Pair of SB15NBAC30-8 5 Black Aluminum Cone Mid-bass speakers. These are great for building 2-way bookshelf speakers or as mid-range drivers in a 3-way system. SB Acoustics crimps the cone in four spots for additional stiffness. Smooth upper midrange especially off-axis.Vented cast aluminum chassis for optimum strength and low compressionGeometrically reinforced aluminum cone for optimum piston operation and reduced break-upSoft low damping rubber surround for improved transient responseNon-conducting fibre glass voice coil former for minimum dampingExtended copper sleeve on pole piece for low inductance and low distortionCCAW voice coil for reduced moving massLong life silver lead wiresVented pole piece for reduced compressionNormal price for a pair of these new is $160. Suggested Alignments Sealed box of 0.2 cubic foot with 3dB down of 79HzVented box of 0.35 cubic foot with 1.5 diameter vent by 6 long for f3 of 46HzVented box of 0.45 cubic foot with 1.5 diameter vent by 5 long for f3 of 42HzTwo SB15BNAC30-8 in 0.7 cubic foot with 2 diameter vent by 7 long for f3 of 45Hz, 93dB at 2.83V Original boxes and packaging included. All photos are of the actual speakers, not downloaded.