Audio Recording with Equalizers – 10 EQ Modes – Part Three – Fixed Versus Variable Frequency Modes
When analyzing the difference between fixed and variable EQ frequencies, we once again visit the importance in the design and construction of the analog EQ and its purpose. Fixed frequencies are common in classic program equalizers and in console EQ’s. Although they can be the option of any EQ design, these are most commonly found in these categories, because they were designed with the purpose to focus on specific frequencies that are most commonly needed for individual vocals and instruments.
The filtering process is specifically chosen in the design of the EQ. In the same way that guidelines can help the user work in a consistent and intentional manner, fixed design can help define one’s creative signature. Some find deliberate, predetermined settings to be a hindrance and prefer freely adjustable frequencies. In mastering, the more options for width, narrowing, frequency adjustment, and fine-tuning of gain the better, but even then, many Mastering Engineers prefer notched or indented settings for reliability and recall.
As I’ve found for many hardware pieces, I prefer fully variable settings for gain and frequency and “Q” for the tougher mastering jobs. Believe it or not, even the highest of the high-end mastering EQ’s are very ‘flexible’ in their precision of markings. I’ve found self-calibrating levels and frequencies with visualization software to be very helpful for honing in on exactly what an EQ is doing.
Variable frequency modes can not only provide the ability to get more specific and surgical in our tracking, mixing and mastering processes, but it can also be used dynamically as a mixing effect. Control and automation of changes in frequencies can become a musical element in composition, sound design, and mixdowns that cross the boundary of the art of mixing into the art of actual song creation. This brings EQ into a new category, not just for an engineer’s task of tracking, mixing, or mastering, but also at the writing stage.
Using EQ as a filter to change the smooth transition of musical content to swell or pass from one frequency to the next in smooth transition can act like a sonic ocean wave sweeping by, telling our ears that sound is gliding upwards or downwards, creating an actual musical response instead of making corrective changes.
This determining factor draws a strong line between fixed and variable frequencies, showing how there is more to EQ than just quality and preferred uses. Now, we see that creative choices can cross the barrier between utility into the actual writing of music. Next, lets take a look at linear phase and minimal phase EQ’s.