Space Generator sites behind main speaker. 2-way, 1.4k Hz xo + global high pass. Passive level control: load impedance varies from 25 ohm @ maximum volume to 40 ohm @ minimum volume. Most main amps can drive main speaker and SG in parallel. When main amp drives Space Generator: SG matches main speaker sensitivity from low 80 dB to low 90 dB. When separate amp with level control and suitable power drives Space Generator: SG matches any main speaker up to mid-high 90 dB sensitivity.