I have quite a few "friends" on Facebook, which would seem like a surefire recipe for time wasted, but sometimes I find something that makes up for all the cute kitties and obituary notices.
Just such a post came across my computer screen recently. Michael Joly Engineering, who manufacture microphones and do Oktava microphone modifications were the creators of the article. The post was actually a three-part post about the history of Neumann microphone circuitry that explained why many modern microphones based on the venerable K67 capsule are too bright.
While I could paraphrase the article for you, that would be unfair to Michael Joly, who obviously has put a lot of time, research, and personal experience into this three-part article.
Also I encourage you to look at the Michael Joly site - his microphones are priced so that even a hobbyist recording engineer could afford a nice set of microphones. I'm very tempted by the MJE-384 matched pair that's currently priced at $699. Another tempting offering are the MJE-384K capsule upgrade MJE1 for Rode NT5 microphones. This "modification" is a simple screw-in upgrade that replaces the stock mic capsules with the MJE-384K capsules. Besides better overall performance you end up with a tightly matched stereo pair, which is difficult to do with an off-the-shelf pair of stock Rode microphone capsules.
For anyone who wants to hear what these the various OktavaMod microphones sound like the site also has a plethora of samples and sound bites comparing the Michael Joly microphones with other microphones, both new and old. Actually even if you aren't in the market for microphones and wouldn't be caught recording if your life depended on it, the sound samples are so educational in terms of how a microphone can color and alter live sound that I think every audiophile will find them useful and educational. I know I did.