Which model Klipsch? Is there a missing ‘link’ between the speaker’s bass and treble sections?

I don’t know these particular speakers, but the first things that come to mind are:

1. You have them set up to be bi-amped and you need to make sure you have speakers A & B switched on. Possibly you only have speakers B on at the moment.
2. You used to have them bi-wired and now you have gone to single wire but have not re-inserted/changed the jumpers on the speaker.
3. The speakers are broke.

I would check their user manual. Do you have another pair of speakers you could try?