ViparSpectra XS4000 PAR & ePAR Tests and Review by Dr MJ Coco

The ViparSpectra XS-4000 is a large quantum board style grow light designed for 5’ x 3’ coverage. It is the largest fixture in XS series, which is the top line from ViparSpectra. The XS series fixtures feature top end Samsung LM301b diodes and Mean Well drivers. I have previously tested the XS-1000, XS-1500, and XS-2000. With this test and review of the XS-4000, I have completed the series.

The cost efficiency for the XS series is among the best I have measured and significantly better than other lights with top-end components. ViparSpectra offers the best deals through Amazon. We have an 8% discount code for the XS series fixtures that will combine with other sales. If you are interested in one of these lights for your grow, use discount code: DrmjcocoXS on Amazon (US Amazon) (Canada Amazon).

The XS series are well made and very easy to use. They feature thick ribbed aluminum heat sinks to help dissipate the heat, and convenient dimmer knobs on the end of the fixtures. They create a great spectrum with excellent density in their ideal coverage areas.

The ViparSpectra XS 4000 features a total of 1152 diodes, which is 2.4 diodes per watt. The XS series fixtures use a combination of 3000k and 5000k full spectrum Samsung LM301b diodes along with 660nm red and 730nm far-red diodes. On the XS-4000, there are 768 3000k diodes, 320 500k diodes, 60 red 660nm diodes, and 4 far-red 730nm diodes.

The far-red light at 730nm is outside of the traditional PAR range (400-700nm), and it is not measured in a traditional PAR test. However, new research has demonstrated that far-red light is Photosynthetically Active when combined with shorter wavelength light. The newly defined extended PAR (ePAR) range is 400-750nm. I now have both the Apogee SQ 500 PAR sensor (400-700nm) and the Apogee SQ 610 ePAR sensor (400-750nm). So I ran both traditional PAR tests and ePAR tests.

The ViparSpectra XS-4000 is a long and relatively skinny quantum board. It measures 110 x 28cm (43.5x11in). It is advertised for 5’ x 3’ coverage, which is not very common. I tested it in both 5’ x 3’ and the more common 4’ x 4’ spaces. It did well in both.

First, I set it up in the 150 x 90cm (5’ x 3’) test area for a traditional PAR test. I adjusted the height until I measured a maximum PPFD of 1000 µmol/m2 at 56cm (22in) above the sensor. The XS-4000 produced a great PAR map in this coverage area with edge values in the 600-800 µmol/m2 range and all of the corners above 500 µmol/m2. The Average PPFD was 732.9 µmol/m2, which is perfect. That average means that a total of 989.3 µmol of Usable Light reached the canopy. I measured the power draw at an even 500 watts, which gives the XS-4000 a Usable PAR Photon Efficiency of 1.98 µmol/w. However, the Usable Photon Efficiency is somewhat higher, because 500 watts is all of the power, but the 400-700nm PAR wavelengths do include all of the light produced by the ViparSpectra XS-4000.




After the PAR test, I ran an ePAR test with the fixture in the exact same position. The ePAR test includes the far-red light, which is not measured in a PAR test. The ViparSpectra XS-4000 produces a decent amount of far-red light, so including those photons led to higher density values across the map. The maximum ePPFD went up to 1033 µmol/m2 and the average ePPFD went up to 765.7 µmol/m2. The XS-4000 delivered a total of 1033.7 µmol of Usable light in the 400-750nm range. That is good for a Usable ePAR Photon Efficiency of 2.07 µmol/w.

The difference between PAR (400-700nm) and ePAR (400-750nm) is far-red light. Comparing the PAR and ePAR data we can evaluate the amount of far-red light that reached the canopy. There was an average density of 32.9 µmol/m2 across the 1.35 m2, which equates to a Usable far-red photon flux of 44.4 µmol/m2. Far-red light accounts for about 4.3% of the total light produced by the XS-4000 and it is well distributed across the canopy. There are only 4 diodes dedicated to far-red, but they are not the only source of this far-red light. The full spectrum 3000k diodes, emit a small portion of their energy in the Far-Red wavelengths. Most of the far-red light comes from them.



If you would like to know more information about XS4000, welcome to our Official Website:

I am impressed with the XS-4000’s performance in the 5’ x 3’ tests. However, 5’x 3’ is not a common size for grow spaces. Although the physical size of the XS-4000 certainly suggests rectangular coverage, the PAR and ePAR test data suggest that it might do well in a 4’ x 4’ space. Since, 4’ x 4’ grow spaces are very common, I decided to repeat the tests over that coverage area.

Moving from 5’ x 3’ to 4’ x 4’ expands the size of the test area by 1 square foot. When the test area expands the Photon Densities will decrease. In the 4’ x 4’ test area, the XS-4000 prodcued a maximum PPFD of 972 µmol/m2. I could have lowered the fixture a few centimeters, however, doing so would negatively affect distribution out to the edges. In order for the 11” wide fixture to cover a 4’ wide space, it cannot be hung too low. I decided to leave the fixture height unchanged at 46cm (22in).

The 4’ x 4’ PAR and ePAR maps are surprisingly good. In the PAR map, the corners fall slightly below the 500 µmol/m2 threshold, but barely. When we count the far-red photons in the ePAR map, we see that the entire canopy is in the prime photosynthetic range. Normally expanding the size of the test area will lead to more light reaching the canopy, but in this case, the Usable PPF and Photon Efficiency ticked down slightly. This is understandable, as we made the space marginally larger, but less well suited for the physical shape of the fixture.





I tested the on-board dimmer with the fixture in the 5’ x 3’ test area with both the Apogee PAR and ePAR sensors. The dimmer is continuously adjustable, with markings at 25, 50, and 75%. As you can see in the data, it is accurate and consistent throughout the dimming range. Both the PAR and ePAR densities dim in unison.

After running the tests, I measured the operating temperature. The heat sink hit a maximum temperature of 58.6C (137.5F). The drivers ran somewhat warmer and hit a maximum temperature of 62.8C (145F). These are reasonable temperatures for a 500-watt quantum board.

The XS series from ViparSpectra are solid grow lights. The have great build quality, feature top end components, perform very well in my tests, and come at amazing prices.

If you would like to know more information about XS4000, welcome to our Official Website: