Tag Archives: Backline

Why Buy An Active DI

An active DI box can cost a bit more, but they have big advantages.

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.

The beat-up device up there with a missing knob is one of my well-loved passive DI boxes. It’s sounded plenty decent on a number of sources, solved at least its own share of ground-loop issues, and has never had any problems (beyond losing its attenuator knob).

Passive DI boxes are very handy creatures. They solve connectivity problems with almost no fuss at all, and the well-designed models are highly resistant to both stupidity and malice. My guess is that, about 80% of the time, they’re a perfectly decent choice.

The thing is, though, that active DI boxes let you cover the full 100% at all times. They’re also cheap enough now that there’s really no reason not to go active (if you’re starting from scratch).

The “cheap enough” bit is pretty self-explanatory. Head on over to your favorite music-gear retailer – Sweetwater, PSSL, Zzounds, whoever – and find their direct box category. Sort by ascending price, and you’re almost sure to find active units before you leave the $30 price point. (Some of the really cheap units are junky, but to be fair, I own two Behringer DI800 units that have never let me down…and at $120 a pop, their per-channel cost is $15.)

What isn’t so self-explanatory is why passive units don’t quite cover 100% of the direct-input situations you’ll encounter. There’s a bit of science involved.

A Few 10s of kOhms Is Usually Enough

Modern audio is all about voltage transfer. Voltage transfer is all about connecting an output device to an input device with an impedance (opposition to current flow) that is high when compared to the output circuit.

Okay, that sounds like gobbledygook. An analogy would be helpful.

Think of a bunch of cars on the freeway. Traffic is flowing nicely. Everybody’s just flying along without a care in the world. This is low impedance. There’s very little opposition to traffic flow.

Now, we construct an exit to the freeway. The exit leads to a one-lane road. The one-lane road, in comparison to the freeway, is a high-impedance device. Fewer cars can flow down that one lane road, and as a result, the freeway has no trouble keeping the little road supplied with cars.

This condition, when applied to electrical connections, is called “bridging impedance.” An output device with low impedance is like a freeway, and an input device with a comparatively high (10x or more) impedance is like a one-lane road. For audio types, we’re not concerned with preserving the amount of electrical flow, so much as we’re concerned with preserving electrical force (voltage). Bridging impedance lets us do that.

Most passive DI boxes have an input impedance that’s in the range of several tens of thousands of Ohms. Some can even be in the 100,000 Ohm range. Connect a device with an output impedance of a few thousand Ohms or less, and – no problem! A lot of devices are perfectly suited to interacting with a passive DI, because a lot of the gear and instruments that get connected are active units. Keyboard outputs are low-impedance creatures. Guitar-processors have low-impedance outputs.

Heck, a lot of acoustic-electric guitar outputs are low impedance. The actual pickup might be anything under the sun, but quite often you’ll find some sort of preamp sitting between the pickup and the output jack.

In a lot of cases, you can even get away with connecting a bass or electric guitar with passive pickups to a passive DI. It’s not theoretically ideal, but it usually sounds fine.

This covers the “80% of the time” thing. The 20% comes in when you encounter an instrument with a very high impedance pickup, and no preamp. Plug one of those into a passive DI, and…yuck.

Easy As Pie-zo. (Yeah, That Was A Cheesy Pun…)

The ur-example of the high-impedance pickup is the piezo. Piezo pickups are neat because they’re small, put in direct contact with the instrument (which makes them resistant to external noises, insofar as the instrument resists those noises), affordable, and simple.

The problem with piezos is that they are passive devices with a very high output impedance – so high that getting into impedance bridging territory requires millions of Ohms or more.

So, you plug one of the little darlings into a passive DI, and what happens?

First, you probably get a weak signal out of the pickup. Poor impedance bridging means poor voltage transfer, and voltage transfer is how we ensure good signals in the world of pro-audio.

Second, the instrument probably sounds terrible.

Why?

A piezo pickup (when connected to another audio device and viewed as a set of electrical building blocks) is a capacitor, inductor, and load resistor in series, with a capacitor connected in parallel before the load resistor.

