Tag Archives: Electric Guitar

The Off-Axis Guitar Conundrum

When you point the guitar amps off-axis to fix an SPL and magnitude response problem, you will often incur a time problem.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

I’m sure that I’m not the only small-venue guy who has ever ended up chasing their tail in terms of how guitars sound in the room. Not too long ago, I did a show where the guitars were a bit much for the room. We ended up pointing both amps at the stage-right wall, which had some acoustical treatment on it.

This helped a fair bit, in terms of cutting a dB or two off the overall volume and alleviating the “guitar screech” issue. What it also did, though, was remove a lot of the articulation from the guitars – to the point that, with the band playing, I knew the guitars were “loud enough,” and yet I couldn’t really hear what they were doing. This was something I’ve experienced before, but this time, it really started to bug me.

“Why,” I thought to myself, “is the guitar sound at this gig kicking my butt so hard?”

The good news is that I think I have an answer.

Starting At The Beginning

When it comes to high(er) frequencies, guitar amps are directional creatures (like just about everything else.) If you apply the ol’ standby, wavelength = velocity/ frequency, you start to see why. At, say, 2500 Hz, the wavelength is roughly five and a half inches. This is rather smaller than the diameter of a 12″ cone – 12″ cones being very common in guitar world. Since the wavelength is smaller than the cone, the cone is able to impart a good amount of directivity to that frequency, as well as just about everything above 1250 Hz or so. As a result, the guitar rig tends to “beam,” or throw high frequency content in a concentrated pattern.

And that’s just the first bit.

There are a good number of guitar speakers that have a sizeable “bump” from about 2 kHz to 4 kHz. Here’s a graph I created from data for the Eminence “Red, White, and Blues” loudspeaker:

Not all guitar speakers exhibit this kind of response, but it’s easy to run into drivers that do. There are a LOT of ’em that exhibit some variation of the “high-mid hill” that you can see in the graph.

Here’s the rub.

Those response peaks often live in the most *!@#%^& annoying parts of the audible spectrum. Seriously. Infants cry in that range because it really, really, REALLY gets the attention of everyone around them. It’s impossible to ignore. It sounds like someone is running a drill inside your ear canal.

…and there are guitar-cab drivers where the “baby-cry peak” is 8 dB higher than everything else in the spectrum. That’s a bit more than six times as intense.

So, you’ve got yourself a device that’s very good at making irritating frequencies, good at focusing those frequencies into a small dispersion area, and (usually) lacks the kind of surgical tone control necessary to fix the screech.

This is what was happening to me at the gig.

Surgery With A Sledgehammer

As an audio human, I am rarely invited to “turn the knobs” on the guitar amps. In this case, though, I had an opportunity with one of the rigs in question.

I rolled the mids down.

Nope, not in the right place.

I pulled the highs back.

Okay, but I was killing the top end entirely by the time the screech was under control.

Most guitar-amp tone stacks use “wide” filters. As a result, you end up affecting a whole bunch of frequencies when you start flipping those knobs around, not just the octave or so that you really want to tame. It’s like doing neurosurgery with a meat cleaver – you cut out your problem area, but you lose half the brain in the process.

In the end, I was able to settle on a spot for the highs that wasn’t total mud, and yet did also help with the screech. It wasn’t a fix, but it was something.

The other amp’s screech factor was rather less pronounced, and I wasn’t in a position to be futzing with the knobs on that rig, so now it was time to step back and assess.

We still needed to take the edge off.

With no more tone-stack solutions to be had, it was time to start pointing the amps in different directions. Initially, we had one amp pointing at the stage-right wall, and the other pointing at the downstage left corner. This sounded pretty good.

Of course, the bartender was getting HAMMERED by the not-terrible-but-still-prominent “screech zone” on the amp pointing his way. We subsequently ended up with both amps being pointed (to different degrees) at the stage-right wall. The overall level was high-ish, but manageable.

…and like I said, I could hear that the amps were loud enough, and yet I couldn’t really make out what the guitarists were doing when everything else was “in play.”

The Breakthrough

At some point, I had to “get on the gas” to put a guitar solo in the right place.

Suddenly, everything clicked. The guitar was in the right place, level wise, and it also had articulation and clarity. It was like a ton of bricks had been dropped on me.

See, the whole time, I was thinking that the issue was a frequency magnitude issue. I figured that, by pointing the amps at the wall, we had killed off so much HF information that the guitars were indistinct due to mud. Sure, there was a lot of low(er) frequency information flying around, but the guitars still had a fair amount of other material to balance it.

