Quoted from hoby1:Does Spike use 8 ohm speakers
If you check the pinballpro website you'll see both the Spike and Sam kits use 8 ohm speakers. Installation instructions are on their site.
http://pinballpro.net/info/installation-help/
The stock #the_walking_dead_le backbox speaker is 8 ohms: https://www.pinballlife.com/stern-4-back-box-speaker.html