What all of that means is that passive EQ is happening – the capacitor, inductor, and load form a classic resonant circuit. The capacitor and inductor in series allow a range of frequencies through, and the parallel capacitance acts as an additional low-pass filter. (Whether or not this low-pass is significant after the capacitor-inductor bandpass is a whole other issue.)

The issue with passive filter circuits is that everything has an effect on everything else. If the load impedance is adequately high, then we get a nicely damped, wideband filter that sounds natural. If the load impedance is too low, however, the filter gets narrow and odd sounding. This effect can become so pronounced that string instruments start to sound like horns(!)

The obvious fix, then, is to connect the piezo pickup to a very-high impedance device. An easy way to do this is to use an active DI box.

The Buffer Zone

Active DI boxes solve the piezo impedance problem because they can employ buffer amplifiers. The great thing about a buffer amplifier is that its input impedance is very, very high (millions or even billions of Ohms). It also does this in a very small package. You could probably construct a passive DI box with an input impedance in the millions of Ohms, but the size and weight of the thing (not to mention the cost) would be really off-putting.

The downside of using a buffer amplifier is that it requires a power supply. This means batteries, or engaging phantom power from the console. In practical reality, though, this downside is almost negligible. Almost any modern console that’s capable of mixing a full band will have phantom available, and a battery in a DI box will probably last for tens (if not a hundred or so) hours.

So – all of this is just a very long way of saying, “Buy active DI boxes.” They’re pretty much guaranteed to work with any kind of instrument output you encounter, and they can be powered by any half-decent console or mic pre. They remove any need for guesswork, and they can even have nifty extras like signal boosters and guitar cab emulations.

Passive direct boxes are the right choice most of the time, but a reliable, full-featured, active DI is the right choice all the time.

No contest.


Buy A Little Amp

Large, powerful amplifiers were necessary in the early days of rock and roll. Not anymore.

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.

Nothing screams “Rock Band” like lots of gear. I myself will readily admit it: I LOVE the look of big, “ugly,” powerful, solidly-built amps and speaker cabs. You get all of that into a room, and by gum, everyone knows that you mean business.

Having people think that you mean business is a really good feeling. Heck, it’s an addictive feeling.

But it’s just a feeling.

What counts a lot more than looking like you mean business is to actually mean business, and then prove it beyond all doubt with your actual music. Proving you mean business in the small-venue context doesn’t require a lot of gear. It simply requires that you have enough gear.

Sure, you do want a bit of “cushion” or headroom, but a whole ton of it isn’t necessary. In fact, it can even be detrimental. We’ll get into that in a bit – but first, let’s talk about where the “big gear” thing came from.

The Days Before PA (As We Know It)

Way back when, in the days when men were real men, women were real women, and cars cost about as much as five tanks of gas today, you could count on one general rule for live-sound reinforcement:

You either made enough noise acoustically, or you had a dedicated amp.

The exception to this (but not by much) was the vocalists. Each vocalist might not have had their own PA, but the typical reality was that the PA only had a handful of inputs – and the PA only did vocals. The idea that you would put all the instruments through one sound rig was a foreign concept.

As a result, if you were doing a big show, you needed big amps. The drums might carry pretty well, but if you were going to get that guitar solo all the way to the back row, you needed serious firepower. Even as PA technology grew by leaps and bounds, the notion that guitarists and bass players would make all their own noise stayed entrenched. Hey – they already had the gear, right? Why fix what isn’t busted?

At this same time, the founding fathers of amplified guitar and bass were creating the tones and textures that would define those instruments for decades. They were getting those sounds through gear that had to be big, heavy, and loud to do its job. Especially for the guitar players, who loved (and still do love, for good reason) the thick, satisfying roar of power tubes being driven hard, the acoustical output was in-freaking-sane.

They got away with that volume because it was expected, and also because they were playing to huge crowds. Most of the audience wasn’t in the first few rows, and so the noise wasn’t as deafening.

Now, fast forward to 2013.

