In my never ending quest to add some very affordable sound treatment to my project studio, I stumbled across the Auralex Aural-Xpanders spot treatment set. The set consists of four 6" trapezoidal, two 8" triangular, and one 14" butterfly foam baffles which mount directly onto your microphone or stand to provide some isolation. Additionally, six PlatFeet are included which are intended sit under a micstand to cut any low end rumble from mics susceptible to vibration. I must admit I had my doubts, I mean could something so small actually have any effect at all?
In my initial tests, I first mounted the two triangular baffles to form an "L" masking the rear and bottom of an AT2020 then tried the butterfly alone. The AT2020 is pretty sensitive and has fairly wide cardiod pattern in my opinion which makes it a tough mic to use in an untreated room. Either configuration didn't seem to do much to quite the room ambience. I was beginning to question whether the products would provide any attenuation at all.
Next, I tried the triangle baffle directly behind an APEX 210 ribbon mic which has a figure 8 polar pattern. In this application, there was significantly less ambience pickup up from the rear side of the mic. As the APEX has a fairly quick roll off off-axis, building a little shell around the mic actually minimized the room enough to be useful.
Well, as my real world results were mixed, I decided to try a semi-scientific test by mounting an SM57 with the rear of the mic pointing directly at a speaker about a foot away and placing the baffles in-between. The small trapezoidal baffles didn't seem to have any noticeable effects; however the triangular and butterfly baffles both cut the signal by about two to three decibels. While three decibels isn't going to completely eliminate any unwanted sounds, it might provide just enough attenuation to save an otherwise spoiled track. In practical usage, ambient sounds are likely to be far more subtle than this test. I imagine the further and/or quieter a sound source (or reflection) is from your mic the more effective the Xpanders will be.
The Auralex Aural-Xpanders certainly aren't a miracle cure for an untreated room. However if you already have a decent sounding room and need just a touch more isolation, these will certainly fit the bill.
Price ~$50 USD
Pros: Light weight spot acoustical treatment
Cons: Limited attenuation