this doc is correct, but i noticed that in the blockbundle that we default the document and admin classes to null in the config and only provide defaults in the Resources/config/admin.xml classes. when using phpcr and sonata admin, this comes down to the same. when not using that, the defaults might be wrong. imho the right place to put the defaults in this bundle would be persistence-phpcr.xml. then we can say default null, but if phpcr is enabled defaults to the phpcr Media class. wdyt?