Using The Sennheiser 415t

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 415T. It came without a box, so this one is a copy. These should always be kept in a case and carefully handled.

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)

Tuchel connectors are smaller than standard XLR connectors, and are secured with a threaded ring. They’re more secure and protect the contacts better, but more expensive and harder to find.

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.

The 415T undressed. Tolerances are very tight. Don’t adjust the chokes without proper test equipment, as you’ll most likely degrade the performance significantly. I repaired mine with a very tiny spot of beeswax, which secured the loose choke cores while maintaining adjustability.

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.

14 responses to “Using The Sennheiser 415t

  1. I too have a Sennheiser 415T that has been lying around since my Stellavox tape recorder was stolen back in ’82 😦
    Do you know if there’s a powered adapter/converter that would allow me to use this mike with modern 3.5 mm mic input sockets found on most non-professional equipment?

    • I don’t believe there is a simple off-the-shelf converter that currently in production would do it. First, check your camera specs to see if that mic input has any sort of power connected to it. Some do, like a 3-5v for powering consumer electret mics. Probably the cheapest thing to do would be to get a Shure FP31 mono mixer to use as a preamp, or other battery powered preamp that can supply T-power. Then you’d need to go unbalanced out to camera in… I believe the FP31 has 3.5mm tape out that would work.

    • I hate to tell you this, but basically, you can’t use this mic with non-professional equipment. A 415T requires T-power, which you’ll only find on a real mixer and requires a balanced (3-pin) connection to operate. It is theoretically possible to generate T-power through a battery box, since T-power is a 12v system and you need fewer batteries than phantom power, which is a 48v system. But it would be a pain in the a$$ both to build and use… I don’t know if you could find a T-power battery supply anywhere other than eBay, and then you’ll be degrading the signal by going to an unbalanced mic-level connection.

      A much better option would be a Shure FP31 used as a mic preamp. These things go for a comparative pittance on eBay since they’re mono mixers, and everyone needs stereo these days. (they have very little resale value, though, so if you think you might want to sell & upgrade later, buy at least an FP32). These mixers have a reputation for not being very quiet at high gains, so if you plan to make critical recordings of quiet sources, then you’ll need to drop the bucks on a Sound Devices preamp or something similar.

      Sorry about the theft, Stellavox was some really nice hardware. Hope this helps, BG

  2. Thanks for your swift reply! I’ll see if I can solve the problem and let you know if I find a workable solution.

  3. “My 415 is fitted with a Tuchel screw-on connector, so I had to build a short Tuchel to XLR adapter..”
    I need to build one of these also. Could you provide any nfo, pics on the one you made? I found Mouser but so many tuchels.. Thank you.

    • The tuchels on the 415 are male, so you’ll need a 3-pin female connector. If I remember correctly, I used a Mouser part # 523-T3261-001, $11.16 each. Hope this helps- BG

  4. Hi Mr. Gilbert,
    I too have a 415T….used….from a TV station from years ago.It had been modified from Tuchel to XLR already. They did not do to hot a job on the solder and now the two wires off the circuit board are detached. Can you give me the pin config.for these two lead wires.I have assumed pin one normally for shield is not used or lifted if you will. So looking at the circuit board from the top as in your earlier post…..which wires go to pis 2 & 3??
    Thanks MUCHO

    • bgilbertsound

      Hi Paul: I’m REALLY uncomfortable giving this sort of advice… what if I say the wrong thing and you fry your mic? But looking at the Sennheiser schematic, you should be able to figure it out yourself pretty easily. The most important wire to get right is pin 1, the ground wire. If I recall correctly, this is connected directly to the body of the mic. The other two pins are connected by wires to components on the circuit board. If these two are connected wrong, it won’t hurt your mic, but you may experience some phase errors when your 415 is used with another mic… the diaphragm should generate a positive voltage when it moves inward, and a negative voltage when it moves outward. If the wires are wrong, you may never notice it unless you use another mic right alongside it and mix the two signals.