The breakthrough came when I overcame the lead guitar, through the PA, and hit a level that was pretty healthy when compared to the stage wash. The PA sound had been heavily band-limited – meaning I had chucked out a lot of LF AND HF information. I realized that the HF content wasn’t the sole, deciding factor.

We had a time problem. That time problem disappeared when the PA took over the sound, because the PA was delivering direct, un-reverberated audio to the dance-floor. The transients were “clean,” even if their HF information had been drastically lopped off.

A lot of audio techs, myself included, tend to fall into the trap of looking at everything as a frequency magnitude issue. Not enough highs, too much low end, mids in the wrong place, whatever. It’s easy to get into this mindset, because we have very powerful tools for fixing frequency magnitude problems. My “go to” EQ plugin is a fully parametric powerhouse with as many bands as the computer can handle. I love it.

But it can’t fix time problems.

The issue with the guitars was that, for all intents and purposes, the audience and I were listening to only the reverberant field. Instead of having a good amount of nice, clean “direct impulse” from the amps, we were mostly listening to audio that had bounced off a wall (or several) before it had ever arrived at us.

Next chance you get, take a pristine vocal track and put it through a reverb that simulates a lot reflections – early and late. Make it wet. REALLY wet. Pretty tough to figure out what the person is saying or singing, isn’t it? Individual notes are kinda hard to place, aren’t they? Sure, the magnitude response has changed, but a huge factor in being able to figure out what’s going on in music is being able to perceive where notes start and end. That’s a LOT harder to do when all the transients are getting smeared around like warm peanut butter.

We had fixed our frequency response problem, but we had precipitated a massive time-smearing issue in the process. Sure, it wasn’t like we were in a cathedral (this is The SMALL Venue Survivalist, after all), but all the reflections involved in the audio were not subtle. At all.

So – audio-techs: Be aware that time is an issue for you. Be aware that solving time problems, especially complex ones (like how something is interacting with the reverberant field) often involves making physical changes to things. Changes to the room. Changes to instrument placement and amplifier direction. You have to physically touch things, and make stage layout choices to the degree that you’re empowered to do so. Sure, you can fix basic alignment problems with a delay line, but everything else pretty much requires fixing things at the source.

Musicians: Be aware that time issues have an effect on the sonics of your show. Especially if you’re a guitar player, and you play in small venues a lot, try to pick gear that sounds good when directed at the audience, so that time smear can be minimized – or, pick gear that can have its major mix contribution come from the (hopefully) smoothly responding and rather more directive PA gear. Reducing the overall stage volume of the entire band can help with this.

In general, I would suggest that what we want to deliver to an audience is sound that is balanced, free of irritating magnitude response spikes, and is only influenced by the venue’s reverberant field to a degree that we have intentionally chosen.


Electric Guitar: Mic Or DI And Why?

Mic the cab if the specific sound made by the cab is “make or break.” Otherwise, you can go direct if you have the right tools.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Very reliable, but not the only valid technique.

So, my last article was precipitated by a question asked by Dee from The Black Smoke Gypsy Band. The group was debating whether to go direct with their electric guitars (in some way) or just mic the cabs. The question had inspired a bit of back and forth in the band, and Dee wanted to know what the right answer was.

Of course, I answered him with what I knew to be the most correct answer in pro-audio: “It depends.”

That’s also the most frustrating and infuriating answer.

The conversation didn’t stop there, though. A tech can’t just throw “It depends” at someone and walk off. You then have to talk about what might work for the questioner, and why.

Micing A Cab: Reliable and (Relatively) Simple

In my article about looking at electric guitar rigs as a kind of vocal (or any other acoustic instrument), I got at the idea that sticking a microphone in the area where “the noise comes out” is a simple and effective choice. All the questions of exactly how an instrument makes the sound it does are back-burnered. You just figure out where enough, decent-sounding level is present, and stick your transducer there.

A transducer is a device that converts one form of energy into another, corresponding form of energy. Mics transduce sound pressure waves into electrical signals. Speakers transduce electrical signals into sound pressure waves.

With the electric guitar as we have come to know it, the sound almost always comes out of a loudspeaker that’s mounted in a cabinet. That cabinet may also house an amplifier (a “combo”), or it might be part of a “stack” with a separate amplifier “head.” In any case, you don’t necessarily have to spend a lot of time philosophizing. The sound comes out of the speakers, so you mic the speakers.

Now, I don’t want to downplay the possible complexities of micing a guitar cab. Indeed, a lot of ink (and sometimes blood) has been spilled on all the intricacies that you can get into when micing a guitar rig:

Should you pick the best-sounding loudspeaker and put the mic up close?

