Digital Equalisers, Phase, and other possible Damage to Sound
Please note I used 'Digital' in the title. I'm not interested in analogue EQ.
I use a Behringer DEQ2496 only in digital mode, located between my CD Transport and DAC. I therefore am only interested in the effects of digital EQ. I use it just for completing the EQ effects of positioning and room treatment.
One of the criticisms levelled at the use of digital EQ is that it only works in the frequency domain but not the time domain. I have also been told it smears transients. What does this mean?
Transient
A musical note consists of '.... the attack, sustain, and decay of a sound. Attack transients consist of changes occurring before the sound reaches its steady-state intensity. Sustain refers to the steady state of a sound at its maximum intensity, and decay is the rate at which it fades to silence.' So the transient is the first thing you hear and is very noticeable on percussion (e.g. bongos), piano, and plucked guitar for example.
Each transient will consist of a number of frequencies (known as harmonics) and in order to get the proper effect they should be heard at pretty much the same time. In other words, when they reach your ears at your listening position they should ideally be heard together in one sharp thud. If these frequencies arrive spread out over time the transient is said to be smeared. You dont get that thud but a longer 'thudddd'.
Smeared Transients
How, in theory at least, can an EQ smear transients? Well, apparently they work by changing the phase of the frequency that is adjusted:
In the beginning all equalizers were analogue electronic circuits using capacitors and inductors. These components shift the phase of AC signals passing through them. If you combine a signal with a phase shifted version of itself (after passing through the capacitor or inductor), the frequency response is altered. As one cycle of the wave is rising, the shifted version is falling, or perhaps it hasn't yet risen as high. So when the two are combined they partially cancel at some frequencies only thus creating a non-flat frequency response. Therefore analogue equalizers work by intentionally shifting phase, and then combining the original signal with the shifted version. In fact, without phase shift they would not work at all!
Most digital equalizers mimic the behaviour of analog equalizers, but with a completely different circuit design.
http://ethanwiner.com/EQPhase.html
(I think hes writing about studio EQ but presumably the Behringer and other digital EQs work the same)
So that is why it is said that EQs smear transients. Different frequencies are altered by different dBs and so each one's phase is changed differently. Now all the harmonics of a transient no longer arrive at your ears at the same time. You get thudddd instead of thud.
The problem is that I dont hear it! I dont hear the EQ smearing transients. Ive tried. I used bypass on it. I took it completely out of the system. I played test recordings of bongos, piano, a drum kit (from Alan Parsons Sound Check 2 CD). I could hear no transient changes. It wasnt easy because I like and am used to the sound with EQ, but I heard nothing negative.
My question then. Has anyone who has actually used digital EQ in their system heard smeared transients, or other phase issues, or any other artifact that caused the sound to deteriorate?
Please note I used 'Digital' in the title. I'm not interested in analogue EQ.
I use a Behringer DEQ2496 only in digital mode, located between my CD Transport and DAC. I therefore am only interested in the effects of digital EQ. I use it just for completing the EQ effects of positioning and room treatment.
One of the criticisms levelled at the use of digital EQ is that it only works in the frequency domain but not the time domain. I have also been told it smears transients. What does this mean?
Transient
A musical note consists of '.... the attack, sustain, and decay of a sound. Attack transients consist of changes occurring before the sound reaches its steady-state intensity. Sustain refers to the steady state of a sound at its maximum intensity, and decay is the rate at which it fades to silence.' So the transient is the first thing you hear and is very noticeable on percussion (e.g. bongos), piano, and plucked guitar for example.
Each transient will consist of a number of frequencies (known as harmonics) and in order to get the proper effect they should be heard at pretty much the same time. In other words, when they reach your ears at your listening position they should ideally be heard together in one sharp thud. If these frequencies arrive spread out over time the transient is said to be smeared. You dont get that thud but a longer 'thudddd'.
Smeared Transients
How, in theory at least, can an EQ smear transients? Well, apparently they work by changing the phase of the frequency that is adjusted:
In the beginning all equalizers were analogue electronic circuits using capacitors and inductors. These components shift the phase of AC signals passing through them. If you combine a signal with a phase shifted version of itself (after passing through the capacitor or inductor), the frequency response is altered. As one cycle of the wave is rising, the shifted version is falling, or perhaps it hasn't yet risen as high. So when the two are combined they partially cancel at some frequencies only thus creating a non-flat frequency response. Therefore analogue equalizers work by intentionally shifting phase, and then combining the original signal with the shifted version. In fact, without phase shift they would not work at all!
Most digital equalizers mimic the behaviour of analog equalizers, but with a completely different circuit design.
http://ethanwiner.com/EQPhase.html
(I think hes writing about studio EQ but presumably the Behringer and other digital EQs work the same)
So that is why it is said that EQs smear transients. Different frequencies are altered by different dBs and so each one's phase is changed differently. Now all the harmonics of a transient no longer arrive at your ears at the same time. You get thudddd instead of thud.
The problem is that I dont hear it! I dont hear the EQ smearing transients. Ive tried. I used bypass on it. I took it completely out of the system. I played test recordings of bongos, piano, a drum kit (from Alan Parsons Sound Check 2 CD). I could hear no transient changes. It wasnt easy because I like and am used to the sound with EQ, but I heard nothing negative.
My question then. Has anyone who has actually used digital EQ in their system heard smeared transients, or other phase issues, or any other artifact that caused the sound to deteriorate?