The spectrum is key! When recording, mixing and mastering, the spectrum is very important. This can be monitored through a spectral analysis tool like Voxengo’s SPAN. There are three concepts that we’ll cover here, and each one corresponds to specific phases of the typical audio project.
First, is reference. The frequency response graph which is included with audio equipment like microphones, amplifiers and speakers is like a birth certificate which tells the accuracy of that equipment. Much like a fingerprint, it’s unique measurement is slightly different than other gear and though the numbers be small, a great divide exists between each and every one; like the tiniest of differences within human voices being all it takes for us to recognize that they’re different. The clarity of this equipment can be seen in how close to a completely flat line it is. Reference mics, which are used for measuring the frequency response of a room during room tuning, are as close to a flat line as the budget and the manufacturer is capable of providing. Reference monitoring speakers are also close to a flat line, each with subtle differences which become critical only as the operation of the monitoring becomes critical. Cheaper reference monitors will suit most fly by night mixing rooms. The more expensive mastering grade monitors, however, are required for getting a mix which will sound clear and professional. This is because of mix translatability. The closer you are to reference, (flat line response), the more accurate it will translate, or playback, on other devices. This means that recording with higher end microphones, using quality preamps, and monitoring with an accurate reference is critical for ensuring that you get the results your ears are telling you you’ll get. If the room acoustics are bad, for instance, the great sound your hearing may not be accurate. Powered speakers are vetted by engineers at the factory as having matched frequency response. This means that amplifying a speaker yourself is not as good as using a speaker with built in power, because the amplifier and speaker have been matched to each other and the cabinet. To take it one step further, you can do acoustic analysis of your listening space and account for any prevalent issues, in order to match the room to your speakers. Then everything becomes an extension of the sound source and accurately represents the truth.
Second, is the curve. Every unique sound sits with its own unique EQ curve. Each instrument or voice, when observed through a spectral analyzer, will reveal its own frequency response. To maximize this curve, the resonant harmonic peaks can be notched with a filter; but this still shows each as having their own part of the spectrum. While processing and mixing it’s imperative that this be factored in. Failure to do so will result in a muddy or busy sounding mix where there is not enough separation or clarity within the spectrum.
Thirdly, is maximization. There is a term thrown about the audio world. It’s the “loudness war”. The tendency we all have to make things sound louder has led some engineers to speak out against this practice in order to preserve clarity and dynamics. The way to make your mix sound commercial without making it overly loud is to establish a smooth frequency response across the spectrum. This is accomplished with equalization, multiband compression/limiting and proper processing of individual tracks.
It can be seen with all of this, that spectrum is an extremely important feature of any music production and must be observed from start to finish so that the end result won’t be like a television whose color is off. By not representing its color spectrum accurately a person’s skin color may look obvious. In the same way, the natural instruments and vocals will also sound obvious if the frequency spectrum is off.