CHAPTER 3: The Ultimate Guide to Acoustic Treatment for Home Recording

When you first start learning about acoustic treatment for home studios…

It’s extremely common to grossly underestimate its importance.

You naturally assume that just because you have a nice condenser microphone and expensive studio monitors…great sound comes automatically.

But here’s the real truth:

The acoustics of your room impact the quality of your work far more than any of your gear.

So it makes perfect sense to get this part handled first, before wasting thousands on any of that other stuff.

And I’ll walk you through the entire process on how to do it, right now.  So let’s begin.

The Basics of Room Acoustics

Before we start buying anything, we’ll begin basic explanation of acoustics.  Starting first with…

1. How Sound Travels in a Room

When a sound is made in a room, here’s what happens:

1. Starting at the source, it projects outward in all directions.
2. A small portion of it (known as direct sound) travels in a straight line to the microphone.
3. The remainder (known as reflected sound) bounces randomly between the surfaces of the room.
4. Some of those reflections reach the microphone by chance, moments later.

Since direct sound does not interact with the room, its frequency balance remains pure, and its tone unaltered.

With reflected sound however, each reflection that makes its way back to the microphone will change the overall tone significantly.

Depending on the size of the room, and the reflective surfaces within it…

This change could be either LARGE or SMALL…GOOD or BAD.

In most rooms it’s BAD.  And here’s why:

2. Why Most Rooms Have Poor Acoustics

Have you ever been in a room with high ceilings and textured walls, like a cathedral for example?

If so…did you notice how great it sounds in there?

That’s because rooms like these are not only designed to LOOK beautiful…they’re designed to SOUND beautiful as well.

But rooms such as these with great acoustics require a LOT of space and money to build.

And since most of us have NEITHER…here’s how we fake it in the studio:

3. How to Fake a Great Room Tone

Way back in the 1960’s…someone invented the awesome machine known as the Echo Chamber.

This machine allowed engineers to simulate the reverb of a room OTHER than the one where it was recorded.

This was the first instance of faking a big room sound from a small studio.

Over the years, the technology grew more sophisticated, and today…software programs known as digital reverb can simulate the sound of virtually any acoustic environment imaginable.

The only catch is…before you can add FAKE reverb, you must first remove the REAL reverb.  Here’s how:

4. Removing Natural Reverb with Acoustic Treatment

By adding acoustic treatment to your studio…

You essentially attempt to absorb all that unflattering small room reverb.

So all that remains is the direct sound from the instrument to the microphone.

That’s how it works “in theory”.

In practice though, many people find that absorption actually works best in combination with another type of acoustic treatment known as diffusion.

Here’s how it works:

5. How Diffusion Improves Your Sound

When using absorption ONLY, you’ll probably find that the room sounds uncomfortably “dead”.

The solution here…is to allow a few reflections to remain, but scatter them with diffusors.

Normally, untreated reflections create problems because they get trapped in one spot, amplifying some frequencies, while canceling out others.

This is how the natural frequency balance gets destroyed.

Diffusors solve this problem work by those scattering reflections so nothing gets trapped, and the natural tone is preserved.

With the right combination of both absorption and diffusion, you can transform the acoustics of virtually any room…into something capable of a world-class recording.

Now up next, let’s clear up a common misconception among newbies…

Soundproofing vs. Acoustic Treatment

Very often, musicians use these terms interchangeably, mistaking one for the other…

When really, they’re completely different.

Soundproofing works to block the sound that travels IN and OUT of the room with:

1. heavy, dense material on the walls.
2. air-tight sealant over gaps in the windows/doors.

The main benefit here is…you can record whenever you wish, without worrying about you and your neighbors disturbing each other.

Acoustic treatment on the other hand, ONLY controls reflections WITHIN the room, to make better sounding recordings.

BOTH of these are valuable, but NEITHER does the job of the other.

