The Princeton Tec Quad is a 5mm LED headlamp with 3 brightness levels and an emergency flash mode. It runs on 3 AAA batteries and is advertised as using a regulator circuit for all modes of operation. It is water resistant to 1 meter and uses an adjustable elastic strap and pivoting headplate for ease of use and comfort.

Body: The body is polymer, with two pieces attached by a hinge. On the back is a knurled screw that holds the two sections together. The screw can be manipulated with your hand, but is also slotted with a groove wide enough to accept the tab on the plastic slider on the headband or a small coin. There is a seal between the two halves to prevent the entry of water and other environmental contaminants. On the top is a rubber panel which covers the switch. The forehead plate has no padded section. Instead the headband threads through 2 slots in the plate and rests directly against your forehead. This creates a complete lack of pressure points and more even distribution of pressure around your head. This makes the headlamp more comfortable during extended wear. The light assembly is tilt adjustable on the forehead plate which allows the light to point where you need it.

Bezel/Head: The bezel is recessed slightly and the LEDs are protected by a polycarbonate shield. Inside are four 5mm LEDs (impervious to all but very serious impacts) which sit in a metallic reflector area. Behind this is the current regulator circuit. Many lights with regulators use PWM circuits which cause the light to flicker when dimmed. You can often see this flicker when the light, or your eyes, move rapidly (such as when reading). This regulator does not cause any flickering of the LEDs. You only see smooth, constant light at all levels of brightness. The headlamp starts out at "high", and moves to the next mode (medium, low, flash) with each click of the switch. Leaving the switch alone for about 3 seconds allows the light to be extinguished by the next press of the switch.

There is a small red LED in the center of the bezel just below the 4 main LEDs. When the batteries are near the end of their functional life, this LED blinks rapidly several times when the light is turned on or off to indicate that a battery change would be a good idea.

Output: Output is in the form of a flood of white light. The white light produced by the LED is a high color temperature and produces good color rendition weighted toward the blue end of the spectrum. A slight bluish tint is detectable, but this tinting is not noticeable during normal use. Runtimes and output are listed in the table below.

Note too, that when the regulator cannot provide constant current to the LEDs, it doesn't just die. It gives you several more hours of "emergency light" which dims over time, hopefully giving you enough time to find your way to a new set of batteries.

Beam at one meter at target center

Runtime Plot: Hmmmmmm... there's supposed to be a regulator in there somewhere, but I certainly don't see it based on this graph of output on High. This looks like a standard alkaline discharge curve. In fact, it looks just like the graph in the instructions that came with the light which is supposed to be an example of what "non-regulated" LED output looks like. Perhaps on High the light switches to direct drive and the regulation kicks in at the medium and low levels. I'll do another runtime, but this time on medium with alkaline cells, and I'll try to fit in a NiMH graph as well... [See UPDATE below for reason why there was little/no regulation on high!]

Runtime completed with Maxell brand batteries. More information on runtime plots is available HERE.

Well, here we are - the runtime graph on Medium. Looks like after about 6 hours it switches to direct drive, hitting 50% after about 11½ hours.

Runtime completed with Energizer brand batteries. More information on runtime plots is available HERE.

Switch: The switch is a simple rubber covered clickie. Press once for high, twice for medium, 3 times for low, 4 times for off. Leaving the light at any particular output level for more than about 3 seconds will cause the next switch press to turn the light off.

Seals / Water Resistance: All around the battery compartment there is a rubber seal to prevent the entry of water. The rest of the light is also sealed and is rated by the manufacturer as being water resistant to 1 meter (dunkable).

If it gets wet inside, just disassemble as much a possible without tools and let it dry before using again.

Ergonomics: Ergonomics: Comfortable on the head, easy to adjust both the light and the headband. The light itself can be tilted on its forehead plate up to 90 deg, and it gently ratchets in place past stops on the hinge to prevent it from easily moving from its set angle.

Batteries: For batteries it takes either 3 alkaline, the new lithium L92 energizer AAA batteries, or rechargables. Yes, that's right, it takes the new lithium L92 batteries as well! This means much better performance than alkalines in cold weather. Rechargables will run the headlamp at reduced runtime and brightness levels.

To change out the batteries: unscrew the retaining screw on the back, open the hinged plate, drop out the old cells, place in new cells observing proper polarity. Close the hinged plate and tighten the screw.

Accessories: None

What I Liked: Waterproof to 1 meter, Tough/impact resistant, Current based regulation, Good battery life, Bright, Easy battery change, Lightweight, Accepts alkaline, lithium and rechargeable batteries, Easy to use.

What I Didn't Like: Not a thing.

Picky Little Things: Does not appear to be regulated on high with alkalines.

Conclusions: A very good headlamp and a definite step-up over other 4-LED 3xAAA cell headlamps. It provides good light and decent runtimes with multiple selectable brightness levels. A good flood-type companion to the PT EOS.

UPDATE from Princeton Tec. Here is why we had no regulation on high:

Initial testing on the Quad was not done with the Nichia super bright LEDs that we are using now. This was a last minute change as the super brights were just coming into production. The end result was less current regulation. With the superbrights you get 7-10 mins of regulation on high. If you use Lithium AAA the current regulation goes up to 1 hour on high. We are addressing the situation to see about adjusting the regulation which in turn will decrease the lumen output. As soon I have have more info I will let you know. We will be updating this info on our website and in consumer materials.

Quick Facts Table: