Works fine with 12" and 15" speakers though i think if you really want to push 15" speakers to the limit you might need crown xls 2000 for the job. I currently use the amplifier to push two 15" sub-woofers 200 watt RMS through the 50 hz crossover and is doing a really nice job. The amplifier stays cool most of the time and variable speed fan is a plus I recommend this amp. Did i mention it is light as a feather? You can easily move it around with practically no effort.