If you want to learn more about soundproofing specifically, check out our next post in this chapter:

• How to Soundproof a Room for Music Recording

Moving on…

Evaluating Your Bare Room

The very first step in building a plan for your room, is to evaluate the extent of its problems.

So here’s how you do it:

Walk around the room and clap your hands as loud as you can from every spot, and listen closely to the reflections that follow.

1. In the WORST case scenario – you’ll hear a harsh metallic ringing sound, which typically occurs in small cubical rooms.
2. In the BEST case scenario – you’ll hear a pleasant reverb, which typically occurs in larger rooms with high ceilings and lots of complex diffusive surfaces.

Most likely, the sound you hear will be somewhere in-between.  Now…

• The closer it is to #1, the more absorption you will need to make the room sound as dry as possible.
• The closer it is to #2, the less acoustic treatment you will need in general, although virtually any room will still benefit from a little.

If you need some reference points to hear the difference between good and bad acoustics, perform the clap test in a wide variety of different rooms, and take notice of which types tend to sound best.

Then later on, when you begin installing acoustic treatment in your room, use the clap test constantly throughout the process to observe how the sound changes.

With each new addition, that nasty ringing should be becoming less prominent, until it disappears completely.

And even if you’re starting with a great sounding room, you may still want to kill those reflections, to give you more options with adding digital reverb in your mixes later on.

Moving on…

The 3 Elements of Acoustic Treatment

Aacoustic treatment requires of a mix of 3 items:

1. Bass Traps – to absorb the low frequencies
2. Acoustic Panels – to absorb the mid/high frequencies
3. Diffusers – to scatter the remaining frequencies

Now let’s learn more about each one…

1. Bass Traps

The first and most important element is bass traps.

If you can only afford 1 thing, get these.  And here’s why:

Bass traps don’t just absorb low frequencies, they absorb ALL frequencies.

So they maintain the natural frequency balance of the reflected sound.

In small rooms especially, where bass frequencies can be particularly problematic, they’re a MUST-HAVE.

To find out which ones I recommend, and get detailed instructions on how to set them up, check out this post:

• The Ultimate Guide to Bass Traps for Home Recording

2. Acoustic Panels

Commonly known as the primary weapons against poor acoustics…

The truth is, acoustic panels are mostly ineffective at absorbing the lowest bass frequencies…

And should therefore be used only AFTER bass traps, not before.

On the other hand, since bass traps are located in the corners of the room, the one thing they can’t do is kill standing waves that exist between opposite parallel walls.  

And THIS, is the main job of the acoustic panels.  (more on this later).

To find out which ones I recommend, and how to set them up, check out this post:

• The Ultimate Guide to Acoustic Foam Panels for Home Recording

3. Diffusers

The truth is, most engineers agree that diffusers are far less effective in small home studios…

Compared to the bigger rooms of pro studios.

Many home studios don’t use them at all.  

Which is actually good news if you’re on a budget, because they’re actually quite expensive.

On the other hand, some folks disagree completely, and use tons of them. So it’s totally up to you.  

But if you do choose to use them, remember to handle the absorption part FIRST…then if you want to add some later, here are 3 great options I recommend:

• Auralex Studiofoam T’Fusor – (Amazon)
• Auralex Sustain Bamboo Waveprism – (Amazon/B&H)
• Auralex Sustain Bamboo Peak Pyramid – (Amazon/B&H)

3 Great All-in-One Acoustic Treatment Packages

If you haven’t figured it out yet…buying all this stuff individually can be a HUGE hassle.

Which is why companies like Auralex and Primacoustic offer complete “room packages” to simplify the process and eliminate the guesswork.

For home studios, here are 3 great packages I recommend:

1. Primacoustic London 12

Known as one of the top brands in acoustic treatment…

Primacoustic offers a ton of great solutions for home studios…

Including their current line of room packages known as the London Series – (Amazon/B&H)

I recommend the mid-sized London 12, which as you can see in the picture, is a perfect solution for standard sized rooms.

