You need to know how the listening position relates to the phase relationship of the drivers. Watch some of the GR Research YouTube videos on the subject, then find out the characteristics of the JBL's. There is likely an optimum listening height (your ears in relation to the drivers).
Speaker stand project
After cleaning out the barn workshop, I reduced my stock of lumber but saved some interesting bits. My plan is to build some speaker stands for a pair of vintage JBL L19's. Yes, I know that these aren't anything great, but it's for a third system and they have sentimental value. After some research, I concluded that I should use a taller stand than the one commonly shown in JBL photos which is about three inches off of the ground and tilted back. To raise the tweeter to listening position, I will need a stand that is approximately 27" tall. After some searching for design ideas, I am hoping to build a modified version of this:
My question is whether four feet on the ground is any different from a platform on the ground - as is used in many designs? Obviously, some of the stick or pole designs need the lateral support, but I see platforms on other designs as well. I guess that the added mass of the platform could make some difference. I will be using some fairly heavy pieces of wood including a two inch thick maple top. I will install an adjustable spike on each foot (for leveling primarily) and to get through the carpet. This will be more of a furniture building exercise than an audio upgrade, but I hope that I won't be making the sound worse by raising the speakers. Any thoughts regarding the design or the proper height for these speakers will be appreciated.