I am trying to record an acoustic guitar and whichever cardioid microphone I use on the fretboard side of the guitar it seems to exaggerate certain higher frequencies in an ugly way. When I switch over to omni however, this smooths out for a more natural sound. Is this a thing with cardioid microphones and why do they do this? Almost all tutorials I have watched/read use cardioid SDC microphones around the 12th fret but how can this be when cardioid microphones exaggerate the shrill frequencies and harmonics of the strings?

Assuming you're placing the mics in exactly the same position each time, I imagine it's because all of your cardioids have an unhelpful presence boost that your omnis lack.

Having said that, I think that most omnis do sound more natural than most cardioids, but that's usually a low- to mid-frequency thing related to the phase-shifts of the labyrinth in most cardioid mics.

What are the various mics and how close are you using them to the guitar?

Like most large(ish) instruments the true sound of a guitar can only be heard from a distance of a couple of metres or more, anything closer emphasises the sound from a specific part of the instrument. An omni will 'hear' more if the guitar at a given distance (or conversely, will give the illusion of being further away).

If you are not happy with the sound your cardioid SDC is picking up then put some cans on and move it around while a friend plays the guitar or, less conveniently in these covid times, do some test recordings with the mic in different positions until you find the place that suits your particular guitar and playing style.

And remember, it's not just the interaction of the mic and guitar, it's the mic, the room and the guitar.

armans wrote:I am trying to record an acoustic guitar and whichever cardioid microphone I use on the fretboard side of the guitar it seems to exaggerate certain higher frequencies in an ugly way

Not sure what you are referencing exactly, but it's stuff like fretboard noise or guitar squeaks, it's often an indication that your mic is too near.

Hugh Robjohns wrote:Assuming you're placing the mics in exactly the same position each time, I imagine it's because all of your cardioids have an unhelpful presence boost that your omnis lack.

Having said that, I think that most omnis do sound more natural than most cardioids, but that's usually a low- to mid-frequency thing related to the phase-shifts of the labyrinth in most cardioid mics.

I am placing them in the same place. Is it not possible that cardioid patterns are more directional when it comes to high frequencies? My SDCs are beyerdynamic mc930 which have quite a flat response so I dont think that it has to do with the mic.

Sam Spoons wrote:What are the various mics and how close are you using them to the guitar?

Like most large(ish) instruments the true sound of a guitar can only be heard from a distance of a couple of metres or more, anything closer emphasises the sound from a specific part of the instrument. An omni will 'hear' more if the guitar at a given distance (or conversely, will give the illusion of being further away).

If you are not happy with the sound your cardioid SDC is picking up then put some cans on and move it around while a friend plays the guitar or, less conveniently in these covid times, do some test recordings with the mic in different positions until you find the place that suits your particular guitar and playing style.

Thanks for the tip. The microphones I have are

Akg c414 and a stereo pair of beyerdynamic mc 930 and they are about 20 - 40cm from the guitar.

CS70 wrote:

armans wrote:I am trying to record an acoustic guitar and whichever cardioid microphone I use on the fretboard side of the guitar it seems to exaggerate certain higher frequencies in an ugly way

Not sure what you are referencing exactly, but it's stuff like fretboard noise or guitar squeaks, it's often an indication that your mic is too near.

It is not fretboard squeeking. From what I can tell it is mainly the sound of the harmonics of the highest two strings and the frequencies are around 2khz where it seems a bit shrill

blinddrew wrote:And remember, it's not just the interaction of the mic and guitar, it's the mic, the room and the guitar.

Thanks. Yes I understand but my room is very well treated and on the dry side. It is definitely coming from the instrument and not the room

Hugh Robjohns wrote:
Having said that, I think that most omnis do sound more natural than most cardioids, but that's usually a low- to mid-frequency thing related to the phase-shifts of the labyrinth in most cardioid mics.

Is 2khz considered mid range? That is where the harmonics are ringing out. Anyhow, beyerdynamic mc930s seem flat in that frequency range

armans wrote:Is it not possible that cardioid patterns are more directional when it comes to high frequencies?