Here’s what’s included:

• Two 24″ x 48″ x 2″ Broadband Panels
• Eight 12″ x 48″ x 2″ Columns
• Twelve 12″ x 12″ x 1″ Scatter Blocks
• various mounting hardware

Also check out the smaller London 10 – (Amazon/B&H) designed for 100 square foot rooms.

2. Auralex Roominators Pro Plus Kit

The only brand more popular and trusted than Primacoustic…

Is of course…Auralex.

And the standard full package option they recommend for project studios is…

The Auralex Roominators Pro Plus Kit – (Amazon/B&H/Thomann)

Included in this kit is:

• 36 Studiofoam 2″ Wedge Panels
• 12 LENRD Bass Trap
• 8 T’Fusor 3D Sound Diffusors
• EZ Stick Pro Adhesive Tabs for mounting

Also check out the smaller, more affordable Auralex Alpha-DST – (Amazon/B&H/Thomann) containing:

• 32 1’x1′ two fin panels
• 32 1’x1′ four fin panels
• 4 LENRD Bass Traps
• EZ Stick Pro Adhesive Tabs for mounting

3. Auralex SFS-184 SonoFlat System

For those of you who don’t care much for the “traditional” look of acoustic foam…

Auralex also offers some sleek and sexy alternatives in the Auralex Sonoflat Series.

At the top of this series, is the Auralex SFS-184 System, – (Amazon) which offers the MOST goodies of any package we’ve seen so far.

Included in this package are:

• Thirty-Two 2′ x 2′ x 2″ SonoFlat Panels
• Eight SonoCollars
• Eight 12″ x 6″ x 28″ SonoColumns
• Six Q’Fusors
• Tubetak Pro for mounting

Also check out the cheaper Auralex SFS-112 SonoFlat System – (Amazon/B&H) which includes:

• Twenty-Four 2′ x 2′ x 2″ Sonoflat Panels
• Four SonoCollars
• Four 12″ x 6″ x 28″ SonoColumns
• Tubetak Pro for Mounting

Up next…

The 3 KEY Points in Any Room

Once you’ve got your bass traps and panels, it’s time to start putting them up.

But before we do, there are 3 key areas of the room we must define:

1. Trihedral corners – shown in the diagram as the red dots
2. Dihedral corners – shown in the diagram as the blue lines
3. The Walls – shown as the white squares

Common strategy states that:

1. the trihedral corners get first priority for coverage
2. the dihedral corners get next priority
3. the walls get last priority

Because this is the order in which they’ll have the greatest impact.

At the trihedral corners, you essentially cover 3 walls at once, which is 3x as effective as covering only 1.

The dihedral corners get next priority, since they cover 2.

How to Set Up Your Acoustic Treatment Package

A typical setup consists of 4 steps:

Step 1:

Since bass traps offer the widest range of broadband absorption…

It makes sense to put them in the areas where they can have the greatest impact.

Which is why the first step in setting up your acoustic treatment is to mount a bass trap at each of the tridhedral corners.

Step 2:

The next step is to fill in the remaining corners with acoustic panels.

To cover the dihedral corners, simply bend them around the edge as shown in the picture…

And be sure to leave an air gap for maximum low-end absorption.

While I recommend using some of your acoustic panels for this purpose, don’t use them all…

Because you still need many of them for the next task…

Step 3:

Whenever two opposing walls are parallel to each other…

Sound waves have a tendency to reflect back and forth in the same spot…

Causing some frequencies to be amplified, and others to be cancelled-out.

To avoid this problem, mount your acoustic panels flat on the walls, and be sure to spread them evenly throughout the entire room.

To get maximum effectiveness from a limited number of panels, avoid placing panels on BOTH points of opposing walls…and instead, stagger their positions as shown in the above picture.

And finally…

Step 4:

The commonly accepted theory when it comes to diffusion is…

It’s far more effective in larger rooms compared to smaller rooms.

