Learn How to Identify and Correct Phase Issues in your Mixes

Has your mix ever sounded “not quite right” but you can’t put your finger on why? You might be experiencing phase cancellation, a phenomenon that can make certain frequencies vanish from your mix. To help you out, this Studio Basics article will help you understand phase — what it is, why it matters, and what it means to be out of phase.

The Laws of Physics

Essentially, phase refers to sound waves — or simply put, the vibration of air. When we listen to sound, what we’re hearing are changes in air pressure. Just like the ripple of a stone in water, sound is created by the movement of air. And just as in water, those movements cause a rippling effect — waves comprised of peaks and troughs. Those waves cause our eardrums to vibrate, and our brains translate that information into sound.

When we record sound, the diaphragms in our microphones essentially replicate the action of our eardrums, vibrating in accordance with those waves. The waves’ peaks cause the mic’s diaphragm to move in one direction, while their troughs generate movement in the opposite direction.

The first illustration below shows what happens when we’ve got two channels of a signal in phase. When both channels are in phase, we hear the sound at the same amplitude level at the same time in both ears.

But if one side of the stereo signal is reversed, as shown in the second illustration, the signals will cancel each other out. In fact, if we were using a pure sine wave, combining both signals out of phase would result in silence, since the sounds would literally cancel each other out.

In the real world, we normally don’t listen to pure sine waves. Since most of the music we hear and the instruments we record are a complex combination of multiple waves and harmonics, the results of phase cancellation will be equally complex.

In the Studio

When recording, phase issues can quickly become complicated, usually becoming a problem when more than one channel is used to record a single source, such as stereo miking a guitar, multi-miking a drum set, or using a microphone/DI combo for bass. As sound waves of different frequencies reach different microphones at different times, the potential for one mic to receive a positive phase while another receives a negative is greatly increased, and the relationship between all of these waves’ phases can be unpredictable. In fact, the more mics in play, the more inevitable some sort of phase issues become.

Let’s look at a simple scenario, like a stereo recording of an acoustic guitar.

Most often, two mics will be set up, with one pointed toward the sound hole to pick up the lower frequencies, and the second mic pointed toward the neck and fingerboard to pick up the attack. Of course, the guitar’s frequency range covers several octaves, which means a wide range of different audio wavelengths. Since the mics are a fixed distance from the source, those different waves will arrive at the mics at different points.

Inevitably, one or more harmonics will end up sounding weaker than the rest. Your best practice would involve moving the mics very slightly — even a fraction of an inch can make a difference — until you achieve the best sound to your ears. Another solution would be to use a mid-side miking technique, which you can read about in our Mid Side (MS) Mic Recording Basics article.

Again, the more microphones used in a recording, the more potential for phase problems. In modern music recording, that usually points to the drum kit. Consider even a single snare drum, miked from above and beneath. Since the top and bottom heads of the drum are usually moving in directly opposing motion (when the top drum head is hit, it moves inward, causing the bottom head to move outward), the two mics will record signals that are directly out of phase.

Now factor in the hi-hat mic, a pair of overheads, at least one kick drum mic and one on every tom, not to mention the relationship to ambient mics, and you’ve got a sonic soup that’s ripe for phase problems. That’s why many microphones, as well as mic preamps and consoles, offer a phase flip switch. It's also why a lot of “old school” recording engineers wax nostalgic about the days when they recorded a kit with only two or three mics!

There are plenty of other “gotchas” that can introduce phase problems into your recordings. For example, a bass track recorded direct (DI) can be too clean sounding, so putting a mic on the bass amp cabinet and mixing the two sounds can give the extra “oomph” it needs — but it can also introduce phase problems.

Even certain delay settings, including pre-delays within a reverb patch, can create a delay of your original signal that ends up being out of phase

Check Your Speakers

Phase cancellation can also occur by simply wiring speakers incorrectly, inadvertently reversing the polarity of one channel. It’s surprising how many home stereos — and even project studios — have their monitors wired out of phase. In some circumstances, it may not even be apparent without careful listening. Though this is commonly referred to as “out of phase wiring,” technically-speaking it’s an issue of polarity. That said, the audible effect of this polarity reversal is the same as you get with phase cancellation.

