Too much bass in acoustic guitar recording

July 20, 2007 12:57 PM

Need help figuring out one problem with recording my acoustic guitar at home.

I'm interested in making recordings of my acoustic guitar playing at home. I'm not looking to get high fidelity, I just need something that will sound decent. There's one obstacle between me and my quest for mediocrity. Here's the problem:

The high strings sound good. However, when I let the low strings ring (low E, A-string, D-string) the result in the recording is an overpowering bass vibration. There's no clarity in the sound. It's just a kind of booming note that continues until I hit the string again. I'm not even hitting the low strings that hard.

So, I've tried a ton of different mic positions relative to the guitar and I haven't been able to find a sweet spot that won't yield this booming base problem without having the entire sound be muted.

Here are my specs:
- MXL .006 USB mic with attenuation set to lo (-10 dB) This page (link in the lower right) has an acoustic recording with the mic that sounds decent so I know it can be done.
- guitar positioned about 6" from the mic at the 12th fret.
- recording with Garageband on a basic audio track.
- listening to recording on a pair of harman/kardon sound sticks.

I'm not an audiophile, but let me know if there's any other relevant info needed.

posted by quadog to technology (17 comments total)

Have you tried moving the mic further away? There is a proximity effect that results in extra bass with close miking.

Can you hear the booming acoustically? Perhaps something nearby is resonating. My drum set does that alot.
posted by waxboy at 1:06 PM on July 20, 2007

Do you use a pick? Maybe a lighter pick could help.

You could also try different set of strings w/ lighter wound strings, though that's hard to A/B.

I've found that proximity effect can really lessen w/ just a few extra inches of space. Also don't be afraid to move the mic up the neck away from the sound hole.
posted by JulianDay at 1:13 PM on July 20, 2007

lower frequencies carry a lot more energy than the higher ones, that's why people talk about 'bone-rattling bass' and not 'bone-rattling flute'. you've got a cardoid condensor mic there whose cardoid directional pattern is still going to be picking up a lot of the bass energy directly from the sound-hole.

you say you've experimented with different mic positions - have you positioned the mic more than a foot away (heck, try 2,5, 10)? what about positioning it by your head (so it'll be hearing what you hear). both of these will reduce the energy those lower frequencies arrive at the mic with.

experiment with the room you're playing in if you can. voices sound a lot different when you're singing in the shower, the same goes for guitars in various rooms.
posted by noloveforned at 1:13 PM on July 20, 2007

How does it sound to your ears in the room? Is it just a boomy guitar? When was the last time you had it set up? Here's the relative impact of all the stuff on the recorded sound of a solo acoustic guitar:

95% guitar+player
4.5% room you are playing in (seriously, try recording with the exact same set up facing the other direction, two feet closer a wall, or with a piece of plywood under your chair.)
.25% mic positioning

What's left over is mic selection, preamps, etc.

Assuming your guitar itself is as good-sounding as you're going to get it (get it set up, fiddle with string choices, etc), some other stuff to think about is:
1) A lot of those 'sound sticks' level monitoring devices have a pronounced response hump in the mid/upper bass that can come across as boomy, especially on this kind of material. This is what makes people buy them in the store, they think "man listen to that bass", but it can be very bogus in this type of situation. Check your recording on the best headphones you have just to factor out some of the sound sticks issue
2) I would turn the pad off on the mic. You shouldn't need to knock 10dB off your acoustic recording. This will give you more flexibility in mic positioning (you mentioned other positions sound less boomy but also mute entire sound)
3) What is the floor of the room all about? Play with the surfaces in the room to add brightness relative to your boominess
4) the 12th fret is the boomiest part of the strings. Try pointing the mic at the bridge, for instance, or the sound hole. Mic positioning changes the sound of things a lot. It can be really unintuitive though so try things that make no sense and see how they are different from the sound you are getting (play close to and facing the wall, mic the wall, for instance).


(On prev: the proximity effect doesn't effect condensors)
posted by jeb at 1:15 PM on July 20, 2007

(sorry, it does, but usually, this will be a lot less pronounced than with eg a small dia tight cardiod dynamic like a 57)
posted by jeb at 1:17 PM on July 20, 2007

sounds to me like you need to either:

1.) properly mic the room with condensors (and a very silent room with good character.)

or

2.) close mic with something like a ribbon mic and use a compressor on the signal (properly) with some post compression equalization.

these approaches will give different results entirely, but they are two ways to get a pleasing sounding recording from your guitar.
posted by n9 at 1:30 PM on July 20, 2007

Try micing the soundhole and turning down the gain a bit, or a lot. If turning down the gain helps the bass notes but makes the high end too quiet, try applying some compression to the track - this is what compressors are for.
posted by ikkyu2 at 2:26 PM on July 20, 2007

I can't agree with jeb's distribution of percentages. The room and the position of the mic make a big difference.

