Stereo recording on smartphones based on lavalier microphones
To be honest, using lavalier microphones for videos is not particularly innovative. My aim in this project was to achieve maximum sound quality for smartphones with a minimum of financial effort. At the same time, the rigs needed to be as pragmatic as possible. The solution: shorter cable lengths than usual and strange suspensions for the microphones.
Here I use microphone capsules that are in the sweet spot of price and performance, the AOM-5024L-HD-R from PUI Audio. They are very low-noise and, unlike the frequency curve below, they have the ability to record far into the ultrasonic range.
Rode has kindly solved the problem of poor preamps in smartphones with the AI-Micro sound interface. It's tiny, the costs are manageable and it works great. I use the Blackmagic Camera app. The app supports the Rode AI-Micro perfectly.
Please contact me if you are interested in custom cable lengths or angled plugs, for example.
Specifications (capsule)
| Directional characteristic: | Omni-directional |
| Sensitivity: | -24 dB ± 3 dB at 1 kHz |
| Signal-to-noise ratio (SNR): | 80 dB at 1 kHz |
| Rated voltage: | 3 V |
| Operating voltage range: | 1 ~ 10 V |
| Current consumption: | 500 μA |
| Max input sound pressure level (SPL): | 110 dB |
Main components
| Capsule: | AOM-5024L-HD-R |
| Cable: | 2697 Mogami miniature microphone cable |
| Plug: | Rean NYS 231 BG |
Typical frequency response
EQ settings to compensate for the drop in high frequencies (to use with any parametrical EQ)
| Frequency | Gain | Q factor |
|---|---|---|
| 3,000 Hz | -1 dB | 0.5 |
| 12,000 Hz | -1.5 dB | 0.2 |
| 16,000 Hz | 15 dB | 3 |
I really recommend using the EQ settings. The high frequency roll-off around 18,000 Hz affects sibilance when recording vocals. For my settings, I not only used the frequency curve, but also a Rode NT5 with the highly regarded NT45-O omnidirectional capsule as a sound reference.