Bleeding old dynamic omnis!

Many good looking vintage microphones were originally designed for interviewing important people, such as the mayor, the world’s most dangerous criminal or your grandma, but not for the purpose of close miking a snare drum. In fact, most of them are actually a really bad choice for that, not because they sound bad, but because they render your brave efforts in close miking absolutely futile. Yep, that’s exactly the sort of problem you get when you mess with bleeding old omnis!

Omnidirectional microphones predate the (nowadays much more common) cardioid pattern mics by nearly a decade; employed mainly as reporter microphones, they have many advantages: they are what’s called “pressure-sensitive”, which makes them a lot less susceptible to the annoying sound your expensive leather jacket makes when you reach out to ask the mayor a question, as well as to the plosives in her answer, when she tells you she’s “perfectly prepared to get papped by flashlight popping paparazzi” – omnidirectional microphones don’t have any significant proximity effect and don’t capture the sharp bursts of sound that some vowels like “p” cause. Perfect for our amateur field reporter!

A classic dynamic omni reporter mic, most of the time hidden away behind news station branded windscreens: The Beyerdynamic M58.

A classic dynamic omni reporter mic, most of the time hidden away behind news station branded windscreens: The Beyerdynamic M58.

In the small studio, omni mics can cause a lot of trouble – or give you that extra mojo you were looking for . They pick up a lot more of the room’s reflections and generally capture the sound of a room fairly well, which might be a good thing. Considering how you’re just reading a site called trashblitz to find some cheap old microphones to use, chances are that it isn’t, and that your recording room sounds like a tiled basement with a broken couch, a CRT TV set and your summer tires in it. Or, as a matter of fact, is a tiled basement with a broken couch, a CRT TV set and your summer tires in it. With an omnidirectional mic, you’ll need to be much closer to the instrument than with a cardioid mic to get a good balance of the instrument’s sound and the sound of the room, (= the direct and indirect sound). You can record some perfectly fine tunes in there, but unless you’re aiming for the natural reverb your room provides, you’re probably better off with directional microphones.

Now, this is true for most instruments, but close miking a drum set with omni mics is especially problematic because you’ll get all sorts of bloody spill and, in the worst case, horrible phase issues caused by omni mics combined with cardioids or other omnis. The snare drum is, in that sense, the worst possible place to put an omnidirectional microphone, simply because it’s such a critical point in the center of the kit, and because the snare sound is in most cases something you’ll want to filter or compress after recording.

So, how do you recognize an omni before you buy that bag of microphones? Cardioid microphones always have ports in their housing to let a controlled flow of sound enter the capsule from the back, which causes frequencies that enter the mic from the front to be reinforced, while others, entering either from the back (cardioid) or the side (super- and hypercardioid), are cancelled. The more ports, or the longer the ported area, the more directional – just think of a hypercardioid shotgun camera mic which is half a meter long and riddled with slits. An omnidirectional microphone does not have any ports, holes or slits. It is a capsule in a closed case with only one single opening at the front. By the way, the microphone you saved from the trash doesn’t even have to be an omni to be unsuitable for drum close miking; from our experience, there are plenty of wonky vintage cardioids with terrible back-rejection around –  better check your risqué dynamic trash drum setup for spill if you are planning on applying effects afterwards.

Yet, there are other beautiful lessons from the omni crypt! A pair of two dynamic omnis as a AB pair on overheads, spaced less than 1m apart and not too far above the drum kit, can give you nice and smooth drum ambiance, funky toms and a pretty ok stereo localisation – depending on the microphones, of course. And these old spillmongers can also come in handy in a recording situation where you don’t have access to phantom power. If you have four of the same make (which is not as unlikely as it sounds, old microphones seem to come in batches), they might also be really nice as dedicated room microphones for drum or band ambient sound in general.

The Grundig GDM 121 = the high impedance version of the 1950s dynamic reporter mic classic Sennheiser MD21, and it's gold coloured!

The Grundig GDM 121 = the high impedance version of the 1950s dynamic reporter mic classic Sennheiser MD21, and it’s gold coloured!

You can also give a particularly nice sounding omni dynamic to singers or speakers who don’t have a particularly nice microphone technique (or if you simply don’t have a pop killer around) – no matter how hard they try, they just won’t pop! And since they don’t exhibit any directional colouring, they might not be the worst choice for recording your voice in your cellar room, after all – complete with natural ambience, no plugins needed. Also, if you have a good sounding room, you can simply embrace the spill and get really big and lively sounding recordings with dynamic omnis. Drums are a very good candidate for that sort of experiment.

Another advantage of those old omnidirectional troublemakers is that they are not really sought-after, at least in our experience, and that makes them cheap. For example, you can get the Grundig GDM 121, the Beyer M55, the Sony F-96 and other dynamic omni mics for dirt cheap if you know where to look, because they have been sold as amateur reporter mics in a bundle with reel-to-reel tape recorders since the late 1950s, and many of them still sleep their mint-packaged sleep in cabinets, basements and drawers all around Europe. Especially the GDM121 are excellent microphones with a fairly linear frequency response up to 18,000 Hz, and they are nearly indestructible.

There are many other vintage dynamic omnis that sound fantastic, and most people don’t really know them because they are kind of tricky to handle in a studio situation. If you are up for finding your way around the dangers of the bleeding omni you will master one of the most important trash challenges and you will emerge victorious!


Bottom line: Congratulations, you found a great mic really cheap – now use its force wisely!


Some German and Austrian vintage omnidirectional dynamic microphones:

AKG D160
AKG D230
Beyer M26
Beyer M55
Beyerdynamic M58
Beyerdynamic M100
Beyerdynamic M101
Funkberater MD 30-2
Grundig GDM 19
Grundig GDM 311
Grundig GDM 312
Grundig GDM 321
Peiker TM 3
RFT DM622
Sennheiser MD21 (= Grundig GDM121)
Sennheiser MD211
Uher M539

4 Comments
  1. beyer m 58s rock looks exactly like my most beat up unit which sounds sweet. I’ve been buying old mics many dynamic omnis this past year. and i agree there’s a whole world of unexamined mics out there. My first time here and first thing I see a Grundig GDM 121 and a Beyer M 58.

    • Hi Steve! The GDM-121 and the M58 were like gateway drugs to me, haha! They were among the first models I checked out when I realized that there are so many undiscovered and undocumented mics out there, and the mere fact that they are omnidirectional and dynamic pretty much blew my mind, I had never seen anything like that in a studio recording environment (even though omni is the most basic construction principle, not cardioid). The most unusual one we currently have is certainly the GDR-made Funkberater MD30-2, do you know that one?

    • Hi – I haven’t had the chance to use one, unfortunately. They are a little out of reach of the feeble trashblitz budget and very well known (anything “Sennheiser” will never go under the radar of the savvy mic hunter community). I can only recommend the MD21, which does sound a bit like an omni version of an MD421, but that’s probably not the sound you are looking for.

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