RadioShack 33-3013 and 33-3003 microphone review

The RadioShack 33-3013 is probably the least expensive microphone available in the U.S. at the moment. You can buy it for about $20 from any RadioShack store. It is a lavalier microphone and it comes complete with a tie clip, LR44 battery, cord, and an in-line power supply. On paper, it has very similar specifications to one of my favorites, the RadioShack 33-3003, but the actual performance is different. Read on if you'd like to find out exactly how different it is.

The RadioShack 33-3003 has been discontinued, but can still be found on eBay. It is my favorite low-cost microphone. I have two of these (though one seems to have gone missing) and love them. I use them in a headset configuration (see here for more information) and they are perfect for small recorders. The have a really nice, medium sensitivity, but they do not overload nearly as easily as the 33-3013. The cord is 6 m long, which completely eliminates the need for an extension cord. They seem to be better built than the 33-3013. Otherwise, they are similar. Because the microphone has been discontinued, I will limit the present discussion to the 33-013, but will include samples of the 33-3003 for comparison.

Design

The microphone is well-designed, primarily because it is complete - there's no need to buy an extra power supply or even cord. You can simply plug it into a 1/8-inch port and start recording. That's what I really like about the 33-3003, as well. The 33-3013 has a shorter cord (1.5 m), so you will need an extension cord if you need to be farther away from the recorder. This microphone should work quite well with most small digital recorder that have the 3.5 mm (1/8-inch) plug-in power input. The same applies to most consumer camcorders.

Figure 1. RadioShack 33-3013 microphone; courtesy of RadioShack.com

Headset configuration

Some small lavaliers of low to medium sensitivity are very good candidates for DIY headset mounting. I tried the same with the RadioShack 33-3013. Figure 2 shows my Hack'n'Shack headset that I made with a cheap computer headset that I had no use for. I threaded the cord through the boom and fastened the end with a little piece of gaffer tape. The headset is a bit flimsy, but perfectly useable. The microphone (and the pre-amp) is very lightweight, so wearing it is effortless. I really do wish the cord were longer. Realistically, such a short cord is only good for the recordist themselves, as they can be close enough to the recorder. You can buy an extension cord at RadioShack, but that is going to cost you at least $10.

Figure 2. RadioShack 33-3013 in a DIY headset configuration

Audio tests

I was really hoping for the same performance as the 33-3003, but even when you compare build quality, you can't help but feel suspicious. Indeed, the performance did not live up to my (yes, overly optimistic) expectations. The microphone works great as a lavalier, but it tends to overload easily when placed close to the mouth. It took me a few tires to set the levels and I was not able to avoid signal overload at least 6 dB lower than expected. That's still not bad, but you will need to be careful setting your recording levels. Please, refer to this article for more information. The other thing that wasn't as good as the 33-3003 was the low end. I found that there is a bit of a bias towards amplifying low frequencies, so the frequency response is not perhaps as flat as one would expect from a good omni-directional microphone. The reverse seemed true in the high frequencies (above 8,000 Hz), but those are typically less critical for speech analysis. This is confirmed by the manufacturer's published frequency response (Figure 3). My suspicion is that the frequency response was purposefully altered to create a better sound.

Figure 3. RadioShack 33-3013 frequency response, according to the manufacturer

Figure 4 shows a spectrogram of the phrase "czarna krowa." It shows a really good detail, but the bias in the low end is clearly visible along the bottom of the spectrogram. The FFT of the vowel /o/ looks good (Figure 5), again with just a tiny bit of low frequency bump, but not significant enough to skew standard formant analysis. DOWNLOAD ORIGINAL AUDIO FILE.

Figure 4. Spectrogram of the phrase "czarna krowa"

Figure 5. FFT of the vowel /o/ in "krowa"

Conclusion

Given the low price, one should not expect too much from this microphone. However, I have seen cheap, but good microphones before, so I was hopeful about this one, too. I was a bit disappointed, but this was precisely because my expectations were too high. As a lavalier mic, this is a decent product; as a headset mic, it takes a bit of work to keep the microphone from overloading. I would recommend the Audio-Technica ATR35S, if you need an inexpensive microphone, or look for the RadioShack 33-3003 on eBay.

RadioShack 33-3003 audio tests

Both the spectrogram (Figure 6) and FFT (Figure 7) look similar to the 33-3013. However, the spectrum is a little more neutral towards the low end, and, most importantly, it was much easier to obtain a high-level signal without clipping. DOWNLOAD ORIGINAL AUDIO

Figure 6. Spectrogram of the phrase "czarna krowa"

Figure 7. FFT of the vowel /o/ in "krowa"

Figure 8. Spectrogram of the Polish word "Bydgoszczy" showing excellent spectral detail

Figure 9. Spectrogram of the phrase "Radio Shack" showing excellent spectral detail

	Description	Quality	Comments
	RadioShack 33-3003 with Fostex FR-LE2	48,000 Hz; 24-bit; mono	In a quiet room, calibrated at -12 dBFS