Jumper A, B are used to control audio effect of bass range. A for lower limit while B for upper limit of the bass audio range. For some speakers, when Bass is turned up too much, the speaker show distortion. When that happens: we remove the jumper cap of jumper A to limit super low Bass to bring distortion lower. When we remove the cap of jumper B, Bass is increased while cap of Jumper B is on, Bass is decreased. Jumper C and D are used to control Treble range. When cap of both jumper C and D are on, the sound of treble is loudest. When only cap C is on, the treble sound is lower. When only cap D is on, further lower. When both caps of C and D are removed, there is no treble sound. (Generally speaking, with the four , you'd sooner or later find your best sound effect. Anywya, all effects still depend on your actual test.) How to use the splitter board: First connect as per our diagram above (Treble, Low, Input), connect to speaker, seal air , begin to hear music while optimize. Normally we use jumper A and let B idle. For jumper C and D: we need to hear the actual effect of treble. A general formula is: A+D = better Bass; A+C = clear Treble and Bass; A+CD = clear Treble and Bass (the overall effect inclined towards Treble); AB+CD = more mediant frequency. When Bass effect is unnecessarily high, remove cap A. Please optimize think the sound is best, and then fix the board with your speaker unit. Power: 400W or lower Resistance: 4-16ohm Frequency: Adjustable Colour: motherboard red Material: ABS + metal Size: 7*5*2.5cm Package Contents: 1 * Frequency Divider Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. Note: 1. Please allow 1-3 mm error due to manual measurement and 1-3g weight error make sure you don't mind before ordering. 2. Due to the lighting of the photos and the difference of monitors, the pictures may not reflect the actual color of the real item. Please make sure you don't mind before ordering, thank you! About Shipping: 1.please pay attention to your delivery address such as: name, street, house number, doorbell/email without name, etc. is correct, or the order will not be delivered correctly. 2.All items will be shipped within 3 business days after the payment is received. Most times you will receive them within 8-12 days then. The specific delivery time is depend on circumstances. 3.During the shopping process, if you have any questions, please feel free to consult us, we will reply you within 24 hours Hope you have a pleasant shopping experience!