How To Bass Trap For Beginners (Full Guide)

07/02/2020
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Too often, when beginners plan their studio…

They forget about the most important element of acoustic treatment…

Which is of course: Bass Traps.

Because while regular acoustic panels are great at absorbing mid-high range frequencies…

They aren’t very good at handling the low-end…where recording studios experience the worst problems…

Especially those with smaller rooms, and larger studio monitors.

What this also means is…bass traps can be one of the most difficult elements in your studio to get “just right“.

So to help you figure it out, for today’s post I’ve created an in-depth guide walking you through the entire process.

First up…

The 2 Categories

The two “umbrella” categories of bass traps commonly used in the studio are:

  1. Porous Absorbers – that work using a dense material such as foam to absorb sound waves.
  2. Resonant Absorbers – that work using a diaphragm to absorb specific bass frequencies through sympathetic vibration.

Now let’s learn more about each type…

1. Porous Absorbers

auralex lenrd

No doubt you’ve seen them before, because for home studios especially…

Porous absorbers are the first-line-of-defense when tackling general problems with room acoustics.

They can be made from a variety of materials such as:

  • acoustic foam
  • fiberglass
  • rockwool

And they’re extremely effective at taming common problems such as:

  • room modes
  • standing waves
  • flutter echo
  • speaker boundary interference response

The reason they’re so versatile is…they offer excellent broadband absorption, meaning they work well across the entire frequency spectrum.

Yet despite their versatility, porous absorbers have one BIG flaw:  They can’t absorb the lowest bass frequencies unless…

  1. They’re built super-thick, or…
  2. They’re spaced far off the wall

And here’s why:

Porous absorption (aka velocity-based absorption) works most effectively where a sound wave is at maximum velocity, which in your room, is 1/4 wavelength from the wall.

For example, a 100 Hz wave is 11.3 feet long, so its point of maximum velocity is 2.8 feet off the wall.

The problem is, few rooms can spare that much space for acoustic treatment.  So manufacturers often build them really thick instead.

And since they’re cheaper and easier-to-build than resonant absorbers…and it’s obvious why porous absorbers occupy probably 95 percent of the market for commercial bass traps.

Up next…

2. Resonant Absorbers

Resonant AbsorbersCompared to porous absorption, which offers great broadband coverage but often lacks in bass absorption…

Resonant absorbers (aka tuned traps, aka narrowband absorbers) essentially do the opposite

By zeroing-in on specific problems with bass frequencies, while ignoring everything in the mid/upper range.

And unlike porous traps which work better when spaced off the wall…

Resonant absorbers (sometimes called “pressure absorbers”) work best up against the wall where the sound waves collide, because that’s where the pressure is highest.

And this is good news, because it means they occupy far less space in the room.

The 2 standard types to know are:

  1. Helmholtz Resonators – which absorb bass frequencies through a small port in an air-tight cavity.
  2. Diaphragmatic Absorbers – which neutralize bass frequencies with a vibrating panel or membrane.

While both can work well in the studio, diaphragmatic absorbers are far more popular, because they’re easier to design, and occupy less space.

Up next…

How They Work Together

In most pro studios, porous and diaphragmatic absorbers work as a team, since each one is strong where the other is weak.

And simply by adjusting the ratio, you can control the type of acoustics you want.

For example:

  • A drier “studio sound” can be achieved with lots of porous absorption, or…
  • An ambient “live sound” can be achieved with less porous absorption, and more diaphragmatic.

Some studios will even design custom “hybrid” bass traps which use a combination of both.

One way to do this is to add porous absorption directly behind a resonant panel.  This has the effect of widening the range of affected frequencies, but as a trade-off, decreasing the effectiveness at the center frequency.

Now that you know the options, let’s pick one…

Choosing YOUR Strategy

For home studios, the standard advice is to skip the resonant absorbers and focus entirely on porous absorbers.

And here’s why:

Effective use of resonant absorption often requires a custom-designer to evaluate the room, diagnose problems, and build a custom trap specifically for that room.

And poorly built…it may be totally ineffective, and even cause problems by resonating at the wrong frequency.

Porous absorption on the other hand, is a “one-size-fits-all” solution, and is far cheaper overall.

Now assuming you’re sold on porous absorption, the next question is whether to use:

  • triangular corner bass traps, or…
  • flat panel bass traps

Corner bass traps have the advantage of more mass, which as we learned earlier, is one way to effectively tame low-end frequencies.

corner bass trap

Panel bass traps use the other method of low-end absorption, by leaving an open “air-gap” between the panel and the wall.  With this strategy, you can cover more surface area, using less material.

panel bass trap

And while each one has its advantages, the truth is…either works fine.

Which is why up next…I’ll show you the top models I recommend for each one.

For corner traps, check these out:

For panel traps:

Choosing a Starting Point

If you just checked out my recommendations, and weren’t too happy about the prices…you’re probably wondering at this point:

How many of these do I really need?

And unfortunately the truth is…most rooms can progressively benefit from as many as two dozen or more.

But since few people can afford that many, I recommend starting with either 4 or 8 at first, then possibly adding more later on…

  • when you can afford it, and…
  • if you deem it necessary.

Up next…

Mounting Them in Your Room

tridedral dihedral cornersJust like any element of acoustic treatment…

Where you position your bass traps has a huge impact on how well they perform.

The standard starting points to mount your traps are the trihedral corners of the room (shown in the picture as red dots).

If you currently have at least 8 traps, simply put one in each corner.  If you only have 4, put them in the upper 4 corners to save yourself floor space.

If that’s all you have, then you’re done.

If you still have more, the next step is to stack them in columns along the vertical dihedral corners, as shown in the picture below.

bass trap columns

And finally, if you still have more to work with, mount them on the upper dihedral corners of the room, as shown in the picture below.

bass trap full

At this point, the amount of low-end absorption in the room is probably as good as it’s gonna get.

And while you won’t need nearly this many bass traps to get a decent sound from your room…

It’s always an option if you choose to take it that far.