Bi amping question


Hi there,

I have some no-name old speakers which should support bi amping, on the back there is this
 type of terminal https://www.parts-express.com/parts-express-bi-amp-speaker-terminal-cup-gold-banana-binding-post--260-281ost--260-281
When I remove those connections between bottom and top posts and plug amplifier to bottom posts, only bass is playing. Which is good I suppose. 
But here is the problem, when I plug amp to top posts, speakers play fullrange ?? Shouldn't only mids and highs be playing ?

I assume it is not safe to bi-amp them right now.
What do you think ?

Thanks

peterb999
Use a VOM to check the resistance between the two sets of posts.  If they aren't isolated from each other you don't want to try biamping as the two amps will interact.
Post removed 
For future reference, it was possible to biamp these speakers. Posts are wired so that the hidden speaker is connected to one binding post and rest of speakers to second binding post.
So basically williewonka was right.
Thanks all