DIY kits, you need solder its yourself.The onboard bass frequency adjustment point device can be used for a wide range of adjustments, so that the subwoofer can be harmoniously integrated into the mid-to-high-pitched atmosphere without a sense of violation. The phase switch is designed to be compatible with both in-phase and inverting amplifiers.Both full frequency and low frequency output signals have separate interfaces for convenience and practicality.Parameter:Product Name: 2.0+0.1 Low Pass Filter PreampChip model: NE5532 78M12Input voltage: DC 12-30V AC 9-20VArchitecture: Dual 5532 2.0 Full Tone + 0.1 BassFrequency range: full tone 20-20KHz bass 20-200HzFeatures: 2.0+0.1 volume controllable bass frequency phase adjustablecolour:blueMaterial:Metal +pcSize: about 98*40*23mmPackage Contents:1* 2.1 channel subwoofer preamp board Diy KitNote: This product is not directly connected to the speaker, you need to match the amplifier to drive the subwoofer. The performance of the bass has a lot to do with the frequency response of the amplifier and the speaker and the cabinet. Please treat it rationally!Only the above package content, other products are not included.Note: Light shooting 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.