A microphone for the kick drum: Is the AKG D12 the only valid choice?
It is commonly, and wrongly, thought that it is essential to use a particular make and model of microphone for a certain instrument. There is no example more classic than the AKG D12 microphone, which is highly regarded for use on the kick drum (or bass drum if you prefer).
The D12 went out of production many years ago, but AKG fortunately replaced it with the similarly-styled D112. (The 'D' stands for 'dynamic', by the way. All of AKG's 'D' models are dynamic mics.)
In 2012, AKG took another step and introduced the D12VR. The 'VR' stands for 'Vintage Reissue') so we can assume that AKG intends that this model should imitate the sound of the original D12. Or at least that buyers should think this is so. Few potential buyers would have access to an original D12 to make a comparison.
There are however some very significant differences in construction, in particular an active filter circuit that requires phantom power to operate (the mic will still work without phantom power, but obviously without the active filter). One important similarity is the internal 'bass chamber' that boosts frequencies around 60 - 120 Hz.
What is interesting is that the D12 was originally intended to be a vocal mic. However it was found to work very well for bass instruments, so a 'classic mic' was born.
Time moves on however and microphone manufacturers seek to improve their products in terms of performance and profitability. Sometimes they have to change design because certain components that were originally used cease to be available.
So the result is that although the D112 is based on the D12, it doesn't quite sound like a D12. And although the D12VR is styled on the D12, it is by no means the same microphone, and you can't expect it to sound the same.
Is this a problem?
If you want to achieve the exact same sounds of yesteryear, then it will be a problem if you can't get hold of an original D12. Even if you can, it will have degraded over the years.
I would say however that just like recording engineers in the 1950s and 1960s sought out new sounds, we should be doing exactly that today. The AKG D12VR may not be a D12, but - having heard what it can do - it is a first-class microphone.
There is no rule that states you have to use an AKG D12, D112 or D12VR on kick drum. You can use any microphone that can stand the high sound pressure level. Try out whatever mics you can get your hands on. In particular try different positions. Then choose the sound you like best; the sound that will excite your client or market most. That is the correct way to choose a microphone, not by following historical precedents or current fashions.