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.

28 Responses to “Homemade Reflection Filter (With Audio Examples)”

  1. Fabrizio

    Nice experiment, maybe if you try it in a really bad room the difference would be bigger, and worth it to make one. I think that some faster sounds (like clapping) would make more difference, am I right?
    From your pictures I see that the walls of your foam blocks put that way are almost parallel, isn’t that bad?
    I have the same question I read down here, if adding a heavy material in the back might help.

    Thanks a lot joe, your posts are really helpful!

  2. Jlird808

    Also…from what I’ve read, the mic shouldnt be too far back into the V of the filter. It will pick up more reflections off the foam, however slight.

    • Joe Gilder

      Yeah, that’s what I tend to hear, too. Any time you put the mic in the corner of something, there tends to be a weird buildup of some frequencies…and a kind of hollow sound.

  3. Jlird808

    U still using this? Was thinking of building one too. I got some OC 705 though…would just have to wrap it. 

    Also, wont using some 1″ plywood behind the foam soak up some of the low end u talked about? Just been learning about that recently

    • Joe Gilder

      I’m actually using a bigger “gobo” style solution now. It’s two 2′ x 4′ panels filled with OC and held together with a hinge. Does a much better job. Will write about it soon.

  4. John

    I’ve taken 3 large (30″ square, 12″ thick) “bean-bag” foam pillows and, using mike stands and clothesline clips, formed them into an artificial “corner”, with two pillows oriented vertically and the third horizontally, by placing it on top of the other two.

    However, now, I mount an AT4040 inside a small (9″ diameter, 15″ high) plastic trashcan, 1/3 the way back from the “front” (top, actually) of the trashcan, with a dual-, nylon-screen pop-filter about 3″ in front of the AT4040, flush with the rim of the trashcan. The trashcan is mounted on top of a boom mike stand with the boom arm oriented vertically. (I had hoped to use the contraption in bed–where I do most of my computer “work”, with voice-recognition software–but it’s much too heavy to allow sideways boom extension. Thus, the boom has to be oriented vertically. It would work equally well on a straight stand.)

    The can is filled (don’t pack it in too tightly) with poly-fill fiber. A cloth “cone” (a pants leg cut from some old sweatpants), secured with tape around the outside of the trashcan, projects into the trashcan and into the fiber-fill; the microphone sits on the opposite side of the “cone”, with the cloth cone between it and the poly-fill, yet still inside the can. The trashcan (with the help of the fiber-fill) forms an acoustical “shadow”–a place where the reflected sound waves are greatly attenuated, the higher the frequency the greater the attenuation. Putting the AT4040 inside the trashcan increases this “shadowing” effect. The poly-fill neutralizes the trashcan’s resonances and cuts off the AT4040’s back-lobe (at 100 Hz, it’s almost an omni; at 8 kHz, a hyper-cardioid with a distinct back-lobe).

    Subjectively, the three-plane pillow “corner” reduced overall pickup of room-resonances by 30-40 %. The trashcan shield, at least, doubles that. Standing 6″ away from the mike, 3″ away from the pop-filter, while singing along with Roger Daltry’s cover of Alce Cooper’s “No More Mr. Nice Guy” (one of my favorite warm-up-/equipment-test-tunes), through in ear monitors, I can hear my tongue clicking on the top of my mouth on the “no, no, no, no…”-s, something that does’t occur when using the AT4040 without the shield.

  5. Lew

    Can I use your vocal as a chorus in a track? Its just what I have been looking for and obviously Ill give you a credit and if things happen withthe track a songwriting credit??



  6. V

    o, and i’m recording rap vocals..maybe a different mic would benefit my situation. still i’m open for suggestions

  7. V

    what type of mic is that you have pictured? the audio sounded very good? Also, would that be good for a corner workstation area in an open livingroom?
    I’m currently using Protools7LE for pc
    I have an AKGC200B, but i’m going to possibly upgrade to the Audio Technica AT4040 or the Bluebird.
    I have a small ART tube micpre
    and a bunch of plugins (WAVES, MERCURY)
    For some reason, im having a very difficult time getting a good quality sound through my set. Maybe you could give some pointers, because i’m interested in copying your setup, i like the way your vocals sounded.
    any suggestions would be much appreciated

      • V

        to what in particular?
        i was told that the presonus tubepre with either the Audio Technica AT4040, BlueBird, RODE NTA-1orRODE NTA-2
        what are your thoughts

  8. lowlights

    Nice – I agree – on the vocal word “colors” – you pick up some room bounce, but the filter kills that – without affecting the sound in any bad way. And the filter on the silence definitely takes down the 8-10K “hiss”. Nice – such a simple solution for the little bit improvement one might need.

    Thanks for sharing this – why, I am definitely gonna slap something similar together and do some tests before dropping money on an SE Reflexion.

  9. KeyOfGrey

    Pretty cool experiment. I’d like to point out that your set up has more impact than one might think. The foam reduces some of the higher frequency noise that might otherwise get in the way of your vocals. If the low end gets through, it’s not all bad because you can just roll of the low frequencies with an EQ. So in the end, your solution might not sound like a big difference when solo’d, but will have a big impact in the mix.

    • Joe Gilder

      Good point. I threw a limiter on the master fader and squashed the life out of the samples, and there was definitely more noise. If you think about it, the 0.6 dB difference becomes more like a 3.6 dB difference when you apply 6dB of gain reduction.



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