I use this eggcrate to tighten up the vocal resolution while it also allows a warmer midbass presence as it still leaks like a sieve albeit diffused. This renders a cleaner image without a boxy sound because nothing resonates, while eliminating much of the image robbing backwave.
This allows free air breathing unlike the comforter tweak which changes the dynamic speaker Qts & makes it dull. It tights the midrange far better than the eggcrate on the rear wall tweak which still makes an image which lacks focus.
Upon experimentation with eggcrate foam to me the optimal distance to mount the eggcrate was fairly adequate anywhere between the back of the speaker & the rear wall. Then, that's when I noticed it wasn't the only distance that bothered me. It was also the dispersed back waves that bypassed this acoustic treatment as they traveled sideways that rendered an artificially enhanced staging whose image wasn’t distinct that bugged the hell out of me.
Thus, I took a couple PartsExpress charcoal gray 2˝"×24"×36" have the longer 3' section of eggcrate bent into an arc from one side to the other & stacked them to cover a 4' length over the driver section which seemed adequate. I originally duct taped them into position & still recommend this for those experimenting with this sound as a completely reversible treatment
I eventually the poor aesthetics provoked me to find a better solution. So, I took some 1˝"x1˝" wooden L-channels from Home Depot & mounted the on the back like this top view
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I then bent the 2½" charcoal-colored eggcrate foam around the back to be supported by the channels. I then got some black string to further support the bent foam rubber by sewing them to "L"channels.