Increasing bass on floor standing speakers


I have some floor standing speakers that were a Visation kit from 30? years ago. 
The treble and mids are amazing but the bass is a little weak. And suggestions on increasing the bass? 
Concrete floor 
Room 3.5 x 11 meters... Speakers on the long wall. 
Rotel ra-01 amp
Project rpm 4 (I think) 
Currently listing to Stevie wonder hotter than july.
Thanks for any suggestions 
speakerboyz
Walls. Proximity to walls is the single biggest factor. Both for the speakers as well as for you. Speakers back against a wall and near the floor with you sitting near a wall, that's about as much bass as you're ever gonna get. Usually people prefer to move them around trying to get smooth and even, and for that it helps to bring things out into the room more.  

Another thing, what I described is very general. But bass isn't one thing its a range and a room isn't one thing either there's different shapes. It may be you are sitting in an area of suckout or cancellation. So try listening closer or further away if you can and see what that does.
Thanks everyone... I've got a few things to try. I noticed that the cable used to wire them was pretty thin so I'll fix this up when I check if they are in phase or not. 
Two suggestions:
1. Mount your floorstanders on isoacoustics Gaia feet. 2. Add (REL) subwoofers. 
Upgrade your speaker cables could make a big difference on bass. They did on mine.