Have you ever noticed that your music has those pesky little peaks that come in and out every so often? The ones that tend to take the listener away from the performance, even if its just for a split second? Well you are probably experiencing resonant frequencies. In the beginning of your mixing career, you may not be able to notice them right away. But as time goes on and your ear develops it becomes more apparent.
Resonance is just a build up of energy at a particular frequency. It can happen anywhere on the frequency spectrum but where I notice it becomes the most troublesome is when it happens in the lower registers. The reason its more of a problem then in the upper register is because its our job as an engineer to try and smooth out that peak without completely taking out all the low end. As most engineers know, its not easy, but the good news is it can be done.
I think its pretty common for most engineers to take a high pass filter and start to take out the low end until it sounds clear. In most cases the sound becomes very thin. The reason why this is common is because those engineers may not even realize that the problem they are hearing is a resonance. Now in certain situations a high pass filter works great, I’m just asking that you see if it might be resonance first. If it is resonance then once it has been dealt with you may not actually have to resort to a high pass filter.
I think the 3 most common ways I try to tackle this problem are with an EQ, a multi-band compressor and a dynamic EQ. Now the dynamic EQ and multi-band compressor are basically the same thing, but each one works better in different situations. Now its really hard to explain these 3 and how each one works, with out actually showing an example this is why I attached the video below.
All in all, make sure you check for resonance first before boosting or making major EQ cuts, because sometimes all a sound really needs is to have its resonance tamed.
YouTube Video Source: Resonant Frequencies