They certainly can be played directly on the floor, however I've always favored a lift of a few inches. Currently I play a 60s Rogers 18, a Remo Master Edge 18, and an 80s Tama Superstar 18.

Agree- without a riser my beater was too high and 'felt off' to play- a riser (to me) is the best way to go with an 18- allowing for better beater placement.

I use a Gibraltar riser on both front and rear hoop of a converted Rogers floor tom. Takes some of the pressure off the spurs as well.

I have played an 18" bass drum on my home made jazz kit for 40+ years and never used a riser. I recommend using a bass drum pedal that has easy to adjust beater height and footboard angle. My current favorite pedal is the new Tama Classic model that sells for around $100. I do understand about having the front of the bass drum off of the floor an inch or two. If you can't do that with your spurs, then get one the old school anchors. My bass drum is a converted Yamaha floor tom from the 1980's with Stern brand calf heads and no muffling. Good luck.

Never a riser for me with an 18" in jazz settings. The fact that the beater hits high on the drum (and the tuning) is part of the allure for a bop sound. If you are trying to use it for a rock sound, perhaps the riser will help. I never needed nor wanted that sound from an 18. I have other drums for that!

Mike B