This amp has a high pass filter. it goes...Flat..30hz...40hz..50hz. i have it on flat.A high pass filter would be a good thing when your using a single LMS Ultra with a big amp and adding boost down low that sealed enclosures need.
Radio Shack used to carry a SPL meter for around $35 but you would have to check and see if it's still available. Most receiver calibrations don't do a great job on the sub channel so that is why it's good to have a SPL meter to double check.
I will check on the spl meter