Why do they mic speakers at live performances?

We take in an absurd amount of live music. At most shows, some (all) speakers have a mic mounted right up against the grille. That’s terribly counter-intuitive–the speakers are being driven by cabling coming through the sound board, so wouldn’t they have a clean signal already? My best guess is that these are stage monitors and the mics are pushed up against them to eliminate feedback, but that’s grasping at Marshalls.


Your basic assumption, that the speakers you see with mics are driven by signals from the sound board, is incorrect. The speakers you see with mics are part of the amplification for individual instruments. The mic is how the signals from those speakers get to the sound board so they can be output from the main PA speakers.

Many performers use an amp/instrument combination that achieves a desirable tone at a specific output level, and that output level is not sufficient to reach the entire audience in a large venue. rather than plug the instrument into a more powerful amp that doesn’t have that perfect tone, the perfect amp is further amplified by putting a microphone in front of it and running it through the PA. Many guitarists like the tone of old, small tube amps that are barely loud enough to be heard over un-mic’d drums, so they mic the amp.

In addition, putting a mic on the amp un-localizes the sound of the individual instrument and enables the sound man to balance the mix.

Crotalus covered most of it. I’d just like to emphasize that a guitar amp is not just electronics, but the speaker associated with it as well. The sound of the guitar that emanates from the speaker would have different (and usually more desirable) characteristics than the sound you would get out of a direct feed of the amp to the mixing board.

What those folks said.

Plus, even if the amps that were being mic’d were loud enough to be heard in a big venue, you wouldn’t get a decent mix for anything but a tiny slice of the audience. The people up front would be having their hide removed by the amplified instruments, the back would be straining to hear them, and somewhere in the middle would be OK. Part of the reason that 60’s/70’s bands had walls of instrument amps was that in terms of watts, the usual PA system wasn’t much more than one of their instrument amps in the first place. The PA usually moved a few more square feet of speakers, but it didn’t project much more than say, two or three 100w stacks.

But by the time I was going to bigger venues in the 80’s, PAs were light years ahead of the 70’s. And today, they’re even more advanced. Any traveling show or even a nightclub that will hold 500-1500 folks in my area has flying overhead speakers. They’re arranged near the audience, so you don’t need as many speakers or as many watts as the old columns that sat on the stage, and it sounds tons better. In that environment, there’s no reason for even a half stack. Everyone would be better off through a practice amp, being mic’d, and hiring a good sound man to mix it right.


So it’s as if the speakers are acting as an organic, analogue effect. Kind of like how a particular guitar (e.g Garcia’s Wolf that Haynes is using on the Symphonic tour) has a close-but-not-quite-reproducible combination of materials and electronics.

Why then are they on stage and seemingly cranking out lots of volume? They’re acting as stage monitors so the musicians can hear and adjust accordingly?

And if it’s such a widespread practice, are there amp cases that have built-in mics? I’d think that the amp manufacturer would be able to incorporate better recording capabilities than sound engineers on the fly.

They already explained it.

A couple things. Speakers sound different at different volumes due to throw. If a speaker is on low volume, it doesn’t move much. Since it can’t move much it cannot physically recreate the full range of frequencies that can be produced when the volume is loud and the speaker has more room to move. So, speakers generally sound better loud. Some bands have a lot of amps on stage to look impressive but actually run one or two amps off stage that are mic’ed and the signal is sent to the PA.

Amp cases generally don’t have built in mics as you want to be able to move the mics around and also be isolated from the physical amp it self. Basically you want just the air moving the diaphragm on the mic. If it attached to an amp, and the amp has any volume, it can be shaken quite a bit*. Additionally, the mic placement in regards to the speak matters a huge amount and can change the tone significantly.


*There are amp clamps/clips that hold mics. Never liked 'em much.

Good posts - not much to add. I will say that over the past 20 years, the amount of volume on the stage has decreased considerably - because there has become much more reliance on the master sound board/mix and not on the amps on the stage.

Back in the day, the guitar amp was expected to account for a much larger percentage of the sound heard by the audience. In small clubs, that is still the case. But for larger amphitheaters and arenas, the amp may not be relied on much at all - especially if the venue needs “repeaters” set up around the space to ensure that the sound hits the audience members in the back in the correct way…

Capt Kirk would be perfect to respond to this type of question - he does sound for bands. But he just went out on tour with a band and I am not sure how often he is able to check the 'Dope.

Thread police begone!


