10 EQ Modes Explained: 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. They can be used in any EQ design, but they’re most commonly found in these categories, and for good reason. Console EQ’s in particular, are designed with a specific purpose to focus on frequencies that are the most commonly needed for specific individual vocals and instruments. The filtering process is specifically chosen in the design of the EQ and can help the user work in a consistent and intentional manner that can define their creative signature, but some find deliberate, predetermined frequencies to be limiting and prefer freely adjustable frequency selection, as is most commonly found in Mastering EQ’s.
Variable Frequency Modes can not only provide the ability to get more specific and surgical in our tracking, mixing and mastering processes, but can also be used dynamically as a song effect. Control and automation of changes in frequency moves 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 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.