At concerts I sometimes see a setup where there is a speaker on stage behind the band, with a microphone mounted directly in front of the speaker pointed at it. I assume the microphone feeds the PA system. This puzzles me. I would think that you would get better fidelity by plugging whatever is feeding the on-stage speaker directly into the PA rather than going through an extra speaker/mic which converts from an electrical signal to an acoustic signal and back to electrical. And if the idea is to provide a stage monitor for the band to hear, I would again think that a better setup would be to split the signal and send one leg to the monitor and one to the PA, rather than introducing an in-line speaker/mic. So why do they do this?
It’s probably a guitar amp or other instrument amp. It’s very carefully setup by the musician and is part of a system that includes the guitar and possibly other effect boxes that together produce the sound that the musician wants to make.
The Amp’s effect on the sound is significant so you’re not wrong that it would be simpler and introduce less noise to go direct and not include the amp but it would not create the sound that the musician wants.
Someone who knows more about current equipment like digital amp emulators will be able to give you an idea about how long it will be until you no longer see amps on stage but that person won’t be me. I don’t know how to make a sound without an amp.
You’re not talking about a Leslie cabinet, are you? Does anyone still use those?
No I’m not talking about a Leslie (rotating speaker). Phil Lesh’s band still uses a Leslie; there’s one permanently on stage at his Terrapin Crossroads club in San Rafael. I’m talking about a standard speaker with a separate mic in front of it. I haven’t found a great close-up photo, but you can see one or maybe two in the photo at the top of this article.
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The two miced cabinets in front of the drum set are guitar amps.
Benmont Tench (keyboards for Tom Petty and the Heartbreakers) always used one. If you watch him on stage, it’s usually right next to him.
As for the mic in front of the amp/speaker, I just always assumed that the band knows exactly how their set up works and what it sounds like so instead of trying to get the mixing board to replicate it, they can send a feed to the mixing board with the exact sound they want coming from the PA and it’s up to that guy to figure out the rest.
I remember at a Tom Petty concert years ago, midway through a song his guitar stopped working. He blew an amp and the concert ‘stopped’ for 5 or 10 minutes while they swapped it out, all on stage*. I say ‘stopped’, but he managed to get a singalong of This Land Is Your Land going with his unelectrictrified electric guitar that was just barely getting picked up by his mic.
*I should clarify, the point was that I surprised that his guitar was running through a rack of electronics sitting a few feet behind him on stage.
I can think of several reasons. One, if the mic is in front of a guitar amp, it’s because the sound man wants the particular sound that comes out of the amp. This might not be as “pure” as a direct link, but it’s what they want to hear.
The other reason, and the reason I often put a mic in front of a speaker or in front of a stage, is to feed a video camera. I prefer a direct feed from the house mixing board, but that is not always available. Also, sometimes not all instruments are fed into the house mix since they may be loud enough (for the audience) without amplification. A videographer might need or want an extra boost from these kinds of instruments, since they will be missing from the house mix.
Ok, @74westy and @Musicat have both mentioned micing a guitar amp to get the amp’s sound to the PA system. I’m not very familiar with guitar amps, but don’t they have some kind of line output as well as the speaker in the cabinet? In other words, why don’t they just plug a cable into the amp to get the sound out, rather than putting a microphone in front of it?
I’m no sound engineer either, but does that even make sense? If you want to bypass the amp you could jack the guitar into a DI box. OTOH if you want the sound of the speaker cabinet, how would you get it without a microphone?
As I said, I know a little about amps. But I would have thought that an amp has a jack that you can plug a cable into to get the same sound that it’s outputting to its internal speaker. Is that incorrect?
I haven’t replied to this yet because I really don’t know but, yes, you could send the signal directly from the amp head to the PA. A couple reasons I’d speculate why they don’t are
- The player needs to hear the amp directly when they adjust it.
- The player spent a sack of money on Celestion Greenbacks or vintage ALNICO speakers or something and that’s where their sound comes from.
- Some other thing Opal understands and I don’t.
The guitar amps AND cabinets are part of the instrument/sound that the musician is wanting you to hear. All the PA does is reinforce that sound. You mic the cabinet so that the guitar techs can travel with the musician and the PA guys can be local since they only need to know their house system.
A few problems.
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Most rock guitarists use valve (aka “tube”) amplifiers.
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Most valve amps don’t have a line out.
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The speakers and cabinet itself plays a big part in shaping the sound.
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If you want your guitar to sound to the audience the way it sounds to you, then you need to send the sound you hear to the PA, i.e., mic the cabinet.
You can send the guitar direct to the PA, but you need to go to some lengths recreating the sound you’re used to and if you get it wrong, it sounds really horrible. Far easier to just mic the amp.
Another factor is that the interaction of the sound from the amp with the guitar’s strings creates extra sustain and feedback. A guitar sent direct to the PA tends to sound a bit lifeless due to a lack of this interaction.
It’s difficult to do this if your guitar is going direct to PA and the PA is projecting out to the audience.
It really needs to be understood that the totality of what we think of as the instrument known as an “electric guitar” actually comprises a guitar and an amplifier and a speaker. The latter components are part of the instrument - in the sense that they form a critical part in shaping the sound you hear. A different amp & speaker would produce something different - to a more or less subtle degree. So a line out may well not reproduce precisely what the guitarist wants.
In my days of mixing live sound every guitarist had their amp mic’d and most still do.
Although the mics are not very obvious, once you are aware of their presence I think you will spot them in most live situations. In fact, in studio recordings it is usual to mic the amps. Here’s Keef for instance. Scroll through the players of the Mesa amps and look at the live photos. Nearly all are mic’d.
A quick Google search of images of any well known guitarist plus “live rig” will show you that nearly all of them have their amps mic’d live.
Yeah, this is the reason they mic the amps. The sound we think of as electric guitar is created by an instrument that is comprised by the guitar, any effects and the amplifier. You can send the guitar’s signal through a direct box to the board, but it sounds awful in comparison to a classic amp+guitar setup*. You can get a sound close to the traditional setup with cabinet emulators and preamps, but that has its own limitations.
I’ve played with bands that have direct setups and use the house PA for all of the amplification. It sounds close, but they’ve never sounded as good as the other acts on the same bill that are using amps.
*I’m a bass player, and it’s pretty common for sound guys to want to send the bass direct to the board. I far prefer they mic my cab. I brought it and the heavy ass head here because I want to make that sound, not the awful hi-fi sound you get from a direct box. I’ll let them take the direct out of my head, but you can put that direct box back in your case.