The easiest way to check your speakers is to sum your mix to mono (more on this later). Many stereos and most mixing consoles allow you to do this, but even in stereo, there are some telltale signs of phase problems.

What does a phase problem sound like? Since phase cancellation is most apparent in low frequency sounds, the audible result of out of phase monitors is typically a thin-sounding signal with little or no bass sound. Another possible result is that the kick drum or bass guitar will move around the mix, rather than coming from a single spot.

Another common artifact of out-of-phase stereo mixes is where signals panned to the center disappear, while sounds panned hard to one side remain. Often this will be the case with a lead vocal or instrument solo — the main part will vanish, leaving only the reverb. In fact, this is how many of those old “remove the lead vocal” karaoke boxes work — they flip the phase of one side of the stereo mix, relying on the assumption that in most commercially recorded tracks, the lead vocal is panned dead center.

So what’s the fix?

As with most things, the answer is “it depends.” Assuming you identify a phase problem during the recording process, a fix is as easy as moving a mic or flipping the phase on a mic or its input channel.

When attempting to capture ambience, there's also a quick cheat: the 3:1 Rule of Mic Placement. Put simply, when using two microphones to record a source, try placing the second mic three times the distance from the first mic, as the first mic is from the source. So if the first mic is one foot from a source, the second mic should be placed three feet from the second mic. Using this simple 3:1 rule can minimize phase problems created by the time delay between mics.

Of course, if the problem doesn’t show itself until you’re mixing, it’s often possible to pull the tracks up in your DAW, zoom in close on their waveforms, and slightly nudge one track just a bit. You’d be amazed what a difference just moving a track by one or two milliseconds can make. There are also some very effective phase alignment plug-ins on the market that can really clean things up — and even serve as great creative tools — one of which is the UAD Little Labs IBP Phase Alignment Tool Plug‑In.

Sum It Up

We’ve only scratched the surface, but the bottom line is that phase issues are a fact of life, and practically unavoidable.

The first order of business is to identify the problem. Most phase problems will not show themselves in stereo, and will only appear when you collapse your mix into a single summed channel. That’s why it’s critically important, as you build your mixes, to check them regularly in mono. Don’t wait until you’ve got a completed mix to sum it into mono. Check the basic tracks, especially drums and bass, early on in the process when the arrangement and the mix are less dense and fewer things are going on. And check it again every time you add a few more instruments, or change a track’s EQ, or add reverb.

As with many things, the sooner you catch a phase problem, the easier it will be to fix. Happy mixing!

Your productions tend to be eclectic, with everything from vintage jazz to soul to hip-hop to alternative rock showing up in your work.

I’ve always done more than just hip-hop. I’m from Boston — between Dorchester and Brookline — so as much as hip-hop was an influence at the time, rock and punk were huge influences on me as well, and I knew as much about them as I did about soul and hip‑hop.

What gear did you start on?

When I started creating beats and sounds, I started on things like the Ensoniq Mirage, Roland S-Series keyboards like the S-50, and an AKAI S900 sampler. All this was well before the MPC was even available, though I would graduate to an MPC-60 eventually.

But at that time, I’d use whatever was available; the school studio at Hampton University, for example, had a Kurzweil K2000S. But I really developed my ability to put tracks together on a rackmount Tascam 134B 4-track Syncaset that belonged to a bass player friend of mine.

In your recent work with A$AP Rocky, as with Wyclef Jean back in the day, you incorporate a nice blend of live instruments and sampled beats.

I suppose that if I’m known for anything, it’s the combination of samples and live instruments. A lot of my commercial work has that combination because that’s really what people come to me for.

When I came into the game, DJ Premier of Gang Starr was a huge inspiration. I was enamored with how he manipulated samples, because when I came up, it was the time when people used to just loop samples, and Premier was one of the first to go to the next level of chopping up samples, and processing them in more experimental ways.

Because I play instruments, I could incorporate them along with this new way of creating beats from samples. It enabled me to be a lot more free and experimental with the productions.

Though it’s easy to see samples as simply pre-recorded sounds and instruments, they’re almost a different medium entirely. What do they bring to the table in a production?

Samples are great because they have interesting textures. Something that was recorded in a dusty room in Memphis in 1966 is going to have a very unique texture and flavor to it — and that’s something that’s very hard to create with live instruments.

