my battery fund.

  7. #7

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Quote Originally Posted by turboBB View Post

    The light respects design symmetries for the most part. The logo on the battery tube is an exception since it's not centered with the head:


    Likewise, aligning the tailcap is the same affair, although in this case, it'll ultimately affect how you can grip the light (more on this later):

    Again, symmetrephobes would feel right at home but this will bug those who have perfect symmetry OCD.
    First: Nice review!

    I tend to like symmetry myself and although not compulsive about it, it does bother me to a certain degree when things don't line up as they should visually. Then again, with the kind of squarish-headed XT20, alignment is more of a challenge than it would be on most flashlights where you have rounded symmetry to deal with (that is, in most cases I don't think logo-to-logo or logo-to-head alignment is as much of an issue as it is visually with the XT20).

    I noticed on mine that the body tube logo didn't seem to line up with the head (initially seeming to be about 1/8th turn off center), but I was able to give mine a bit of additional twist and it did finally align (it took a bit of a power twist for me to make it align, though).

    I wonder if the body tube alignment is hit or miss on all of them or if they've made some manufacturing adjustment to the released sales versions compared to the review versions they sent out.

    The tailcap on mine is another story. When fully tightened, mine is off center by exactly one quarter turn, which is aesthetically a bit strange to see. Depending on where the tailcap tightening ends for any given XT20, it may causes the user to have to hold the light at a slight "roll" in orientation when holding it in tactical position for momentary use. That's not a big deal to me since it really doesn't cause any problem with the actual effectiveness of the beam.

    I'm posting this pic to show the logo alignment on mine, but it also gives some size perspective with a couple of other lights that use 18650 batteries (ZebraLight SC600 and Dereelight DBS V2).

    Last edited by varuscelli; 09-09-2011 at 02:05 PM.

  8. #8

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Another shot that shows the alignment of the body tube logo with the head (in the case of mine, it lines up nicely) -- and this shows one of the ways I'm using the XT20. It might be considered by some to be a bit long for a bike light, but when mounted like this with two attachment points it's very nicely workable (good ease-of-use placement and sturdily attached).


  9. #9

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Thx for the comments (& additional pics) guys! I'm a bit swamped ATM so will reply to each q when I get home.

    Cheers,
    Tim

  10. #10

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Sorry, I previously posted this elsewhere, but I think it's relevant to such a nice review. Here's an image of the mixed reflectors (one orange peel, one smooth) as seem to be initially shipping with first batch of XT20 lights.

    I don't have a beam shot to show this, but here's something I've noticed with mine. When I cover the OP reflector for a wall test so that I can see the difference between the two, the smooth reflector seems to show a small dark spot in the middle of the hot spot (very small, maybe an inch across at a 10 foot distance as seen on a wall test). When I cover the smooth reflector, there is no dark spot associated with the OP reflector. With both together, the smoothness of the center spot of the OP reflector masks over the dark spot I see with the smooth reflector...although knowing that the small dark spot is there, I can still somewhat see it even with the "masking" effect of the OP reflector. And I hope my description is not too convoluted to make sense.

    The way I view that small dark spot associated with the smooth reflector is that it's going to be noticed only on a wall test and not in real use of the light, so I don't see it as an issue. And perhaps the small dark spot I'm seeing with the smooth reflector is an anomaly with my own light and not necessarily something anyone else is seeing.

    Last edited by varuscelli; 09-09-2011 at 03:59 PM.

  11. #11

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    @DM51 - Thx, will do!

    @Enzo - Thx! So in this light, the cells are in series. If I'm not mistaken, the problem is more prone with lights in series than parallel (someone please correct me if I'm wrong).


    @candle lamp @ Selfbuilt - Thx guys! As for the runtime, it's conducted on a Extech HD450 data logging light meter and I'm capturing data in 400K range @ 1 second intervals for the H setting and at 20 seconds for M. What you see on the chart is actually not perceptible to the eyes (except for the step down). The chart may lead you to think that is slowly ramping up and down when in fact it's the PWM effect it's capturing. Given the PWM frequency is much faster than the rate the light meter is capturing, it just so happens that sometimes it catches it at it's peak and other times at its trough (or anywhere in between for that matter). Think of it this way, you are trying to take a picture of a hummingbird's wing while it's flapping. Once you get focus and snap a pic, there's a chance you'll capture a frame when the wing is at the peak of a cycle and then at other times at its trough (and again, anywhere in between really).

    Seflbuilt, it's funny you mentioned about the fan, I've taken to using my son's mini RC heli and checking out the blade patterns. Too bad it doesn't show up as well in pics. Thx for the safety advice, I normally am around just in this particular run, I was trying to get my kids to bed so had left this running. I'll be amending my testing going forward and cutting off the light as soon as it starts dimming.

    @varuscelli - Thx and for sharing the pics too! I no longer ride but if I do, I'm going to rig a setup like yours. As for the symmetry, I suppose the folks on the machining thread would know as I'm pretty sure depending on where the thread starts, it'll always thread in pretty much in set locations. It's akin to how certain wristwatch owners are very particular about how the logo on the crown lines up on the ones that are screwed-down. It's great that you got one to line up, again it doesn't really bug me but I'm sure it will bother others. The tailcap is a different story since it's not just about aesthetics and will impact the head orientation realtive to your grip so the slot must be parallel with your thumb. Ultimately it shouldn't be that big a deal but again people may be particular to how the light is oriended in their hand. I'll clarify this in my review with updates and new pics this weekend.

    EDIT: re: the data capturing, check out this thread I previously posted about it. I'd pay for an upgrade to the software if anyone can re-engineer to capture more than 10K rows and also to raise an alarm as soon as output starts dropping.

