Small vs. Large Diaphragm

[derekcgullett]

Hey y’all!

I’ve decided that it’s time to upgrade to a stereo pair of mics. I have the opportunity to purchase a stereo pair of small diaphragm condenser mics or large diaphragm condenser ones of the same manufacturing quality for around the same price.

I’ve heard that large diaphragm condensers are generally better but not exactly why. When I try googling differences between the two, I get either really hard-to-understand explanations or accounts that don’t apply well to recording a trombone.
When I’ve played with orchestras I’ve only ever seen small diaphragm condensers placed throughout the group. I’m sure this has to do with their space-efficiency but is there another reason?

I should note that I’m largely a classical trombonist and am wondering which of these options would be more likely to yield a quality recording (mainly for audition tapes and whatnot). Also, it’s not a high-pressure scenario as to which pair I end up choosing because I can return either following a short trial period, but I wanted to see if anyone would advise me to go one way or the other.

Thank you all so much!

[ithinknot]

SDC vs LDC is a bit like asking small vs large bore. They're just different, the traditional usages didn't happen by accident, and the attributes that make them ideal for one purpose are the same things that make them less than ideal in other situations.

The short answer, for classical/acoustic/audition-type purposes: a pair of Line Audio CM4 (mounted on a stereo bar in ORTF/NOS/AB40ish depending on the room) into a basic Focusrite/MOTU/RME interface (w/ computer) or a standalone Sound Devices or Zoom recorder. You can't do better for the money, and you can do a lot worse. In this case, the question isn't trombone-specific; a well-placed pair of SDCs is the straightforward way to record classical music in a real acoustic.



Massively generalizing: SDCs can have a more consistent frequency response (at the level of physics - doesn't mean they all do, and some are designed not to), better ability to capture transients, and far less off-axis coloration, at the cost of slightly higher self noise. The off-axis part is perhaps the most important: if we're talking about a cardioid pickup pattern (100% directly in front, down about 6dB at 90 deg, and theoretically a null at 180 deg) then ideally the frequency response is identical from any angle, and only the sensitivity (ie volume) changes. This never happens in reality, but SDCs do much better than LDCs - talking into the back of a cardioid LDC can sound pretty weird, whereas the back of a cardioid SDC should be a quieter, somewhat duller version of what you get from the front. In stereo pairs, this means that SDCs tend to give significantly better stereo imaging. For orchestral multimiking, this means that you're not stacking up multiple versions of weird bleed. (You'll see LDCs used as spots in studio settings, where the placements can be closer and the acoustic is drier, making the bleed coloration less of a problem.)

LDCs have a slower transient response, slightly lower self noise, a less consistent frequency response (often with a boost in the high-mids that enhances vocal clarity, and gives the illusion of 'detail'), and much more/worse off-axis coloration. However, the type of distortion they introduce (and the HF and transient detail they miss) tends to have an appealling/flattering/embiggening effect, hence their use as vocal and spot mics in situations where their off-axis anomalies don't matter, and where the character they add is specifically desirable.

Sometimes you want watercolors, sometimes you want a photocopier.

[harrisonreed]

LDC. Or a Ribbon.

I have CM4s, and they are great for miking an ensemble. I don't use them for solo trombone anything. In an artistic recording, you don't want to hear what it actually sounded like. In an artistic photo, you don't want to see what it actually looked like.

That sounds bad. But it's true.

[robcat2075]

What is stopping someone from using an equalizer to take the recording from the mic that sounds like what it actually sounds like and making it more flattering?

[harrisonreed]

What is stopping someone from using an equalizer to take the recording from the mic that sounds like what it actually sounds like and making it more flattering?

This is only my experience, but recordings I've done with the CM4's (SDC) placed where the trombone sounds like what I imagine it should be (about 6 ft away) also include hyper detailed reproductions of every click, scratch, sniff, and throat sound -- these are baked into the recording. You can EQ to minimize them, but you aren't just affecting those unwanted sounds, you're changing the trombone as well. If I place the CM4s far enough away to minimize these hyper detailed "artifacts", then I find that I get way too much room sound and you can't EQ that away either. Also, at that distance the trombone now does not sound like what I imagine a trombone should sound like. Recording, say, a BQ would be perfect, but you lose a lot of creative options on a solo instrument with the mics that far away.

With LDCs, you can get in around 5-6ft away and these rotor clicks and undesirable sounds aren't picked up to begin with. The sound is closer to what I am after without EQ, and that is already baked in. Then I can EQ to make tweaks, and there is no room sound to deal with.

There is a place for both. In a great room with a group that can record without making mistakes, absolutely I would use a couple SDCs. On a piano, I have used both, depending on how intimate I want the sound to be. But we have to remember, even on a recording of a piano, where the sound of the hammers and strings sizzling and the mechanical action of the piano sounds insane through the headphones, in real life as a listener your head would not be inside the piano with CM4s sticking out of your ears. That recording is a lie. Nor would your ears be amplifying every click and scratch with hyperactive realism from 6ft away listening to a trombone. That recording is just as much of a lie as one done with flattering LDCs.

Use the right tool for the job, and don't go in to record knowing you're going to have to EQ out rotor clicks and the sound of your throat closing when you don't have to, or baking in your room sound when you don't have to.