ReviewTheLight: Acebeam K40M (3000 Lumen MT-G2 + Control Ring)

Bigmac_79

Flashlight Enthusiast
Joined
Jun 3, 2011
Messages
1,511
Location
Kansas
my reviews on facebook!
Don't forget to click "Like" after the page loads!

to my YouTube channel!


Supbeam recently upgraded their name to Acebeam, and consequently have upgraded a few of their models. The K40 has been upgraded from an XM-L to the MT-G2 emitter, a larger and brighter (though slightly less efficient) emitter, and renamed the K40M. It still includes the large reflector for long throw, and the control ring user interface. Presenting the Acebeam K40M:


Thanks to Acebeam for providing the K40M for review.


I'll be reviewing the K40M in two sections: first, I'll discuss the light objectively (the facts about the light itself), then I'll discuss the light subjectively (my impressions about the light's performance when used for specific applications). If you have any other specific applications you'd like the light tested for, let me know and I'll see what I can do.

Video Review

Below is a video review of the K40M. Due to my old image hosting site closing down, I've got new restrictions on image uploads and have replaced the "Construction" section of my reviews with a more detailed video review.


This video is available in 1080p HD, but defaults to a lower quality. To select the playback quality click the settings button (looks like a gear) after you've started the video.


Objective

Manufacturer's Specifications

Price: 120 USD




Product Manual




Dimensions




Plus, here's a few shots with some good detail.








User Interface

The K40M has six brightness levels, a Standby mode, and a Strobe mode, controlled by the rear tail switch and the control ring.

To turn the light on and off, click the rear tail switch. To choose the mode, rotate the ring to the desired mode position. An arrow on the ring indicates the mode chosen. From left to right (with the light pointing away form you), the modes are Level 1 - Level 2 - Level 3 - Level 4 - Level 5 - Level 6 - Standby - Strobe, with Level 1 being the dimmest and Level 6 being the brightest. Each position on the ring has a detent so that the ring "clicks" into position, and is unlikely to be moved by accident.


Action Shots

You can click on any of these shots to see them full size.

Light in Hand


MugShot


BeamSlice


White Wall
ISO 100, f/3.5, 1/20"


Indoor Shots
ISO 100, f/3.5, 1"


Outdoor Shots

ISO 100, f/3.5, 2.5"


Long-Range Shots

ISO 100, f/3.5, 15"


Fun Shots ;)




Performance

Submersion: I submersed the K40M under a foot of water for about an hour, clicking the switch and turning the ring several times. I found no evidence of water entering or damaging the light.

Heat: The K40M heats up in just a few minutes on Level 6, and the batteries can get hot as well, so I recommend using the highest level for short intervals.

PWM: I detect no pulse-width modulation on any mode of the K40M.

Drop: I dropped the K40M from about a meter onto various surfaces (including grass, carpet, dirt, and hard wood), and found no cosmetic or functional damage.

Reverse Polarity Protection:

Over-Discharge Protection: The K40M begins to flash intermittently when the batteries get low, so that's your warning that to change or charge them.


Spectral Analysis


All light that we see as white is actually made up of several different colors put together. The relative intensities of the different colors in the mix are what determine the tint of the white we see. For example, cool white LED's have a lot of blue, and warm white LED's have more red or yellow. This measurement was done on a home made spectrometer. The plot below the picture is corrected for the spectral sensitivity of the human eye. Note: the peak in the 900nm region doesn't really exist, it's a piece of the second-order spectrum that's showing up here because of the high intensity of the light source.

Output and Runtime


ANSI FL-1 runtime ratings are the time it takes for a light to fall to 10% of it's original output (counting from 30 seconds after turning the light on).

The vertical axis of the graphs below represents a relative brightness measurement using a home made light box. The horizontal axis is time in hours:minutes:seconds. Runtimes are stated in hours:minutes:seconds. These graphs may be truncated to show detail.

Mode Comparison


Level 6


Level 5


Level 4



Throwing Distance

ANSI FL-1 standard for stating a light's throwing distance is the distance at which the peak beam intensity (usually at the center of the beam) is 0.25 lux. I calculate throwing distance and candela (lux at 1 meter) by measuring peak beam intensity at five different distances and using the formula lux*distance^2=constant.





