Creating an Audio Recording with my iPhone

I would like to create an audio recording, of a speech, with my iPhone and then convert it into an MP3 file that I can then place on my website. I have done a test recording, the conversion (it recorded as an MP4), and I have gotten it onto the website. The problem is, that I have to turn the speakers on my computer up really high to hear the end product. I am using the standard Voice Memo app that came with my phone and I am wondering if an app from the App Store would be better?? Or is there a cable that I can purchase that will connect into my phone that I can then plug into the sound board at the facility where the speech is taking place? It's a good (if old) system, but I don't know if getting a cable is an option. I see that there are a number of microphones that are compatible with smartphones, but I am not experienced enough with anything like that to know if something is quality or not. Does anyone have any suggestions or guidance?