If you have a recording studio, home theater, library, or zen room, achieving the best acoustics, as well as maintaining silence, is important to you. Perhaps you’re an audiophile persnickety about music production, or simply someone who doesn’t appreciate sound in certain frequencies, like bass.
If you’re concerned with tightening low-end frequencies and removing excessive coloration, then perhaps soundproofing with bass traps is the answer.
Bass traps help with soundproofing if the objective is to block excess low-frequency sounds, which are the hardest to tame. Bass traps are designed to make the sound in a room smoother and make a real acoustic difference in terms of numbers, measurements, music production, and sound mixing.
For a detailed look at bass traps and how they contribute to amazing audio, read on.
What Are Bass Traps?
Bass traps are acoustic products designed to absorb low-frequency energy and convert it into heat . They’re used as part of sound solution systems in live rooms, vocal booths, rehearsal halls, mixing rooms, control cubicles, drum booths, dedicated listening rooms, home cinemas, and any project requiring effective soundproofing solutions.
How Effective Are They?
Arqen, specialists in architectural acoustics, explain the value of capturing low-frequency sound with different types of bass traps. The broadband kinds absorb a wide range of frequencies, but with limited efficiency. In contrast, tuned bass traps (aka narrowband absorbers) absorb extremely efficiently over a narrow range of frequencies.
How Do Bass Traps Help With Soundproofing?
Whether for tracking or mixing, bass traps are critical for recording or practicing audio production because they define low frequencies better, helping to achieve optimum results. The work for soundproofing as well but not to a great degree as they do not have too much mass.
To appreciate their importance in sound control, we have to consider the different sound frequencies. Mid to high frequencies have shorter waves. Low frequencies have strong, very long wavelengths.
Regular acoustic panels are great at absorbing mid- to high-range frequencies, but they aren’t very good at handling the low-end ones, where recording studios experience the worst problems. This is especially true with smaller rooms and larger studio monitors.
The latter refers to loudspeakers in enclosures designed for professional audio production applications, such as recording studios, television networks, radio stations, movie productions, and home theaters, where accurate audio reproduction is crucial.
Normal absorption panels are great for taking care of reflections, but bass needs a heavier approach. Standard acoustic tiles are thin and can only absorb shorter waves. If these alone are installed, there isn’t enough foam to absorb more powerful waves. More foam is needed to absorb low frequencies. This is where bass traps come in.
They are available in various formats—especially triangles—as these fit in the corners of a room, where frequencies tend to build up (Noise can be six decibels louder in corners).
Most studios don’t have enough space or funds to treat whole walls with thick, bass-trapping foam. So they just focus on corners. Often, this is satisfactory for general sound control.
For the more discerning, larger bass traps are recommended. The wider the bass traps, the lower the frequency they can absorb. Standard traps are usually 12” wide—not enough to absorb very low frequencies.
Types of Bass Traps
E-Home Recording Studio, an online resource for building home recording studios, categorizes them as such:
These offer excellent broadband absorption (meaning they work well across the entire frequency spectrum). They’re made of dense material, such as fiberglass, or Rockwool, for absorbing sound waves.
They’re used for common problems, such as room nodes (resonance bumps in a room’s frequency response), standing waves, flutter echo, and speaker boundary interference response.
An example of Rockwool is Roxul’s Rockwool Acoustic Mineral Wool Insulation (Amazon).
Porous absorbers can’t absorb the lowest bass frequencies unless they’re very thick or mounted far from the wall. Porous absorption (aka velocity-based absorption) works most effectively where a sound wave is at maximum velocity, which is 1/4 wavelength from the wall.
Porous absorbers are cheaper and easier to build, so they occupy about 95% of the bass trapping market.
Also known as tuned traps, pressure absorbers, or narrowband absorbers, these use a diaphragm to absorb specific bass frequencies through sympathetic vibration but ignore everything in the mid/upper range.
They work best up against walls where sound waves collide because that’s where the pressure is highest. This means they occupy less space.
Types of Resonant Absorbers
- Helmholtz resonators—absorb bass frequencies through a small port in an airtight cavity.
- Diaphragmatic absorbers—neutralize bass frequencies with a vibrating panel or membrane. They’re more popular, as they’re easier to design and occupy less space.
Both trap categories can co-exist. Control your chosen type of acoustics by adjusting the ratio. If you want a drier studio sound, use porous absorption. If you prefer an ambient live sound, go diaphragmatic.
There are custom-made “hybrid” bass traps that use a combination of absorber types. You can make one by adding a porous absorber directly behind a resonant panel. This will widen the range of affected frequencies but will decrease the effectiveness at the center frequency.
