This lets you compensate for deficiencies in your hearing that may be dramatically different for each ear. By equalizing the frequency response of both ears, you vastly improve speech intelligibility.
The MFJ-618 Sound-Field ExpansionTM adds a 3-dimensional spatial presence that can greatly improve speech intelligibility by up to an additional 3 dB. It’s like hearing and feeling the presence of a person directly in front of you. 10Wx3Hx6D. 12VDC or 110 VAC w/MFJ-1316.