I only have a vintage ipad 3, and I use HD558s, so my impressions might be a little whacked. Plus, I'm in a quiet room. (the Sennheisers are open back.)
But, they'll sound loud with the volume turned up to 70-80%. They won't sound amazing. They won't sound like anything special They won't sound ultra deep.
In this respect, better than Grado SR-80s, which need a lot of power for the deep stuff, and sound mediocre on my ipad. But not really anything to get excited about, unless you have some sort of amp (and my only amp is non portable, so I can't help you there).