acoustic treatment

A Poor Man’s Vocal Booth?

by Paul Strikwerda in Articles, Studio 13 Comments

Sometimes I come across a certain product and wonder:

It looks promising, but is it any good?

The CAD Audio Acousti-Shield 32 is one of those things.

Designed to “substantially reduce unwanted reflections, echo flutter and environmental unwanted acoustic interference,” does it deliver as promised?

At about $85, could it be the poor man’s vocal booth, or is it a waste of space, and money?

SOUNDPROOFING

Before I tell you what I think, let’s briefly discuss the whole concept of soundproofing and room treatment. As I wrote in my booklet Building a Vocal Booth on a Budget:

“In this noisy world, soundproofing has become big business. I just Googled the word and got almost two million results. Buyer beware, because the same search will take you into the realm of grotesque claims and pseudo-scientific truths:

“These Soundproof windows will totally eliminate your noise problems.”

“This soundproof foam absorbs up to 66% of sound waves.”

“Our soundproof curtains offer the highest STC performance.”

Do the makers of these products assume we’re that stupid? Think about it for a moment. What does “soundproof” really mean? Most dictionaries describe it as:

impervious to, or not penetrable by sound

Going by the aforementioned claims one could argue that the minds of the makers of these products seem impervious to, or not penetrable by logic. Then again, advertising is all about making noise and not about offering sound proof.”

Gluing some acoustic panels to your wall or on to a “shield” will do nothing to block outside noise from coming in. Auralex foam and its many clones will change the characteristic of the sound inside your recording space, diminishing reflection and reverberation. It absorbs the sound but it does not reduce it.

Yet, CAD claims that their shield can substantially reduce “environmental unwanted acoustic interference.” What does that mean? Would this shield be able to diminish ambient noise? Why not find out? For the test, I purposely chose one of the worst acoustic locations in my house: my basement.

TESTING

Let’s say you want to use your laptop for a quick recording and you place your microphone in the same room. Before you know it, the computer fan kicks in and starts making noise. Could CAD’s Acousti-Shield magically neutralize the noise? 

I’ll let you listen to the same script twice. You might want to put your headphones on. First you’ll hear my voice without the shield in place. The second time I read the script, the Acousti-Shield cradles the microphone. Just notice if this device is able to get rid of the noise the laptop fan makes.

 

That’s pretty clear, isn’t it? It confirmed my suspicion. The shield does very little to keep unwanted noise out of the recording. As expected, this thing is no substitute for a properly isolated room. But will it deliver on the second promise? Could it make a room sound more dry? 

Before I play the second soundbite, you should know that I recorded the audio with an AKG C 3000 B microphone, plugged into a Grace Design m101 preamplifier. The 16 bit, 48,000 Hz WAVE recording was converted to MP3 format for this blog.

For the next track I removed the laptop from the room. Once again, you’ll first hear me without the shield. Then I’ll read the same text with the Acousti-Shield 32 in place.

 

Did you hear a significant difference? A difference worth over one hundred dollars? To be honest with you, I was disappointed. The room didn’t sound dry to me at all. How could a company with such a good reputation bring such a poor product to market? It just didn’t make sense.

WRONG APPROACH 

The next day I woke up with an idea. What if the product wasn’t the problem? Perhaps I was not using it properly.

I went on a few online forums to find out what others thought of the Acousti-Shield, and I found my answer. The recordings you just heard were made at 9 inches from the microphone. What would happen if I would come closer? 

Once again you’ll hear me read the script twice. First I’ll read it at 5 inches from the mic. Then I’ll add the shield, and keep the same distance.

 

Now, this is more like it! Distance makes a huge difference.

Thanks to a clever design, you can also move the microphone closer or further away from the 53mm high density micro cell foam. This obviously changes the acoustic result.

The question remains, would I recommend using such a shield for voice-over recordings? Let’s first look at the positives.