Add to that, the fact that commercially-made diffusers are expensive, and it’s no surprise that most home studios skip it entirely.

But, if you do use them…place them on the ceiling and upper portions of the wall, above head level, as shown in the diagram.

Everything below this area should be entirely absorption.

Up next…

Control Room vs Live Room Acoustic Treatment Strategies

In pro studios, where control rooms are used for mixing and live rooms are used for recording…different acoustic treatment strategies exist for each purpose.

The strategies we just covered are what you would typically use for a live room.

In the control room, where the main goal is to maximize the accuracy of your studio monitors from the seated mixing position…

A different set of strategies exist, which I reveal in this post:

• Studio Monitor Placement: Positioning Tips for Optimal Sound

If your studio (like most home studios), is one that uses one room as both the control room AND live room…

Your acoustic treatment setup will need to blend elements from both strategies into a single “hybrid” plan.

5 Cheap Acoustic Treatment Tricks for Broke Musicians

If you don’t currently have the budget for a “proper” acoustic treatment setup, here are 5 great tricks you can use for now, to significantly improve the sound of your room without spending much money:

1. Close-miking

In rooms with poor acoustics, close-miking is one technique you can use to get decent sound from a less-than-ideal situation.

Here’s how it works:

By positioning the mic as close to the instrument as you can (without ruining the tone)…

You increase the portion of direct sound from the instrument, while decreasing the portion of reflected sound from the room…thus minimizing the impact of the acoustics on the recording.

To take this concept one step further, you can also try…

2. Using dynamic mics

Since dynamic mics are typically “less-sensitive” than condenser mics…

They also tend to pick up less ambience, which is good in rooms with poor acoustics.

Which is why, in untreated rooms, you should use dynamic mics whenever possible…especially on vocals, where the difference is often enormous.

You won’t get the sparkling highs of a condenser mic, but it will still sound much better overall.

Up next…

3. Household Absorbers

While acoustic foam manufacturers would prefer you believe that theirs is the only material that works…

It simply isn’t true.

Because really, any type of soft porous material such as pillows, blankets, couches, or even clothes, can offer similar absorption.

And since you already have plenty of that stuff lying around your house, it won’t cost a dime to simply store some of it in your studio.

While it might not look as professional as “real” acoustic treatment, it does help a lot…as long as you remember to stack everything as thick as possible, so all frequencies absorb evenly.

Up next…

4. The “Mattress Vocal Booth”

Even better than pillows and blankets…

Often times, the best natural sound absorber in your house is a mattress.

Which is why the most popular DIY method of recording vocals is to prop an old mattress against your wall so its directly behind the singers back as he performs.

Remember though, that making this technique work requires effective broadband absorption.  And to do that:

1. You MUST use a heavy solid-core mattress, and NOT a light inner-spring mattress. 
2. The most sensitive side of the mic should face TOWARD the mattress, to shield it from incoming reflections.

5. Reflection Filters

If commercial acoustic foam is currently beyond your budget…

But you think mattress and blankets are a little bit too ghetto…

A great “in-between” solution many project studios use is a reflection filter.

Rather than the absorbing reflections scattered about the room, reflection filters work by absorbing them before they even enter the room…

Using a semi-circle absorption panel which mounts to your mic stand and wraps neatly around the mic.

And while they may not work quite as well as proper acoustic treatment…

• they still work decently.
• there’s virtually no set up.
• they’re about 1/10th the cost of a stand room package.

Even though they may not work as well as “proper acoustic treatment”…

By using your reflection filter in combination with the previous 4 techniques we covered, your recordings will sound 1000x better than they otherwise would in a completely bare room.

And they’re a great temporary solution until you can afford something better.  To see which ones I recommend, check out this post:

• The 6 Best Reflection Filters for Recording Vocals

Related Content:

• How to Set Up Your Recording Room
• Bass Traps
• Acoustic Panels
• How to Soundproof a Room
• Reflection Filters