I can't use a condenser mic for vocal because my room is bad

[mshilarious]

Or so the oft-told story goes. Is it true? Let's find out.

First, we must understand the signal output by a microphone capsule as a function of its frequency response and polar pattern. If we can surmise two microphones, one dynamic, one condenser, with identical frequency response and polar pattern, it stands to reason that the signal output by those two capsules should be identical, no?

In reality that wouldn't happen very often. Condenser capsules have better transient response and usually better high-frequency response than dynamic moving-coil capsules. We know that; we understand that. Could that be the source of this observation? I don't think so, because troubling noises aren't usually high-frequency. And if they were, we could just close the door, or turn the mic around, or something, because high frequencies don't travel through walls or around barriers too well.

We also know that condenser microphones tend to be more sensitive than dynamic microphones. That has no effect on the microphone's signal-to-ambient noise ratio per se. But it does impact the way that we use microphones. Most people don't eat a condenser mic when they are singing. Many people do eat dynamic mics, often out of the necessity of getting a strong enough signal to get above the electrical noise of a preamp. That would have a very definite impact on the impression that dynamic mics don't pick up room noise well. The truth may simply be that they don't pick up anything well!

Enough theory, let's try a test. Here are two microphones; one dynamic, one condenser, both cardioid, neither built by me (they are very well known and regarded brands). Both are about six inches from my face, fed into two channels of a stereo preamp. I apologize because one channel of my preamp needs repair; it has a buzz that partially invalidates the test, but it's the best I can do at the moment, and it is instructive in a way that I will describe after people have a chance to react.

Directly off-axis to the mics is my computer, which isn't very loud, but it's there, about three feet back. 90 degrees is my door, and my kids are watching TV a couple of rooms away. Again, not loud, but you wouldn't want to try to record a fingerpicked guitar from two feet away with an omnidirectional mic with that door open!

File is 24/44.1 wav, uncompressed, unprocessed other than peak normalization (RMS is quite close as well). 6MB download, it's just 20 secs. Left is one mic and right the other.

Tell me what you can hear . . . beyond guessing which is which, listen closely to the quiet parts and make observations about what's going on.

Room Noise Test


PS I am the world's biggest fan of room treatment, next to maybe Ethan Winer. This is not to discourage room treatment or good isolation techniques!

 

[Weasel9992]

I hear the TV in the left ear...sounds like maybe a cartoon or something...like a flute part in the soundtrack to Bugs Bunny cartoon. I might just be making that up in my head because you said your kids were watching. It's definitely in the left ear though. I couldn't hear the computer at all.

I'm going to guess that the condenser was in the left ear, dynamic in the right.

Frank

 

[mshilarious]

I can hear the TV in both ears (well, I have to swap the headphones left to right, my right ear doesn't work very well), but then I know what to listen for. It does seem easier in one ear vs. the other, doesn't it? Can you tell why?

Hint: it's not precisely because of a dynamic vs. condenser difference, rather a side effect of the type of microphone.

 

[Shadow_7]

The room is not much of a factor for me. I play trombone and other brasses. So the gain on the preamp(s) is normally at it's minimum. At least for condensers. Although I can't use all of them due to SPL limits and proximity effects. I was able to make my SM81's clip as a lone solo trombonist (I normally record brass ensembles, with many more players and decibels). Granted that I was closer to the mic than I probably would be in typical studio conditions. But still, why is it so hard to find a mic(or pair) for me?

I record remotely, so virtually no room treatments (ever). Even this country trailer can be plagued with crickets and birds (INDOORS) a lot of the time. Needless to say, we have sufficient motivation to avoid clutter around here. aka critter habitat. The birds are NOT actually indoors, but through the vent in the bathroom or for the dryer, they can be quite audible indoors. Or even just through the clearances around the doors

Okay, that's a hard one to play (when partially downloaded)

$ aplay -c 2 -r 44100 -f S24_3LE room_noise_test.wav

$ sox -t raw -c 2 -r 44100 -s -b 24 --endian little room_noise_test.wav -c 2 -s -b 16 -r 44100 a_little_more_normal.wav

The left is the condenser. The speaker is dehydrated. (or eating peanut butter). And that's just what I hear on my PC speakers.

 

[mshilarious]

Wow, only two people want to play. That's too bad, since this is a near-universal belief, and it's false.

OK, both participants are correct in their identification, not too hard and I hoped it wouldn't be. But let's analyze further. First, yes, yours truly has no VO talent, no surprise there either.

Next, let's zoom in on a quiet part where the TV noise is most obvious - 5.9 to 6.2 sec, as shown. Loop that and listen to it, you should hear a tone clearly, at 1kHz and 1.5kHz--somehow the 500Hz fundamental isn't prominent, lost to other ambient noise probably.

I have zoomed in to maximum vertical resolution. Left channel is condenser, right is dynamic. Recall these channels were peak normalized which also yielded a very good RMS normalization--but RMS normalization algos usually ignore the silent portions, below -50dBRMS in this case. So this zoomed-in view isn't particularly normal, is it?