But if you were to choose one, use porous absorbers for home studios because they’re cheaper, simpler to install, and offer a “one-size-fits-all” solution. With resonant absorption, you need a professional for room evaluation, problem diagnosis, and custom builds.
Factors to Consider When Buying Bass Traps
Types of Sound
To choose accurate acoustic treatment, you have to know what kind of sound you’re dealing with. From its source, sound travels in outward directions.
- Direct sound—travels in a straight line. When it gets reflected, the original sound changes. The effect may be good or bad, depending on the size of the room and its properties. Large venues, such as cathedrals and concert halls, don’t have acoustic problems. But with smaller spaces, one has to modify elements in these structures to get better sound.
- Indirect (aka reflected) sound—randomly bounces within the room and between its surfaces. It comes in the form of echoes, reverbs, or vibrations.
Soundproofing vs. Sound Absorption
The correct acoustic treatment depends on your objective. Do you want to reduce the echo? Do you want to block all sound except for the one you’re producing? What are the dimensions of your room? Where is your studio located? Both methods reduce unwanted sound but use different means to do so.
Soundproofing or sound isolation blocks or minimizes the levels of unwanted sounds traveling in and out of the room, but keeps desired ones in. This is done either by blocking—using heavy and dense building material, or sealing—closing tiny gaps, specifically in windows and doors.
- Decoupling—detaching two objects or elements that are in contact with each other to prevent vibration. Do this by placing that element on a stand made from dense material. Or get anti-vibration rubber pads, like RevTime anti-vibration mats ($100 for a pack of two).
- Adding mass to walls—prevents sound from traveling. Dense materials come in many forms, such as mass-loaded vinyl (MLV). An example is Second Skin Audio’s Luxury Liner MLV Roll ($160).
- Dampening/damping—applying compounds called “sound deadeners” between two stiff panels. Deadeners are filled with asphaltic acoustical materials that reduce the resonant vibration of panels that radiate noise. They reduce noise upon impact, as well as its duration.
Sound absorption controls indirect sounds exclusively inside the room. It reduces echoing or reverberation. Bass traps fall under this category but also count as soundproofing products because they eliminate unwanted sounds.
Read my article on soundproofing vs sound absorption for a more detailed explanation.
The size and shape of the room/studio are important in deciding how many traps you need. The standard is one in each corner, so eight in total.
According to E-Home Recording Studio, the position of bass traps has a huge impact on how well they perform. Low-frequency buildup usually happens in corners.
So place all your traps at a 45° angle in the corners, where they will absorb the most amount of bass and reduce reflections. Try to minimize as many 90° corners as possible. This will also help scatter and diffuse sound waves in the room.
Here is a layout from Realtraps. All panels numbered ‘2’ are bass traps and the rest are acoustic panels.
For tighter sound control, Justin Colletti from SonicScoop—an online resource for audio technology—suggests mounting panels an inch or two away from walls. Putting distance between absorptive material and the wall can help in decreasing even lower low-frequency sound.
The standard starting points for mounting traps are the trihedral (having three sides in addition to the base or ends) corners of the room. If you have eight traps, put one in each corner. If you have only four, put them in the upper four corners to save on floor space. If that’s all you have, you’re done.
If you have more, stack them in columns along the vertical dihedral (an angle formed by two plane faces) corners. If you still have more, mount them on the upper dihedral corners of the room.
Do Bass Traps Have to Be Floor-to-Ceiling?
Fricker claims that installing traps this way “ensures a gigantic improvement in the bottom end.” The traps also work as mid- and high-frequency absorbers.” ARCACOUSTICS™, experts in acoustics and noise control, however, claim it isn’t necessary to have floor-to-ceiling bass traps at the corners. Two in each corner is enough. You can also treat only two corners—the ones closest to the speakers.
For decent low-frequency control, Colletti says absorber panels can be made of foam or rigid fiberglass insulation, preferably 6” thick. Fiberglass is the pink cotton candy-like material found in attics and between walls.
When rigid and tightly compacted, it’s a good absorber of low-frequency sound. An example is the Owens Corning 703 Fiberglass Acoustic Insulation (Amazon).
For corners, Colletti recommends Acoustimac’s DMD-BT6000C ($147). Apart from cleaning up low frequencies, these thick, corner-mounted absorbers keep bass from being too boomy or muddy.
Evaluate the sound in your room to determine if you need only bass traps or panels too. You get better performance if you use both. Place traps along the middle of a wall to knock down excessive reflections and standing waves.
The thicker the absorptive panel is, the lower the frequency it can absorb, and the more control you have over acoustics. The more affordable general foam-style absorption products work well with mid to high frequencies, but they’re not thick enough to absorb low-end ones.
