Photo by lrargerich

Photo by lrargerich

In the recent shoot-out I did between the Shure SM7B and SM58, I discussed some of the reasons why you would use a dynamic microphone for lead vocals as opposed to a condenser.

One of the main reasons is that dynamics tend to pick up less of your room, so if you have a noisy room or just an acoustically bad-sounding room, a dynamic microphone might allow you to still record a decent vocal.

That said, sometimes a condenser microphone simply sounds better.

The next obvious step would be to do everything you can to minimize the amount of room the microphone picks up. The first thing people usually try is to throw the vocalist and microphone into a nearby closet. Problem solved, right? No more room!

Eh…this will usually introduce more problems than solutions. One of the main problems with most home studio rooms is that they are rectangular, chock full of right angles, corners, and parallel surfaces, which cause all sorts of room nodes, standing waves, bass build-up, etc.

Putting the microphone into a smaller rectangle (i.e. a closet) only really brings the microphone closer to all those parallel surfaces and corners. You may think that all your flannel shirts and fur coats will absorb all of those issues, but just like acoustic foam, these materials won’t touch any of the low frequency problems.

While being in a closet MAY drown out some of the computer/hard drive noise, you’ll most likely end up with a boomy, lifeless vocal.

As always, give it a shot and hear for yourself. You may get the perfect vocal sound in your closet…but I doubt it.

Some Options

When it comes to do-it-yourself acoustic treatment, there is a wealth of information on the internet. I was recently perusing the studio construction and acoustics section of the Gearslutz forums, and it’s all pretty fascinating (and inexpensive, too).

In case you’re wondering, I certainly don’t have a perfect room. It’s a spare bedroom, and I tend to pick up a lot of computer, hard drive, traffic, A/C, and neighbor noise when I record.

A few weeks ago, I thought I’d try something. I’m rather familiar with Auralex’s Aural Xpanders, which are little pieces of foam designed to block out unwanted bleed from the microphone. And I’m also familiar with the SE Electronics Reflexion Filter, which is a beast of a contraption that surrounds the microphone, providing some good isolation. I’ve actually heard A/B samples of the Reflexion Filter in action, and it’s quite impressive.

However, I’d rather not spend $300 on the Reflexion Filter, at least not without attempting to remedy the situation myself first.

I turned to some leftover Auralex foam I had lying around. Last year I bought a box of the DST-114 panels to treat the area around the mix position in my studio, and I had a few pieces leftover, so I decided to make my own little reflection filter.

reflection-filter-1As you can see from the picture, the two foam pieces placed together make a “V” shape, which surrounds a microphone rather well. I just grabbed a few pull-ties and jammed ’em through the grooves and tied the foam together.

From here I just feed the foam over the mic and let it “hang” behind the microphone.

So…how well does it work?

I’ve been using these filters for several weeks, but I’ve been looking forward to actually testing them to see if they’re actually doing anything.

I recorded some samples with and without the makeshift filter. I’ll be honest, there’s not a life-changing difference between the two. However, there is a small difference.

The first two samples are of me singing a few lines. Here they are: (Right-click to download)


Obviously, neither vocal sound is all that bad. In fact, I would argue that on the quieter parts there’s pretty much no difference. However, the vocal recorded with the filter sounds a bit tighter to me on the louder parts. On the words “like” and “colors” you can definitely hear the sound my voice bouncing around the room.

While the first set of samples is a bit subtle, the next two were a bit more revealing for me. All I did was crank up the gain on the preamp and simply recorded the mic for around 15 seconds — once with the filter, once without. Here they are:

The best way to listen to these is to open them up and switch back and forth between the two while they are playing. You can do this in QuickTime by just selecting back and forth between the windows. Or you can just import them into a DAW and solo each one.

As you can hear, the filter does nothing for the low frequency noise in the room. However, it does roll off quite a bit of the high frequency noise. I measured the two waveforms and found that the recording with the filter is 0.6 dB quieter than the other.

That’s certainly not a huge difference, but once you add compression to the vocal and the entire mix, this noise will be made louder. Cutting out the high frequency “hiss” could really make a difference in the sound of a final mix.


As I recorded these samples, I was a little disappointed that the differences weren’t more obvious. But as I thought about it, it makes perfect sense. Foam doesn’t do anything to stop low frequencies. It’s a high frequency absorber.

Even though the results won’t take your breath away, I decided it would still be good to post them. After all, this is real life. Sometimes you make changes to your studio that don’t improve things all that much. Or maybe the improvement is a subtle one. Either way, until I build some really nice gobos for myself, these little foam filters will get a lot of use.