I hate to nag, but it sounds to me as if you people don't realize how much current the 451s draw when they're powered at 48 Volts. It's 5.5 to 6 mA per microphone, which is higher than almost anything else that people use nowadays. The microphones are from the earlier years of phantom-powered studio microphones. AKG was in Austria, not Germany, and they flatly violated the DIN standard of the time, which specified a maximum of 2 mA per microphone at 48 Volts.
The C 451 was really a 9-Volt microphone, capable of running on as low as 7.5 Volts. For the sake of compatibility with other professional equipment, its circuitry was protected internally for use with 48-Volt supplies, which may go up to 52 Volts. But the higher the supply voltage, the more energy is simply thrown away (converted to heat) inside the mike. When these mikes are run at 48 Volts, about 3/4 of the energy from the power supply is turned into heat, and doesn't enhance performance in any way.
The supplies that this person is said to have used (AKG B-46E) weren't 48-Volt supplies; see the schematic below. They didn't contain (as do the Neumann and Denecke supplies) an oscillator/voltage multiplier circuit that steps the 9 Volts of the battery up to 48 (always at less than 100% efficiency). Rather, the B-46E was a simple 9-Volt, linear supply for ONE microphone, and at that lower supply voltage, the mike used that power nearly four times as efficiently as it does at 48 Volts. So it was about a seven or eight times better arrangement, as far as the use of battery power was concerned.
JFTR, AKG's AC phantom supply for this microphone series, the N-46E, was also a linear 12-Volt phantom supply, not 48.
If you're being a purist about this historical re-enactment, you might also consider the fact that the B-46E had an output transformer built in to the case. That's how it blocked DC from reaching the input to which it was connected. I don't know the specifications of that transformer, but it may have had some effect on the sound quality.
I'm really sorry that I no longer own a pair of these supplies, or I would gladly have lent them to this project. But when I moved up to 12-Volt Schoeps mikes (CMC 3-- series), I wrote and asked the company if these supplies were compatible. The reply was positive, but I was told that the Schoeps mikes wouldn't be able to reach their proper maximum SPL with only a 9-Volt supply, so I retired the B-46s and eventually (if I recall correctly) discarded them.
[edited later to add:] I found a pair of B-46E supplies in apparent good condition, and have them here now. I will probably run some tests with Schoeps CMC 6-- mikes just to see what happens to the maximum SPL of the Schoeps when powered at only 9 Volts--but after that, the supplies will be available in case anyone else on the forum needs them.