This four-jumper kit provides precise bass and treble control using jumpers labeled A, B, C, and D. How it works - Bridge A: removing the jumper cap limits the super low bass and reduces distortion. - Bridge B: removing the jumper cap increases bass; with the B cap on, bass is reduced. - Bridges C and D: control the high frequency range; when the caps on C and D light up, the treble is the loudest. Bass control details - Jumpers A and B shape the bass range: A defines the lower limit, B defines the upper limit of the bass range. - Some speakers can distort if the bass is set too high. Treble control details - Jumpers C and D govern the high frequency range; lighting up their caps increases treble output. Benefits - Fine-tune bass and treble to match your speaker system and room conditions. - Reduce distortion by adjusting low-bass settings with Bridge A. - Increase bass impact or reduce bass presence with Bridge B as needed. - Boost treble when desired by enabling Caps on Jumpers C and D. What you get and compatibility - Includes four labeled jumpers (A, B, C, D) and corresponding caps for sound shaping. - Designed for systems that use jumper-cap based adjustments; compatible with equipment that supports A-D bass/treble control. Use scenarios - Home stereo or bookshelf speakers in small to medium rooms needing less distortion at high bass power. - Studio or monitoring setups where precise treble boost is required without changing hardware. - Quick on-the-fly tuning for different music genres, from bass-heavy tracks to bright, detailed mixes. Note: This description reflects the original product functions and jumpers A–D behavior without adding new features or claims.