If the mic is close to the cone, what area of the cone should it be closest to? (The dust cap area usually has more high-frequency information than the cone edges.) Should the mic diaphragm be parallel to the baffle? At an angle? Which mic should you use anyway? Should you use more than one mic? Should you try to time-align those mics, or should you pull one back slightly so that phase effects cancel out the frequencies you dislike?

…or, should you pull the mic back far enough to get the whole cab? (This rarely happens in small-venue work, but hey, you never know.)

Things can get very wooly.

For a sound reinforcement human, a lot of the time you end up making choices that are based on simple utility, and not “the very best sound possible, ever.” You close-mic a cone because you need maximum separation between the guitar and everything else making noise on stage. You pick the cone you do because you can get the mic stand in the right place easily, and because the mic setup will be the least in the way of the guitar player (and everybody else). You go for a placement that’s somewhere between the dust-cap crease and cone edge, figuring EQ will fix anything you don’t like.

Anyway.

Why mic a guitar cab? Why make that choice over other choices?

In the end, it comes down to this:

You should definitely use a mic for electric guitar if the specific sound produced by specific speakers in a specific cab is a crucial and non-replicable part of the guitar player’s sound.

See, electric guitar players can be incredibly choosy about their sound. Pretty much everything has an effect. There are folks who will spend days (if not more) trying to figure out which material for a pick has the best sound when used with their setup.

I’m dead serious.

In some cases, a critical, irreplaceable part of a guitar player’s sound is a certain brand and make of loudspeaker, with a certain amount of “miles” on it, with a certain amount of power flowing through it, that has been bolted into a specific kind of cabinet. If you were to even do something like replacing that speaker with a brand-new unit of the same model, their tone just wouldn’t be there.

You have to mic that. There’s no way around it. All other tricks and tactics are unacceptable.

However!

There are plenty of guitar players for whom this is not the case. There are lots of folks who like the sound of their cab just fine, but who aren’t “married” to its very specific effect on their overall sound.

So, to restate, you definitely want to mic an electric guitar rig if you are unable to get a sound that’s acceptable via some other method.

(Whether or not a guitar player having “their sound” is a good/ bad/ selfish/ team oriented/ stupid/ smart/ pleasant/ unpleasant/ crazy/ sane/ impossible/ doable thing in the context of the band in a particular venue is a whole other question, by the way.)

Going Direct: Might Be Easy, Might Be Hard

There’s a lot of mythology that goes around in guitar circles regarding the practice of going direct. It usually boils down to “going direct sucks.”

Horsefeathers.

If you want to hear a direct-in guitar that sounds good, just come on down to Fats Grill when Blues 66 is playing. Leroy’s guitar sound has a workable bottom end, a plenty-usable midrange growl (that I sometimes add to a bit, depending on the night), and a top end free of annoying hash and sizzle (that I sometimes low-pass anyway, again, depending on the night). He has no amp – just a POD HD…something…could be a 500.

It sounds like guitar to me, anyway. Nobody’s ever complained about it. The same thing was true for a band I used to work for, called Puddlestone. We ran the guitar processor through a cab-sim DI. It sounded fine. Great, even.

The point is that going direct with an electric guitar is entirely possible. You just have to use the right tools, and know which part of the signal chain you want to pull the line from.

So, where do you want to go to get that signal split?

When running an electric guitar direct to the console, you should take your signal at some point that is post the devices that have the greatest contribution to the essential components of the player’s sound.

This actually holds true for micing, because (as I said), the loudspeakers and cabinet may be an essential component of the player’s tone. If they are, then you have to get your signal “post” the loudspeaker. That means a mic.

In other situations, though, you have a number of different possibilities. For some folks, the essential components of their sound are created through processing. This processing may happen through stompboxes, or a rackmount processor, or both. When that’s the case, you need to take your split from a point that’s downstream of the processing chain, usually straight from the output of that process chain.

For other players, an essential component of their sound is the power amplification itself. There are coveted guitar amplifiers that produce a signature tone by driving, a power tube (or tubes) into saturation. If that saturation is an essential to the guitar player’s sound – not just a nice extra, but a critical piece of the puzzle – then you need to find a way to take a split from the output of the power amplification section. You can do this with a DI that has a 20+ dB PAD (Pre Attenuation Device) included, along with a parallel output to feed a cabinet. The parallel output is very important, because:

If you take a split from a point post the power amp, you must be very careful that an appropriate load is still being presented to the amplifier. Failure to do so can mean a costly repair.

