Cabling Question -Only One Prong of Spade is Contacting Terminal.

I recently got new speakers, the opening on the spades on my speaker wire is too small to fit over the post on the terminal.  I can fit one prong of the spade through the hole in the middle of the post, but the second prong sits off to the side.  Tho contact is solid and is secure, but only about one-third of the spade is in contact with the speaker terminal. Will this affect sound quality?  there any reason to change out the spades to something larger or switch to banana plugs? 
Not affect sound quality if there's enough, but yes, preventing shorts is a great reason not to do this.

They do make larger spades as well as bananas.
As long as the free fork portion of the spade is sticking out to the outer side of both posts and they are tight you should be fine. You could remove the spade and use the bare wire, install a wider spade or use a spade to banana adapter. Over the years I have done all these choices at different times.
Helpful input.  That resolves the issue for me- I will likely leave it for now. I have a number of other projects that can use my attention. 
Get a small chain-saw tooth file the size of the binding post and custom fit the spade?
It is recommended that you go back in and check the tension a few times, check the tightness.

as this arrangement can loosen more easily than a best fit spade arrangement.

the vibrations and subtle motions can make it so, and will.

So check those connections again, and then do it again about a week later. Just to be sure.

Just..check the security and quality of the connectivity every now and then -- is the byword on this particular methodology of spade application.. 

Essentially, there is enough connectivity for a excellent electrical contact quality..but..not enough friction or frictive area in contact, to ensure a stable connection in the physical realm, in comparison to a properly fit spade.
I have used that method previously, and whatever degradation in sound, it was so slight as to be negligible, if audible. 

Watch out how vigorously you cinch down on the spade, because you could bend/compromise it. 
Actually I ran my Magnepan speakers just like that for years....
Dont worry, just enjoy the music!