My room has "zero" slap echo. Do I need room treatments?

Slap echo is one hing and early reflections are another. You still want sound deadening at the early reflection points on the walls next to the speakers and the walls behind the speakers. Find those points using the mirror method. 

I agree, I had no echo either. I found tall silk plants/trees and some open shelving for my vinyl placed at first reflection points to bring everything into place. I have open timber running across the ceiling which is great for helping with diffusion and de fraction.

Thank you for your suggestions.  My ceiling has wood beams as well and is probably helping as you suggested and I have a tall silk plant (8') in the front wall corner.  Hope it is helping as well.  Thanks tom6897.

The left wall is all glass with full length vertical blinds.  I have put a tall backed upholstered chair at the reflection point.  Thanks mijostyn.

I am going to try some diffusion behind the speakers on the front wall.  Should they be placed in same manner as you would place absorbers?  IE where the reflection point would be.  Thanks bkeske

I have absorption panels on the rear wall directly behind the speakers, but also diffusion panels on the adjacent side walls behind the speakers as well, and also between the speakers. Also have diffusion panels on the side walls well in front of the speakers,

But, that’s in my case, with my Vandy 2CE Sigs, in my room. 2CE’s and not like normal ‘box speakers’ and the sound truly surrounds them because of how they are designed. Thus, as I say, you may need to experiment for your particular speakers and room.

Without measurements, the best advice I have for you is to listen to your speakers 2’ away from them. The difference between that and your normal seat is your room.

Best,

E