Transformer-coupled amplifiers must have a minimum load present, and that load must be able to dissipate the power from the amplifier. Otherwise, the output transformer can be cooked by an internal arc, or other components can be wrecked by “flyback” voltage. When it comes to putting a DI on a power-amp output, you’re connecting a device that probably is NOT going to be seen as a proper load. Most modern, solid-state amplifiers don’t exhibit this behavior, because they don’t use output transformers, BUT ASSUME NOTHING.

When in doubt, parallel connect a suitable load to the amp.

Now – there’s one more thing about going direct.

Remember up there where I said that you have to use the right tools? This is an essential of getting a direct signal that actually sounds good. A generic, run of the mill DI box is not, in itself and without help, a sufficiently good tool for this job.

Why?

It all comes back around to those loudspeakers in guitar cabs.

Your average guitar loudspeaker starts significantly rolling off the high frequency information in the signal after about 3 – 4 kHz or so. For example, here’s a frequency response graph that I made from data provided by Eminence for their “Red, White, and Blues” loudspeaker. After about 3 kHz, the frequency response is “goin’ downhill in a decent hurry.”

This rolloff is a critical component of what we know as “the electric guitar sound.” The problem is that a half-decent, bog-standard DI doesn’t roll off the high end. Even cheap ones can be essentially “flat” to 20 kHz. The basic DI actually preserves high-frequency information that the basic guitar speaker just chucks out the window (to one degree or another). This is why a lot of people think that direct-fed electric guitar “just sounds bad – all fizzy and high endy.” That’s actually what a guitar signal is, right up until it gets pumped through a loudspeaker.

Whaddya gonna do?

Some guitar processors have a dedicated direct out. These direct outs almost always have “cab simulation” applied, and so they sound reasonably like a miced rig without any other intervention. The fancier they get, the more they take into account the effects of different speakers loaded into different cabinets. Some even simulate different mics. Some even add a bit of “room” sound to the mix. Most importantly, though, they low pass the raw signal in a way that’s similar to a loudspeaker.

If all you’ve got is a basic DI that’s pulling a signal from somewhere, there’s still hope. If you can find an EQ to insert on the guitar channel, one that has a sweepable low-pass filter, you may be able to “build your own” cab simulator. Just twist that frequency selector knob until you get the frequency in the neighborhood of 4 kHz, and then tweak a bit more until your taste is as satisfied as possible. From there, you can do more shaping with other EQ bands.

To close, I’m going to leave you with some bullet points about when it’s good to attempt a proper DI solution. Remember that there’s an assumption here: You’ve already determined that any particular cabinet is not an absolutely crucial part of the guitar player’s sound:

  • If the amp and cab sound terrible and/ or painful. (It can happen to anyone. I’ve heard some ostensibly all-tube rigs that sounded dreadfully screechy.)
  • When you need to run high monitor levels with the guitar without worrying about mic feedback. (This does happen, just not that often.)
  • When you can’t get good separation between the guitar rig and everything else on stage. (This can happen when a guitar rig is run a bit quietly, and then a bunch of guys who want to be disproportionately loud with everything else get on stage.)
  • When you can’t get even a half-decent mic placement for some reason.
  • When you don’t want to chew up stage space with mic stands.
  • You think it would be cool to try something different, and the player is on board with that idea.

Micing can be done well, and direct input can be done well. You just have to figure out what’s appropriate, and then execute your chosen strategy in the right way.


The Guitar Rig As A Singing Voice

When it comes down to it, you can look at an electric guitar setup as being a sort of “alien” vocal system.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Last weekend, I was having a conversation with Dee from The Black Smoke Gypsy Band. We were setting up for their show at Fats, and the discussion came around to a question that the band was kicking back and forth:

“Should we go direct with the guitars, or is a mic’ed amp THE way to go?”

Now, I ended up giving Dee a ton of information – information that I will be soon passing along to you folks. However, Dee’s question ended up getting me to look differently at the issue of how electric guitar sounds get into a PA system. The reason that my perspective changed is that I wanted to be able to generalize the answers – that is, I wanted to be able to give advice that could be applied conceptually, instead of just as a procedure.

To be able to talk about something conceptually, you have to understand “why.” What can sometimes catch you off guard is how deep the “why” goes. When it comes to choosing a technique for reinforcing electric guitar, the “why” ends up extending all the way down into the basic principles of how any instrument creates its own signature sonics.

Why Does Anything Sound Like It Does?

