Where to Place Acoustic Panels?
Below is a diagram of a typical room orientation of desk, listening position, speaker placement and probable acoustic panel placement.
The black arrow lines represent the line of trajectory for sound waves emanating from the speaker and their destination at the listener’s ear.
The off-red colored rectangular blocks represent the acoustic panels.
The phenomenon that occurs in this situation is much more drastic to the quality and frequency response as perceived by the listener than one would imagine. What occurs in this situation is that the initial sound waves that radiate from the speakers radiate out in all directions.
When those sound waves make contact with hard surfaces such as walls and ceilings, they bounce off and radiate back to the listener’s ear not unlike a bank shot with a pool ball. When these frequencies arrive at your ear at various different times they cause cancellation and amplification of certain frequencies making it impossible for the listener to get an accurate representation of the frequency response of, not only the entire mix but of individual instruments as well.
The results of this can be quite dramatic. When I tested my own room for the first time using a piece of software that analyzes the frequency response at the listening position, I was shocked at the results. For example, I had a – 40-decibel drop at 150 Hertz.
The problem that occurs in a situation like this is that the listeners’ perception leads them to believe that the 150 Hertz frequency is missing from the overall spectrum of the mix. Therefore, there is a temptation to add more of this frequency to compensate.
What happens later on in a different listening environment is that the hundred 50 hertz frequency seems to be overly dominant in the mix. Of course, this will vary from room to room since every different room has its own set of cancellation and amplification anomalies. There is no perfect listening room. So if that’s the case, you might ask, what’s the point of having a flat listening response in your mix room if every room is going to sound different.
This was the question I initially had until I researched further. Here is why it is important to have a flat frequency response in a mix room. Given that all rooms are going to be anomalous, then if the mix room is as flat as possible you are not going to get double amplifications and double reductions in the rest of the variety of listening environments that people will consume the music.
Let me explain.
In the case of the missing hundred and 50-hertz frequency in mind mix room here is the scenario that would take place in other environments for example. Let’s say that I do what I would naturally do and start boosting the hundred and 50-hertz frequency on say bass guitar, guitar, drums, and any other elements in the mix that would naturally benefit from this low frequency.
Then, I play back that mix in a room that happens to have the opposite and opposing anomaly of having a boost at 150-Hertz. Let’s say that boost was 20 decibels. By compensating for the 150 Hertz frequency in the mix room, I am naturally going to have a boost of 40db in any other room given that, theoretically, it will have a flat frequency response. If another listening room has a boost of 20db as a room anomaly then the combined boost of 150 Hertz in the listening room will be on the order of 60 decibels.
That get’s ugly fast!
So How Do We Fix This?
You can never fix this situation completely unless you have a ridiculously high budget. ( Think $200,000 )
I have done a couple of room treatments for others. When they asked me what the potential cost will be I say this. For $2,000 you can fix about 80% of the frequency response anomalies in your room. To fix the rest will cost an additional $200,000. You have to know when to say when. After all, it’s just a home studio.
The first thing you want to do is deal with the early reflections that are laid out in the diagram at the top of the page.
It would be tempting to go out and buy acoustic foam panels to solve this problem because they look kind of cool and they are touted to be a great solution. After installing these in your room you will notice a difference that’s for sure.
The problem is that the main frequency spectrum that these foam panels contend with is the frequencies above 3 kilohertz. This tricks the ear into thinking that you have solved the problem because high-frequency reflections are the most obvious to the human ear. The underlying problem will still remain. The underlying problem will be that the less perceptible frequencies below 3 kilohertz will still be causing huge problems in the translation of your mix to other environments.
For this reason, it is my humble opinion that using a product like Roxul Rockboard 60 or Owens Corning high-density insulation is a far better solution. These materials have the ability to absorb frequencies all across the Spectrum. Obviously, any material is going to do a far better job at absorbing higher frequencies and mid-range frequencies then it will in dealing with low frequencies. We do the best that we can in this situation.
It’s tempting, as I said, to go with the pre-constructed route and by the acoustic foam, but you will notice much greater benefit if you spend the extra time and build out some panels yourself from the materials listed above.
There are plenty of tutorials on Youtube that walk you through the steps involved. http://howtomixmusic.net