Those mics are not just for the overall PA. They also go to master recordings, which may end up released to the public. That sound is not tweaked by the imperfect-to-horrible acoustics of the venue.

When I was looking for wireless microphones and various ways to wire up a guitar, I stumbled across a YouTube video that was showing “How to mic your amplifier for the stage.”

It was literally a small amp on a small stage (like an elementary school’s auditorium/cafeteria stage) with a desktop-sized mic stand and a microphone. The producers would say, “If you want a deep resonating tone, put your microphone in this corner…” and demonstrate the placement and some guy off-screen would play an appropriate guitar chunk. Then they’d say, “If you want a sharp edgy sound, put your microphone here…” and so on and so on.

[I have no idea how to find that video again. It was over a year ago and it wasn’t what I was looking for so I didn’t pay that much attention. Otherwise I’d link to it here. ]

So, in addition to the knobs on your instruments and the FX pedals and/or multiFX processors and/or computer software, you can adjust your sound for the audience by changing how and where a microphone receives the amplified sound. Then it sends that sound to a mixing board and it gets delivered to the audience – ideally so that everyone hears the same song at the same time.

It’s gonna be quite a while before I’m ready to perform in front of an audience again, so I haven’t studied those details any further.


One point that I think hasn’t been made is that, for guitars, playing it through a loud amp close to the guitar can create low-level feedback. Done right, you don’t have the ear-piercing squeal of out-of-control mike feedback, but just enhanced tone and sustain.

For guitarists who want that sound, they need a stage amp near them-- even if you could get a PA that mimiced exactly the tone of the stage amp itself, the overall sound still wouldn’t be the same if you ran the guitar output right to the PA.

Yep, absolutely true. When you’re playing an electric guitar, you’re playing an instrument that doesn’t end with the thing you’re holding in your hands. It’s a system that includes the guitar and everything connected between its output and the amp, and back again through space between the speaker to the guitar via air and magnetism. Hence, guitar amps are normally mic’d.

Being most often a bass player these days, I usually get the option of going direct to the board, or having the amp mic’d. Compared to guitar, bass usually is helped greatly by going direct to the board and out to the P.A. With my old combo, I always decided to go direct. Their system always outclassed mine by leaps and bounds. However, since I’ve bought the bass equivalent of a half stack, I’m choosing mic’d. But it has nothing do do with the volume, it’s because they seem to be concerned when the overdriven channel on the amp goes direct to their board. P.A. systems don’t seem to want that being sent to them. Once I do that, they’d rather treat my instrument like they’d normally treat a guitar.

Ok, this is kind of a hijack, but I have to get it out of my system this morning;

Similarly, the sound of drums is really dependent on the room that they are in, and it’s almost impossible to capture them properly with microphones - live, or in the studio. I’ve heard plenty of recorded instruments that sound identical to what I heard live when I hear the playback. Heck, guitar is probably the one that’s captured most realistically and reliably. But I can’t think of one time I’ve heard that happen with drums. I’ve heard good drum mixes, but when I can compare, it’s never as good as it is live.

I think that it’s partly because it’s a big instrument, and a mic system that would capture its sound like our ears do (or how mine do when standing a foot away from it, at least), would be catching the whole stage. I’ve heard lifelike drums on old jazz recordings produced before I was born, but that was done by geniuses of the art of mic placement for a large ensemble, before more than two tracks became common. I imagine the close mic placement you get with multitracking and live sound these days makes placing mics for a live recording a kind of lost art, and that’s why I’ve never personally heard a performance where the drums sounded “live” when recorded. It kind of boggles the mind that they really do apply some processing/reverb to even most “live” drums sent through a P.A. to reproduce a “room”. But then again, the best overhead P.A.'s apply delay to their signal to the furthest speakers, to compensate for the space the original sounds have to cover. It’s the best that tech can do to bridge the gap between a “live” sound and a “good” sound.

You could easily say: What do you want, scabs? drums that sound naturally like crap? Ideally, I’d reply: No, but I’d like them to sound as big and as crisp and beautiful as they did when I was standing there with them.

An example of what I mean would be the recording of Joe Morello on “Take Five”. It was written as a drum solo for him, so it’s no surprise the drums are recorded well. It’s rare for a kick drum to sound that way these days, but you can hear the room that drum set is in. Even then, it’s a fiction. Snare hits, even light ones like that, pop harder when you’re there in real life.

Off topic, but do you mean grasping at martials? Martial laws -> straws?