You should be able to hear a pronounced difference in the sound as you record with the mic pointing at different parts of the guitar. If you're getting too much bass, the conventional wisdom would be to point the mic further away from the soundhole, and possibly to move it further from the guitar (6" is quite close - try a foot).

Are the bass notes clipping your preamp? If they are, then you should turn down the gain. If not, that's probably not going to make a big difference.

You should be able to get a decent sound right off the bat, but a little EQ after the fact can go a long way. Once you get the mic and room stuff worked out as best you can, record a bit of bassy stuff to a track, add an EQ to the track, and sweep a large, wide boost across the low end while listening to it until you find the spot that most highlights the bad sound. Then tighten the EQ bandwidth and repeat until you've narrowed it down to maybe a half-octave range, then make it into a cut in that spot until it sounds balanced. Some gentle compression with a moderate attack and fast release might help as well.
posted by ludwig_van at 2:38 PM on July 20, 2007

Imagine a line running down the neck of your guitar, across the sound hole, across the bridge, terminating at the end of the guitar. In general you are going to start by pointing the mic somewhere along this line. The more you point it towards the sound hole, the more bass you get. As you start to point it up the fingerboard, less bass, but more string noise. So I prefer to point away from the sound hole, towards the bridge.

There are some other techniques worth mentioning. I sometimes record with the mic UNDER the guitar. Like, if I'm holding the guitar, looking down over it, the mic is half visible, like a sunrise. It works OK. I usually use another room mic 4-ish feet away with this (and sometimes with other recording techniques)

If you can keep your string noise down, I sometimes like to mic 6-ish inches off the 12th fret. This doesn't work well with some people's playing style.

I agree that 6" might be too close for you...
posted by RustyBrooks at 2:46 PM on July 20, 2007

Don't mic the guitar at the hole. I find for most acoustic guitar recording, the best position is right where the neck meets the body (that is, where the highest fret ends).

The preamp is important too. If it's not a very clean preamp, it might be boosting the low-end frequencies more than you'd like.

Alternatively, you could record it so that it's fairly quiet, then use either a multiband compressor to compress the bass a bit more, and bring up the high-ends, or just EQ the the signal. EQing, of course, is an artform, and unless you test your sound on a wide range of speakers, it's hard to get right.
posted by spiderskull at 3:03 PM on July 20, 2007

EQing is certainly simpler than multiband compression.
posted by ludwig_van at 3:10 PM on July 20, 2007

Sorry, but it is the mic. No $129 USB mic is going to work well for acoustic recording.
posted by spitbull at 3:25 PM on July 20, 2007

I think that's probably wrong, too. I've made good acoustic guitar recordings with cheaper mics.
posted by ludwig_van at 3:36 PM on July 20, 2007

Lot's of great info here. It sounds like there's multiple ways of attacking this and it's just going to take some empirical research. Until I get the results back I won't know which one to marks as best answer!

On preview, I just discovered all the EQ settings in Garageband (didn't even know they were there) and I've been able to tweak some existing tracks for the better. I still have to figure out what all these settings mean . . .

One point to clarify, I don't have a preamp. The usb mic just plugs right into my mac. Maybe a preamp is needed for more serious recording?
posted by quadog at 4:03 PM on July 20, 2007

High-end mics have an XLR connector which you plug into a preamp, and the preamp plugs into your audio interface/sound card. I don't think any preamps take a USB input, and it sounds like your mic is not meant to use one.
posted by ludwig_van at 4:33 PM on July 20, 2007

Stop overthinking this plate of beans.

Move the mic about a foot away from the guitar. If your doing heavy strumming, point it at the neck.

If you're finger picking, point it more towards the neck.

The thing that will help you the most, in this case, is eq. I see you have Garageband. Use the Manual setting on the eq. The bass gain slider is just a bass roll-off. Adjust this to your liking.

If it still to boomy, move the mic further away.
posted by chillmost at 5:25 PM on July 20, 2007

Have you listened to your recordings on anything other than the soundsticks? I wouldn't say they're really suited to critical listening...

Do the low strings sound boomy while you play them?

If you can, get someone else to play the guitar in the room where you make your recordings. Put a finger in one ear and move around the room until you find a spot that sounds like you want it to sound, and put the mic there.
posted by the duck by the oboe at 7:35 PM on July 20, 2007