Re: Question about headroom with dj mixers
I'm worried that you aren't powering the 728 subs properly. The MPA750 only shows a 4ohm bridge rating at 1khz in the manual, producing the 2000watts as you state. Given the 728 can handle program power at 3200watts, peaks of 6400watts, I'm thinking you're not getting everything out of them. The amps also have thermally based power limiting and muting if the temps get high enough inside.
That said, a 418 sub is +3db more sensitive than a 728. It doesn't go down as low of course, but four of them may actually sound louder than two underpowered 728's.
Double check your gain structure.
Check your Driverack settings and amp settings. The 728 subs have a -3db cutoff that's 7hz lower than the 418 subs, 33hz, which could be sucking the amps dry, and if you're running a high pass filter in the Driverack above that point, you're losing out on their performance advantages as well as underpowering them.
Best regards,
John