What are some ways you add texture to a sample?

Guitar pedals — I carry around at least 50 of them. You can use them to distort and disrupt clean-sounding signals in unexpected ways. In fact, I especially like pedals from the ’60s and ’70s, like an old Maestro Fuzz, for instance, for that very reason. They add so much character and texture to live sound, and get them much closer to the vibe you get from a really great vintage sample.

Are there dangers to the wide availability of commercial samples and beats, perhaps a certain sameness creeping in?

Sure. Someone recently commented that 95% of today’s beats sound the same, and I think that’s basically true. Don’t get me wrong; I’m someone who’s very aware of the evolution of music technology, and I care about what the kids are into, because as far as I’m concerned, everything begins with the present generation of kids, just like it did in my day.

Not all hip-hop is going in that direction however.

No. I mean, you think of an album like Kanye’s Yeezus and Life of Pablo — they are very different than the majority of rap records. I recently read a quote with 50-Cent talking about Jay-Z’s last album, 4:44, and his “criticism” was really more of a compliment. He said it was too grown-up, too mature. I thought, the man’s a 47-year-old rapper! He should be making mature albums. You could say the same thing about a Kendrick Lamar album — the incredibly high level of intelligence and sophistication — or J Cole’s new album,KOD, that everyone’s talking about.

Let’s talk about the Apollo Artist Session you did with the Preservation Hall Jazz Band in New Orleans. What were the particular challenges of recording in that space, completely live?

The biggest problem was separation. Normally, I’ll isolate things and baffle up different instruments in the studio, but in this live setting I didn’t have that luxury. We had one AKG C24 stereo room mic; we had the brass miked on the left; the reeds on the right, and we had an overhead Neumann U47 vocal mic on the brass side, too, because there’s a vocal part on the song.

The brass players are sort of playing into the horn mic, and then leaning up to the overhead mic when they do their vocal. The idea was to really stay away as much as possible from making choices that wouldn’t have been used in a session in the ’60s, and except for the fact that we used nine tracks, without any bouncing, I’d say we kept it pretty tight.

You opted for the UA 610-B Tube Preamp & EQ plug-in to get that period sound, right?

Yeah, we put a UA 610-B Tube Preamp plug-in in the Unison slot on every channel in Console to give us the equivalent of a Universal Audio 610 desk. In fact, the ability to create a custom Neve, API, or SSL desk is one thing I love about the Console app.

So each channel had the 610-B plug-in, Studer A800 Multichannel Tape Recorder, and Fairchild 660 Limiter plug-ins. Very simple and straightforward.

Did you need to add any ambience?

I didn’t add anything in terms of reverb because we’re recording in this old hall that was built in the 1700s, then burned down and rebuilt in the 1800s, so you really can’t get more character than that. Just really nice, rich old wood. Although the room was smaller than I’d anticipated.

You’ve got the resources and the skills to use pretty much any plug-in, so what makes Apollo and UAD plug-ins special for you?

When I discovered Apollo interfaces, it changed my life. I came up in the era of tape, recording on SSL and Neve boards, and tweaking real Lexicon reverbs, and being able to actually touch and control all that stuff. So, even as digital recording became the norm, and it was easy to get kind of “plug-in happy,” I wouldn’t say that there were ever very many of them that I really loved using.

Then I started using Apollo interfaces and UAD plug-ins in Console, and my productions sounded so much better than what I had before.

I mean, I’d even A/B the UAD plug-ins against the comparable hardware units when I was in big studios — recording through a vintage hardware Neve 1073, for example, then comparing it to the UAD Neve 1073, and they always sounded great against the “real thing.”

What would say to someone hoping to emulate your success as both producer/composer and business person?

You have to take control of your schedule! I can only speak for myself, but I really can’t mix being a producer and a businessman. If you’re following a musical idea in your studio, you’re focused, you’re locked in. And if you have to interrupt that with an email or a phone call, it’s completely disruptive to your creative process.

I did this thing a few years back I call “Taking Back Your Schedule,” where I made some firm decisions about, y’know, this is my phone call and email time. This is when I’m reachable. And this is when I go into creative mode without any interruptions, unless they’re urgent.

