The bass and treble control jumper set uses removable jumpers A, B, C and D to tailor speaker sound. A and B adjust the bass range; C and D adjust the treble range. Cap state (on or removed) determines the effect. Key functions - A and B control bass: A sets the lower limit, B the upper limit of the bass range. - C and D control treble: both contribute to treble output when caps are used. - Cap on B reduces bass; remove the cap from B to increase bass. - Cap on A is used to limit ultra-deep bass and reduce distortion; removing the cap from A achieves this effect. - Cap on C and D makes treble the loudest; removing caps from C and D reduces treble. Why you need it - Fine-tune sound to your room and listening preferences without electronics or software. - Reduce bass-related distortion on compatible speakers by adjusting A. - Increase or decrease bass presence quickly with B, for music or movie content. - Maximize or soften treble by managing C and D caps, for brightness or calmness. Compatibility and use - Designed for speakers that use removable jumpers labeled A, B, C and D. - Simple mechanical adjustments provide immediate, repeatable results. Use scenarios - In a small room with bass distortion: remove the cap from A to limit extremely deep bass and reduce distortion. - Want more bass for musical passages: remove the cap from B to boost bass; re-install B’s cap to reduce bass. - Prefer brighter sound: install caps on C and D to achieve the loudest treble; remove caps for a softer treble. Note: Some speakers may respond differently; adjust gradually and test with your typical content to find the best balance.