From now-on in this article "guitar" means "electric guitar".
If you post a question about how to record guitars, someone who might know how to do it will eventually offer a list of contributing factors in order of importance - it'll be something like this;
In descending order of importance; The Music, The Player, The Amp, The Guitar, The Room, The Engineer, The Mic, The Pre, and then cables and converters and other bits of kit...and other stuff like decent monitoring and room treatment.
After obsessing for a while about "which mic" and "which pre" they must have, some people will notice that the shiny toys are actually all relegated to the dusty end of the list, and will start to wonder about "The Engineer". This covers the whole gamut of "what do I need to do..." and includes "and where do I put this mic thing". Take a quick break and go check You Tube - search for "guitar cab mic" and you will find over 48 thousand videos, many of them showing you how to put a mic near a cab. Alternatively, go try it yourself.
When I started I spent hours recording guitar cabs - I placed different kinds of mics on the grill, just off the grill, a few inches from the grill, a few more inches from the grill, a foot from the grill, a couple of feet from the grill and six feet from the grill (most of my mics are imperial - I have one metric one but I didn't use that) and for each of those positions I tried dead-centre, edge of dust cap, an inch off dustcap (my speakers are imperial too), halfway between dustcap and edge of cone, just off edge of cone, on the edge of the cone, and then repeated for straight, 30 degrees, 45 degrees and 60 degrees off axis. For each of 4 mics. Yup - 672 recordings , all catalogued, listened to, evaluated and ranked.
And not one of them sounded like I thought they should sound! WTF - I'd tried EVERY single mic position and none of them work. In almost every single case the sound was like poor pizza, a bit too thin and a bit too crispy.
Here's the funny thing; I don't actually do a lot or recording, I generally work with tracks that other people have recorded. Most of the guitar tracks that I hear from other people are very similar to those tests that I recorded.
OK, let's take a step back and fire-up one of those amp sims that are all over the place. If you don't have one pop over to IK Mulitimedia and get yourself a copy of the free Amplitube CS - it's a bit limited but it'll do for now. Find yourself a patch and remove all the effects and processing - just an amp into a cab into a mic. Unless it's a mega distortion patch it's probably sounding a bit thin and crispy (if it is a mega distortion patch it's probably sounding a bit thick and fizzy) and not a million miles away from what you recorded with your amp and mic. Now go to the cabinets tab and move the virtual mic about - different flavours of thin and crispy until it eventually tips over into dark and muddy. These sims are not perfect but the better ones are certainly good enough to illustrate this point. So what gives?
What gives is that most people don't actually know what recorded guitar sounds like because they only ever hear it in the context of a mix. It's no secret, but it seems to elude a lot of people, but that guitar sound you are used to hearing is usually at least
· a combination of guitar and bass, and possibly some sneaky synth pads buried down deep
· 2 or 3 or more multi tracked guitars
· recording channel or mix Eq
And that's why thin and crispy sounds thick and chewy when the civilians hear it.
Now people who do a lot or recording and appear to know what they are talking about claim that moving a mic a few microns can make the difference of night and day, so I need to keep doing this until I get the one magic spot that pours on the cream. Right?
You will of course do what you want to - but here's a hard-learned recommendation; if you are not getting the sound you think you should when you are trying to record guitar parts - try this key mic position first. Place your mic a long way away from the speaker and turn-off the mic pre. Now stick your head in front of the cab (careful here, you WILL destroy your hearing if you do this too loud) and listen to what your amp really sounds like from directly in front of the cab. Most likely it's a bit too thin and crispy. And that is the sound that your rig presents to your mic.
Here's the promised simple recommendation - if you are starting out recording guitar or if your results are not what you think they should be, put your mic on a stand, place it one inch away from the grill of your cabinet, at 90 degrees to the grill cloth, pointing at where the dustcap joins to the cone, check that your pre isn't overloading, that your converters aren't overloading, and stop worrying about it. Just leave that mic where it is and give your attention to the amp. Most of us who play guitar have our own range of settings, mine sound pretty good for a set of ears a few feet above the cab and several feet in front of it, but they are utterly and completely wrong for a mic at cab level. You can either put a mic where your ears tend to be when you play and struggle with room noise, or you can close-mic and adjust the amp to suit. Be warned, you may rebel at the amp settings - be prepared to turn that treble knob all the way off if needs be - this is NOT a stage setting - it's for an audience of one who is 9 inches tall and is standing an inch from your cab. Do it.
Now try your recordings in context - even if it's only with a drum machine track and a basic bass (sorry) track. Try lo-passing with a filter at 12K or 9K or 7K and see how many problems that solves. Try a hi-pass at 100Hz to keep it out of the way of the bass. Here's another eye opener - if you want your guitarist to sound good, get a great bass player. We're not going to delve into mixing here, but try it and understand that those two simple filter moves that almost everyone uses are making a huge difference to what you hear.
You will read recommendations that suggest that you should record with less gain on the amp than you think you need and it's true that more extreme gain settings tend to become smaller sounding on mic, but too little gain is just as bad. You will find that there is a position on the gain control where over the space of a few degrees of movement you will hear a huge increase in harmonic richness of the sound. Providing you are using an amp suitable for your style of music (so not the lead channel of a 5150 for bluegrass then) this generally is a pretty good starting point. Overall volume in the real world is often governed by pain thresholds and law enforcement agencies so apply common sense.
One of the biggest problems in recording guitars for many people is actually hearing the recorded sound over the direct sound - if you can't physically isolate the cabs from the monitors then you will almost always hear the direct sound bleeding through even with isolating headphones. If this is the case and if you really want to use your real amps rather than sims, then get hold of a dummy load box and plug the output of the amp into it, take the line-out into your audio interface and use a cab impulse (check out Redwirez - they have some free samples). I use a THD Hot Plate attenuator, and in dummy load mode I can have a tube head dimed and hear the monitored sound at mix level in the same room, I don't have to trip over mic leads and I actually find it far less tiring whether I'm engineering or playing. Your load box will affect the sound to a greater or lesser degree but I've heard very useable results even from a very cheap Behringer box so give it a try.
Remember my 672 recordings - yup it makes a difference, but honestly, not that much. Here's the basic set of rules;
- A mic close to the speaker hears a small part of the sound so small movements make more difference. A mic further away hears a more complex set of tones from different parts of the driver and small movements make less difference.
- Move the mic towards the grill for a slightly harder attack and bassier response (if you are using a cardioid mic), away from the grill for softer attack and less bass. The attack thing is subtle, the bass thing can be quite noticeable depending on mic.
- Closer to the centre of the speaker for more high end, closer to the edge for less.
- Square on for fullest frequency response (whatever that is for your mic), angled for less top (as a rule)
This is not the complete story - there are still multi-mic set-ups, multi tracking and a thousand and one mixing tricks to consider, but this approach will get you 80% of the way to your goal by concentrating on what makes the real difference. Once you get the basics nailed feel free to try those different mic positions, they do make a difference, but until you've got a cake you probably don't need to obsess too much about the icing. If the recording is important, and if you're really not sure, use a DI box and record a simultaneous safety track that you can re-amp or DI later.