PROS and CONS

The Acousti-Shield 32 is well-made and easy to assemble. For its size it is very light, and unless you have a cheap mic stand on which to mount it, it won’t tip over. Compared to a product like Harlan Hogan’s Porta-Booth Plus ($189), it is affordable. As long as you stay close to the mic, it manages to tame unwanted reflections.

Here’s what I like less. CAD’s Acousti-Shield is not a unique product. sE Electronics was one of the first companies to come out with such a solution. They called it the Reflexion Filter X. Although I haven’t tested it, it looks very similar.

Unlike Harlan’s porta-booths, the CAD shield isn’t very compact. It’s meant for the studio, not for the road. Even though the shield accommodates a variety of microphones, a popular voice-over shotgun such as the Sennheiser MKH 416 does not fit.

Here’s the big one: where to put the voice-over script? 

I’m usually reading my copy from the monitor in front of me. The CAD shield would block my field of vision. Even if I were to read it from a tablet or smart phone, there is no place to put them as long as the shield is mounted on a mic stand.

In the end I came up with a simple solution. I put the shield on a flat surface that was resting on an old loudspeaker stand. With the microphone on a table stand, there was room for my Nook or iPhone. 

EXPECTATIONS

So, is this shield a good investment?

In the end it’s all about expectations. If you get the Acousti-Shield 32 because you need a portable studio, you’re not going to be happy. If you need something to keep ambient noise out of your recordings, this is useless. 

However, if you cannot acoustically treat the room you’re in, and you’d like your recordings to sound more dry, this is an affordable solution, as long as you know how to use it. 

Paul Strikwerda ©nethervoice

PS CAD Audio kindly donated an evaluation model to the author of this blog. Though very much appreciated, this did not influence his opinion.

PS Read more on taming unwanted reflections in “Get the boom out of the room.”


Get the boom out of the room

by Paul Strikwerda in Articles, Studio 21 Comments

When I decided to become a full-time voice-over artist, I made myself a promise.

I would never lose an audition because of poor audio quality.

They might not like my voice. They might not like my read, but I would not let them ditch me because I wasn’t able to deliver broadcast-ready audio. In order to get there, I needed two things:

1. A dedicated, isolated and treated recording space

2. Quality equipment 

I purposely put them in that order. You can place the best equipment in a poorly isolated and barely treated room, and you’re still going to sound like an amateur at the kitchen table. I’d rather take an affordable microphone and preamp into a (semi)-professional booth, because the end result will be much better.

So, if you’re wondering where to spend your money, buy a Studiobricks cabin, or build your own space like I did. Then we’ll talk about getting that coveted Neumann U87 Ai, okay?

I still remember the day my 7′ by 7′ recording space was finally ready. The floating studio walls consisted of multiple layers. Auralex® Mineral Fiber and Green Glue were sandwiched between several sheets of 5/8″ drywall. All the seams were caulked with SilenSeal.

Outside noise was kept at bay, but inside, the space sounded like this:

 

CHAMBER OF HORRORS

Unknowingly, I had created an echo chamber! It was an ugly beast, waiting to be tamed. Especially in small spaces with parallel walls like mine, flutter echoes can be a big problem.

The best way to kill those echoes, is to put foam or other absorbing materials on the side walls. As a rule of thumb, the smaller the space, the more acoustical treatment you’ll need. Thankfully, I had a whole bunch of Auralex® Studiofoam Wedgies left over from my previous space.

I covered parts of the wall with SoundTrax™ from NextAcoustics™ and I added four CornerBlox™ bass traps, also from NextAcoustics™. The SoundTrax™ took care of the mid- and high frequency reflections. The bass traps absorbed the lower frequencies.

If you’ve ever seen pictures of my studio, you probably know that it’s also my office. My Mac Mini, Grace Design preamp and A/D converter sit right next to me in a small cabinet. Behind me are two bookcases, and I’ve lined the backs of those cases with Sonex Mini acoustical Panels.

