This attenuator has three knobs for tonal control. The main volume is controlled by the BASS knob. Then to control the mids and treble, use the MIDDLE knob and TREBLE knob. The middle and treble controls are always dependent on the main volume control. Be aware that the higher the setting on the main knob, the less the effect of the treble compensation. For instance, if you turn the main knob all the way to 10, you'll notice very little change in the tone as you turn the treble compensation from one end to the other. The line out signal EQ is dependent on your amplifier settings, with only a volume and tone control on the unit.
May be used on 4, 8, and 16 ohm amplifiers. This MASS is unique in that it has an actual tone stack for the speaker signal -- BASS - MIDS - TREBLE. It also has the internal speaker motor for the load, and has a variable line out signal with volume and tone. The unit has two speaker output jacks to support multiple cabinets. The three tone controls can take the signal from whisper quiet to full on with slight humps in the bass, mids, and treble.
Additionally, the MASS III has an active bypass circuit with a footswitch so you can run attenuated or bypassed. The footswitch has a 12' cable, and the power pack for the switching relays is a 7.5VDC wall wart. With no power applied, the attenuator is still usable. The power is just for the footswitch circuitry.
Like all Weber attenuators, you can turn all attenuator controls to zero, pull the speaker, and just use the line out, making the MASS III a dummy load.
Optional wings may be employed for rackmounting the MASS (sold separately). The MASS III occupies two rack spaces and requires adequate ventilation for proper operation.