Emerald Physics BOM Bass Equalizer (EQ) Analog Bass Optimization Module

Tested and works great. Condition is excellent. First two photos are mine and second two are from the manufacturer so you can more easily read the front and back panels.
Use with any brand speaker for improved bass performance.
The Bass Optimization Module (BOM) is a fully adjustable 4-pole Linkwitz Transform Function analog bass equalizer. It is designed to tailor the bass response of any speaker by adding an addition 5-15Hz of low bass and optimize the amount of bass from the speaker to match your room's acoustics. You use two of the pots to enter the "Q" (type of design. ie acoustic suspension, ported or open baffle) and "Fs" resonance (more or less the -3dB point) of your speaker. Then, you use the other two pots to dial in your target additional bass required and target "Fs" (expressed as boost). The EQ changes the woofer output from your actual curve to the target curve.The BOM works with any speaker and can add an extra 5-15Hz of low bass and offers level adjustment of that bass.
Size: 8"w x 1.9"h x 5"d 6" with controls & inputs
Includes: Power adaptor