Increasing bass on floor standing speakers

If the aforementioned suggestions do not yield the results needed, add a subwoofer. I recently ran into a similar issue. Found a little subwoofer at the thrift store and added it. Big improvement. Found a bigger better subwoofer on c.l. for a song. Daisy chained it together and it sounds much better. $60 and a couple sets of interconnects that were boxed up and problem resolved. Good luck!

Does tilting the speakers help improves bass?

Do you have another music source to try, aside from the TT?

It could be the TT/cartridge setup.

Also, what cartridge?

I asume that you meant Visaton and if so see if anything looks similar here in order to let us know what general type of speaker you have.

https://impactaudio.co.uk/collections/visaton-loudspeaker-kits-accessories#.VdoIMZdU4Q0

DeKay

These look the closest however there is a slit in the bottom at the front. https://impactaudio.co.uk/collections/visaton-loudspeaker-kits-accessories/products/visaton-vib-2000...
I have the ortofon 2m red cartridge (new). 
I also have cd player (nad) and a computer attached. 
I'll try moving the speakers but it's not a practical solution unfortunately and I'll do a test with tilting them. The bass is also light with the cd player. 

Don't know if it's been mentioned, but you could try placing them on soft footers (I usually recommend first trying something from around the house like cutting up an old mouse pad/rubber mat, et cetera).

Does the Rotel's LF boost (6dB @ 100Hz) help?

As far as moving the speakers goes sometimes just a few inches will make a difference.

DeKay