[selfbuilt]

Warning: pic heavy, as usual.




The S18 is a new offering in the Maelstrom line from 4Sevens, clearly designed to compete the other "big gun" SST-90 lights. This review is of an engineering sample, but the shipping lights should have the same performance and features.

Manufacturer's Specifications:

• LED: Luminus SST-90
• Hi: 1200 OTF Lumens, 0.6 hours runtime
• Med: 400 OTF Lumens, 3.5 hours runtime
• Lo: 80 OTF Lumens, 17.5 hours runtime
• Strobe: 1200 lumens, 1.5 hours runtime
• SOS: 2.5 hours runtime
• Battery: 6xCR123A or 6x3.7V RCR Li-ion
• Operating Range: 4.5V~8.4V (reviewer note: I presume this refers to each of the 3 channels in the carrier)
• Body Material: Type-III hard-anodized aircraft-grade aluminum
• Bezel Material: Stainless steel strike-Bezel
• Lens Material: Optical-grade hardened glass lens with external sapphire coating to resist scratches and internal anti-reflective coating to maximize output
• Smooth reflector
• Water Resistance: IPX-8
• Included Accessories: Holster, instruction manual, 6xCR123A batteries, and spare o-rings
• Dimensions: Length 9.3 in, Diameter (Body) 1.8in, Diameter (Head) 2.48 in, Weight (without battery): 24.5 oz
• MSRP: $259 (before discounts)

Packaging is unknown, since I only had the light to go by. But I expect it will be fairly typical for the 4Sevens Maelstrom line.



From left to right: CR123A, 4Sevens X7, X10, S18, Olight SR90, Thrunite Catapult V3

All dimensions are given with no batteries installed, unless otherwise stated:

4Sevens S18: Weight: 700g (800g with 6xCR123A), Length: 233mm, Width (bezel) 63.0mm, (tailcap) 25.6mm
4Sevens X10: Weight: 156.9g (245.7g with 1x26650), Length: 135.5mm, Width (bezel): 46.0mm
Olight SR90: Weight: 1.6 kg (with battery pack), Length: 335mm, Width (bezel): 97mm
Catapult V3: Weight: 434.8g (500g with 4xCR123A), Length: 254mm, Width (bezel) 58.0mm, (tailcap) 35.1mm.

The S18 is a lot smaller and lighter than the SR90, and even smaller than the SR91 (which I don’t have, but is rated at 1.2 kg with battery pack, 286mm length, and 76mm bezel width).








The S12 is a hefty light (reminds me of a small mace ). Black anodizing (manufacturer claims type III = HA) is slightly glossy on the smooth areas, very much like the X10 and the rest of the Maelstrom line. Knurling is of reasonable strength (not overly aggressive), but there is a good amount of it. I found the grip to be very good.

Lettering is bright and clear on the body, but less distinct on the tailcap (may be due to my engineering sample, though).

One of the most distinctive things about this light is the battery carrier – it is integrated into the tailcap. Although the tailcap superficially looks a lot like the X10 I reviewed recently, the S18 uses an actual clicky switch (press for momentary, click for locked-on). Traverse is deeper than typical for a clicky switch, and this one feels very substantial. The whole tailcap/holder assembly has a very solid feel.

The holder fits six cells, is a 3x2 configuration. Both primary CR123A and protected 16340 (RCR) fit and work in the light. Note the light cannot take 3x18650. Contact points between the carrier and the head seem robust.

Light uses square-cut machinist threads, which are anodized. Threads feel somewhat gritty and stiff to me. Note that it takes a full one-and-a-quarter turn to lock out the light at the tailcap (i.e. the switch is internal to the battery carrier assembly, so you need the further distance to break the contact in the head). The tailcap remains firmly attached to the light at this distance.

Let’s take a closer look at the mode-selection aspect of the switch:




The tailcap is actually in two portions – the bottom portion (including the tailcap switch) can rotate relative to the rest of the carrier and base. The feel is not really a detent per se, but you will feel a slight click when the mode changes. Note the ring is quite stiff to turn, so you won’t be accidentally changing modes.

