This is the original, vintage C451 which is discontinued, not the current mic with a similar model number.
The mic is a system consisting of a preamp body and various capsules, pads, and accessories. The configuration this review primarily pertains to is the body with the CK1 cardioid capsule and 10 and 20 dB screw-in pads. The pads are attacked between the capsule and body as needed. In this configuration (the most common) the mic is a typical professional quality SDC conderser mic, front address, pencil form factor. It's commonly used on anything where good definition of high frequencies is desired, such as overheads, strings, snare drum (with a pad installed), piano, etc.
However, with the addition of some of the accessories this mic becomes extremely versatile. In addition to the various interchangeable capsules (omni, cardiod, hypercardiod, and shotgun) and the pads, accessories include a pop filter for use as a vocal mic (that makes it look like a ball mic), and extender (non-flexible gooseneck) tubes for use on lecterns, over choirs, and many other applications. There are photos of The Beatles using 451s with the gooseneck and pop filter on vocals. If you've seen a pic of Paul singing into a ball windscreen mounted on a very long, thin tube with an approximately 45 degree angle about 2/3 of the way toward the head and wondered "What the heck is THAT???", now you know. There are also, of course, the usual shock mounts and clips available. Here is a website that shows pic of many of the capsules, as well as many other vintage AKG mics. Vintage microphones
The 451 stuff starts at the bottom of the page and continues on the next.
Back when I worked for Bill Graham's FM Productions we had a flight case about the size of a guitar case that contained a matched pair of C451Es along with the full set of accessories. Very impressive and cool.
The 451EB is the slightly newer model of the 451E - both take the same interchangeable accessories. Discontinued in 1984.
I have been using a trio of AKG c451eb's with CK1 capsules and A-51 elbow joints (to angle the capsule) for several years now. I find this mic to be very excellent on drum overheads and acoustic guitar.
-On vintage acoustic guitar, this mic/capsule combination can provide a great sound. The high end sound capture of the microphone provides a very vibrant nuance when recording older guitars (or guitars with slightly dead strings). However, I tried putting the c451eb up on a very expensive and new Taylor acoustic, and the sound was as harsh as can be. It has never taken me long to decide what sources this mic sounds great on, and what sources it doesn't. In my experience, it sounds either good or bad, and it's easy to discern the difference.
-On drum overheads, I have found this mic/capsule combination to be fantastic. It excels at making the drum set sound lively when mixed with the drum mics. Now again, I must say that although I really love this mic on overheads, there are situations where it doesn't work for me. If a drummer is a heavy hitter on their cymbals, you will not want to use these mics. If the drummer is big on accenting the beat with hihats, then you will not want to use these mics. However, if the drummer is big on beating their drums, and they don't put as much emphasis on the cymbals while they play, then you may love these mics like I do. They provide a certain recognizable attack to the drums (when used on overheads) that combines so well with the drum mics.
Three other points I should mention:1) The c451e/eb has a transformer on the output. This may be why many people love these discontinued models, while disliking the current c451b, which does not have a transformer. While both old and new versions of this mic have a priority to display their high frequency, I hear countless people say the c451b's (current) are brittle, and the c451e/eb (vintage) are pleasantly focused.
2) When using the mics as a trio, I was also able to get some great drum sounds. By using a pair on overheads, as well as the third mic on the snare top paired with either an Audix i5 or Shure SM57, I was able to get some huge drum sounds.
3) Lastly, I should mention that as of lately, I have been putting my CK1 capsules on my Chameleon Labs TS-1 mkII microphone bodies. These allow me to put a tube and transformer behind that amazing capsule, and also drive that tube at variable voltages, which is an interesting capability that the power supply of the TS-1 mkII provides. This combination has given me some of the greatest drum sounds I have ever achieved.
I'd say these are fairly iconic mics, having been around since the 60's, and still in production today. I have a pair of the C 451 E with CK1 capsules that I have owned a short while. One of them has an intermittent noise but I think I have narrowed it down to a shorted capacitor and am waiting on a replacement.
These mics really are bright, but the amplifier, which terminates to a small audio transformer, provides a bit of vintage "warmth" or sheen. What I really like also is how the low end comes across really tight and snappy. There's that good fast SDC response going on.
I have only used these on a few things so far. On acoustic guitar the sound is superb, particularly on picked parts more than strummed ones, a classic sound you might recognize. On drum overheads, you basically get the "OK Computer" sound, bright cymbals and strong attack from the drums themselves which combines nicely with the close mics. Another iconic sound for me. I'd place a bet these were used on that album. It's bright and in your face, but not at all harsh. Just a bit aggressive, and airy.
As a distant percussion mic on a pair of tom toms with a snare, I was so pleased at the resulting track. There was a nice sizzle and sense of room tone.
I'm seeing some promise as a close mic on amplifiers! Steve Albini tipped me off. Haven't used it on a real mix yet but I have used KSM137 and KM184 successfully to date. As a beginner, SDC on amps sounded like a crazy idea but I really like the tightness of the sound now that I've gone there.
I've come close to selling these a few times but I think they're maybe worth keeping now, even if I don't use them every day. A light to the more usual dark, maybe.