High Frequency Drivers

Model	Tenure	Original Impedance	AES Power Rating	Recommended Replacement Diaphragm	Comments
288	1945-1949	20-22 Ohms	20 Watts	20221 24 ohms 25885 16 ohms 25884   8 ohms	First permanent magnet high quality theater high frequency driver. Magnetic shorting ring must be removed by Altec  factory before installing new diaphragm.
288B	1949-1959	20-22-24Ohms	20 Watts	Same as above	Has deeper top plate than 288, otherwise similar to 288. Also must be converted by Altec before rediaphragming.
288C	1959-1972	24 Ohms	20 Watts	Same as above	Similar to 288B, has no shorting ring, however ought to be remagnetized.
288D	1959-1970	16 Ohms	20 Watts	Same as above	16 Ohm version of 288C
288-8E	1970-1972	8 Ohms	20 Watts	25884 8 Ohms 50 Watts	8 Ohm version of 288C.
288G Series	1972-1979	8, 16, 32 Ohms	20 Watts	34400 32, 20W 25885 16, 50W 25884   8, 50W	Improved larger Alnico magnet models, has 2 db more sensitivity over previous units. Also 2 db more output over 10KHZ.
288H Series	1979-1980	Same as above	20 watts	Same as above	Has new radial phasing plug, some increase of extreme high frequency performance over 288G, same magnet. Last of Alnico magnet models.
288K Series	1980-1987	Same as above	20 watts	Same as above	Ferrite magnet version of 288H. Same specifications.
288L Series	1987-----	8,16 Ohms	20 watts	25885 16, 50W 25884   8, 50W	Virtually identical to 288K. Built to more stringent tolerance.
291-16A 291-16B	1968-1973	16 Ohms	40 watts	25885 16, 50W	Composite diaphragm version of 288C. Has somewhat less high frequency performance and less transient response than 288s. Later 291s followed magnet development of 288s. Rediaphragm with 299 diaphragms.
299A	1987-----	8, 16 Ohms	50 watts	25885 16, 50W 25884   8, 50W	Newest Altec high frequency driver. Has good sound of 288 with 2½ times the power handling. Costs less. Use this unit whenever possible. When rebuilding older 288s or 291s, use its diaphragm.

Model	Tenure	Original Impedance	AES Power rating	Recommended replacement diaphragm	Comments
515	1945-1955	16-20 Ohms	35 watts	R515-16G, 75W R515-  8G, 75W	Original 515, has great midrange, lacks low bass.
515B	1955-1978	16 Ohms	75 Watts	Same as above	Has great low bass, impedance drops below 16 ohms in earlier versions at midrange. Later reconed units lack midrange. Recone with 515C series cones for bass horns will solve this problem. Works great in vented bass with standard cone.
515C	1978-1982	16 Ohms	75 Watts	Same as above	16" frame version of 515B. has regular constant impedance voice coil, lacks mids in horn enclosures. Great vented box woofer. Same remedies apply as 515B, last Alnico magnet 515.
515E	1982-1984	16 Ohms	75 Watts	Same as above	Ferrite magnet version of 515C. Lacks even more mids in horn enclosures. Don't use in larger VOT cabinets (210, 211). Great vented box woofer. Ok for A5, A7.
515G Series	1984-----	8, 16 Ohms	75 Watts	Same as above	Newest version of 515C. Built exclusively for horn enclosures. Don't use in vented or sealed boxes. Works better than any previous model. Great woofer.