Since their introduction in the last few months, the XM 15000K metal halide lamps have generated a lot of interest. This article presents a complete analysis of these lamps. The lamps and ballasts used for the evaluation are presented in Table 1 below. As usual these lamps were tested using the identical setup to all my previous tests [1], thus allowing for direct comparison between the lamps.

Table 1: List of XM 15000K lamps and ballast tests reported in this article

XM 400W 15000K

Table 2: XM 400W 15000K performance on all ballasts

Figure 1: Spectral data for XM 400W 15000K Lamps on all ballasts

XM 250W 15000K Mogul Base

Table 3: XM 250W 15000K Mogul Base performance on all ballasts

Figure 2: Spectral data for XM 250W 15000K Mogul Base Lamps on all ballasts

XM 250W 15000K Double Ended Lamps

Table 4: XM 250W 15000K Double Ended Lamps performance on all ballasts (unshielded)

Figure 3: Spectral data for XM 250W 15000K Double Ended Lamps on all ballasts (Unshielded)

Table 5: XM 250W 15000K Double Ended Lamps Performance on all ballasts (Shielded)

Figure 4: Spectral data for XM 250W 15000K Double Ended Lamps on all ballasts (Shielded)

XM 175W 15000K Mogul base

Table 6: XM 175W 15000K Mogul base performance on all ballasts

Figure 5: Spectral data for XM 175W 15000K Mogul base Lamps on all ballasts

XM 150W 15000K Double Ended

Table 7: XM 150W 15000K Double Ended performance on all ballasts (Unshielded)

Figure 6: Spectral data for XM 150W 15000K Double Ended Lamps on all ballasts (UnShielded)

Table 8: XM 150W 15000K Double Ended performance on all ballasts (Shielded)

Figure 7: Spectral data for XM 150W 15000K Double Ended Lamps on all ballasts (Shielded)

Discussion and Summary

A question of interest for most hobbyists is – How do this lamps compare to the XM 20000K lamps.? Table 9 shows a comparison of the PPFD values for the XM 15000K lamps and the XM 20000K lamps. What is interesting to note is that several of the lamps – the 250W mogul ended, 250W DE, and 150W DE lamps had in fact correlated color temperatures around 15000K. For the other lamps the Licor software used with the spectroradiometer was unable to compute the correlated color temperature. Spectral plots of all these lamps on “HQI” ballasts (except 175 which is on magnetic ballast) are shown in figure 8. They all have very similar spectral shape, yet the color temperature was not computable in all cases (More on Color Temperature in a future article).

Figure 8: Spectral plots of all XM 15000K lamps on “HQI” ballasts

Table 9: Comparison of PPFD with XM 20000K lamps

Figure 9: Spectral comparison of a XM 400W 15000K lamp with a XM 20000K lamp

na – data not available

A comparison with the spectral plot of a XM 20000K lamp is shown in figure 9. As seen from the figure, the XM 15000K when compared to a XM 20000K on the same ballast does have less output in the blue region at 454nm and 420nm, and has higher output from 460 nm -700nm (except for around 550 nm). This would tend to indicate that this lamp would appear less blue than a XM 400W 20000K lamp and hence a rating of 15000K.

Comparison of the 250W Mogul XM 15000K with its 20000K counterpart reveals very similar results to that of the 400W lamp, as seen in figure 10, and similarly for the 250W DE lamps as seen in figure 11.

Acknowledgements

I would like to thank several people whose help made this study possible. They were kind enough to provide us with lamps and ballasts for testing: Jason Ghee from Hellolights.com for supplying the lamps used in this study, Patrick at PFO Lighting, Andy at IceCap Inc, Perry at Sunlight Supply, Vince at Ocean Encounters, Champion Lighting, and Reef Fanatics for the ballasts. Finally, I would like to thank Dr. Paul Walker of Penn State University for the use of the spectroradiometer.

Figure 10: Spectral comparison of a XM 250W 15000K lamp with a XM 20000K lamp

References

1. www.reeflightinginfo.arvixe.com

Figure 11: Spectral comparison of a XM 250W DE 15000K lamp with a XM 20000K lamp