EQ Artifacts            Back to fader8's audio blog Index

fader8's EQ Artifact page

Let's face it. EQ's ring. It's a fact of life for us so we just need to accept it. Since we must persevere and embrace the artifact, I decided to take all the eq's in my plug-in arsenal and test just how much they ring. Note that this test isn't comprehensive for all frequencies, and it certainly shouldn't be considered the "be all-end all" in deciding what EQ you should buy. In fact, some of the EQ's that look pretty good here have some pretty wild phase shift. But that's for a future web page when I get around to it.

To perform this test, you need to have an analyzer that can do a 2 channel transfer function. Essentially, run an unprocessed reference pink noise signal into channel 1 and the same, but effected signal into channel 2. Then the analyzer shows you the difference between them. Spectrafoo is awesome for this. This is what you see in the reference curve pic, and all the eq's in this test were set up to match this reference curve with the analyzer, using pink noise. It's the only reliable way as you can't always trust what the EQ's interface is telling you and everybody seems to have their own idea about how to specify Q!  (I determined the ref curve by looking at the minimum Q for the UAD Precision and the Waves Lin and Ren EQ's.)   Note that as you tighten the bandwidth, (Q) of the EQ, the results get worse, which is why I'm making sure the filter slopes are constant for each measurement.

The UAD Pultec Pro and others are not included here as their midrange band can't achieve a wide enough Q. Also, DUY Spectrum isn't included as I couldn't achieve a symmetrical filter shape.

Hosts:  Logic Pro 8.01 or Pro Tools 7.4 

Reference Curve:  (All EQ's were set to match this curve)

The test signal for the waveform plots below is a 700Hz burst, 2 wavelengths long. All eq's were set to 700Hz, (or as close as possible) with a -6dB dip. The test signal pic is the result of bouncing my test signal. This shows that the host isn't contributing anything. After each EQ is calibrated with the analyzer, the 700Hz snippet is bounced in real time. 

Note: I need to see what else I might have that will give me a decent grid and repeatable zoom settings. These snaps were from Logic's sample editor. There may be slight differences in waveform height, but the relative signal to artifact ratio is accurate.

Test Signal:

Logic Pro 8 EQ's:

Pro Tools 7 EQ's

Ableton Live 7 EQ

Third Party EQ's:

MasterQ Phase page

To show an example of how much worse the artifacts can get as you tighten the bandwidth of an EQ, 

here's a comparison of Waves Linear Phase EQ with its tightest Q at 516Hz, boosted 24dB. 

Logic's Lin Phase EQ is set up to match. Input was the same perfect 700Hz, 2 cycle burst, 

so everything outside the shading is created by the EQ. 

Note also the significant change of level in the waveform heights of the original signal.

The Waves Linear EQ has a slight edge over Logic's bundled Linear EQ in this regard, but not by much.

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