You could easily get 12 in your small bed,Iv’e got 48 plants in three double rows that are 15 foot wide (third year so getting really excited)I can’t remember the total area.I’m popping up to the plot tomorrow so I will measure and let you know.
I’m sure you could get twenty in the large bed though.
If you are in the UK have a look at “A grade asparagus” based in Norfolk their crowns are amazing.
Whatever you do DON’T buy the emaciated tiny crowns,that are available at Every garden centre..