It’s tough. There have been times I’ve been working with artists, and it’s been very problematic when business keeps interrupting the flow. So I’ve been working more and more to make sure that separation really sticks.

In general, mornings up to about 2pm are for business calls and emails and all that; 3pm on is for creating music. Look, if you’re going to do both — and in many ways you especially need to do both these days — you need to craft a system that works for you. Doing so will make a significant impact on your ability to be productive in your creative and business life.

A well-sung lead vocal can make your tracks soar. But producers far and wide will also tell you that vocals can be the single most difficult element of a production to get just right.

For a recent demo project, I experimented with a handful of UAD plug-ins to help me tune and tweak, deepen and sweeten a raw performance towards a polished, powerful vocal track.

Go to the Chorus

“Nobody’s Savior” is a new original song that I recently had to work up as a demo under a very short deadline. The vibe is meant to be saucy and a little bit anthemic, somewhat similar to Adele’s “Rolling In The Deep” when it comes to bluesy, rhythmic character — but with a bit of an “Eleanor Rigby” chamber feel in the arrangement.

Here’s a snippet of the first chorus vocal, with minimal accompaniment and just a little EQ.

Since the tracking and production timeline was very tight — start to finish in a few hours — lots of vocal editing, comping, and re-tracking was not an option.

I liked the quality and attitude of an early take, so I ran the whole thing through the Antares Auto-Tune Realtime plug-in to see if it added the perfect amount of pitch polish.

Given that the vocals were solid to begin with and had an expressive, earthy quality to them, I didn’t want to over-process and iron out any vitality. Instead, after tweaking a few variables, I found this very subtle Auto‑Tune setting.

Listen to how smoothly and transparently the plug-in locks the vocals’ pitch into place, especially where it’s most needed on key notes like the words “savior” and “fool.” The vocals had some bluesy slides in them, and I loved how this setting left the character and grit of those glissandi in place, yet made sure that the sustained notes on words like “rules” and “go” were right on, allowing them to gel more organically with the instrumental arrangement.

Manley Vocal

Next, I wanted to add some compression, warmth, and sizzle to the voice, so I dialed up the Manley VOXBOX, scrolled through a few presets, and discovered this setting:

The VOXBOX is a powerful sonic Swiss Army knife that includes a tube mic preamp, EQ, compression, and de-esser/limiter. Several years ago, I recorded an entire album using a hardware VOXBOX as the primary vocal chain preamp. Even though the settings that we used for that project were pretty minimal, I loved the warmth, color, subtle sizzle, shape, and organic texture that the box added to the album’s male and female lead and backing vocal tracks before the sounds were captured in Pro Tools.

The UAD version lived up to my memory of the hardware, and the VOXBOX plug-in made my quickly-tracked vocals sound meatier, far less digital, and much more alive. I paged through a few different presets and was pleasantly surprised to find that the Joe Chiccarelli-Rock Vox setting gave me the mixture of warmth, presence, grit, and electricity that I was looking for.

I started tweaking the input gain, compression threshold, and overall output, but ended up reverting back to the preset when all was said and done, since it sounded so good right off the bat. You can hear the result here:

Go Deep

Finally, it was time to add some depth. I pulled up the UAD Pure Plate Reverb plug-in and, as time was still very much of the essence, again started with factory presets. When I got to the RC-Long Warm Plate setting, shown below, I knew I had found the winner:

I had the Pure Plate set up on an aux channel and experimented with how much of my vocal signal to send, in order to get the depth and ambience that the arrangement needed. After some trial and error, I ended up with about 25% and love how, as a result, the vocal sounded not only more organic and in-tune, but like it was living in three dimensions:

Working with these UAD plug-ins, I loved how far I could take my raw vocal track — literally in minutes. When it came to the time-sensitive task of building a demo on deadline, this trio of UAD plug-ins gave me exactly what I needed.

In this video, you’ll learn how to quickly connect, setup, and start recording tracks with Universal Audio’s Arrow audio interface. Producer Christian “Leggy” Langdon (Banks, Meg Myers, Ed Sheeran) and singer/songwriter AMES demonstrate how easy it is to get started recording with Arrow.

Learn how Arrow's hardware controls and Console software work together for a seamless recording workflow, as "Leggy" Langdon tracks guitar through Arrow's included Marshall Plexi Classic plug-in, and records AMES’ vocal through the UAD Neve 1073 Preamp & EQ and UA 1176LN plug-ins - all in real time with no latency.