Scroll down to my UI section for a discussion of how it works.



The S18 uses the Luminus SST-90 emitter, well centered on my sample, with a smooth reflector (although there are some fine concentric rings in it). There were a few specs of dust inside the head on my sample, but that may also be due to the engineering sample nature of the light they sent me.

Here is how it compares to the Olight SR90:



And now the white-wall beamshots. All lights are on their respective rechargeable Li-ion battery source, except for the S18 which is on 4Sevens brand CR123A. Lights are about ~0.75 meter from a white wall (with the camera ~1.25 meters back from the wall). Automatic white balance on the camera, to minimize tint differences.

Let’s start with the Hi outputs:









Despite only using six CR123A, output on the S18 is pretty close to the Olight SR90 (which uses a custom battery back consisting of 6x18650). Note that on 6xRCR, the S18 is pretty equivalent to my SR90 in output.

Of course, the S18 doesn’t throw as far with the smaller head (i.e. the SR90 has a much more tightly-defined hotspot). I don’t have one to compare, but I imagine the S18 probably has a fairly similar beam to the Olight SR91.

To better compare to other lights, here is a comparison with the S18 on Med and the SR90 on Lo, compared to the X10 and TK35 on Hi:













UPDATE AUGUST 21, 2011: I have now done 100-yard outdoor beamshots, in the style of my earlier 100-yard round-up reviews.



User Interface

The S18 uses a forward-style clicky switch, with a longer than typical traverse. Press for momentary, click for locked-on.

Mode switching is controlled by turning the selection ring/tailcap relative to the rest of the carrier handle. Line up the arrow on the base with the appropriate pictogram on the carrier handle. Lo/Med/Hi are represented by the size of the solid dot on the carrier handle portion, Strobe is the lightning bolt, and SOS is self-explanatory.

PWM/Strobe

I could detect no sign of PWM on any constant-output mode, leading me to conclude the S18 is current-controlled on its Lo/Med modes.



Strobe frequency is 9.5 Hz in my testing.

Testing Method:

All my output numbers are relative for my home-made light box setup, a la Quickbeam's flashlightreviews.com method. 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.

I have recently devised a method for converting my lightbox relative output values (ROV) to estimated Lumens. See my How to convert Selfbuilt's Lighbox values to Lumens thread for more info.

Throw/Output Summary Chart:

Effective November 2010, I have revised my summary tables to match with the current ANSI FL-1 standard for flashlight testing. Please see http://www.sliderule.ca/FL1... for a description of the terms used in these tables.

It’s hard to accurately measure overall output on the SST90-based lights, as the heads are too large to fit in my lightbox. I have adjusted my lightbox relative output values to compensate for the lost output (based on a comparison of all my ceiling bounce numbers). But for lumen estimates, I have little comparison data at these levels, so take these lumen "guestimates" with a very BIG grain of salt. While the relative differences should hold pretty well, I have no data on absolute lumen values taken in a properly calibrated sphere at this range. I have rounded my Max "(est)" estimates to +/- 50 lumens, but accuracy should NOT be inferred to this level of precision - rely on those with properly calibrated spheres for that.



On 4Sevens brand CR123A, max output on the S18 seems to be at least as good as the manufacturer’s spec of 1200 lumens (I "guestimate" above 1300 lumens at activation). RCR is even brighter, over the first minutes at least (I guestimate over 1400 lumens at activation). This puts RCR output pretty much bang on with the Olight SR90. But of course, all of these lights drop in output over the course of their runs (i.e. even by ANSI FL-1 standard 3 mins, as shown the table above). Scroll down to the output/runtime graphs for a much better idea of what this looks like over time.

Throw is good for the size, but of course the S18 can’t throw as far as the much larger SR90 (or even a really well-focused XM-L light, like the Catapult).

Any way you slice it, the S18 definitely puts out a lot of light!

