The 545SD frequency response chart is similar, but not identical to the SM57; the 545SD would appear to have slightly more pronounced high-end response. Sorry if I'm wrong here, just trying to share an experience. Fuck my memory. It did sound more like a newer 57 than a 545. Shipped connected for low-impedance operation, the 545SD features a silent magnetic reed on/off switch with lock-on option. A favorite for instrument pickup and recording, the 545SD can also be used on lecterns in public address systems. The PE54 and 545 are almost exactly the same mic, not the same as the SM57 at all. It makes the SM57 sound like a flat response mic (although the SM57 is a great mic for its uses, just a different critter). I know what I've seen and heard - a very old SM57, exactly the same as a brand new one except that the label did not say "SM57" on it anywhere. What polar pattern does the 545SD have? The Shure SM57 unidirectional dynamic microphone is exceptional for musical instrument pickup or for vocals. If I remember correctly, the only real difference in the PE54 vs the 545 is the baffles. Manufacture of the SM57 moved to Shure’s Mexican manufacturing facility in 1985. I don't think it said Shure on it either, just unidyne III. The 545SD Classic Unidyne® Instrument Microphone is a dual-impedance, unidirectional, dynamic microphone. Are new SM57s as good as old SM57s? Grille for Shure SM57 and 545SD: RK244G: Cartridge for SM56 and SM57: R57: Certifications. With its bright, clean sound and carefully contoured presence rise, the SM57 is ideal for live sound reinforcement and recording. The predecessor to the SM57, the 545SD Classic Unidyne® Instrument Microphone is a dual-impedance, unidirectional, dynamic microphone. My description could not have been any better. Shure SM57: Shure Unidyne III 545 SD: These frequency response graphs pictured above are current, 2009 data based on production models, and they show that the Unidyne III sounds particularly different in the high range - quite possibly giving it a nice boost in that area that many engineers find desirable and "mojo" worthy.