Some do get noticeably more directional at higher frequencies, some are reasonably consistent. But then, the same is true of many omnidirectional mics, too!

Having said that, most stay pretty consistent across the +/-60 degree angle. which is the important area pointing at the instrument!

It's an easy thing to test for, though: just make a constant hissing sound and rotate the mic slowly in front of your mouth over, say, 180 degrees, maintaining a constant distance between capsule and mouth, while listening for any significant level and response changes...

The Beyer MC930 is a nice mic for the money, and doesn't have a big presence peak -- but there is certainly a gentle lift about about 5kHz. the polar pattern does also narrow a little towards the HF, but that shouldn't affect the timbre of the guitar under normal circumstances.

But usually, 'harshness' of the form you describe is down to a combination of mic placement, the quality of the instrument, the nature of the playing, and the instrument's tuning.

Fundamentally, close miking results in each mic hearing the instrument in a way which isn't the norm, or even natural, for a human listener, so the sound can seem unnatural too....

In your case, you may find tweaking the tuning of the guitar helps, or spacing the mic a little further away...

armans wrote:It is not fretboard squeeking. From what I can tell it is mainly the sound of the harmonics of the highest two strings and the frequencies are around 2khz where it seems a bit shrill

It's definitely worth trying out some different mic positions, even around the same place but a bit higher up (vertically, not higher up the guitar neck) may even the balance a little. Somewhere around the neck/body joint is usually my starting point as well if I'm using a single mic on an acoustic guitar, but it doesn't work for every instrument/room. Down near the bridge can work well for a more mellow sound with a bit less going on in the high end, given what you're saying about the sound you're getting that could be worth a go.

Although if you're happy with what an omni does in the original place, maybe that's your answer for this particular use.

I always find personally that if the room allows it, then a bit of distance works wonders with lots of acoustic instruments. Although it has a lot to do with the intended use of the recording as well. If it's a part that needs to cut through a busy mix then an up-front sound that seems unnatural on it's own may be just what you need, if it's a solo acoustic guitar piece, then it'll probably require a different technique.

As Luke says, if the C414 works in omni mode then that is your answer. If it still doesn't;t quite give you what you want then, as you room is very dry, try more distance and different positions for the mics. If you find that this results in the sound lacking in 'sparkle' then, if the room is carpeted, a hard surface under the guitarist can restore some liveliness.

Another trap for regular players is being used to the sound of the acoustic guitar as they're playing it which is usually somewhat muffled and lacking presence. A recording of the same guitar from a more front on mic position might appear too bright when it might actually be closer to how it sounds from that position.

Hugh Robjohns wrote:

armans wrote:Is it not possible that cardioid patterns are more directional when it comes to high frequencies?

Some do get noticeably more directional at higher frequencies, some are reasonably consistent. But then, the same is true of many omnidirectional mics, too!

Having said that, most stay pretty consistent across the +/-60 degree angle. which is the important area pointing at the instrument!

It's an easy thing to test for, though: just make a constant hissing sound and rotate the mic slowly in front of your mouth over, say, 180 degrees, maintaining a constant distance between capsule and mouth, while listening for any significant level and response changes...

The Beyer MC930 is a nice mic for the money, and doesn't have a big presence peak -- but there is certainly a gentle lift about about 5kHz. the polar pattern does also narrow a little towards the HF, but that shouldn't affect the timbre of the guitar under normal circumstances.

But usually, 'harshness' of the form you describe is down to a combination of mic placement, the quality of the instrument, the nature of the playing, and the instrument's tuning.

Fundamentally, close miking results in each mic hearing the instrument in a way which isn't the norm, or even natural, for a human listener, so the sound can seem unnatural too....

In your case, you may find tweaking the tuning of the guitar helps, or spacing the mic a little further away...

It was the strings. I put new strings on and now the harmonics sound more balanced in that area. The high frequencies can stil sound harsh too close to the guitar but I think when strings get old they must do something to the harmonic overtones in that region because after changing the strings it sounds better.

Just to add, my strings werent that old...well actually they were about 3 months old but considering I only play the guitar every week once or twice I would have thought that the strings should last 3 months.... I guess I was wrong... if you want even tone :(