Langdon also shows you how to create headphone mixes with reverb, quickly toggle speakers and headphones, and dozens of other tips and tricks that show why Arrow is the easiest to use pro-quality audio interface available.

Congratulations on the immense success of Beerbongs & Bentleys.

Thank you. It took two years to get everything just right. We started working on it toward the end of the Stoney era, [Malone’s 2016 debut] so it was a big deal finally getting it all done. We really believed in the record and we knew that it was going to be different and not pandering to the trends.

Is it true that you use only an Apollo Twin as both your interface and preamp for vocals?

Yeah, I keep it very simple. I start with the Sony C800 microphone, which is what I use for most vocalists I work with, unless they request their own mic. I connect that via XLR to the back of the Apollo Twin, and I’m just using the preamp that’s built into the Twin. I want to make sure that I can change the color of the vocal sound after the take, or tweak it if the singer requests something different from whatever we’ve printed on the vocal track in Pro Tools.

Why does that flow work so well for you?

I had certain plug-ins I’d use on my vocal chain for years, but once I discovered UAD plug-ins, I found it became really easy to get results. Suddenly, I didn’t need to tweak all that much to get a good vocal sound. UAD plug-ins get right to the point.

Everyone assumes I use all this outboard gear, but one of the things I love about the Apollo Twin and UAD plug-ins, is that I can get incredible sounds on the go, in a hotel room if I have to.

I also like the stability of the Apollo Twin — outboard gear has good days and bad days, or you suddenly need to replace a tube. If I’m trying to finish a record, and suddenly there’s an issue with the gear, that’s a big problem. That’s not going to happen with Apollo Twin.

You’re also able to stay in the artistic zone.

Yes. When I’m working with singers, I can’t afford to have any down time, because those creative juices can dry up pretty quickly. I need tools that are consistent and reliable.

What UAD plug-ins do you use after you've tracked the vocal?

For vocals, the 1176 Compressor is a go-to for me, because it gives the vocals a certain attack and a roundness, along with a nice warmth, that just immediately makes my job easier. I’ll also use the Neve 1073 or the API 550A or 550B plug-ins in a vocal chain.

On vocal ad-libs, I really like the Brigade Chorus Pedal. I tweak the input control to give the vocals a "not your typical," in the background sound. Instead of just putting reverb on them, I like to give them some extra flavor and a unique quality, something to differentiate them from the lead vocal.

A really cool tool that I also love is the Sonnox Oxford Inflator. Throw that on vocals and you can press them to the point where they have a brightness and a volume that you can’t get with any other effect.

How do you make space for parts in a dense mix?

To be honest, I’m tempted to use the Cambridge EQ on absolutely everything, because almost every sound can be improved with it, by clearing out a little space in the frequency spectrum.

It’s like organizing furniture in your living room; you can always carve out more space around each piece by nudging things just an inch this way or that, so you’re not stepping on yourself and every piece has some air around it.

What do you use on your master bus?

I love the Shadow Hills Mastering plug-in. In the final stages, it glues everything together. The Precision Multiband helps me do that too, especially on the master bus; it’s really helpful when you can actually see as well as hear the way you’re attenuating each specific frequency band.

The low-end is really impressive on your records: meaty, gritty and subby, but very much part of the overall mix, and never swallowing the instruments.

Thanks. For low-end, I love the bx_Subsynth Subharmonic Synthesizer by Brainworx, which is great at adding low-end to kick drums if there’s no actual 808 there or a natural sub creator. The bx_subsynth gives you a really clean, driving kick and bass tone that’s not distracting to the overall mix — and you can even focus it only on the middle channel without affecting the left and right sides of your mix — but it still adds a lot of beef.

Bass is tricky; especially with hip-hop, you want a lot of bass in there, but at the same time you don’t want it to eat up the whole track, or the whole stereo field. You have to find a happy medium, and the bx_subsynth is pretty amazing at that.

It’s funny, if you soloed the bass on a lot of my tracks, you might think it sounded distorted and over saturated, but in the mix, those are the exact things that allow the bass to cut through. People sometimes imagine the bass should sound all nice on its own, but you need that lion roar to make it cut through all the other instruments.

