Mic the speaker, or use the line output?
A question from a Audio Masterclass reader...
"Why it is important to mic the combo instead of using line outs or preamp outs?"
I assume this question refers to the electric guitar. Indeed it is very common to mic up the speaker, whether it is mounted in a separate cabinet or in a combo. It would be a lot easier just to use the line out, so why don't we always do it that way?
On taking the easy way out
My first point is that in recording, we don't just take the easy way. They often do in broadcasting, but that's a different industry with much more of a priority on efficiency and throughput. They have plenty of other things to worry about that really are difficult. But if you're taking the 'easy way out' in recording, you're doing it wrong (unless the easy way really does sound better!)
The natural sound of the electric guitar
My second point, which could have been the first because it really is a toss-up, is that the sound of the electric guitar that we hear naturally comes from a loudspeaker. Ask an electric guitarist to play a few bars of Stairway to Heaven for you and you will expect just to hear it, not to have to plug your ears into the line output.
Taking a feed from the line output and recording that will remove three important elements from the natural signal chain - the speaker, the cabinet and the acoustics of the room, and add to that the air through which the sound travels, even if it is just a couple of inches.
Normally you would expect the sound from the line output to be very dry and lacking in texture in comparison to the natural sound.
Some amplifiers have a speaker simulator that attempts to replicate the natural sound of the instrument. Some are better than others, and some are actually quite realistic. But even if the speaker simulation sounds totally realistic there is a new problem - you now sound like everyone else who is using the same amp. Clearly this isn't the way to make great art.
What the player hears
The key however to the reason why the speaker is often miked up is that the sound that is recorded is much closer to what the player hears. Think of the player practising with that amp and speaker. Through hour after hour of hard work and dedication, he or she gets to know every little nuance of what that amp and speaker combination can do. The speaker is as much a part of the instrument as the belly of a violin, which which it is exactly analogous.
Granted, there will be some differences in the recorded sound between what the guitarist hears and what the mic hears, but it will be much closer than what comes from the line output.
This isn't to say that you should never use the line output. What you should always do however is record by the method that sounds best. And if that takes a little extra time and effort, then that will be time and effort well spent.
P.S. Some amps, like the one pictured, don't have a line output. That will save you the decision!