A DIY REFLECTION SCREEN

In spite of those panels, I felt I was still getting too much reflection from the back. I tried to remedy that by taking a room divider and placing it behind my chair. I then took an old duvet cover, a few blankets and a sleeping bag, and hung them over the divider for absorption, creating a rear reflection screen. It wasn’t pretty, but it did the trick. The boom was out of the room!

Unfortunately, my improvised contraption was heavy and unstable. It also had a life of its own. I can’t tell you how many times it decided to fall down on me, usually in the middle of a recording. Two months ago, I had had it with this thing and I started looking for a replacement.

My search lead me to GIK Acoustics, a company that is selling in the U.S. as well as in Europe. They make a wide range of high-quality acoustic panels, bass traps and diffusors.

I especially like the fact that GIK uses ECOSE® Technology in their products, a formaldehyde-free binder, based on renewable materials instead of petroleum-based chemicals. It’s used in wood based panels and glass, rock and mineral wool.

GIK makes a versatile screen panel (32″W x 72″H x 3″ thick) that seemed ideal for my booth. Audio engineers would call it a Gobo. That’s slang for a portable acoustic isolation panel. Some people believe the word “Gobo” comes from “go between.”

Being the gearhead I am, I enjoy watching these types of videos. But when I watch something that’s put together by a manufacturer, the skeptic in me always wonders: does the product actually live up to the hype? I’ll let you be the judge, because I ordered a Gobo!

First, let’s listen to something I recorded in my booth without the GIK screen panel. You might want to use your headphones for this. 

 

As you can hear, compared to the first sample, room treatment makes a huge difference. However, for me the sound wasn’t quite dry enough. You can hear a bit of reverb at the end of each sentence.  

Once the GIK panel came in, I made two modifications. I added wheels so I could easily roll the panel into position, and I added handles. That way, I wouldn’t have to touch the coffee-colored fabric while moving the panel.

Here’s me reading the same lines from my booklet “Building a Vocal Booth on a Budget,” which is available in my store. This time, the Gobo is in place. By the way, both samples were recorded in WAV-format and converted to MP3.

 

Having used the screen panel for a few weeks now, I can confirm that it absolutely delivers as promised. It’s well-made, easy to position and it comes in many colors.

REVERB ON THE ROAD 

Even though this screen panel is portable, it’s great for a studio but too big for road trips. So, what do you do when you’re fighting flutter echoes in a hotel room? Well, there’s a solution that fits into your computer. It’s a De-Verb plug-in made by SPL, which stands for Sound Performance Lab. It’s a German company.

Originally developed to shorten the sustain period for drums and guitars, I’ve found that it also works well in the vocal booth, as long as you use it wisely. Once you’ve recorded your audio, you simply select the De-Verb plug-in from the effects list. This what you’ll see:

Screen Shot 2013-04-24 at 8.22.34 PM

The left button controls the level of reverb reduction and the right one the output gain. Both can be operated with the mouse wheel. When diminishing the reverb, you also diminish the output a little bit, and that’s why it’s good to turn up the gain slightly.

Now, don’t expect this plug-in to “fix” the first bit of audio you listened to (that’s the sample I recorded before I added any treatment to my booth). It’s by no means a substitute for acoustic panels or foam. However, if you’re recording in a less than ideal setting or you like your audio “extra dry,” this will definitely add the finishing touch.

Here’s the sample I recorded without the screen panel in my studio. This time, I added a bit of De-Verb. Once again, I recommend you listen with your headphones on. You might want to start by listening to the first sample, followed by this one. That will give you a nice contrast. 

 

Perhaps you find the difference quite subtle. To me, it’s just one of those small changes that, when you add it all up, can set you apart and take your product to the next level.

But how do you know that these changes really matter? Couldn’t it just be between the ears?  

Well, in our profession everything is pretty much between the ears, isn’t it?

You’ll know you’re on the right track when nobody comments on your audio improvements, because they could not be picked up.

It comes down to this.

Bad audio is an obvious earsore.

Quality audio is blissfully inconspicuous.

Paul Strikwerda ©nethervoice