    Cheers,
    Tim
    Last edited by turboBB; 09-09-2011 at 08:55 PM.

  12. #12

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Quote Originally Posted by candle lamp View Post
    Many thanks for the reply & the thread related to PWM. Yes, I know the very informative thread.

    I still wonder the swing range is too big than expected even though the light is on high mode.
    I think light meter capturing (every second interval) will not affect the swing of the output on high mode. There may be other reason.

    It surprises me that you could find each LED's just the opposite in that the LED is now shifted just slightly towards the left & right, and this creates a nice giant beam.
    I'm working on graphing the PWM w/my Fluke so when that's ready, I'll post it up and hopefully it'll clarify what I'm trying to explain. And yes, outdoors with some particles in the air, you can clearly see the beams converging. I'll get a shot of that soon and post that as well.

    Quote Originally Posted by scaramanga View Post
    Very nice review, my XT20 is just about ready to be picked up at the local post office... Can't wait to get my hands on Mjolnir!
    Congrats, feel free to share your experiences with it!

    Quote Originally Posted by varuscelli View Post
    Comments removed for the greater good of the thread.

    fyrstormer: sorry for the slight misunderstanding. No harm done, I hope.
    Thx guys! It would've been a shame had this thread got locked down. Can we get a

    Also, thx for sharing those pics varuscelli, great idea using that diffuser on the XT20!

    Cheers,
    Tim

  13. #13
    HKJ's Avatar
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    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Quote Originally Posted by turboBB View Post
    I'm working on graphing the PWM w/my Fluke so when that's ready, I'll post it up and hopefully it'll clarify what I'm trying to explain. And yes, outdoors with some particles in the air, you can clearly see the beams converging. I'll get a shot of that soon and post that as well.
    Your lux meter is fast to capture the pwm, I measured it at nearly 1 kHz and did not see anything on the lux meter. You can see the actual pwm in my review, captured with a oscilloscope.
    My website with flashlight, battery and charger information: lygte-info.
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  14. #14

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Thx HKJ!! As a FYI I'm using an Extech HD450 and capturing at a rate of 1 sec. interval.

    @Candlelamp, if you check out HKJ's review, it's basically where the time interval gridline (in his case in ms) intersects with the PWM curve. So in my case, imagine there were more gridlines for the y axis and you can envision how certain of those lines will intersect with the curve at the peak of a curve and certain at the trough and others in between thus the major swings you're seeing in my runtime charts. Who knows, maybe it could just be my sample that exhibits this but again, I'll post up a chart later to demonstrate clearly what I'm talking about.

    Cheers,
    Tim

  15. #15
    HKJ's Avatar
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    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Quote Originally Posted by turboBB View Post
    Thx HKJ!! As a FYI I'm using an Extech HD450 and capturing at a rate of 1 sec. interval.
    I am also using the HD450, but at a slower sample rate and have newer seen any problems with pwm.
    My website with flashlight, battery and charger information: lygte-info.
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  16. #16
    Flashaholic* candle lamp's Avatar
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    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Quote Originally Posted by turboBB View Post
    @Candlelamp, if you check out HKJ's review, it's basically where the time interval gridline (in his case in ms) intersects with the PWM curve. So in my case, imagine there were more gridlines for the y axis and you can envision how certain of those lines will intersect with the curve at the peak of a curve and certain at the trough and others in between thus the major swings you're seeing in my runtime charts. Who knows, maybe it could just be my sample that exhibits this but again, I'll post up a chart later to demonstrate clearly what I'm talking about.

    Cheers,
    Tim
    I understand what you mean. Thanks a lot for your reply again. Tim!

  17. #17
    Flashaholic* tobrien's Avatar
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    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    interesting design, but you write amazing reviews!
    aka Edgar Allan Bro, Brosama Bin Liftin, Walter Crunkite, Bro Namath, Teddy Brosevelt, and the Tomahawk Crunkmissile.
    my lights - review of PrecisionWorks - that's Gucci Mane in my avatar

  18. #18

    Default Re: Mjölnir, thy competition has a name: KLARUS XT20 (review, runtimes, pics, beamsho

    Quote Originally Posted by turboBB View Post
    @varuscelli - Thx and for sharing the pics too! I no longer ride but if I do, I'm going to rig a setup like yours. As for the symmetry, I suppose the folks on the machining thread would know as I'm pretty sure depending on where the thread starts, it'll always thread in pretty much in set locations. It's akin to how certain wristwatch owners are very particular about how the logo on the crown lines up on the ones that are screwed-down. It's great that you got one to line up, again it doesn't really bug me but I'm sure it will bother others. The tailcap is a different story since it's not just about aesthetics and will impact the head orientation realtive to your grip so the slot must be parallel with your thumb. Ultimately it shouldn't be that big a deal but again people may be particular to how the light is oriended in their hand. I'll clarify this in my review with updates and new pics this weekend.
    Yeah, again I wonder if maybe Klarus corrected the threading thing for the body-to-head for the ones that are being sold now. I have seen ernsanada's Klarus XT20 review and it's evident from the photos that it's not aligned either (his was a review edition, too).

    But (shooting down my idea of machining thread corrections), Going Gear has a YouTube video on the XT20 which seems to be the version that's being sold (with two different reflectors) and the body and head on the one they show seems to align in such a way that the body logo and head logo are on opposite sides (when the light is flipped you see either the head or body logo) but at least symmetrically so (that is, the logo alignment seems to be exactly 180 degrees, exactly on the flip side). So really, alignment looks more hit or miss to me, whether it's one of the review versions or the first shipment versions.

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