Most mixers choose one environment to mix in – speakers or headphones – and then stick to that for the majority of the mix, referencing their work in the other periodically, or as the mix is wrapping up. Regardless of the character, quality, or response of the chosen reference, this provides a consistent monitoring experience, which can help the mixer maintain an overall internal tonal reference for the mix. But this isn’t always possible, especially for mixers working in home-based studios – whether they’re big or small affairs, there may come a time when the sound of the same song playing over and over in bits and pieces becomes too much for family and neighbors, and, especially as the mix drags on into the wee hours, it may become necessary to switch over from speakers to headphone monitoring.

Speakers vs Headphones

Now this can potentially be an impediment to not only getting a good mix, but to getting the mix done in general. If the headphone monitoring experience is different enough than speaker monitoring, the mixer may end up second-guessing his decisions as he moves back and forth between the two environments, wasting time, and throwing off his internal tonal reference, possibly compromising the mix in the process. And as we all know, headphone monitoring is different from speaker monitoring. Besides the spatial differences, the lack of inter-aural crosstalk, and the often distinctly different frequency response in the phones, it may be distracting to have to make level, panning, and EQ choices for an unfinished mix when the environment is so inconsistent— it’s one thing to compare a mostly-finished mix between speakers and headphones, it’s another to have to bounce between those monitoring environments at earlier mix stages.

01_Fig 1 Speakers vs Headphones

Moving Back & Forth

If a mixer has to frequently shift from monitoring on speakers to monitoring in headphones, a glaringly different frequency balance can easily cause him to make EQ and level changes in the phones based on those differences, only to reverse them when he’s back on speakers – and vice versa – potentially slowing down and interfering with a smooth mix process. With a matching flat response for both speakers and phones, that issue can be largely put to rest – of course, there will still be inevitable small variations, due to the inconsistencies of headphone response for different users, thanks to the unique effects of how the phones physically interact with the users’ head and ears – but the overall mixing experience in both environments can be much improved, especially when it comes to crafting mixes that “travel” well (sound good on many different playback systems), an important aspect of any commercial mix.

Besides the mixer not fighting himself with different EQ decisions as he moves back and forth between monitoring environments, more subtle aspects of the mix can benefit as well from a more consistent frequency balance between speakers and cans. There are inherent differences in these two environments – the lack of inter- aural crosstalk in headphones, where each ear only hears the corresponding stereo channel (rather than both ears hearing both channels, as with speakers), results in a different perception of subtle elements of the mix; these include the sense of depth and stereo image, the correct amount of reverb and ambience – which is more prominent in headphones – and the audibility of background parts in the musical arrangement, as well as some subtle time-based effects, like doublings and very short slap echoes. One of the useful aspects of mixing in headphones is that it can reveal these details more readily than speaker monitoring, but a distractingly unfamiliar headphone frequency balance or a response with more drastic peaks and dips can obscure some of these details that mixers may rely on headphone monitoring to bring to their attention. Then when they inevitably turn to speakers to verify how any mix decisions made in the phones regarding those aspects hold up in the less-forgiving outside world, they can again be thrown off by having to adapt to a very different tonal balance, and much of the benefit of comparing the mix between phones and speakers can be lost to that subconscious distraction.

Reference 4 with Headphones

The Reference 4 software can be used to calibrate both the main monitors and the headphones used for mixing to the same flat response, even if that response is tweaked very slightly to meet the user’s preferences (that’s what those very subtle Tilt controls and predefined target curve options are for). With a consistent tonal balance between speakers and phones, the mixer should be able to focus more easily on the other details of the mix, and utilize the differences in depth, imaging, and perception of detail between speakers and phones to his advantage, to craft a mix that works in both environments equally well, especially when it comes to the small, subtle aspects.

02_Fig 2 Reference 4 in Pro Tools

Measuring headphone response is a particularly finicky business, so there’s no user-operated headphone version of the Reference 4 Measure software for calibrating speakers – instead Sonarworks maintains a collection of calibrated responses for a wide range of studio headphones. Even though there may be some variation among different runs of the same headphone model, these predefined calibration curves can achieve suitably flat response, especially with some popular studio headphones which might not otherwise serve well for mixing purposes. A perfect example would be the Sony MDR-7506 phones, a pair I’ve used with its corresponding Reference 4 calibration curve for mixing.

03_Fig 3 Sony MDR-7506 Headphones

Most studio engineers are familiar with the 7506 as a tracking headphone, but emphatically not as a mixing headphone. Their excessively bright and harsh upper-midrange response may help voices and instruments cut through in a room full of other loud sound sources, but for mixing, that peak is edgy and fatigue-inducing, making these phones useful (and popular) for live recording but pretty much unsuitable for mix applications – at least in their natural state. But once calibrated with the Sony MDR-7506 Average curve from Sonarworks’ profile library, they can be as useful as any headphone for mixing applications. From my own experience, despite the fact that I’d never use the 7506s to mix with their inherent peaky response, I’ve been able to shift between mixing on them through the Reference 4 plug-in with the proper calibrated response and on a pair of Reference 4-calibrated KRKs which, on their own, have an almost polar-opposite balance to the Sonys. While they still might not be my first choice as a mixing headphone, the calibrated 7506s are up to the task.

04_Fig 4 Reference 4 7506 Calibration Profile

Moving back and forth between properly calibrated speakers and cans can make for a much more seamless mix process, for anyone who might need to spend more than a little of their mixing time in headphones, letting the mixer focus on the details that do inherently differ between speaker and headphone monitoring, like imaging and the balance of background parts, instead of being distracted and tripped up by simple frequency response imbalances – a mixing experience that can take advantage of the best of both worlds.