Output/Runtime Comparison:

Note: Unlike the Summary tables above, my runtime graphs are all based the actual relative output of my lightbox. However, my relative output scale is not linear for output across this range (which is why I convert to estimated lumens for the Summary tables). And again, since the large heads of the S18 and SR90 don’t fit in my lightbox, I have had to adjust my lightbox calibration to compensate for the lost output (based on a comparison of my ceiling bounce numbers).

As a reminder again, all my runtimes are done under a cooling fan. Primary CR123A runtimes are done on Titanium Innovations cells.





The S18 seems to use a very similar regulation/thermal step-down feature as the X10 I reviewed recently. On 6xCR123A on Max, there is little evidence of the thermal management cutting in, except at the very end of the "regulated" run (but again, this is under a cooling fan). On 6xRCR, the pattern is very similar to the X10 - output is initially a bit higher, until the first thermal step-down occurs.

Like the X10, 4Sevens seems to be conservatively using the lowest “regulated” lumen level for their specs on this light, even though it spends most of the time above this level. But again, that is with a cooling fan – it’s likely output would have dropped more if I was hand-holding, or using no external cooling. And again, I don’t have a calibrated integrating sphere to provide exact numbers.

Potential Issues

18650 cells cannot be used in the light, only CR123A and 16340 (RCR). Since the light doesn’t use a custom battery pack, it is critical the user ensure that all cells are of comparable quality, capacity and charge state (at all times).

Mode selection ring is stiff to turn, and lacks defined detents (although you will feel a slight "click" as it enters each mode).

Tailcap needs to be turned at least one-and-a-quarter full turns to lock out the light. But there are still plenty threads at this length, so the light remains securely assembled when locked out.

The S18 is a hefty light to carry around. There is no wrist/shoulder lanyard attachment point for carry.

The light cannot tailstand.

Preliminary Observations

The S18 is a powerhouse light.

On 6xRCR on Max, output matches my SST-90-based Olight SR90 (although of course, runtime is far less). 6xCR123A Max output is a slightly lower, but not by much – and runtime is noticeably improved. Although throw is of course less on the S18 (due to the smaller head – think SR91 for a comparable), this level of performance on standard batteries is amazing.

The S18 superficially resembles the S12/X10, but on a much larger scale. More importantly, the switch button conceals an actual clicky switch here (press for momentary, click for locked-on). One of the main complaints on the S12/X10 was the pressure-switch-only option.

The other issue on the S12/X10 was the Hi/Lo user interface. I am happy to report the S18 also has multiple modes (including blinky modes for those who like them ), all easily accessible from a turn of the labeled tailcap control ring. I actually like the fact the selection ring is stiff on my sample, it reduces the risk of accidental mode changes.

I originally wondered why there were so many threads to screw this light together, but it quickly became apparent – in order to lock out the light, you need to move the whole battery carrier away from the contact plate in the head. Since that takes a full one-and-a-quarter turns of the tailcap, you want to make sure the light is still securely held together at this distance (which it is). Threads are fairly stiff and gritty on my sample, but I found the lock-out to work reliably.

While I always recommend you lock-out you lights when not in use, I’m thinking it is even more critical than usual here - due to the user-controlled six-cell arrangement. A custom rechargeable battery pack (as Olight developed for the SR50/90 series lights) adds to cost and limits flexibility, but it does offer the safety of balancing circuitry. On the S18, it is up to the user to ensure the cells are all from the same batch of the same brand (important for age, chemistry, etc), with comparable charge state, at all times.

I am sure one of the main selling features of this light for "search and rescue" will be the ability to use standard CR1213A cells. Max output on 6xCR123A is comparable to the thermally-regulated level of the 6xRCR configuration - and the runtime is impressive. Again, just make sure you use quality cells, ideally those already balanced and packaged in pairs (and all from the same batch). It's too bad the light can't take 18650, but I guess 3x sources just weren't sufficient to power the light.

In summary, the S18 is an impressive light, well suited to its intended S&R role. Built around commonly available CR123A and RCR cells, it pretty much matches the Olight SR90/91 series in overall output, while being only 1/2 to 2/3rds the weight of the SR90 and SR91, respectively. I can’t think of anything else quite like it on the market at the moment.

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S18 provided by 4Sevens for review.