The iconic gear that defined the sound of rock and roll instruments is still very much in fashion. Sure, there have been various improvements in materials, construction, cost management, and design, but all of these creatures of the amplifier kingdom are fundamentally the same animals as their counterparts from 1969. They’re big, they’re heavy, and their most rockin’ sounds require stadium volume (or a power soak, if you don’t want stadium volume).

The problem is that stadium volume from amplifiers is no longer required, or even desirable – especially not in small rooms.

The 100 Watt Amp Problem

Let’s talk about some of what’s going on when an all-tube, 100 watt, gorgeous sounding amp is really doing its thing. Let’s make some conservative assumptions to start:

  • The 100 watt rating is the continuous power generated by the amp at a full-tilt, maximum overdrive, supersaturated roar.
  • The cab is a 4×12, wired so that each loudspeaker gets 25 watts.
  • Each loudspeaker has an average sensitivity of 95 dB SPL at 1 watt, measured at 1 meter.

The tone is killer. So is the volume.

Each cone is producing about 109 dB SPL, continuous. The summation of those four cones is 115 dB SPL, continuous, at 1 meter. The average audience member is probably sitting about 22 feet (6.7 meters) away. The venue isn’t totally dead, acoustically, so the average SPL decay is 5 dB per doubling of distance, as opposed to 6. This works out to 13.7 dB of volume decay for the average audience member.

So, for the most part, the audience is hearing about 101 dB SPL, continuous, of just the one guitar. Add another guitar of similar volume, and the continuous level is 104 dB SPL. The bass player fits in with a 99 dB SPL contribution, which takes our total to 105 dB SPL. The drummer is a spirited lad, able to make 100 dB SPL himself. Now we’re at 106 dB SPL. The vocals probably have to be at a minimum continuous level of 102 dB in order to be distinguishable, so that takes us to a grand total of…

Just under 108 dB SPL, continuous, for the average audience member, and that’s not including monitor wash.

For most people, that’s pretty dang loud. In a bar, that kind of level is hard to deal with when placing or taking orders (assuming that the bar is in the “average level” zone – which IS the case in a good number of rooms).

There’s no denying that the tone of the guitar is spectacular, but that spectacular tone is causing an audience discomfort problem, and potentially an economic problem for the venue.

This is bad for you.

Also bad for you is that, to get really good separation, the singer (who’s about 12 feet from the cab) has to be able to produce about 125 dB SPL at their mic capsule. This means that you need a singer with lots of power, stamina, and great pitch control at full volume…or less pitch control, but more raw power in reserve.

On top of that, for the vocalist to feel like they’re really hearing themselves in the monitors, the wedges will need to be making about 115 dB SPL continuous at the singer’s ears. If the singer is really powerful, and the wedges are good, then this should be achievable. If the singer isn’t really powerful, or is having an off day, or if the wedges are a little cheap, getting that kind of level may be a battle. Now, you’ve potentially got gain-before-feedback issues.

The Upshot

That arena-ready amp rig sure does sound good, but:

  • It probably costs a fair amount of money to acquire.
  • It takes up a lot of room.
  • It’s heavy.
  • It has to get really loud before it sounds right.
  • It forces everybody else to keep up.
  • It makes monitors harder to manage.
  • It can drive audience members away.
  • The venue can lose money.
  • It reduces the FOH audio tech’s options for the rest of the band (because the tech’s first priority can be forced towards just keeping up with you).

Bummer.

There’s a fix.

Buy a little amp.

There are plenty of all-tube combos out there that top out at 10 watts. That’s really all that you need. Get those tubes really hot to get the tone you want, and you’ll probably have about 105 – 110 dB SPL at 1 meter.

And you’ll be able to do it with a piece of gear that’s easy to carry.

And you’ll be able to do it with a piece of gear that you can fit anywhere.

And you’ll be able to do it without making your vocalist work themselves to death.

And you’ll be able to do it without forcing everybody else to keep up with you, whether in terms of volume or equipment purposes.