If you’re going to make a decision about how to put an instrument into a PA system, you will make much more informed choices if you have a handle on what makes that instrument actually produce sonic information. The critical question in this part of the puzzle is “What are the components of the whole instrument that makes it recognizable as itself, in an auditory sense?”

Okay, that was very “sciencey,” but maybe not very helpful all by itself. Let me explain a bit.

With acoustical instruments, the whole question of how to get the thing into the PA is pretty easy, right? You mic the thingamabob wherever the best sound is coming out.

I mean, you don’t put a vocalist into a sound reinforcement rig by plugging a cable into their chest cavity. You don’t stick a mic next to their shin. The sound comes out of their mouth. That’s where the mic goes. We rarely ask ourselves “why,” because (especially with vocalists) we don’t have a lot of workable variations in mic placement. For other instruments, you can get a bit more creative. Again, though, we still end up sticking a mic in the general vicinity of where the instrument’s sound is going into the room. There’s a TON that has to do with why the sound coming out of the instrument actually sounds like that instrument, but it often gets reduced to being a question of where the noise actually gets emitted.

…but think about it:

Why can’t we run vocals direct from the vocal cords, even if we could install a pickup there? That’s what actually makes the vibration that becomes singing, right?

Yes, but there are a lot of other components in the vocal “signal chain” that  are critical to the vocal being recognizable as a vocal, and that particular vocalist being recognizable as themselves.

The vocal cords create a vibration at a certain fundamental frequency, along with harmonics and other overtones, but that’s not enough. The singer’s chest cavity and head provide important overall resonances, and a skilled vocalist can utilize and shape those basic resonances at will. The singer’s airway, tongue, hard palate, and lips produce lots of dynamic resonance shifts on the fly. The tongue, lips, and teeth are also essential to final frequency shifts and subtle (or not so subtle) sound pressure dynamics. You can’t change or delete any part of that acoustical signal chain without greatly affecting the final sound of the vocalist.

Seriously, folks. Freddie Mercury of Queen had plenty of money to have his teeth fixed. He never did, because he was concerned about lousing up his vocal sound.

You can absolutely use this same model when you think about an electric guitar.

Why Do Electric Guitars Sound Like They Do?

An electric guitar signal chain is a lot like a vocal acoustics chain.

Really!

The comparison isn’t 1:1, especially because various parts are duplicated, or occur in a different order than what you find in a human voice. Still, there is striking “sameness” to be had. Check it out:

  • The guitar strings are like vocal cords. They create the basic vibration that makes the whole thing work.
  • The guitar’s body resonances are a lot like the chest and head resonances for a vocal. The creation of the core elements of the guitar’s tone happens here.
  • The guitarist’s pick choice, picking technique, and fretting technique are like the throat, mouth, tongue and teeth. The fundamental articulation in the guitar’s tone happens here.
  • Processing that happens between the guitar and the amp has all kinds of functions. Overdrive and distortion add resonances and harmonics like a singer’s chest, head, mouth, and vocal cord stress. EQ is very much the same as a singer changing the tension and breath flow in their head, chest, neck, mouth, and nose. Heck, a wah-wah pedal is just a resonant filter with an adjustable center-frequency, which is pretty much what a mouth is for.
  • The guitar amplifier itself is like another head, chest, throat, and mouth. The preamp section might be adding harmonics and resonances. The tone stack further alters frequency balance. The power amp section can add even more harmonics and resonances.
  • Then you’ve got loudspeaker, which functions like another vocal cord. (More resonances! More harmonics!) That vocal cord is mounted inside an enclosure, which acts like another chest cavity, head, and mouth.

It’s pretty wild when you translate all the parts of an electric guitar setup into their vocal equivalents. If taken as a unit, the result is a wild sort of space creature with bodies inside of other bodies. Fractal geometries. Alien architecture. Somebody, call H.P. Lovecraft!

Anyway.

The sum total of all the interaction of all this stuff is a distinctive guitar tone. To paraphrase the recording engineer called “Slipperman,” every component in the system is dependent upon every OTHER component of the system. Change or omit something, and it’s not the same guitar tone anymore.

By the way, Slipperman wrote some incredible (and incredibly) educational material on an Internet forum. The knowledge from that thread, entitled “Slipperman’s Recording Distorted Guitars Thread From Hell” is available, for free, at this link.

Still, for different players and different guitar rigs, certain parts of the setup may be more or less essential to their fundamental sound. When you can determine the bits that are really critical to making the noise that the guitar player is after, you can then determine your options for reinforcing that sound.

We’ll get into the specifics of THAT in another article. (Sequel hook!)