For more mass, use triangular corner bass traps, such as the Auralex LENRD (pack of eight from $446). LENRD (low-end node reduction device) bass traps are extremely effective at smoothing out low-frequency room nodes at an affordable price. A mega LENRD trap offers twice the width and length of a normal one.
If you want to cover more surface area with less material, opt for a flat-panel bass trap. This leaves an open-air gap between the panel and the wall. An example is the Auralex Acoustics SonoLite Bass Trap ($136).
Sometimes price dictates quality, but many acoustic products are affordable. We have provided the links to products the audio and soundproofing experts have recommended in this article.
How many traps do you need?
E-Home Recording Studio claims that most rooms can benefit from 24 or more. Musician, audio engineer, and bestselling author Björgvin Benediktsson confirms that it’s okay to put in as many bass traps as you can because the bass is difficult to manage.
He adds that it’s acceptable to line every corner with low-end traps. Multi-placement works best for bass trapping and also helps scatter and diffuse sound waves across the room.
If you’re budget-conscious, however, this may not be currently feasible. Start with four or eight first, then add more later.
You may install mid- to high-frequency absorbers around the room to give it an even sound, but you shouldn’t tile it completely, unless you intend to create a completely dead recording space, like a vocal booth.
Testing Bass Traps
We like soundproofing enthusiast Tommy Callaway’s “before-and-after’’ demonstration. In this video, he wanted to determine if just a few bass traps mounted on the corners of his studio would make an audible difference that anyone with an untrained ear could hear.
After his experimentation, he confirmed that bass traps do make a marked difference and even helped create a richer overall sound.
Build Your Own Bass Traps Cheaply
Construction is not that complicated, but you need to flex some math muscle and consult an acoustician to help you with the design. If you are unfazed by this and are of the DIY persuasion, scour the many online demos by audio and soundproofing experts.
We like Fricker’s tutorial because, despite acknowledging that cheap foam treatments don’t work very well and the best ones are very expensive, he has shown how to create traps for around $40 per unit.
You can also check out my guide.
Where to Buy Affordable Supplies
Callaway claims that bass trapping material is cheaper online than in brick-and-mortar stores. Fricker buys supplies from building supply companies because big box home improvement retailers don’t stock them.
Fricker prefers rigid fiberglass because “insulation is hyper-compressed, and it has excellent sound absorption qualities, especially in the mids, low-mids, and bass.” Callaway cites Foam by Mail as 80% cheaper than RLX (Room Layout Express), a division of Auralex Acoustics, a dealer in acoustic products. A pack of eight corner bass traps costs $25 each at Amazon. (Leave the foam to expand for 24 hours before installing.)
Callaway recommends Advantus Gem T-pins (Amazon) for mounting bass traps because they don’t damage walls. “They’re great for drywall, but not so much for brick or concrete,” he explains.
How to Trap Bass in a Room
For those with carpentry and math skills, do this prep first. Test the sound in your room using a measurement microphone. From your listening position, find out where the most significant peaks or nulls in the bass are. You can then make some tuned absorbers to help you specifically with those frequencies.
The company created a flicker noise (aka pink noise) audio file that’s filtered, so just the lower end is coming through. You can download that file here.
After you’ve downloaded it, play it in your room while examining all corners to hear where the bass is building up. The best place for base trapping is wherever you notice an increase in volume.
A well-balanced acoustic space, whether in a studio or serenity room, isn’t just about cool gadgets or mindfulness tools, but also getting a professional sounding mix out of it. Treating and tuning it with the correct acoustic treatment is essential if you want stellar audio quality.
Logic dictates choosing one method over the other, but if you want complete sound control, consider both soundproofing and sound absorption. Bass traps, used in conjunction with various soundproofing products, offer the full scope for stabilizing frequencies.
-  ARCACOUSTICS™: Where Should I Locate Bass Traps?
- E-Home Recording Studio: The Ultimate Guide to Bass Traps for Home Recording
- Audio Issues: What Are Bass Traps and Why Do You Need Them?
- GIK Acoustics: Room Testing for Bass Trap Placement
- SonicScoop: Guide to Acoustic Treatment: A Must for Better Recordings & Mixes
- Tommy Callaway: Do Bass Traps Make an Audible Difference?
- eNoise Control: Damping Compound
- Wikipedia: Studio monitors
- Wikipedia: Terminal velocity
- Oxford Reference/Lexico: dihedral
- Oxford Reference/Lexico: trihedral
- Arqen: Bass Traps 101-Placement Guide
- TC Electronic: Glenn Fricker
- Facebook: Glenn Fricker
- Spectre Sound Studios: Build Your Own Bass Traps
- University of New South Wales: Helmholtz resonance
- Acoustic Fields: Diaphragmatic Absorbers—All Powerful