I have owned 16 of these in total and now have 8 left. It took me a few months to work out exactly how to get these boxes to play comfortably and to the best of their abilities.
Stacked on their sides in pairs or using 4 on their sides mouth to mouth (feet to feet) is the best way to use them otherwise they bottom out and sometimes pop on lower notes. The throw and depth of 4 is very very effective and can be used for very large crowds, I have used them in large 500+ capacity venues and outside.
Using them one box a side or stacked like the rock n roll package is not very effective but can fill out the bottom end down to about 50-60hz. You won't get much lower then that in singles or stacked on top of each other.
I have tested 2 of these against 1 of my double Tp218a active boxes and these definitely get louder in pairs, the double beats them in lower frequencies but does not have the throw and clips a lot quicker. I will do a separate review on them.
These are a nightmare to move on your own, the handles are useless but if you have someone with you to lift, lift them with one hand on the wheel and one hand on the top corner. They are quite easy to throw on a van with lots of practice but moving 12 got tiring after the 4th lol. Covers and wheels are essential, paint scratches very very very easily.
Very good boxes for the money but very heavy and awkward to lift. I would always use in pairs or more, use a double 18 or single 18 active reflex box if you need single bass bins a side. Horn boxes just don't work in singles. Ideal crossover settings for these would be 38hz-80ish with a bit of eq boost around 50hz. Anything lower or higher then that will cause honking or port noise. I use these to play a variety of "Urban" music like r&b, reggae, soul, soca, house, garage and they handle it all very well.
I hope this review helps.