Subjective Review

Quick break down:

+ One minute of crazy bright ;)
+ Sub-lumen low mode
+ Excellent output range, six levels
+ Control ring UI
+ Firm detents in ring
+ Good grip on ring
+ Perfect regulation :twothumbs on all modes!
+ Long throw
+ Beautiful warm tint

- Big
- Battery carrier instead of solid body
- No cutouts in tail rim

When I received the K40M from Acebeam, a little known company previously known as Supbeam (and I think spending a little time going by MicroBlueBear), I was expecting a pretty middle-of-the-road light that would have mediocre construction and little or no regulation. Instead, I get the K40M, a well constructed beast that has an excellent interface and even better performance. I'm very impressed with this light :cool:.

Let's start with the output. It claims 3000 lumens, and it just barely touches that point on startup, but can't quite hold it for the ANSI spec 30 seconds, so I rate it at just shy of 2900 at the 30 second mark. That's still very impressive, and I was surprised to see it from this less known company. It keeps this output level for a couple minutes, then drops to hover around 2500-2600, and maintains that solidly for the rest of the run. When the battery begins to get low, the K40M will start to give some flashes periodically as a warning. Then, there is a sharp drop to a very low output (near 0) that's just enough to get around in total dark and find replacement batteries or another light. Every mode behaves this way, except that the lower modes don't have the initial drop that Level 6 does. In my opinion, this is the perfect output pattern--holding the initial output for the entire run, until the very end when they give the warning blinks then drop to the very dim output for a while. In addition to the perfect regulation, the K40M has an excellent output range. It's six output levels cover a range from 3000 lumens all the way down to 0.9 lumens, which is one of the most impressive ranges I've seen in a single light. I think most multi-cell lights like this one go with the idea that if you're carrying something this huge, you're probably not trying to read a book in bed. Generally, it's true, if I'm carrying a light this size I've got something smaller in my pocket to handle low-illumination jobs, but I have to say it's really nice to have the ability to have a super-low all the way up to a super-high on the same light. I find it useful to set to Level 1 and tailstand the light in the middle of a small room, and it can give just enough illumination make the room visible. Also, I appreciate that I don't have to switch the light I'm using if I need to go from a very low to very high output quickly. Particularly, if I'm doing a task that requires very little light I can use the Level 1 and preserve night vision, but have quick access to up to 3000 lumens if I need it quickly. Finally, having three 3100mAh batteries driving a sub-lumen mode means some pretty long runtimes. Acebeam's claim of 1000 hours on Level 1 (I didn't test this :eek:) is about 42 days, which isn't particularly efficient, but still very nice to have available if you need it.

Ok, enough about the output. Next, the control ring. If you've read my reviews before, you'll know I'm a sucker for control rings, because they're the best thing to happen to flashlights since the p-n junction. In summary, it's the most intuitive and simple user-interface I've ever used--you can increase brightness when you want more light, or decrease brightness when you need less light, and never have to move through modes too bright or too dim to get where you want. So, you're not left in the dark for moments when trying to access a high mode or blinded when trying to access a low mode. If you've never used a control ring light, you're in for a treat. If you have used a control ring light and you disagree with me, you're free to go write your own review :p. Anyway, the control ring on the K40M is very well implemented. They basically come in two flavors, the infinitely variable and the preset modes. The K40M has preset modes, and solid detents that "click" the ring into position and hold it from shifting to some other mode when you're not turning it on purpose. In addition, the control ring on the K40M has some good grooves cut into it, which means you'll be able to get a grip on it even when your hands are a bit cold or wet. The choice of preset modes means you obviously don't have as many output choices as on an infinitely variable ring, but the advantage is that you can memorize the output levels available and their runtimes, and don't have to guess how much time you have, plus they're generally a bit more efficient than the infinitely variable variety.

