Having had the hypercardioid (CK93) capsule of the the AKG Blueline modular mics for some years (with the SE 300B body/pre-amplifier), I picked up the fig 8 capsule (CK94) and another SE 300B a few months ago (see my post on it here), and have just now added the CK91 cardioid and CK92 omni capsules to the family: a good used bargain, all the way from Shetland, in excellent condition. Although the CK91 cardioid was apparently a staple of radio studios etc. for many years, in the filmmaking world a myth has built up that the hypercardioid was the cream of the crop and by far the best capsule. I suspect this came about since the AKG CK93 is an excellent hypercardioid, and much better than the few alternatives that were available for a modest price (e.g. the Oktava MK012) rather than based on any actual hands-on comparison between the different Blueline capsules.
Certainly, I have begun doing tests and am impressed straight away by how remarkably similar the capsules sound – initially just testing on acoustic guitar and vocals. There really is no stand out or weaker capsule amongst these four (I can’t speak for the CK98 shotgun capsule, which I don’t have and haven’t heard). And equally impressive is how rounded or smooth they all are. For instance, the CK91 cardioid has none of the brittleness of my Rode NT55 cardioid capsules. A surprising extra is that the AKG CK91, CK92 and CK93 capsules also have less evident self-noise than the Rode NT55 mics, despite the specifications suggesting the reverse (17dB vs 15dB). These really have to be some of the most underrated mics out there: great value new (if you can find stock still, as they appear to be being discontinued) and even better used.
I bought the latest two AKG capsules to give me more options for a mid-side pair with the CK94 fig 8 capsule. OK I could use other SDC mics I have (such as the NT55s), but it is nicer to have a more consistent sound across the pair in the mid-side array: that the AKG capsules also sound better is a bonus. When I get the opportunity I will post some samples with the various capsules.