Wiki lists eight specters, although it's fair to wish for more.
Really not trying to sound rude and come off as an elitist prick, I love you guys, but I wish some more time was spent researching any questions you guys had about the trilogy. Parts such as the long 1 minute segment of Shipwreck doubleguessing saving Kaiden's survival for males, confusion about the origin of the Collectors, or questioning how the Alliance secured the Cerebus Normandy (It's explained through consoles EDI guides you through) made me facepalm a little bit... While I'm sure most wouldn't care about it, for the most part it would make folks like me get anal about the facts and it just adds to the confusion.
I still liked it and a lot of my complaints may be me expecting too much, especially when you all have more pressing matters than to discuss lore for a fictional game. But I hope future discussions about the plots of different games would be slightly more prepared and researched beforehand instead of acting confused and wasting time during the recording.
Once again, sorry if I'm coming off rude, keep up the good work and thanks for the early podcast.