And you’ll be able to do it without flattening the audience.

And you’ll be able to do it while the bar still makes money.

And you’ll be able to do it while allowing the audio tech to make meaningful choices to get you the best sound possible.

And, because PA technology has come a very long way, that one amp will still work for you when you’re playing stadiums. The crew will just stick a mic in front of it, and turn that 10 watt amp into a 10,000+ watt amp with great coverage and smooth frequency response across the entire audience.

I can certainly understand that you might want a big rig because of the way it looks, or because there’s something very specific about the sound that can’t be perfectly replicated by other means. I do get that.

But big amps just aren’t necessary anymore, and they can be more trouble than they’re worth.


Only So Much Addition

A PA system can only do so much – the band’s overall volume has to be right, and their proportionality has to be right, too.

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.

My last article was primarily written to technicians. However, the issue of “only being able to get so much, in comparison to full-tilt boogie” has big implications for musicians playing live. Small venue, big venue, whatever venue, there’s an important reality that has to be faced:

There’s only so much that a PA system or monitor rig can add to the sound of an instrument or vocal.

Now, this certainly holds true in the aesthetic sense. There’s a practical limit to the amount of sweetening that can be applied to any particular sonic event. A drumkit (for example) that sounds truly horrific can’t really be “fixed in the mix,” especially if the tech doesn’t have hours to spend on making it sound like a different, much better drumkit. What really needs to happen is for that set of drums to sound decent, or even amazing, without any outside help. At that point, the PA’s job is to make those drums loud enough for the audience (if the drums aren’t already), and maybe add some “boom” and reverb – if appropriate.

There’s another sense of “what the sound system can add”, though, that’s much easier to quantify. This is the relatively simple reality of how much SPL (Sound Pressure Level) an audio rig can deliver for a given input from a given acoustical source. This “amount of level deliverable” is often less – even a LOT less – than what the rig can do on the spec sheet. (This can often be surprising, especially to musicians and techs who are still working on gaining practical experience with live performance.) The other side of the coin is how much overall level the PA should be adding to the show to have the result sound decent, and be at a comfortable for the audience.

How Much Should The PA Contribute?

When trying to get a handle on how much the FOH (Front Of House) PA should add to the show, there are a number of things to consider:

  • How loud is the band, all by itself?
  • What do you really want the PA to be doing? (Carrying the room? Just putting a bit more “thump” in the drums? Vocals only?)
  • How much level will the audience and venue operators be happy with?

It can actually be helpful to work backwards through these points.

In small venues, the amount of tolerable level usually isn’t very high. Although some “pure music” rooms might work with 115+ dBC SPL continuous (decibels Sound Pressure Level, “slow” average), most places that cater to 200 patrons or less will probably see 110 dBC continuous as very, very loud. The problem is that, with a band and monitor rig that are REALLY cookin’, 110 dBC is very easy to achieve – and the PA isn’t even turned on yet!

In general, I recommend an upper limit of 105 dBC continuous for everything when working in a small venue. Band, monitor bleed, and FOH. Even that might be too much for some places, but it’s a start.

Once you’ve established how loud the whole show ought to be, you can begin figuring out what the PA’s contribution should entail. The handy rule of thumb here is that, for a given maximum volume, greater PA contribution requires you to keep a tighter rein on the stage volume.

To help illustrate this point (and others), I’ve prepared some audio samples in OGG format. I’ve used a live recording of a drum kit from Fats Grill, along with a reverb processor, to roughly simulate three conditions:

Of course, this is an imperfect representation. Although most PA loudspeakers are designed to be somewhat directional, they still excite the reverberant field – they often don’t “dry out” the sound quite as much as these samples do.

Still, these clips give you an idea of what happens as more PA is applied. The overall level goes up, the PA sound starts to overcome the stage volume, and the transients get more defined. Putting more direct sound, with clean transient response into the audience is usually a good thing – but notice how much volume the PA had to add before the drumkit really “cleaned up.”

