These are incredible speakers that come out a monstrous power stroke using a crossover cut to 200 or 250 Hz mine are equipped with RCF L18S800
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amps monsters 800W parts to which it does not last long these HOLDS boxes have a very long range because the inverted flag sysem provides this feature. I highly recommend it although the weight and size are not his main asset (+-85kg, height 1.20m X 60 X 65) are for me the most subwoofers performance (in return) with its most powerful if they are fitted with good presenters!
Attention the price is not for nothing because the original boxes are very rare!