I recently got the chance to break out my old Sennheiser MKH415T. This jewel of a mic doesn’t get used a lot because its high-impedance circuitry is very sensitive to humidity and doesn’t do well with rough handling. It was a favorite among film crews back when it was new. The “T” refers to its power requirements, meaning 12-volt T power, sometimes called AB power. T power is less popular because it has a greater potential to damage microphones… if you plug a dynamic mic into a T-powered input, it can burn out the capsule, where 48 volt phantom generally won’t harm your mic unless the wiring is faulty. (Still, it’s good practice to plug in the mic first, THEN turn on the phantom power.) But T-power excels in battery-powered gear, with generally longer operating times and simpler circuitry.
My mic was formerly owned by the The Office de Radiodiffusion-Télévision Française, as it’s engraved ORTF. The ORTF was the French equivalent of PBS. Mine came without a case, so I copied the construction of the case from my 815t and built a box that is a close copy to the factory original. My 415 is fitted with a Tuchel screw-on connector, so I had to build a short Tuchel to XLR adapter. It needed minor repairs as well… one of the tuning chokes would shift whenever the mic was moved from side to side. This was repaired with a small lob of beeswax to secure the choke. (the original Sennheiser service manual can be seen here)
At one point, I compared the sound from the 415t to my more-often-used Sennheiser ME66/k6. The only way to do this is to set up both side-by-side and switch between the two. The ME66 sounds good, but the 415 sounds better. It’s hard to describe, of course… the differences are subtle. But it’s most noticeable in the top end, which is definitely smoother.
These microphones are often available on the web. There were two variants – the 415T and the 415T-U, the difference being Tuchel or XLR. The 3-pin Tuchel connectors can still be found, but it’ll take some hunting… I bought mine from Mouser, if I remember correctly. Accessories for these mics used the “MZ” prefix… Sennheiser MZA15 (Tuchel) or MZA15-U (XLR) is an in-line battery-powered T supply, it’d be very handy if you could find one. MZF15 is a 6bD roll-off filter @25Hz. MZA56P-U would be a real prize… this converts from phantom power to 12vT.
In the real world, my 415T doesn’t get quite as much use as I’d like, since it needs kid gloves. It’s pointless to use it on a noisy set, or outdoors unless we’re shooting in Arizona… the Tennessee humidity is generally on the high side. But when conditions are right, it’s a fantastic peace of old gear that gives great results.