Picture your ideal recording or listening space. What does it look like? It’s large, right? With plenty of wood surfaces and a lovely high ceiling? That’s what we’d go for if given the chance.
But back here in the real world, think about the spaces where people make or listen to sound at home. In nearly all cases, our real spaces don’t look like that ideal. Most at-home recording musicians and audio enthusiasts don’t have the luxury of large, acoustically designed spaces in their homes. They end up doing their work in a small room. The same goes for a home theater: as large as your man cave might be, it’s not large enough to be a truly acoustically friendly space.
The small to medium rooms where most of us do our listening, watching, or recording has some notable acoustic drawbacks. In particular, they tend to be brutally bassy. They amplify low-end frequencies—both the natural ones and the ones your music produces.
One of the big reasons for this is that especially low frequencies have a wavelength that’s longer than the room itself. The sound wave begins reflecting backward before it’s even finished one wavelength, creating some unpleasant effects as the wave doubles back on itself. Add in tangential and oblique reflections, or room modes (more on that below), and the sound field gets even muddier.
Bass traps are the go-to solution for taming unruly low-end sound. They are the simplest and most affordable solution to this complex problem.
When you finish this guide, you’ll understand what bass traps are, why they are necessary for smaller rooms, proper corner bass trap placement, and the best ways to install them. We’ll also answer some other common questions.
Ready to dive in? Let’s go!
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Understanding Room Modes
Before we jump into discussing bass trap placement, let’s talk about why bass traps are necessary. As you likely know by now, every room has its own acoustical profile. Each room you step foot in has its own unique natural resonance.
Numerous factors go into this unique sound signature. The shape of the room, the angle of the walls, the height of the ceiling, and the materials used in the space are the primary influences on a room’s natural acoustic.
Understanding that each room has a unique natural acoustic is only the starting place, though. To understand how bass traps function, we have to go deeper into what causes that natural acoustic. With that in mind, let’s talk about room modes.
Room modes can get pretty complicated, but in layperson’s terms, they’re essentially the ways that sound can reflect in a space. There are three room modes: axial, tangential, and oblique. These reflections don’t happen uniformly. Axial modes essentially reflect straight back, while tangential and oblique modes reflect in angular, sometimes unusual patterns.
These reflected sound waves can begin to mix with one another, leading to an uneven sound.
Start Low
Understanding room modes can be a bit complex, but doing so will help you make a coherent plan to tame your room acoustics. If this is sounding a little overwhelming, we have some good news: you don’t have to understand everything all at once. (But if you do want to take an extremely deep dive into room modes, here’s a great resource.)
No matter what your level of comfort or understanding, you should always start low. Low-frequency waves are the starting point because they reflect in all directions. Because the low-frequency waves are longer, they tend to build up in the corners of a room. And in a smaller space, those corners are closer to your listening space, making the buildup far more noticeable.
Enter the Bass Trap
The simplest, most economical solution to overly intense low frequencies is the bass trap. This sound-absorbing device goes where the bass builds up and “traps” the sound (technically, converts it to heat). While you’ll never wholly muffle low frequencies, properly installing bass traps in your space can adequately tame them.
In other words, bass traps flatten the frequency response in the room, significantly improving the muddled, overly bassy sound that’s characteristic of most small to medium untreated rooms.
As the resource linked above indicates, you can go deep down the rabbit hole of room modes, using complex formulas to calculate exact modes and modify accordingly. But for most DIY enthusiasts and musicians, outfitting the space with appropriate bass traps will be a great and significant first step.
Why Bass Traps in Corners Work
You’ll most frequently see bass traps placed in corners. Why is this, exactly?
The short answer is because they work. But do corner bass traps really offer advantages over other placements? If so, why?
There are two going theories for why corner bass traps are so effective. First, conventional wisdom. Sound pressure naturally tends to build up more in corners than anywhere else, and it reaches its peak in the trihedral corners (more on that later). So it stands to reason that installing a bass trap in that location will be pretty useful.
The second theory is the 1/4 wavelength rule. This rule applies to porous traps, which include those made from fabric, acoustic insulation and other similar products. The 1/4 wavelength rule states that to reduce a frequency optimally, you must have enough space to absorb at least a quarter of the frequency.
