Raid5 with 2 bad drives

Hi,

I have a raid5 out of 4 drives where 2 drives failed and were
removed.  Since it happened during backup I would very much like to
reactivate the array to rescue as much data as there are intact.

When I try to assemble the array with mdadm it tells me that there are
not enough devices.  Is there a way to convince mdadm to use the
faulty drive to get a working array?

Matthias