The MB58R 122 P-4 is a 2x12" bass guitar cabinet in the Markbass MB58R series. It uses two Markbass classic ceramic speakers together with a new piezo tweeter, and handles 600 W (AES standard) at 4 ohms. A crossover at 3.5 kHz hands the top end to the tweeter.

The enclosure is built from a lightweight material that brings the weight down to 18.1 kg (39.9 lbs), which is the main point of the P line: traditional speaker character without the load. The cabinet has a rear reflex port and is built in Italy. Frequency response is stated as 40 Hz to 18 kHz with a sensitivity of 103 dB SPL.

Connection is as a passive speaker cabinet driven by a bass amplifier head. It measures 57.8 x 60 x 47 cm (W x H x D). The manufacturer lists product code MBL100121Y and offers a downloadable manual.