EQ-ing Headphones with PEQdB

Setting up your EQ is widely recognized to be one of the best things one can do for audio quality on any reasonably decent set of headphones - but if you've ever tried something like autoeq.app you'll probably have found that far from improving the sound, it tends to make your headphones sound flat and aenemic.

After far too much toying around in this space, I wanted to share the process I followed to get my headphones set up just the way I like - and I expect it should be fairly reproducible for others.

The Theory

The first thing to recognize is that there are several different variables which play a role in how headphones sound:

• The headphones themselves have their own sound profile (sometimes money can buy a "nicer" sounding profile, but in general this is quite subjective).
• Your head and ear shape influences how you perceive sounds, leading to some frequencies appearing louder or softer.
• The way the headphones sit on your head also influences how you perceive sounds (and even something as simple as wearing glasses with them can change this).

When we talk about "EQ-ing" your headphones, what we're generally talking about is attempting to compensate for these three different sources of variance such that you perceive the sound as it was originally intended (i.e. in a recording studio), with some allowance made for individual bass/treble preferences.

Preference Curves

A ton of research has been conducted on what the "ideal" headphone response curve looks like, taking into account user preferences across very large sample sizes - with the Harman Curve being the most common example in common usage.

More recent research appears to indicate that individual preferences are for slightly more bass and treble than the original Harman research revealed, with the PEQdB Diamond curve delivering on both of these - and subjectively sounding a bit nicer to my ears.

Regardless of your personal preference, the process we're going to follow remains roughly the same.

Compensating for your Headphone

The first thing we're going to do here is try to compensate for the baseline profile of your headphones. This relies on a large database of lab-like measurements showing the performance of different headphones on reference head analogues to provide a basis against which we can make adjustments.

For example, the Sennheiser HD800S have a response curve which looks like the following (when compared to the PEQdB Diamond curve):

You'll note a few things about this measurement; for starters, it's not perfectly aligned with the curve despite the fact that these are objectively very good headphones.

The second thing you'll notice as you start to look closer is that there's a distinct lack of bass and sub-bass, with somewhere on the order of a 10dB difference (i.e. half the volume) between the preference curve and what the stock headphone delivers. Listening to the headphones, you'll notice this lack of bass - with them emphasizing strings and vocals over drums and sounding quite "light" and "flat" as a result.

Finally, you'll also see that there's spike in response around 6kHz - which results in the headphones sounding very "sharp" and "ringy" at this frequency (with a ~60% jump in volume here relative to 4kHz).

We're going to ignore the oscillations above 10kHz for now - since these tend to be the result of individual head and ear shape - so we'll adjust for them later.

In the mean time, let's use PEQdB to construct a baseline profile to bring our headphones closer to our preference curve.

Using PEQdB

Head on over to PEQdB's website and use the search bar on the left to find your headphone model. Once you have that selected, go ahead and select your reference curve at the bottom of the graph. When you're done you should end up with something like the following:

The next step will be to use the Equalizer controls in the top left to construct an AutoEQ profile for your headphone.

Upon doing so, you'll be greeted with an updated graph showing the resulting response curve for your headphones - it should closely match your selected preference curve. We're going to download this adjustment using the download button in the bottom left of the UI.

Once you have the equalizer file downloaded, import it into your equalizer of choice (I personally use Equalizer APO on Windows). At this point your headphones should ideally sound a lot closer to a common reference - and now we can get started with making adjustments to ensure they suit you well.

Compensating for your Ears

While PEQdB will show you a graph which implies that your headphones are now perfect, the reality is unfortunately a lot more complicated. PEQdB doesn't know anything about your head and ears, or the way the headphones sit on your head - and those high frequency peaks and valleys are usually an artifact of those factors (indeed, the measurement head contributes its own version of them).

What we're going to do next is introduce your own personal EQ overlay which compensates for the impact that your own perception differs from the reference head shape. To do that, we're going to use a tone generator to sweep through the frequency range and make adjustments for anything which sounds significantly louder or softer than the adjacent frequencies.

I personally find that this Online Tone Generator works reasonably well for doing this - simply start playing a tone at a very low frequency (30Hz should do) and slowly move the slider to the right to increase the frequency.

You're listening for any frequencies which suddenly jump in volume to your ears (it'll often sound like there's a resonance/bell effect) or which suddenly drop out (keeping in mind that depending on your age and hearing damage, you are likely going to experience a natural drop-off above 15kHz - you'll know where the limit of your hearing is because increasing the frequency won't cause the volume to return).

When you find a frequency which needs adjustment, add a Peaking Filter in your equalizer software, and adjust the Q factor to even out the transition (start with a Q factor of 10 and decrease it, moving the center frequency until you can't discern a difference in volume as you sweep over the range which stood out previously).

With this done you should now have a reasonably consistent frequency response for your headphones - and indeed this is where I stopped, with the PEQdB Diamond target doing a good job of matching my personal preferences around bass and treble quantity.

That said, if you'd like, this is the point where you'd add your own preference EQ (or simply re-tune using a different preference curve in PEQdB).

Conclusion

There's no "one size fits all" calibration for headphones, if there were then the entire market for high-end audio products would just be the same headphone (or at least the same sound) and the wonders of competition would drive the price down until budget headphones were every bit as good as the best.

Instead, the number of unique variables means that different headphones will sound different to each listener - creating plenty of opportunities for different designs and tuning to win loyal audiences. But before you go and spend obscene money chasing "the perfect headphone for you", give EQ a try - with the right configuration you'll likely find that any semi-decent headphone is capable of sounding incredible to you.