Mid-bass speakers cover the frequency range from roughly 80–500 Hz — bass and lower midrange. In a Harley Touring build, they're typically installed in lower fairing, saddlebag, or dedicated cut-in positions to add low-frequency reinforcement below what fairing speakers can produce.
Mid-bass drivers generally require enclosures for proper performance — the available volume and shape at your chosen mounting position will affect which driver is appropriate. A dedicated amplifier channel with sufficient power is required. MAA can advise on sizing, enclosure requirements, and amplifier pairing for common Harley install positions.