Next, let's hit a few on the K40M's negatives. First, it's big. No helping that, if you want high output, long throw, and decent runtimes, you'll need a big light, until we have more hi-tech available. The control ring makes the K40M a bit bigger than other lights with similar output and throw, but I consider it certainly worth it. After all, if you're carrying a light this big, a bit of extra volume and weight isn't going to make too much difference in most situations. Second, it has a battery carrier. This is a bit nitpicky, but I do prefer when multi-cell lights have a solid body with slots drilled out for the batteries, vs a removable battery carrier. The solid body design is heavier, but it is better at soaking up heat and is more sturdy than a battery carrier. Again, I tend not to mind some extra weight, so I prefer the solid body design over the battery carrier. Finally, I think the tail section could be improved with some cutouts in the rim around the button. The ring extends beyond the rubber switch cover, which I really appreciate because it gives the solid tailstand ability, but it also makes it a bit harder to reach your thumb around there to hit the switch on such a large light. A few cutouts in that raised section would make reaching the tail switch a bit more comfortable.

A few more points to cover before we're done. First, this thing can throw. A large emitter like the MT-G2 can handle higher output than something like an XM-L2, but with a larger emitter size, it takes a larger reflector to get the same focus on the beam. The K40M's reflector is plenty large to get that good focus on the beam. There are certainly lights out there that can throw farther, but the K40M runs with the big dogs when it comes to throw. In addition, the beam is a very pleasant warm tint. MT-G2 emitters only come in the 5000 to 2700K range, which is what most people would call neutral to warm white, and I'd say this beam looks around 3500 - 4000K (see the spectral analysis for a quantitative comparison to other lights). Most high-output lights that go with XM-L emitters generally choose cool white tints to get maximum output, so that means the MT-G2 emitter lights stand out with their warmer beams. Generally, warm tints have the advantage of showing colors more accurately and giving better contrast, especially in outdoor environments.

Overall, I've been very impressed with Acebeam's K40M, and with the high quality I've seen here I'm looking forward to seeing what else Acebeam can do. The K40M is an excellent high output thrower, one of few sporting a control ring interface, and is priced very competitively. If you're looking for a thrower and like the control ring UI, the K40M would be a great choice.


Long Term Impressions
I'll fill this part in after carrying the light for a while. If nothing get's added here, either I find nothing else worth noting about the light, or I end up not using it often.
 
Last edited:

joshjp

Enlightened
Joined
Jul 23, 2014
Messages
429
Location
Twin Cities
Thanks for this review, were can i buy this light?, also it seems like its compareably to the ThruNite TN35.
 

Bigmac_79

Flashlight Enthusiast
Joined
Jun 3, 2011
Messages
1,511
Location
Kansas
Thanks for this review, were can i buy this light?, also it seems like its compareably to the ThruNite TN35.

On Acebeam's website they have a "submit order inquiry" button on the K40M product page. I also see it listed on banggood and ebay for about 120 USD. I don't know if it will become available from other retailers, but it might (it just recently was released).
 

blackFFM

Newly Enlightened
Joined
Nov 25, 2012
Messages
179
Thanks for the review. I like your graphs. I scored one from BG for 95$
 

phantom23

Flashlight Enthusiast
Joined
Nov 3, 2007
Messages
2,044
About a month ago the price was lower (still under Supbeam brand), and there's still a coupon that currently drops the price down to ~$110.

PS. I got mine as well, it's crazy bright, makes my Xtar Howitzer (which is much bigger) look dim... But it's also pretty big, I have small hands and I can't cross or even touch my fingers with my thumb.
 
Last edited:

Bigmac_79

Flashlight Enthusiast
Joined
Jun 3, 2011
Messages
1,511
Location
Kansas
About a month ago the price was lower (still under Supbeam brand), and there's still a coupon that currently drops the price down to ~$110.

PS. I got mine as well, it's crazy bright, makes my Xtar Howitzer (which is much bigger) look dim... But it's also pretty big, I have small hands and I can't cross or even touch my fingers with my thumb.

