Feature: Jumpers A, B are used to control the bass range audio effect. A for the lower limit and B for the upper limit of the bass audio range. For some speakers, when the Bass is raised too much, the speaker will show distortion. When this happens: We remove the jumper cap of jumper A to limit the super low bass to reduce distortion. When we remove the cap of the jumper B, the bass increases while the cap of the jumper B is active, the bass decreases. Jumpers C and D are used to control the treble range. When the hoods of both jumpers C and D are active, the treble sound is louder. When only cap C is active, the treble sound is lower. When only cap D is active, lower further. When both caps of C and D are removed, there is no high pitched sound. (In general, with the four jumpers, sooner or later you may find your best sound effect. However, all effects still depend on your actual test.) How to use the splitter card: First connect according to our diagram above (Treble, Bass, Input), connect to the speaker, seal the air gap, we can start hearing the music by optimizing. We normally use jumper A and leave B inactive. For jumpers C and D: we need to hear the real effect of the treble. A general formula is: A + D = better bass; A + C = cancel ups and downs; A + CD = Clear Treble and Bass (the overall effect inclined towards Treble); AB + CD = most average frequency. When the bass effect is unnecessarily high, we can remove the cap A. Optimize until you think the sound is the best, then fix the board with your speaker. Specification 100% new and high quality Model: YL-2088 Size: 7 x 5 x 2.5cm ColourAs shown Power: 400W or lower Resistance: 4-16ohm Frequency: Adjustable With 4 jumpers onboard to optimize your audio effect: Jumper A, B for bass; Jumper C, D for treble Package include : 1 x Audio Speaker Frequency Divider Note: Please be aware that due to your computer monitor display the color may have some difference between the picture and the real item. There is 2-3% difference according to manual measurement.