There are typical two different types of ballasts for HID bulbs, magnetic and electronic (or digital). Although magnetic ballasts are reliable and last for a long time, they have obvious drawbacks such as bulky, heavy, making noises, and un-controllable. In recently years, electronic ballasts have gained popularity especially in the horticulture industry. While the majority of digital ballasts, which are high and ultra high frequency ballast with range of 50 KHz to 200 KHz, work well with Metal Halide and High Pressure Sodium, they may have resonance issues when used with Ceramic Metal Halide. A low frequency digital ballast, 100-400 Hz, is a perfect match-up with CMH bulbs. Compared with high frequency ballast, the low frequency ballast has the following advantages:


  • Compatible with CMH, MH, and HPS
  • The output frequency does not change when the output wattage tuned down or high. So that the bulb spectrum does not change when wattage changes
  • Much less Radio Frequency (RF) interference
  • Lasts longer
  • Completely avoid resonance problem for HID bulbs

High Pressure Sodium (HPS), Metal Halides (MH) and Ceramic Metal Halides (CMH) are different types of High Intensity Discharge (HID) bulbs. Their wattages range from 50W to 1000W. The typical arc tubes in HPS, MH and CMH are made of translucent aluminum oxide, quartz, and ceramic respectively. Ballasts are needed to light up those HID bulbs. Since ceramic arc tubes will sustain much higher arc tube temperatures, the CMH bulbs will deliver better efficacy, color rendering and color stability.

A typical HID bulb has a frequency between 10 KHz and 300 KHz. While the bulb is lit by an ultra frequency ballast, both ballast output frequency and bulb internal frequencies will gradually change. When those two frequency get close, resonance occurs. The HID bulbs, particularly CMH bulbs, will fail if resonance is not stopped quickly. However some ballasts may have a senor to avoid resonance. Check your ballast manufacture for detail information.

For the indoor grow horticulture industry, light acts like food for the plant. When humans consume food, we are interested not only in the amount of food but nutrition as well. For example, we can eat a lot of “junk” food, however that will not provide any health benefit to our body. On the other side of the spectrum, if we only eat Vitamin C or other nutrition, we could starve to death.

It’s the same for horticulture lighting, the Par Value is the amount of food and the light Spectrum is the nutrition for plants.

LEDs are good nutrition but do not provide amount of “Food” (low Par value).

HPS and MH are good amount of food but lack nutrition.

CMH is the perfect combination of amount of food (high Par value) and excellent nutrition (some UV, full spectrum)

Therefore, Cultilux CMH is the best overall nutrition for plants, because the Cultilux CMH spectrum peaks match Chlorophyll A and Chlorophyll B.