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LDC vs SDC vs dynamic Why?

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Stephen Swaffer:
As the topic suggests, when and why would you choose an LDC, SDC, or dynamic mic?

My application specifically is ambient/room sound for a livestream-specifically geared more towards a congregation singing-but on a larger scale I am curious where the different mic types shine and why you would choose them?  I have all three available and have been experimenting with mics and placement trying to find something that I like.  With our very live room, getting primarily the congregation is proving challenging.

Chris Grimshaw:
In my experience, a good small-diaphragm condenser is about as good as it gets in terms of fidelity and directivity control. I like my Beyer MC930s for when I need a neutral sound with a cardioid pattern.

However, the other mics do have advantages:
- Large-diaphragm condensers will typically have lower electrical noise figures. The broad reason is that a bigger diaphragm means more sound becomes electricity, so needs less amplification. It's more complex than that, though. A larger diaphragm does mean the off-axis response typically doesn't hold up as well as it might with a small-diaphragm model, so there's a tradeoff there.

- Dynamic mics have negligible electrical noise, but often 10-20dB less sensitivity*. You can still use them for distant pickup, but you'll need very low-noise mic preamps to do it well. Dynamics typically have a more, er, colourful response than a condenser mic - check the frequency response curves of an SM57, for example. Their big advantage is that they can handle very high SPLs without much/any distortion, so they're often the first pick for live sound where everything tends to be close-mic'd.

- Ribbon mics are a sub-type of dynamic mics. They don't like large air movements (the ribbon tends to stretch out), and they almost always have a figure-of-8 pickup pattern. Vintage ribbons had a very dark/smooth sound, but modern ones can tend towards condenser-like clarity. The fig-8 pickup is due to the mechanical layout of the device, and tends to be very consistent across the frequency range. I like to use them for mid-side work.


*It's important to note that, by "sensitivity", I refer to the output in mV/Pa. Not a subjective measure of sound quality.


In all, they each do roughly the same job - convert sound to electricity. Each type of mic can vary wildly in how well or badly it does that job. If I was recording a choir, for instance, my choice of mics would typically be a Beyer MC930 and an SE VR1 (a modern ribbon) in an M/S array. They're both decent, neutral mics.

If I was given a box of random mics to work with, I'd be looking for the good mics instead of a mic that happens to use a particular technology.

For instance, I'd pick a Beyer M201 instead of an EV Cardinal for literally any job. I've worked with both a lot and I don't care that the EV is a condenser - the Beyer is a better mic.

Chris

Caleb Dueck:
Chris summed it up very well.

As a general rule, I prefer non-cheap-quality condensers over dynamics.  Especially outdated dynamics (SM57/58/etc). 

Try this - have a single speaker play back speech or fairly open, uncompressed music into a large room.  Speaker on a tripod on stage type of thing.  Set up a number of mics a ways away, just not too close to a wall.  Multitrack record the mics, level matched, as they pick up the speaker.

One by one, listen to the audio clip of each mic vs the "live" sound of the speaker, to see how accurate each one is.  Try EQ on each mic track you play back, to really hear the time domain issues and weaknesses of each mic. 

In a church setting, I like to have a few options for small diaphragm condensers for this application, and most other non-standard application (IE, everything in addition to drums, close-miced vocals, guitar cabs, etc). 

Chris Grimshaw:
Playing sound into a room with mics at varying distances is an interesting idea - you're not only varying the direct-to-reverb sound, but also the weighting of the direction from which the mic is receiving signal. English is weird sometimes. What I mean is that the more distant mics will have more sound hitting them from the sides and rear, while a mic close to the speaker will receive most/all of its signal from the front.

The mics with a well-controlled polar pattern should sound pretty natural at any distance, but as you move away from the source, you'll simply hear more "room". Listening to omni mics makes this obvious, but omni patterns are pretty easy to do well.

If a mic is directional, chances are the polar pattern will vary with frequency. I can't think of a mic that's consistent across the entire range, but the good ones get close.

Here's one for an e935:


We can see that the pickup at 90 degrees is pretty consistently -6dB compared to on-axis, except for at 16kHz where the pickup area is considerably narrower.
Not bad, overall, at 90 degrees - reflections from the side walls will be missing a bit of treble, but should sound pretty natural.

Sound hitting the rear of the mic after bouncing off the wall would be another story, though. It's all attenuated a bit, but there'll be 10dB more at 125Hz compared to 1kHz. There'll be some colouration to that sound, for sure.


I think I might give this a try in practice - seems like an interesting investigation.

Chris

Brian Jojade:
Another thing to consider is durability of the mic.  Condenser mics by design can be more fragile.  They also do not like humidity or extreme temperatures.

I've done plenty of shows where there's unexpected rainfall and the show must go on.  My Sure handhelds have Beta 58 or SM58 heads on them.  SM58's keep working through the rain.  Beta 58's, not so much.  In extreme cases such as that, I'll ALWAYS use the dynamic mic, regardless of the difference in sound quality.  Because some sound is better than no sound!

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