The 15" Altec Lansing 421A Bass Musical Instrument Speaker DIA-Cone is a vintage audio unit manufactured by Altec Lansing in the United States. This speaker model is designed specifically for musical instruments and provides a rich, deep bass sound. With its unique DIA-Cone design, it delivers a powerful and clear audio experience, making it a popular choice for musicians and audio enthusiasts looking for a high-quality speaker for their vintage audio collection.