Needless to say that there is a lot of misinformation online, especially when it comes to the dark art of music production and mixing. The humble High Pass Filter has become shrouded in its own mystery - one that I'll explore and debunk in this post.

While the internet is an incredible resource and it's amazing that we now have access to such a wealth of information and experiences to draw upon, it can also be pretty darn confusing, with a lot of conflicting facts out there.

There are a lot of audio myths out there that get taken as read, purely because they're repeated over and over again. This is to such an extent that it's almost impossible to distinguish truth from fact.

Many myths start from a genuine place, but become misinterpreted and misconstrued over time.

The problem is, this can actually be harmful to new producers. Getting into bad habits can potentially set you back a long me!

I've certainly fallen foul of a few misleading 'facts' here and there, that's life! We all do it and there's no shame in it, after all we're just trying to make good music and improve our skills wherever we can.

Do your mixes sound weak, harsh or struggle to translate?

The reason why this topic resonates so much with me is because I, too, fell into this very trap when I was starting out. Oh yes, it got me hook, line and sinker, and I'm not ashamed to admit it!

My mixes were sounding weak in the low-end, harsh in the mid- and high-end, and generally lacked warmth overall. Just ask my good friend Lee House, who was working alongside me at the time!

To top it off, I was mixing in a decently treated control room with high quality reference monitors, so I knew the problem was more likely to be me!

Through various tutorials, research and recommendations I'd begun making liberal use of the High Pass Filter throughout my mixes. Yes, often on every track. It took me a long time to figure out what I was doing wrong, and I want to share this knowledge with you so that you don't make the same mistakes.

In this post I set out to debunk the myths and misinformation surrounding the recommendation to use a High Pass Filter by default. By the end, you'll be able to:

  • Describe why the misuse of High Pass Filters has come about;
  • Identify 4 problems caused by improper use of High Pass Filters;
  • Apply this knowledge to improve the sound of your own mixes.

High Pass Filter madness

Earlier this year I happened across a video that's title immediately stood out to me. It read: 'Stop the High Pass Filter Madness'. Straight away I knew what this video was going to be about, and I also knew I needed to check it out.

I've been following MixbusTV for a while and they have a YouTube channel with tons of great content.

In this video, David from MixbusTV refers to one of the most misunderstood concepts in all of music production.

Many tutorials instruct you to cut all of the lows on your individual tracks. I've certainly seen this time and time again. At the setup stage, even before the start of a mix, producers will add a High Pass Filter to every single one of their tracks.

Depending on the instrument, sometimes they'll roll off at 40 Hz, sometimes 80 Hz and sometimes even as much as 500 Hz and below.

Where does it come from?

Let's face it, most people don't have perfectly acoustically treated rooms (I certainly don't), so the biggest challenge is low-end. It's almost impossible to tell how the low-end in your track will translate elsewhere on other systems if your room is not properly treated and your monitors aren't calibrated for the space.

We've all been there. You spend a long time adjusting and sculpting the kick and bass, only to discover that the track sounds very boomy in other environments, or even that there's barely any bass at all.

The issue is, if you can't hear it, you can't mix it.

Therefore, the prevailing philosophy has been that it's better to cut the lows and have a thinner sounding low-end, than to have a boomy and unpredictable low-end. It's a trade-off, a compromise due to practical limitations.

This approach is a workaround to compensate for the reality of mixing in problematic residential spaces, not a solution.

The average home studio environment has at least a couple of parallel lines and reflective surfaces, and the average bedroom producer is working in a cube. If you could design the worst acoustic space imaginable, it would pretty much be a cube.

Digital audio production and home studio mixing have grown up alongside the development of the internet. As a result of this, the High Pass Filter advice has been repeated and echoed so many times that it's become a false rule that, unfortunately, many producers now live by.

Debunking the High Pass Filter myth

As with most things in life, the reality is a lot more complex and there isn't a quick and simple fix.