Ideal Air Gap (ft) = ¼ (1,125/Freq)
A trap that’s flat against the wall can’t do that. A corner bass trap that’s angled in the corner with some space behind can potentially do so.
The science here gets deep pretty fast, but at the end of the day, you want results. And corner bass traps will give you results!
Remember that corner traps need space between the insulation and the corner to work, ideally a quarter wavelength gap from the wall. This does mean that a properly installed corner bass trap won’t cut all bass frequencies equally. It will cut most aggressively the frequency of whatever length is four times the space between the wall and the back of the trap.
The lower the frequency you’re having trouble with, the bigger the ideal air gap. Or, if you need to trap a broader range of frequencies, you may need a thicker bass trap.
Ideal Corner Bass Trap Placement
By this point, it should be clear that installing a bass trap is a bit more complicated than just shoving some foam in the corners of your room. Now that we know the how and why let’s tackle the where.
1. Tri-Corners (Trihedral)
The first location for corner bass trap placement is the tri-corners of the room. These are where two walls and the ceiling (or floor) converge. There are eight trihedral corners (four wall-wall-ceiling and four wall-wall-floor) in every rectangular room.
These locations can be awkward for mounting bass traps. They either require complicated ceiling mounts (remember, you have to leave space behind, so they can’t go flush on the wall) or they take up valuable floor space. For most spaces, floor-to-ceiling traps are more convenient.
2. Wall-Wall Corners (Dihedral)
These are your corners where two walls come together, but disregarding floors and ceilings. Rectangular rooms will have four dihedral bass trap opportunities. Dihedral traps pretty much ignore the floor and ceiling but fill some or all of the space in between.
If your space allows you to install floor-to-ceiling dihedral bass traps, do it. These offer many of the advantages of trihedral, plus additional coverage. They also tend to be much easier to install.
3. Walls & Ceilings
You’ll see some bass trap products offered that are designed to mitigate low frequencies along a flat surface, either a wall or the ceiling. We generally advise against these. You may well treat these spaces with acoustic foam later on, especially if you’re doing a home recording. That foam addresses other, higher frequencies as a priority, but it will help some with low-frequency issues, too.
Best Bass Trap Placement Examples & Priorities
If you’re new to the world of bass traps or other acoustic treatments, it can be tempting to go overboard at the outset. Before you start stuffing bass traps and foam all over your space, it would be smart (and easier on your wallet!) to start small. Below is our recommended prioritization plan for bass traps.
Floor to Ceiling Dihedral Corner Bass Traps
Whether you’re strapped for cash or have a near unlimited budget, this is the place to start. Your first priority should be treating the four vertical wall-wall corners. By using a floor-to-ceiling approach, you get the benefit of covering all eight of the tri-corners in the room, as well as the four vertical wall-wall corners.
If you can, treat all four floor-to-ceiling dihedral corners. The front two are the higher priority, though. If budget or room design limits you to two, treat the front first.
Partial Wall-Wall Corner Bass Traps
Not every room will allow you to install bass traps from floor to ceiling. Home theater installs that aren’t in a dedicated theater-style room are one example. There’s more happening in the room, and you can’t go bonkers with acoustic treatments like these.
Whatever the reason, if you have limitations in your space, you’ll still get a lot of bang for your buck by partially covering your dihedral wall-wall corners. If doors, your budget, or room aesthetics prevent full floor to ceiling corner traps, then a partial coverage is still likely to accomplish more on its own than the options below would.
Upper Wall-Ceiling Corners
If corners are bad for bass frequencies, then what about the places where the ceiling joins the upper wall? We don’t tend to think of them as functional corners, but they have the same shape.
These spaces can also create low-frequency trouble, but they are less of a concern than the spaces we’ve discussed so far. If you’ve treated your wall-wall dihedral corners and are still dealing with too much sound on the low end, treating your upper wall-ceiling dihedrals is the next priority.
Start with the front of the room. The next priority is the back, and the sides are the lowest priority in this grouping.
