Quad CREE XT-E build

[Techjunkie]

I collected the parts to do a Quad LED Mag 2C build a while ago, but wasn't feeling very inspired to put it all together. On hearing of the new CREE XT-E emitter, I decided it was time. Here's the parts:

(Some assembly required)


I'm hoping that the 20x20mm SMO reflectors on the left will focus well. If they don't, my backup options are what you see on the right.

The boost driver runs from 2x Li-Ion cells. I'll probably hone the tube to accept the AW IMR26500 cells, but I'll also do the tailcap to allow the light to run on 22650s (and 18650s).

Not sure when I'll get started, but now that I have all the parts, it probably won't be long.

[seven11]

It'll be interesting to see what those smooth reflectors do with that optic. It'd be awesome if it gave the light some nice throw. Did you make the heatsink yourself or did you purchase it somewhere?

[Techjunkie]

It'll be interesting to see what those smooth reflectors do with that optic. It'd be awesome if it gave the light some nice throw. Did you make the heatsink yourself or did you purchase it somewhere?

The heatsink is a PES C that's been machined flat (Perfect Emitter Sink). It's either the optic or the reflectors, not both. The XT-E is an odd emitter. The LED under the dome isn't flat, it's got four little crests like the paper wish-maker kids used to fold up. The design is probably intended to improve side emitting. I'm hoping that translates to the reflectors being able to gather more light and concentrate it forward. (It'll probably look horrible in an aspheric.) We soon shall see.

[Mike S]

I'm eager to see how the XT-E works with those different optics. It didn't look very nice when I used them with an XP-G reflector. The corona had a very strong blue tint with some shades of yellow.

[Techjunkie]

Just a quick update that I can finally post now that CPF is back from maintenance for the time being...

XT-E is a tough emitter to focus when throw is your goal, especially the warm white ones that I've chosen. If you're disappointed by the way that the color of an XM-L emitter's beam profile, when used in a smooth mirror reflector, completely differs from spot to corona to spill, you'd hate the XT-E altogether, especially the warm tinted ones.

The emitter itself focused rather well in the small but deep SMO reflectors I had intended to use, but the hotspot was a crazy bulls-eye of warm and cold light. No matter how I played with it, it was the ugliest I'd ever seen. A Mag LED reflector did a better job of maintaining a single color hotspot, but one XT-E by itself in one of those reflectors still isn't very pretty and the output isn't worth the bother. Don't tune out yet though, success will follow...

Trying orange peel textured reflectors didn't yield much of an improvement in aesthetics. Small ones scattered the light around too much to form much of a hotspot or provide much intensity. A large 53mm MOP reflector cast a strong hotspot, but there was a detectable two-tone nature to the hotspot there as well.

This called for something that would combine all parts/tints of the emitter output into one unified color and still maintain decent intensity. That's where the Ledil Boom Spot (20mm microfaceted) reflectors excelled above all others. Anyone who's used them with MC-E emitters for which they're intended knows that they don't provide the spot that their name would seem to imply. Despite being smaller, the XT-E is no different in this case, the beam is pretty floody, but is definitely brighter / more intense than with the little MOP reflectors and it's all one lovely consistent hi-CRI color. I've discovered that placing a SuprlusShed L6692 Aspheric lens (from my aspheric-enhanced incan light projects) over all four Ledil Booms helps to intensify the beam even more by concentrating the wide swath of light into a narrower angle. (This not the traditional flood to zoom LED + aspheric approach.)

If I had selected the coldest possible tint XT-E instead of the 3000K variety, there might not have been such tint variation from one part of the profile to the next and I could have stuck it out with the SMO reflectors. I might never know, because I don't realistically see myself starting any projects with XT-Es after this. They just have too many limitations, and I prefer a neutral 5000K tint throwers most of all.

The challenge to finishing this project now is to grind away the Ledil Booms and the Mag head's ID just enough to allow four to fit (silly me, I thought they would fit in the head just because the fit in the bezel - oops, big difference.)

Also, in the process of all the fiddling and testing I shorted out the coil on that lovely boost driver and killed it. I think now I'll switch the circuit to a 2x2 8135 recipe, which I'll describe later. That will provide for 3 nicely spaced modes with no disco strobe and a higher output on high, but it will also eliminate the LiFePO4 3.0V cell option that was possible with the boost driver.

I now have to decide between my available IMR battery options:
2 x BestInOne 18650 cells ~$10 shipped
2x AW 26500 cells ~$40 shipped
2x BatterySpace 22650 ~20 shipped (B.I.W. 22650 have recessed tops and can't be used in series)
swap the 2C host for a 3C host and use 2x 26650 cells I have available ~$20

Right now, I'm inclined toward the cheapest battery solution.

[Mike S]

Thanks for the update. Have you tried the TIR optic? I'm not real familiar with the acronyms and may have missed it. Also, what are you're thoughts on switching to the XB-D with its smaller apparent die size?