Reviewer's Note: Due to a large backlog of lights that I have to test, I will limit some of the descriptive text in my reviews for the time being. Full commentaries are still provided under the Potential Issues and the Preliminary Discussion sections, but I will let the pictures and graphs speak more themselves in the body of the review.
The stock K40 is a slightly smaller version of the K50 that I reviewed previously (under the SupBeam name). It lacks the in-light charging of the larger K50, and will of course have less throw. In this review, I am looking at the MT-G2 version, known as the K40M
Note that this review sample was provided by GearBest.com for review a couple of months, and I don't believe Acebeam models are currently available there at the moment.
Acebeam Reported Specifications:
Note: as usual, this is just what the manufacturer provides. Scroll down to see my actual testing results.
- LED: LED: Cree MT-G2 LED
- Max 3000lumens output (3x 18650 batteries)
- Output (select by magnetic ring): Level 1 : 0.9lm(1000hrs); Level 2 : 42lm(70hrs); Level 3 : 430lm(11hrs); Level 4 : 1150lm(4.5hrs); Level 5 : 1900lm(1.5hrs); Level 6 : 3000lm(0.9hrs); Strobe : 3000lm; Strobe : 3000lm
- Standby : 65uA
- Working voltage: 4V - 13V;
- Max Runtime: 1000 hours;
- Max beam distance: 509meters;
- Peak beam intensity: 65000cd;
- Impact resistant: 1.2meters;
- Waterproof : IPX-8 Standard;
- Size: 186mm(length) x 76.2mm(head diameter)*49mm(tube diameter);
- Weight: 700.8g(without batteries);
- Aircraft grade aluminum body structure;
- Premium type III hard anodized anti-reflective coating;
- Accessories include: 1x Replacement O - ring and Tailcap gummi; 1x user manual; 1x holster; 1x lanyard; 1x warranty card;
- Integrated cool fins design provide better cooling;
- Smooth polished reflector creates maximum throw;
- Aircraft grade aluminum, mil-spec hard anodized for maximum wear;
- Large cooper heat sink pad for superior thermal conductivity;
- Magnetic ring control switch allows you to select desired output easily;
- Mechanical reversed polarity protection design for battery carrier;
- Intelligent highly efficient circuit board design for max performance and long run time;
- Ultra-clear tempered glass lens with anti-reflective coating, which achieves a 98.3% light transmittance.
- MSRP: ~$115
The K40M comes in a plain cardboard box with packing foam. Along with the light is a holster, extra o-rings, spare boot switch cover, decent quality wrist strap, warranty card, manual.
From left to right: Keeppower protected 18650 3100mAh; Acebeam K40Lvn, K40M; SupBeam K50; Thrunite TN35.
All dimensions are directly measured, and given with no batteries installed:
AceBeam K40M: Weight: 498.4g, Length: 188mm, Width (bezel): 76.2mm
SupBeam K50: Weight: 645.0g, Length: 230mm, Width (bezel): 90.1mm
Crelant 7G10: Weight 643.4g (827g with 4x18650), Length: 198mm, Width (bezel): 79.0mm
Eagletac MX25L3C 3x18650: Weight: 345.9g, 352.0g with kit tailcap (485-491g with 4x18650), Length: 141.9mm, 143.6mm with kit tailcap, Width (bezel): 61.9mm
Fenix TK61: Weight: 605.7g (790g with 4x18650), Length: 218mm, Width (bezel): 96.0mm
Fenix TK75: Weight: 516.0g (700g with 4x18650), Length: 184mm, Width (bezel): 87.5mm
Niwalker BK-FA02: Weight: 687.6g (870g with 4x18650), Length: 209mm, Width (bezel): 80.0mm, Width (tailcap): 50.3mm
Olight SR52: Weight: 396.7g (497g with 6xCR123A), Length: 162mm, Width (bezel): 63.1mm
Thrunite TN35 (MT-G2): Weight: 571.4g (723g with 3x18650), Length: 201mm, Width (bezel): 78.9mm
The K40M build is similar to the K50 reviewed previously, minus the magnetic charging dock and in-light charger. As before, overall build is reminiscent of the Thrunite TN3x-series lights. Anodizing is a flat black, and seems to be in very good shape on my sample. Labels are sharp and clear, and include a serial number.
Rather than traditional knurling, the handle has a checkered pattern. Combined with the ridge detail on the control ring and head, overall grip is pretty good. The light can roll easily however.
The control ring feels and looks like K50. All black, there are slight indents (and raised checkered regions) on the control ring to help with feel. There is a label mark on the control ring that lines up with the labels on the head. The six constant output modes are not individually labeled, but there is a graded output bar pictogram over the first four levels (i.e., shows the direction to turn to raise or lower the output). There are firm detents at each level, with a slight click as you enter into each one.
Screw threads are traditional triangular cut, but seem of good quality. They are anodized, but it is the tension on the spring in the head than determines if you cam lock out the light by a twist. On my sample, a quick turn is enough to lock out the light.
The lights can tailstand. Tailcap has cut-outs to facilitate access to the switch. Switch is a forward clicky switch (i.e., press for momentary, click for locked-on).
Let's take a closer look at the battery carrier:
The positive contact points inside the carrier are slightly raised, so all types of 18650 cells should work fine (i.e., true flat-tops, wide and small button-tops). There seems to be plenty of room in the carrier for length, so longer cells should fit fine. All the cells point the same way here (i.e., negative terminals at the base, positive terminals toward the head).
MT-G2 emitter was well centered on my sample. Scroll down for beamshots.
Turn the light off/on by the tailcap clicky – press for momentary, press and release (i.e., click) for constant on.
Change output modes by turning the control ring in the head. Arranged from left-to-right (looking down at the light, held in traditional flashlight carry), the modes are level 1 > level 2 > level 3 > level 4 > level 5 > level 6 (max) > standby > tactical strobe.
No light is produced on standby, but a miniscule current will be drawn to allow the circuit to respond to a ring turn (see below). As always, I recommend you store the light clicked-off at the tailcap, or locked-out by a head twist.
For more information on the K40M, please see my brief overview here:
As with all my videos, I recommend you have annotations turned on. I commonly update the commentary with additional information or clarifications before publicly releasing the video.
There is no sign of PWM on any level – the light is current-controlled.
The K40M uses an oscillating strobe design, switching between two frequencies every ~0.6secs or so. Here is a blow up of the two frequencies:
As you can see, it rapidly switches between 15.0Hz and 6.4Hz. This is exactly the same as the K50 I previously tested.
There must be a standby drain when the clicky switch is turned on and the light is in standby position of the control ring. I measured this traditional standby current as 60uA on 3x18650. This is similar to my K50, and not a major concern. Given the in-series arrangement, that would take almost 6 years to fully drain 3100mAh cells.
Note that on other lights that use a similar design (e.g., Thrunite TN3x series), I know there is an additional circuit to assist the switch when high current draw is required. This necessitates a secondary circuit in the tailcap that has its own standby drain when connected to the carrier. Typically, these are in the uA range and not a concern in practice (although it would be additive to the carrier drain below when fully connected).
And now, what you have all been waiting for. All lights are on their respective 18650 battery sources, about ~0.75 meter from a white wall (with the camera ~1.25 meters back from the wall). Daylight white balance used on the V54 modded lights.
Spillbeam width is slightly wider than the Thrunite TN35 - but otherwise, the two lights share a very similar beam profile. Although you can't see it in the beamshots above, my sample of the K40M seems a bit cooler than typical for a Neutral White emitter.
For outdoor shots, these are done in the style of my earlier 100-yard round-up review. Please see that thread for a discussion of the topography (i.e. the road dips in the distance, to better show you the corona in the mid-ground). Note there are a lot of bugs out at this time of year, so expect to see some flight trails.
The Nitecore TM16 (4xXM-L2) and AceBeam K60 (1xXHP70) will be examined in upcoming reviews.
Scroll down for direct beam measurements.
All my output numbers are relative for my home-made light box setup, as described on my flashlightreviews.ca website. You can directly compare all my relative output values from different reviews - i.e. an output value of "10" in one graph is the same as "10" in another. All runtimes are done under a cooling fan, except for any extended run Lo/Min modes (i.e. >12 hours) which are done without cooling.
I have devised a method for converting my lightbox relative output values (ROV) to estimated Lumens. See my How to convert Selfbuilt's Lightbox values to Lumens thread for more info.
Throw/Output Summary Chart:
My summary tables are reported in a manner consistent with the ANSI FL-1 standard for flashlight testing. Please see http://www.flashlightreviews.ca/FL1.htm for a discussion, and a description of all the terms used in these tables. Effective July 2012, I have updated all my Peak Intensity/Beam Distance measures with a NIST-certified Extech EA31 lightmeter (orange highlights).
The K40M is the highest output 1xMT-G2 light I've tested yet, marginally exceeding the Thrunite TN35 for output and throw. However, for all practical purposes, you could consider these two lights equivalent.
Here is how the K40M compares to the Vinh Nguyen K40Lvn lights I've been testing at the same time.
As with all lights that share this design, there is a stand-by current when in the "Stand By" mode of the control ring. But this current is very low (60uA), and will not be problem for regular use. And you can easily break this current by clicking the tailswitch off, or loosening the head a quarter turn.
Only 18650 Li-ion cells may be used in the light (i.e., doesn't support multiple CR123A primary cells).
The K40M is another good choice in the 1xMT-G2 class from Acebeam.
Building off the existing K40-series build, you get a solid offering here from AceBeam, with a lot of the popular features I described on my review the K50 (under the former company name of SupBeam). Note that the in-light charging feature of the larger 4xx18650 K50 is not available on the 3x18650 K40-series lights.
The K40M is also very similar to the Thrunite TN35 – with virtually identical performance (i.e., nearly equivalent max output and throw). Unfortunately, I hadn't tested my TN35 on 3100mAh 18650, but I would expect largely indistinguishable runtime performance there too. Like the earlier Acebeam/SupBeam and Thrunite lights, you get very flat regulation and excellent runtime on the K40M. Note that flat regulation is rare on the MT-G2 class lights as a whole.
Personally, I've always been a fan of the Acebeam/Thrunite builds. The user interface is clear and uncluttered, with a good ring feel. The ring has clear and firm detents, and the output levels are well spaced. The battery carrier is of solid construction, and works well. And the presence of an actual clicky switch is always welcomed, to cut any unnecessary standby drain.
For those who haven’t seen one in real life, the MT-G2 emitter typically produces a beautiful "floody" appearance, with a nice, soft neutral white tint. Thanks to the large reflector on the K40M, a good amount of throw is also provided (i.e., the more "traditional" flashlight beam pattern overall). While still not what most would consider a "thrower", you get a good combination beam here, with reasonable throw for excellent overall output.
For those looking for decent throw and super high output in a reasonably compact form (with a pleasing neutral white tint), the K40M is another strong option to consider. Beam pattern, user interface, output/runtime efficiency and regulation were all excellent in my testing.
K40M provided by GearBest.com for review.