On a discussion forum, I believe that Mark from audiopile.net made a simple, profound, and very true statement with important implications: “Audio engineers don’t feel like they have control until they are 10 dB louder than everything else in the room.” With this guideline in mind, the issue crosses into the first point:

If you want the PA to really define how your band is heard by the audience, then the band’s stage volume should be about 10 dB below the PA. If the maximum volume for a small venue is about 105 dBC SPL continuous, this means that the band and monitor rig need to stay in the close vicinity of 94.5 dBC SPL continuous.

I’m not gonna lie – squishing a rock band into a box smaller than 95 – 100 dBC SPL is tricky. It can be done, but not everybody is willing to take on the challenge and make the decisions involved.

This is why, most of the time, small venue sound involves careful compromises. The PA is often used only to “fill spaces.” That is, the guitar amps might carry the room with only occasional reinforcement for solos, while the midrange and high-end from the drums is stage volume with a bit of “kick” from the subs. The vocals will be getting pretty much constant attention from the FOH rig, of course. In the end, the contribution from the FOH PA is minimal…or at least kept under tight control.

Proportionality Can Kick Your Butt

Beyond the issue of raw volume, though, is the conundrum of how much an audio reproduction system (be it an FOH PA or a monitor rig) can add to a given acoustical event on stage. This is where “sounding like a band without the PA” becomes really critical.

Here’s why.

For most audio rigs that are even half-decent, gain-before-feedback is at least as critical, if not more, than total output power. That is, a loudspeaker might be physically capable of creating earth-shattering SPL, but the squeals and howls of feedback will prevent you from actually getting there. Either the overall differentiation between the stage volume and the PA volume is too great, or the differentiation between on-stage sources is too great.

This is a little abstract, so here’s an object example.

Every so often, I’ll run into a group that has a proportionality problem. They’re not too loud for the room by any means – they might be an acoustic duo, for instance. The issue is that one person is vigorously strumming a big-body guitar, using a pick. Another person is playing a different guitar, with a much smaller body.

…and they’re playing fingerstyle.

Delicately.

Hoo, boy.

Depending on the players, that big guitar might already be a LOT louder than the small guitar – and then, the player of the big guitar decides that they want a pretty healthy amount of monitor level. No problem for the big guitar, especially if the instrument is free of resonance problems and includes a decent pickup. The small guitar? Well – it doesn’t have a pickup installed, so we had to mic it. We were only able to get “so” close, and the player’s not making a whole lot of level anyway.

The chances are that feedback issues will prevent even the most competent monitor operator from making that fingerstyle guitar compete with the big boy.

It’s not the absolute volume that’s the problem. It’s the proportionality. The massive level differential between the two instruments just can’t be dealt with in a live situation. In the studio, where feedback is basically non-existent, it’s another story. Here, though, getting through the set will be a struggle.

As a generality, I would propose the following guidelines for the feasibility of what a small-venue audio system can add to an onstage source’s volume – especially when talking about monitors on deck:

  • +3 dB – Usually trivial.
  • +6 dB – Usually very simple, if not entirely trivial. Depends on the situation.
  • +10 dB – Average, may be challenging for sources that are resonant, or when using certain microphones.
  • +20 dB – Difficult to impossible, can be done in certain cases with instruments that have well-isolated pickups and physical feedback reduction. May be possible with certain microphones in certain orientations relative to the monitors, or with common microphones and in-ear monitors. With line-inputs, noise may also be a problem.
  • +30 dB – Generally impossible unless the source is completely feedback isolated. Noise from line inputs will probably be a big issue.

The way to get around these issues is to fix them before you arrive at the venue. If somebody is getting positively drowned during rehearsals, it’s simply not a safe assumption that a PA system (even a professionally operated one) will fix the issue. If everybody is clearly audible in rehearsal, on the other hand, then your proportionalities are either right on the money or “plenty close enough.”