Span the Ceiling Corners
At this point you might be wondering: if it was smart to install floor-to-ceiling wall-wall corner bass traps, wouldn’t it make sense to install ceiling-spanning ones, too?
There is some value to doing so. You’ll reclaim much more floor space by taking this approach compared to the ones above. But you don’t get the same acoustic value from it. Ceiling-spanning bass traps just aren’t as effective in reducing bass frequencies as floor-to-ceiling bass traps.
So, is it worth spanning the ceiling? Not for most people. That said, if you’ve implemented every option above that’s feasible for your space, and it still isn’t enough, you might consider adding these in.
Do you Need a Bass Trap in Every Corner?
This is a very popular question, and the answer is usually no. It’s exceedingly rare for a room to need a bass trap in every single corner. And it’s usually not feasible to install one in every corner, either.
As we’ve discussed above, there’s a clear progression of priorities for corner bass trap placement. In just about every room, we recommend starting with wall-wall corner bass traps from floor to ceiling. Ideally, install these in all four corners if the room and your budget will allow. The front two are more important than the rear two.
Once you’ve installed your wall-wall dihedral traps, you may feel like you aren’t getting the dampening effect you’re looking for. If so, follow the priorities listed above.
Do Bass Traps Behind Monitors Work?
This question can get technical pretty quickly, as many on this topic do! So what are we talking about here? Ideally, you want to have your monitor speakers (as opposed to the computer display sort of monitor, which isn’t what we’re talking about) placed appropriately far from the front wall. Where exactly to put them is beyond the scope of this already lengthy article. Suffice it to say that most at-home musicians try to leave some space.
But in a small room, this isn’t always possible. Having your monitors too close to the wall can create distortions to an otherwise pristine sound distribution. This is especially noticeable if you have rear-ported monitors, as they are blasting low frequencies backward, right at your front wall.
Putting some sound treatment behind monitors that are too close to the front wall is generally a good idea. However, doing so isn’t likely to make a massive difference in your room’s overall “bassiness”. It will help in other ways, but your main corner bass traps will still do the heavy lifting here.
That said, if you’ve already installed bass traps as described earlier and still don’t feel like you’re getting the reduction needed on your monitors, it doesn’t hurt to try one more thing. Go ahead and install bass traps behind the monitors and see if it solves your issue.
How to Mount Bass Traps in Corners
We’ve covered just about everything imaginable about bass traps by now, but there’s just one more thing: how do you actually install these things?
Mounting methods vary depending on the type of material your bass traps are made of. Here are installation tips for three common styles.
Wood Frame Corner Bass Traps
Many bass traps consist of a wood frame holding some kind of sound-absorbing material. These are usually intended to hang from above, and many can be hung using simple eye-hooks and wire. Use what you need to get the bass trap hanging at the appropriate angle to cover the needed corner.
Other wood frame corner bass traps must be wall-mounted using brackets and screws. Remember, though, that ideal porous bass traps need space between themselves and the wall. Other more complex technologies that we didn’t discuss may not need this space, though. Before you mount something to the wall, make sure a wall installation will be effective for the bass trap you’re using.
Acoustic Foam Wedges
Acoustic foam wedges are tremendously lightweight. As a result, mounting them to surfaces is usually very easy to do. That said, shoving wedges tightly into your corners is not our recommendation; you want some space if you can get it. But we know that some spaces don’t allow for the ideal, and if you choose this route, we still want you to know how to install them.
Some acoustic foam wedge products are designed to mount flush to the two walls comprising a corner but with a gap in the corner itself. These are preferable for our purposes of reducing low frequencies.
3M Command strips are enough to hold these lightweight bass traps to your wall or ceiling. You can use spray foam adhesive for a more permanent mounting solution, as well.
Tube Style Bass Traps
Cylindrical tube-style bass traps are a simple style of bass trap that’s popular among the DIY crowd. With some cheap supplies and a tiny amount of elbow grease, you can build your own.
Tube-style bass traps typically consist of a rigid cylinder stuffed with rags, insulation, or some such material. They can be wrapped in burlap for added acoustic absorption. They are designed to be freestanding and just sit there on the floor. You can also stack multiple tube-style bass traps on top of one another for added low-frequency absorption.
