DIY acoustics testing, part 4: starting measurements
Acoustics are huge part of achieving a high quality end result in music production, and the cost of the tools used to improve the acoustics of your home music studio have dropped significantly in recent years.
In this series, we’re going through all of the basics of how to run acoustics tests in a DIY setting.
In previous articles, we’ve figured out our hardware situation by purchasing an affordable, plug and play USB measurement microphone, and we’ve connected that microphone into our software setup using Room EQ Wizard (REW), a free/open-source program that can do basic acoustics testing. We’re now ready to take some measurements!
Today, we’re going to start using our acoustics testing rig to find the best acoustic position within your individual music room. This is the first step in developing your overall acoustics design. We need to start our acoustics design working from the best naturally sounding area in your space, in order to get to the best end result.
Acoustics design within an existing space, where you’re not doing new construction, can only control and improve the existing acoustics you already have, it can’t completely change them into something they’re not. We can turn an apple into a shinier apple here, but we can’t turn an apple into an orange.
If you don’t start your acoustics design working from the best possible area in your room as it naturally sounds, you’ll never get results that are as good as they could be, no matter how much money or time you spend on acoustic control later on in the process. So, this is a critical first step, and it’s important to take your time and get it right.
The waterfall graph from RoomEQ Wizard acoustics measurement software
Finding the ideal acoustic position inside your music room
Before we can determine where to best place your mixing position from an acoustics perspective, we need to collect a bunch of different baseline data points and run some graphs that will help us visualize what we’re working with. All of these data points will differ for every individual space you measure, so it’s important to do this analysis from scratch each time you set up a new room. Here’s the steps.
Step 1: find and mark your room’s centerline
This should be pretty simple: grab a tape measure and write down the length and width of your room. Then, mark the centerline of your room down its longest dimension:
Step 2: find your 38% points off the front and back walls
Calculate 38% of the length dimension of your room, and mark those positions off of both the front and back walls, on the centerline you just found.
For example: if your room was 100 feet in length, you would mark two points measuring 38 feet off of both the front and back walls, on the rooms centerline. These are your “38% points”, and they’re a general rule of thumb to get us into a good starting area, before doing more detailed measurements.
In this not-to-scale diagram, the 38% points are shown by the red X’s:
Step 3: measure at these two points and pick the best one before continuing
Next, take measurements by running an acoustic sweep at each of these two different 38% points, with your microphone placed at your ear level when sitting down.
Interpret these measurements, and pick the “best” of these two points, whichever turns out the best for your individual room.
One of these two points might be a better fit acoustically (your measurements will tell you that), or there may be physical space constraints within your room to consider. Whether you choose to be placed off of the front or back wall will depend on how you’re able to organize your individual space.
Step 4: refine with micro-measurements
Once you’ve decided whether to be placed off of your front or back wall 38% point, you’ll run a series of micro-measurement acoustic sweeps around that point, working in 3-6 inch increments forward and backward, along the room’s centerline.
Yes, moving your acoustic position forward or backward on the centerline just 3-6 inches can result in very noticeable differences in sound quality, depending on your room!
Continuing with our not-to-scale diagram, let’s assume we’ve picked the front wall 38% point to work with. This is what your micro-measurements might look like surrounding that point:
Step 5: interpret the data from your measurements
Now that we’ve collected a series of different data points, it’s time to interpret our data. In this example, I’d look at my data from points X, X1, X2, X3, and X4, and choose the point that had the best natural room acoustics.
When you’re interpreting the graphical data from your various measurement points, you’re looking for two primary things:
The most minimal sharp “nulls”.
The most minimal bass or sub area weirdness, when compared to your other data points.
Remember, these are baseline measurements, ideally taken inside an untreated and empty room. So, we’re not looking for our acoustic measurement graphs to look “perfect” at this point in the process. Rather, we’re just looking for the best option of what we have available to start out with. Your measurement graphs will all look pretty crazy at this point if you’re measuring an untreated room, and that’s OK: they’ll settle down later after the proper acoustic treatment has been installed.
Once you’ve found your best acoustic position, mark it on the floor (painters tape works great for this). This point we’ve found is the point around which we’ll build the rest of your acoustic design.
This article has dealt with the top-level process for how to take an initial set of acoustics measurements inside of a small room. But, the hard part isn’t actually taking these measurements, it’s interpreting the data that you collect accurately. We’ll get into the details of how to do that, next time.
