Fixing Low or Distorted Audio with Podcast

We use Garageband to record audio for our podcast. I use a Wordpress site to create new podcast posts. We're having problems with the audio sounding too low or sounding distorted when someone tries to listen to our podcast with their phone--but only if they are not using earbuds. If someone plugs in earbuds, it sounds fine. If I play the podcast on my laptop with iTunes it sounds fine with or without earbuds. The problem only occurs with a phone (iPhone or Android) and no earbuds.

We started having the problem after we installed a new sound board, so it's related to that, but I don't know what might be happening to cause this issue.

Any ideas what might be causing the problem?