This may sound a bit preachy, but I want to assure you that there are big benefits to “sounding like a band” before a PA system is added to the equation. If you’ve done the hard work of being balanced without outside help, then you have a much better shot at sounding killer with PA and monitor rigs that are only minimally adequate – or operated by a minimally competent audio human. Even better, when you get to work with great gear and great techs, they’ll be able to put their maximum effort towards presenting a flat-out amazing sonic experience for your fans. They’ll be able to do this because they won’t have to make the compromises necessary to fix big imbalances amongst instruments, or between the instruments and the vocals.

Bottom line? Being at the right volume, both in terms of absolute levels and relative balance, is a huge part of creating a brilliant stage show.


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” thatĀ  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!)


The Heck Do You Mean By “Small?”

When I say “small,” what I mean is “seating capacity for 200 or fewer,” amongst other things.

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 a fan of defining words clearly, no doubt about it. When it comes to subjective terms being used in technical contexts, my blood pressure can rise in a hurry. “Loud” means different things to different people. “Great monitor mix” means different things to different people.

I mean, even something as not-subjective-sounding as, “50% less lead guitar in this wedge” means different things to different people. Somebody might actually want the guitar down by 3 dB, which is actually half power. Somebody might think that 50% less is -6 dB. Some folks think it’s -9 dB. Geeze.

Subjectivity – it’s not as easy as it looks. Anyway…where was I?

If you’re U2, or Metallica, or Pink Floyd, or [insert ginormously popular act here], “small venue” could probably mean anything less than 20,000 seats. For other bands, filling a 1000 seat auditorium would be a huge show. The biggest. In the history of ever.

For the purposes of this site, my definition of “small venue” looks like this:

  • 200 patrons or fewer can be seated.
  • The square footage of the stage plus the audience area is 3500 square feet or smaller.
  • Backline producing x dB SPL (Sound Pressure Level) at the downstage edge – the place where the stage meets the rest of the venue – is perceived by someone sitting in the farthest seat as producing a minimum of x-12 dB SPL. This is assuming that the venue is otherwise empty and unobstructed.

(That last condition is pretty darn easy to accomplish in a 100′ long venue with a stage that’s 25′ deep. The distance from the downstage edge to the back wall is 75′. The farthest away that anyone can sit is only four times as far away from the backline as the downstage edge. The level decay at a fourfold increase in distance is 12 dB SPL, and that’s assuming that there are no acoustic reflections in the venue at all. It’s theoretically possible to build an indoor venue where the SPL contribution from acoustical reflections is negligible, but it would be really, really expensive.)

I should mention that each point is not necessarily dependent on any other point. You could build a venue where the longest dimension was only 30′, and then add a soundproof wall between the performers and the audience. The wall would break the x-12 dB SPL condition for the farthest seat, but the capacity and square footage points would hold up just fine.

Of course, I do have some subjective definitions of a small venue:

  • Anywhere that loading in an 8×10 bass cab causes someone (especially the audio tech) to think/ mutter/ say “Geeze,” or “Why?”
  • Anywhere that micing backline is optional for FOH (Front Of House) sound.
  • Anywhere that the settings on an amp from a previous gig or practice cause someone (especially the audio tech) to think/ mutter/ say/ exclaim “Geeze,” “Wow,” “Gosh,” “Whoa,” “Holy !@#$,” orĀ  “That’s only on [number less than 5]?!”
  • Anywhere that somebody’s prized tone causes intestinal discomfort, bleeding, psychological problems, etc. (Also, sometimes where somebody’s prized tone is caused BY psychological problems, but that’s another issue).
  • Anywhere when a drummer is playing at a volume that seems easy and comfortable to him/ her/ it, and yet the SNARE HIT -ompletely drowns ou – TOM ROLL -verything els- KICK KICK KICK TOM ROLL KICK KICK CRASH CRASH CRASH SNARE HIT -hinks he’s John Bonha- SNARE FLAM SNARE FLAM KICK KICK CRASH -oo loud with earplugs.
  • Anywhere that the PA can be run at a continuous level that’s no more than 1/8 of its maximum continuous power, and still be considered “loud” by half the audience or more.

There’s the implication here that musicians and audio techs can make almost any venue too small, but that’s probably a topic for another time.