brand new and high quality Introduction: The radiator, used to replace the inverted tube, is also called passive speaker. The low frequency dive depth is equivalent to the reverse type. However, the sense of speed is obviously faster than that of the reverse type, which has the advantage of a certain closed box, and at the same for time completely eliminates the drawback of the inverted structure - that is, the wind noise brought by the inverted nozzle. The best choice for speed to make subwoofers with radiation basins. Instructions: The speaker to open a subwoofer hole, the film installed, the entire box closed, airtight. Working Principle: Speakers in the work will be up and down vibration, vibration will produce airflow between the film by this air flow driven low frequency. Features: Using excellent for raw materials, lower power consumption. Bass passive film effect: to enhance the sound effect. Bass strengthening agent, to strengthen the , easy to design and debug. Great accessories for sand table, war game or WWII scenery layout. Used for Speaker,Woofer, Loudspeaker, vibrating. Vibrating Membrane only, other accessories demo in the picture are not included! Specification: Material: Rubber Type: Speaker Accessories Number of Channels: Multi-channel Color: Black Diameter: 113.6mm/ 4.47in Quantity: 2 Pcs Note: 1.No retail package. 2.Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. 3.Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package includes: 1 Set x Vibrating Membrane