      The negative wire should go to pin 3, and the positive to pin 2. This should be marked on the mic’s circuit board somewhere, But if it isn’t, then trace the connection back on the circuit board. The negative wire goes to a capacitor and a coil, and then to two more capacitors. The positive wire goes to a capacitor and a coil, (identical to the negative) but then to a transistor. On my mic, both these wires are blue, so wire color isn’t an indicator here.

      It was a long time ago that I did any work on my mic, and your mic will most likely be different than mine. Hope this helps, and good luck. BG

  5. Hi Brian,

    Good post. I’m looking at a Sennheiser 415T with Tuchel connectors. If I buy a 48-12T adaptor, (three options listed below) doesn’t that mean I can use this mic on gear that supplies 48V power (H4N or SQN)?

    Tuchel adaptor:
    http://www.ebay.de/itm/48-12-Tonaderspeisung-T-Power-Adapter-mit-Tuchelbuchse-/400340197718?fromMakeTrack=true&ssPageName=VIP:watchlink:top:de
    OR Tuchel adaptor cable:
    http://www.ebay.de/itm/400306980065?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1558.l2649
    OR the PSC Barrel 48PH – 12T, but will need a Tuchel to XLR converter
    http://www.soundkit.co.uk/acatalog/PSC_Adapter_Barrels.html

    That Tuchel adaptor cable looks like the perfect solution as it doesn’t make the mic any bigger. Ok I’m not a sound man so excuse this question: what is unbalanced, are my options above giving me unbalanced and what will that mean in practical terms?

    Is this mic really that difficult to handle, surely good suspension takes care of those issues?

    Neal

    • bgilbertsound

      Hi Neal:

      The thing to remember about the 415 series is that while they are beautiful-sounding mics, they are rather delicate. They don’t work in any sort of humidity… I never take mine outside. Make sure to keep it dry and well-protected, like inside a zeppelin.

      Before you buy a 48-12 adapter, check your mixer carefully. An SQN mixer can supply T-power, but BE CAREFUL as T power can damage conventional mics.

      Forget using this with a Zoom H4N. Trew Audio did a test to see how long the batteries would last in this unit. With phantom power turned on, they got something in the neighborhood of 45 minutes before the batteries died. It won’t be so bad if you use this with some kind of mixer before the recorder.(A mixer that supplies T-power, not a Behringer or anything like that.)

      A tuchel-XLR adapter cable would be greatly preferred over some kind of barrel adapter, which will put a lot of strain on your mic connector as well as add a bunch of unnecessary weight to the end of your boompole. You can wire up your own and save about half the cost. A longer adapter cable will save weight as well.

      Lastly, balanced vs unbalanced… in a word, unbalanced cables are 2-pin, like an RCA connection on your stereo. OK for short line-level runs, but generally consumer-grade, especially for mics. Balanced (3-pin XLR) is a professional standard for mics with the exception of lav mics to transmitters. A balanced cable will work if pin 2 or pin 3 is open or shorted, but the level will be quite low. Unbalanced cables often suffer from noise pickup from radio sources or hum from AC power cables. Do some reading on the internet… Rane has a number of good papers on system interconnection and proper cable construction,

      Hope this helps.
      BG

  6. Hi Brian,

    I have a 145T-U with the Sennheiser BP-2 power supply. There are times when I’d rather not be lugging around the little box and extra XLR cable so I’m considering the Sennheiser 12TP48 – 48V Phantom to 12T Power Adapter. Is that a safe alternative to use?

    Thanks,
    Rob

    • Sorry about the typo above. I meant 415T-U.
      Rob

    • bgilbertsound

      I’d think it would be perfectly safe, especially if it’s from Sennheiser. Probably not a bad idea either, since you would be far less likely to leave your mixer switched for T-power and damage another mic.

  7. Thanks Brian. I really love the old 415 and would hate to damage it just for the sake of convenience.

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