Why Room Ratios Don't Work...Most of the time 

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If you are reading this, you may be facing some room ratio madness yourself. If you are trying to find the perfect room ratio, reading obsessively about room modes and genuinely feel like you have gone down a rabbit hole then you are in the right place. In this article I will ease your stress around room modes, and room ratios and hopefully send you back out in the world with a plan for your home recording studio.
1) Why Room Ratios Don't Work...most of the time
Room ratios were created to give acoustic designers (aka you) the ability to design rooms with relatively small volumes that will still sound "good." I write good in quotes because we can never achieve a perfect room. Even the best room ratios will have flaws that need to be addressed.
This said you may have jumped on a few room ratio calculators on the internet and found that with your ceiling height the room ratio given leads to a very small room. This is a common problem with using room ratios in basement, bedroom or garage home studio designs. We are always held back by our ceiling height because the ratio is based off of ceiling height to width to length and a low ceiling height means smaller length and widths to meet the ratio numbers. Meaning, if we can't raise up our ceiling height we can't get a big enough room to do our work in.
Totally maddening...I know! So what is the solution. Well let me tell you, but first let's learn what makes a room "good" to begin with.
2) What Makes A Room Sound "Good"
There has been a lot of research on what makes a room sound pleasing or good to the human ear. This is a subjective term and has been argued over the years by some of the world's top acousticians.
One thing that makes a room sound good is having what is known as an even distribution of modes. (Now I am not going to get into what a room mode is in this article, but if you don't know, take a break and google it real quick.)
Okay great, so an even distribution of modes means that modes are spaced evenly through each 1/3 octave frequency band. The human ear perceives sound based on a logarithmic scale and acousticians have plotted frequencies based on this scale. The key here is to know how to read it, not try to fully comprehend the science.
Next, another thing that makes a room sound "good" is to never have modes fall on top of each other. This means two different types of modes (axial, tangential, oblique) line up at exactly the same frequency thus causing that frequency to ring out more in your room making your room sound "bad."
To do this I am going to show you a really good room ratio and a very very bad room ratio. This will help you see what an even distribution of modes looks like and what the lining up or coincidence of modes looks like.
3) Arguably, The Best Room Ratio
Arguably, one of the best room ratios is Sepmeyer's first ratio of 1: 1.14 : 1.39. Now, we will see in a moment how best can be misleading, but stick with me here. The image below is from the AMROC room mode calculator. It shows Sepmeyer's first ratio with a ceiling height of 15 feet.
Now we don't really need to look at anything above 125 Hz. The reason is that we can easily treat those frequencies with velocity based acoustic panels. What is harder to treat are room modes below 125 Hz. Now what we notice first is that in the lower frequencies we have a relatively even spacing of room modes. That is good! In a second you will see what big gaps will look like. We also want to look at the Bonello chart. It shows a smooth increase in modes per 1/3 octave. That is also considered "good." If that number goes up then drops down, then your room will not sound as good.
3) Size Matters!
I know I hate seeing that statement too, but in room acoustics the volume of our room also matters. You could use that awesome Sepmeyer ratio, but if you have an 8 foot ceiling it will not sound as good. Let me show you why.
Below is another screen shot from the same Sepmeyer ratio we used on the 15 foot tall room. However, this chart shows the room modes for an 8 foot tall room.
At first glance they look the same, right? But wait! The relative distribution, meaning the spacing between the modes is the same, but where the modes fall on the musical scale has changed. In a smaller room those same modes have been shifted up in the low end...read the full blog article at www.soundproofyourstudio.com/....
0:00 - Intro
1:59 - Why Room Ratios Don't Work...most of the time
3:37 - What Makes A Room Sound Great
9:13 - Size Matters
12:44 - A Truly Crappy Room
14:03 - The Bolt Area
20:04 - Conclusion