Linear VS Natural Phase on Low End: How do they compare?
(Featuring the FabFilter Pro-Q 2)

In this review/showcase we will be comparing and checking out the difference between natural and linear phase EQs using a popular EQ that does both types, the FabFilter Pro-Q 2.

We will be focusing on how these different design types react in the low end by looking at low end boosts and also HPF filters so you can make a decision for yourself which you like and understand why a bit more too.
Natural phase filters as used in the Pro-Q 2 are based on traditional analog EQs. Because of how these EQs work and the circuitry involved a phase shift is exerted on the signal. It has been argued back and forth that this phase shift involved is a good or a bad thing, it definitely changes the tone of the sound. We are not here to join in that argument (well maybe not till after we have had a listen).
Linear phase EQs were developed to alleviate this phase/time shift issue. These EQs do not however, come without faults of their own. Firstly they require a large amount of processing power (less of a problem these days with the processing capabilities of many computers). Linear Phase EQs also exhibit a phenomena called ‘pre ringing’ which causes transient smearing and removes punch (See Fig.11), which can be particularly noticeable in the low end, so we’ll do a bit of a show and tell there.

We have put together some image examples of phase shift and pre ringing at the end of the review in case you are interested - to view click HERE

So, as said, for this shootout we have been using this lovely plugin Fab Filter Pro-Q 2 (but not with such extreme settings of course!).

Fabfilter ProQ2

We think it is a really good and useful EQ worth supporting. If you want to check out the Fab Filter Pro-Q 2 or purchase it - Go HERE



Low End - 50Hz +10dB boost

Our comments below player - to open the player in the shootout window so you can add to it click here

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Quick point to note - please check the unprocessed loop in LUFS and non LUFS normalization, [as at this level of extra bass the unprocessed loop won’t be as accurately level matching to ears].

For this low end shootout the natural phase comes off (we think) more...'natural' sounding.
It retains more integrity in the lows and and sounds punchier. The linear phase EQ sounds not as defined to our ears and a bit lacking in the lower mids area, or, to use a term of phrase ‘woolly’.
On the “Bass - Splinters” sample;
You may also notice the most difference between the two in the 100-300Hz area where the first harmonics above the fundamentals of the bass notes sit. Listen to that area and see what you think.
The linear phase EQ just sounds a bit ‘flatter’ in comparison to the Natural phase EQ.
When listening to the songs the natural phase EQ setting has more punch in the low end than the linear phase EQ (listen to the kick drum on Splinters).



Low End - 100Hz HPF 24dB

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Listening between the two the natural phase EQ again sounds more coherent and punchy.

It’s a very slight difference but there are a few things to listen to to pick up on this difference.

The low end in the snare changes between the natural and linear phase EQs on the song “Splinters”. On the natural phase the snare retains a bit more low end than it does on the Linear Phase EQ.
On the Song “Getting it on” listen out for how present the low end/low mids that haven’t been cut out change between the two.
The natural phase EQ seems to keep more of the low end/low mids than the linear phase EQ. And the slight bit of low end in the kick that is left in the track has more punch in the natural phase EQ than the linear phase, which doesn’t seem quite as round or natural.


Extra things to note: These examples just show the effect of a single band of EQ, the more EQs you add to a mix the more the difference of effect will add up.   This will likely have more effect in the low end than high end, where you have a lot more 'real estate' to work with.   Definitely watch the FabFilter video if you get a chance and also experiment for yourself.


Here are some photos showing the phase difference between linear and natural phase EQs using Plugin Doctor 

Fig.1 50Hz +10dB FabFilter Pro-Q 2 Natural Phase

Fig.2 50Hz +10dB FabFilter Pro-Q 2 Linear Phase


Here are a some photos showing the difference in phase with different filter slopes on a natural phase EQ

Fig.3 Natural Phase 100Hz HPF 12dB Slope

Fig.4 Linear Phase 100Hz HPF 12dB Slope


Fig.5 Natural Phase 100Hz HPF 18dB Slope

Fig.6 Linear Phase 100Hz HPF 18dB Slope


Fig.7 Natural Phase 100Hz HPF 24dB Slope

Fig.8 Linear Phase 100Hz HPF 24dB Slope

Note that with extreme slope settings there is still a phase shift even when using a Linear Phase EQ

Fig.9 Natural Phase 100Hz HPF 96dB Slope

Fig.10 Linear Phase 100Hz HPF 96dB Slope


Fig.11 Showing Pre Ringing on testing.
First track shows unprocessed track
The next 3 tracks show 2, 5 and 10 dB boosts consecutively at 50Hz
The Waveform you see coming up before the original program is the pre ringing from using the linear phase setting on the Pro-Q 2


Found this review useful? Can we ask you to like our Facebook Page or Sign up to our Newsletter at the bottom of the page so we can let you know when new ones are available?

Handy Links -
Check out the Fab Filter Pro-Q 2 Here

Check out an article of FabFilter explaining the different EQ types here

Extra info for those interested in how we make our calls on what stuff sounds like -

Listening tests and assumptions are determined, double checked or signed off at Gearshoot HQ on ATC110ASL Pro monitors.   We reckon that they give us a pretty good chance at getting it pretty well in the ballpark of what it is going to sound like on most other people’s monitors.   We also headphone check on Extreme Isolation EX-29’s to hear what is going on in that spectrum and to hear what the world of headphones can show us.


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