It certainly is big, but I have big hands so it feels pretty comfortable for me. Is one-handed operation of the control ring difficult at all for you?
 

joshjp

Enlightened
Joined
Jul 23, 2014
Messages
429
Location
Twin Cities
On Acebeam's website they have a "submit order inquiry" button on the K40M product page. I also see it listed on banggood and ebay for about 120 USD. I don't know if it will become available from other retailers, but it might (it just recently was released).
TY, can i trust banggood? This seems like a steal at $120.
 

phantom23

Flashlight Enthusiast
Joined
Nov 3, 2007
Messages
2,044
Yes, you can. I bough mine from them.
It certainly is big, but I have big hands so it feels pretty comfortable for me. Is one-handed operation of the control ring difficult at all for you?
Actually one handed operation is not a problem although control ring is a little bit stiff.
 

Bigmac_79

Flashlight Enthusiast
Joined
Jun 3, 2011
Messages
1,511
Location
Kansas
Yes, you can. I bough mine from them.

Actually one handed operation is not a problem although control ring is a little bit stiff.

Glad to hear it! The control ring on my review sample, I wouldn't call it stiff, but the detents are substantial, so that it requires some force to get it up and out, but the space in between the detents is smooth.
 

Bigmac_79

Flashlight Enthusiast
Joined
Jun 3, 2011
Messages
1,511
Location
Kansas
TY, can i trust banggood? This seems like a steal at $120.

I'm amused that we're carrying this conversation both here and on youtube ;). Like I said there, I haven't ordered anything from banggood myself, but I know several others have successfully. I'd suggest running a search here on cpf for banggood and scanning through everyone's experiences.
 

joshjp

Enlightened
Joined
Jul 23, 2014
Messages
429
Location
Twin Cities
I'm sorry about that, I JUST NOW figured how to type on here with my phone, as before it wouldn't let me type, I will now have to order from banggood, I was gonna get the Olight SR Mini, but this is cheaper and seems better, although that should be much floodier. Thanks again for the review♿
 

phantom23

Flashlight Enthusiast
Joined
Nov 3, 2007
Messages
2,044
Shipping from BG is fairly slow but that's not exactly their fault - China Post is quite slow overall.
Glad to hear it! The control ring on my review sample, I wouldn't call it stiff, but the detents are substantial, so that it requires some force to get it up and out, but the space in between the detents is smooth.
It is smooth indeed but there's more resistance than in other control rings (and I have/had quite a few).
 

Bigmac_79

Flashlight Enthusiast
Joined
Jun 3, 2011
Messages
1,511
Location
Kansas
I'm sorry about that, I JUST NOW figured how to type on here with my phone, as before it wouldn't let me type, I will now have to order from banggood, I was gonna get the Olight SR Mini, but this is cheaper and seems better, although that should be much floodier. Thanks again for the review♿

No worries ;). Yeah, the K40M is going to have more throw, and I really love the control ring interface. The SR Mini is floodier, and a lot more compact.
 

Bigmac_79

Flashlight Enthusiast
Joined
Jun 3, 2011
Messages
1,511
Location
Kansas
Shipping from BG is fairly slow but that's not exactly their fault - China Post is quite slow overall.

It is smooth indeed but there's more resistance than in other control rings (and I have/had quite a few).

Yes, definitely more resistance than other control rings. Thankfully there is good grip on the ring.
 

Ernst from Germany

Newly Enlightened
Joined
Apr 20, 2013
Messages
109
Thanks for the Review! It seems so that the Beam is a good compromise between Flood and Throw. Is my opinion right?
Ernst from Germany
 

Bigmac_79

Flashlight Enthusiast
Joined
Jun 3, 2011
Messages
1,511
Location
Kansas
Thanks for the Review! It seems so that the Beam is a good compromise between Flood and Throw. Is my opinion right?
Ernst from Germany

Hi Ernst! The K40M does have a lot of flood light in it's spill region, but the hotspot is so bright, I'd classify it pretty definitely as a thrower.
 

Danielsan

Enlightened
Joined
Aug 24, 2010
Messages
398
Location
Germany - Darmstadt
To start from max is a bit stupid in my mind, whoever decided this, it was was a bad decision. That basically means when you need firefly you will be get blinded by 3000lumen first?
 
Top