Why? Because the low-output dynamic mic is suffering from poorer signal to preamp noise ratio, so the higher amplitude of the signal reflects that. Even more importantly, it is picking up a lot more low-frequency rumble--12dB more! Your ears aren't very sensitive to that, but it makes those big fat waveforms appear. It's also quite clear on the FFT and the high-frequency hiss is easily audible as well. But the objectionable noise mostly lives in the >3kHz range, so we can hear our TV signal easily. However, any ambient noise that is up in that range will be masked to the extent that it's quieter than the preamp's noise.

Whereas the hotter condenser enjoys a wider signal-to-noise ratio. In my case, that is compromised by the preamp's buzz, but fortunately here it is mainly 60Hz, 120Hz, 180Hz, and much higher multiples in the 5-6kHz range--our TV signal is mostly unaffected.

So we can clearly hear the TV signal on both mics--in fact, our FFT shows that the dynamic is picking up more 1kHz ambient noise than the condenser! Conventional wisdom says that is impossible, but ears and eyes prove otherwise here. Note that 1.5kHz is less prominent in the dynamic--maybe the off-axis response of the mics, maybe one mic body shadowing the other, I dunno.

The conclusion is that the only factor mitigating the dynamic's pickup of ambient noise is its poorer signal-to-noise ratio. Not all dynamic mic/preamp combinations will have that problem though, and it's not exactly a feature you'd go looking for . . .

 

[darrin_h2000]

Condensers are too sensitive and they exploit what is wrong with a room...if you dont believe me just try a condencer in your shower with all the tiles...then a Dynamic...both recording will be crappy...but the condencer will be much worse.

 

[quickmill]

The argument will be made that it's not about ambient noise but "room reflections". I'm not sure if/how this would differ but that's the angle that's always used.

I've never bought into the thought entirely and have expressed that prior to this thread. However, even I tend to think my ugly room reflections are more apparent with a condenser. Maybe it's true or maybe I've told myself that due to internet legend. You can bet I'll have all my mics out tomorrow finding out.

I hope you're wrong though, otherwise how are we going to "push" people into that shiny new SM7.

 

[jasonbmerrill]

ive thought and posted about this for years, and always felt like i was crazy.

 

[dgatwood]

Room reflections sound bad on any mic. What matters there is how tight the pickup pattern is.

 

[mixsit]

I'm mostly surprised the dynamic (R) has so much more low end room tone. I shouldn’t presume the mics you picked fit the typical ‘dynamic = rolled off at distance, condenser flatter at distance though. Maybe you picked an RE20?

 

[darrin_h2000]

Of course most of us turn off the tele while tracking.

 

[mattr]

Condensers are too sensitive and they exploit what is wrong with a room...

If a mic is more sensitive that means that the pickup of the wanted signal is also more sensitive, and so the ratio of background noise to desired sound stays the same. Its like turning up the gain on a preamp - you just get more of everything, and so more of nothing. Mshilarious mentioned about the tendency for people to work closer to dynamics than condensers which is fairly true, but that's a technique difference causing the difference in picked up noise and not necessarily to do with how the mics pick up.

If the mic is really too sensitive then you probably need to be using a pad first rather than acoustic treatment.

On the other hand, how 'sensitive' (not really a great word) a mic is in different directions, i.e. its polar pattern, is very important.

 

[PhilGood]

Reader's Digest version.

Get to the point, and quickly!

 

[mshilarious]

Of course most of us turn off the tele while tracking.

True, but I don't have a bad room when I close the door . . . double sheetrock, staggered stud walls, solid core exterior doors, 4 boxes of rigid fiberglass insulation . . . therefore, if I want a bad room test, I leave the door open

Your post about the shower is wrong. Take two mics in your shower and try it. If you don't, I will.

 

[mshilarious]

I'm mostly surprised the dynamic (R) has so much more low end room tone. I shouldn’t presume the mics you picked fit the typical ‘dynamic = rolled off at distance, condenser flatter at distance though. Maybe you picked an RE20?

That just depends on the individual capsules in question. I didn't make too much of that for that reason.

Mics were an AT3060 and 55SH. The AT3060 shows a bit more low-end in its spec, but the 55SH is also more like a subcardioid. Both mics (and nearly all cardioids) get omnish in the lows though. Both mics are in their proximity zone on the vocal, so you can only consider the bass response difference in the unspoken parts.

 

[darrin_h2000]

Your post about the shower is wrong. Take two mics in your shower and try it. If you don't, I will.

Be sure to use soap and clean behind your ears...and PM me about a stronger deoderant.

I think my first recordings I ever did was in the shower in 7th grade using 2 boomboxes...and the girl liked the song even though the quality was shit.

 

[omtayslick]

and the girl liked the song even though the quality was shit.

There's the bottom line.