Once you've imported your podcast to Omny Studio, you can easily migrate to Omny Studio without losing your existing subscribers. All you need to do is tell Apple Podcasts and the other podcast directories and apps to pull from your new RSS feeds. This is done by applying a re-direct from your old feed to your new feed.
To move from Podbean:
1. Log into your Podbean account
2. On the same browser, go to http://www.podbean.com/podcast-new-feed-url. If you’ve got multiple channels, you may select one from the list.
3. Copy and paste your Omny RSS feed into the “New Feed URL” text box
4. Click "Save".
Podbean will now redirect your feed to Omny Studio.
Note: Although iTunes will normally pick up on changes within a few days, you should leave the old feed in place for a few weeks to ensure all subscribers are moved across.