Mixing is both an art and a science. It is a nuanced process, and therefore slamming a High Pass Filter on every track in your mix creates a number of issues that you may not even be aware of. Side effects, if you will.

As I say, there is always a trade-off! Here are some of the consequences that can occur as the result of improper use of a High Pass Filter:

#1 A weak mix

Cutting low-end (e.g. anything below 200-250 Hz) is, as David puts it, "the best way to cut off your mix's balls." I couldn't have put it better myself, and I think this statement sums up the issue quite succinctly.

In doing so, your mix will immediately sound weaker, as most of the energy is delivered by the lower frequencies. If they're gone, the balls are gone with them.

#2 A harsh mix

Many producers' mixes sound harsh - you only need to spend 10 minutes surfing SoundCloud to find evidence of this.

What they don't realise is that when they remove the low-end from their mixes, this affects how the mid-range and high-end are perceived by the human ear.

It's all about balance. Lower frequencies provide warmth and, without them, high frequencies sound even harsher.

Bass frequencies have a lot of energy and are quite literally 'felt' by the body. You'll know this if you've ever been to a festival with a decent sound system. If you take a mix that lacks low-end and play it on a good system with a wide frequency range, you'll immediately notice the difference.

Bass frequencies drive the speaker cones further, physically moving the air further, and you're missing out on this experience with a weaker mix.

#3 Phase shift

Every time you make a move with your EQ, you change the phase of a track.

The phase quite literally shifts, and you need to keep this in mind. This may not be an issue when listening to the track in isolation, but you're actually altering the phase correlation between the other elements in your mix.

This becomes a problem when you're mixing multi-mic'd sources, such as a drum kit, for example. It's important not to EQ these tracks independently. An alternative solution is to bus, say, two kick mics together, and EQ them as one.

Another common example is acoustic guitar - you could do the same here by bussing the two mic signals and EQing them together, not separately. If you EQ them separately you can negatively affect the phase. This can lead to a hollow sound and lack a sense of body.

This can also affect the phase relationship between different instruments. For example, it's important to have your kick and bass working together like glue, but this relationship can become weak if their relative phase no longer correlates.

[To get around this you can use Linear Phase EQ - this will not shift the phase of your track when you EQ it. However, Linear Phase EQ is a big topic and deserves an article all of its own!]

#4 Frequency build-up

Whether or not your EQ visualiser displays it, there is actually a little amplitude peak at the point of the High Pass Filter roll-off curve i.e. a 'bump'.

You should therefore avoid high-passing all your tracks at the same frequency. This will create a buildup and subsequent resonance in the cut frequency (e.g. 40 Hz) as it becomes multiplied, as well as increasing the amount of phase shift.

Always ask yourself: "Why?"

There needs to be a rationale behind every decision that you make when mixing.

Of course you should use a High Pass Filter where necessary. After all, it's an extremely useful tool! However, you shouldn't use it just because you're told to.

In my opinion, the strongest point that David makes in the video below is this:

"Do not do anything by default."

You need to know why you're making certain decisions and be able to justify them. Ask yourself, "Are there any specific problems with this track?"; "What am I trying to achieve, specifically?"

It's no good EQing or compressing something just for the sake of it because you heard it in a YouTube video or read it on a forum. Not only is this a waste of time and processing power, it can also ruin your mix.

No two mixes are the same

You're working on a different piece of music with a different set of problems. While there are a number of key principles that you can apply, there is no 'one-size-fits-all' solution. I'm sorry if that's frustrating, but it's the truth, so deal with it.

Many people recommend cutting the lows from electric guitars, for example, such as below 80 Hz. Well, you need those lows, as it happens. You don't need all of them and you may need to attenuate specific frequencies, but you definitely need the lows and shouldn't cut them out altogether.

Watch the video for yourself, and be sure to check out more of David's tutorials and thoughts on all things mixing at MixbusTV: