Bulls Hit said:
But isn't there more to it than that?
Any time you fiddle with a sonic signal you will potentially introduce artefacts like phase distortion etc.
But what about how our ears worK - both as mechanical/accoustic devices in their own right, or psychoaccoustically with the brain.
A fundamental feature of the human ear is that it detects additive eq much more easily than subtractive eq. We've all heard this for ourselves.
So if you can fix a sound by subtractive eq instead of additive eq, surely that has to be a more desirable outcome
Phase distortion is the cornerstone of analog equalization... in fact, you can't do analog equalization without it. Digital EQ works quite differently, which is actually why you will usually apply way higher levels of equalization in the digital domain than the analog domain... you don't hear the phase distortion artifacts [because there aren't supposed to be any] so it's not quite as a dramatic effect... but I digress
The way an analog equalizer works [all analog EQ's] is that you have some filters... they determine at which frequency the signal will be added or "subtracted" from the signal [you can have all kinds of groovy controls... from 31 filter sets in a graphic EQ to variable bandwidth in a parametric EQ but it's all still filters]. If you're adding to the signal you're taking a section of the frequency spectrum, isolating that area, then adding more of that area to the original signal... with "subtractive" EQ you're adding the same information you would have been adding with positive EQ, except that information is 180 degrees out of polarity, and will cancel that section of the original signal, thus causing a "dip" in the signal.
Any time you run through a filter you will get phase distortion... when you run through a low pass filter it will "slow down" the high end... when you use a hi pass filter it will "slow down" the low end, this is called phase distortion [OK, it's a really oversimplified explanation but work with me]. For the most part this is why we like, or dislike the tone of an equalizer... the other big reason we will like or dislike an equalizer is a function of the equalizer's headroom, and it's ability to deliver "current on demand" to the circuit.
Ever notice that the guitar player with his 30watt Vox amp is burying the bass player with his 300watt SVT? It quite simply takes more energy to form a bass wave... in this case the energy is called electricity, so to properly form a bass wave you will require some extra current from the unit's power supply to be delivered to the equalizer pretty much instantaneously so the low end wave will be faithfully reproduced.
Consoles like the Mackie have really [I mean
REALLY] shitty power supplies [same with Allen & Heath, and Soundcraft, etc.]. This means they're not going to deliver the power requested by the circuit in order to pass a proper bass wave... coupled with the phase shift that is produced from the circuit rolling off too high on the bottom [20Hz-20kHz is woefully insufficient from a linear phase perspective... 3Hz-300kHz will give you a pretty linear phase response throughout the audio specturm, but "20 to 20" won't], and we get what we perceive as a thin, nasty, shitty sounding event... which is why those desks don't cost all that much... because when you start to get into bigger power supplies, a grounding scheme that can handle the dissapation of the power after it's been used, making a circuit that can pass low end almost down to DC, and on it's way up to 'light'... you're talking about some pretty tricked out components in a pretty tricked out design... sorta like why a Bentley is a tad more expensive than a Honda, again... I digress.
A fundamental feature of the human ear is that it detects additive eq much more easily than subtractive eq. We've all heard this for ourselves.
So if you can fix a sound by subtractive eq instead of additive eq, surely that has to be a more desirable outcome
It ain't necessarily so... because us humans perceive additive eq more easily than subtractive EQ we tend to use less EQ when boosting than when cutting... which means you'll use less gain in the area of the EQ's action [remember, that subtractive EQ is just additive EQ 180' out of phase to the original signal]... which gives us the net result of not taxing the power supply of the desk as heavily, and not getting into quite as steep filter slopes which add even more artifacts [phase distortion] to the signal... which leads directly back to that it's an urban myth [and suburban, and probably country too] that subtractive EQ is "better" than additive EQ.
I will say that I too have heard this myth recited a whole bunch of times... I just got a bit curious as to why subtractive EQ was "better"... so I asked around to some of my buddies who are audio hardware designers and they sorta came up with an answer for me [the answer being "it isn't"]. Just because something is repeated a whole bunch of times... like you can't have the phantom power on when you're using a ribbon microphone, that doesn't make it a reality... it only makes it a commonly repeated mis-statement.