Your productions have strong chord progressions, not just static bassline vamps like a lot of harder hip-hop music. I’m even hearing proper keyboard-style slash chords, like F/A in some of the songs.

The goal with hip-hop has often been more about creating a kind of musical discomfort, or even a cacophony. When you analyze the music, you do wonder how it even all works, at least in terms of traditional harmony. There can be a real genius in that, because it’s very instinctive.

Post has been playing guitar for years, and I’ve been playing piano for years, so collectively, we can create the music beds pretty easily because of our background and our understanding of how music moves. But we also try to have fun while we’re doing it, we go with our instincts when it comes to getting ideas, and we see where that takes us, what kind of song it becomes as we work it. Post is a young guy who knows exactly what he’s doing, and is so aware of what he likes.

Describe the collaboration process with Post on a track like “Psycho” or “Candy Paint.”

Those tracks are a good example of Post getting the beats and vibe together at home in Fruity Loops. He’ll send me the basic elements, and I ask myself, “How can I make his vision sound as clear as possible, and what musical elements can I add to develop it? How do I get the best song out of it?”

That’s a really fun process. I know that if I’m feeling something, he’s going to feel it, because we have a very similar musical barometer for what we like, and similarly eclectic tastes. It’s a big advantage when you’re not dealing with competing visions for a project where you can get stuck in a cycle of compromising, and no one’s really enjoying it. Happily, that’s not the case with us.

While the vocal is always very much front-and-center in your work with Post Malone, DJ Snake and others, there are invariably lots of nuanced layers of production — tucked-in synths, background vocals, and lots of reverbs and delays working together.

There are always layers in my work, but at the same time, I want the average listener who may not really understand music at all, to enjoy the songs on a purely surface level.

I can throw in additional elements that aren’t distracting to that listener, while also adding things that a more sophisticated listener can appreciate. I also think layering gives these tracks much more replay value, because people may not notice all those layers the first few times they listen.

On tracks like Post Malone’s “Candy Paint” or DJ Snake’s “Let Me Love You,” you make a few elements sound like a fairly large, orchestrated production. How do you do that?

Those synth parts on “Candy Paint” are an interesting example. The trick with that song was “enveloping.” If you can low pass those pads at the right moments, then release the low pass, much as a DJ would do it, you can make the track sound like it’s doing way more than it’s actually doing.

During the verses it can sound more mellow, but when the hook comes in, you don’t have to add more elements. You can just filter or unfilter things you already have going. And then they’ll suddenly pop out like you’re introducing something brand new.

“Candy Paint” works because you don’t have 18 elements all happening at once. Using lush pads, you get a lot of space in the mix, so you can hit the drums a lot harder underneath them to produce a nice contrast. That’s what gives “Candy Paint” what I’d call an “urban easy-listening” vibe.

What advice do you have for young producers and writers crafting their own approach to recording and building tracks?

You know, I have a 20TB drum and sound library that I’ve been collecting and tweaking since 1999. And I make sure to devote entire days where all I do is organize all my sounds. That’s immensely important. If your library is well organized, and you know exactly where sounds, and families of sounds, are located, then you’re more able to be a pure creator. If you hear a certain sound in your head, you should never settle for less than that. You should find that exact sound.

Artists are always impressed that I can find a sound in seconds. They want to be writing and working — they don’t want to sit there while you try to dial in a sound for a half‑hour.

Ultimately, you have to be organized. I think of it like this; the artist is driving down the street, trying to get somewhere, and I’m building the road in front of them — as they drive — anticipating their changes of direction. So I need to move quick. Because if they run out of road, they fall off a cliff. I’m not going to let that happen.

The Precision K-Stereo Ambience Recovery plug-in for UAD hardware and UA Audio Interfaces allows you to precisely adjust the stereo depth and imaging of your mixes without unwanted artifacts.

In this video, you’ll learn how to dial in the perfect stereo width, enhance reverb and effects during the mastering stage, and enhance the dimension and character of your mix using the ambience recovery feature.

Also, learn how to easily transform the perspective of a drum overhead mic with the Precision K-Stereo Ambience Recovery plug-in, and add distance and vibe using the ambience filters to refine the natural room reverb captured by the mics.