The following is email I sent to two friends verbatim (
Here is Youthman using REW and the umik-1 mic. He'll mention a calibration file and those are made by minidsp (make of umik-1). These have calibration files, but they are made for a batch of microphones and not as precise. Buy from Crossspectrum and you get a mic with precise measurement file made for your microphone which is very important especially when measuring bass 20hz and below.
Kind of a fail on his part not mentioning how far microphone was from subs, but he's probably just comparing the two subs in his listening position.
He's measuring these to the point where they are reaching compression where the amps and drivers are running out of steam. I wouldn't do this with normal speakers as they don't have the protection circuitry of subwoofers.
Monolith 15 vs the SVS PB3000 - the SVS is flatter, but the Monolith 15 puts out more bass especially in the low, low frequencies below 20 hz. In short the Monolith 15 crushes the SVS. One can use a minidsp to tame the upper bass if that bothers you and make the Monolith smoother than the SVS!
Above is the minidsp. The other side of the unit are the 4 RCA outputs that go to your subwoofers (you could also do two subs and two speakers). So if you have stereo bass you could take that to two subs for each channel, but normally you just take one of the two rca inputs to up to 4 subwoofer outputs. The unit is controlled by a USB connection from a laptop typically. You use the umik setup like youthman to measure and the test signals may be sent by either hdmi or the USB connection which in our case just drives the subwoofers (kind of like a usb dac of sorts and the HD unit does have an internal USB dac).
Once you have the USB connection running its very easy to use minidsp to adjust your subwoofer settings manually:
PEQ is parametric equalizer and we are on the outputs tab which kind of correlates with those 4 rca outputs.
Above is the inputs tab which is pretty simple and the matrix for routing which tells which input to go to which output(s).
Here is the basic view of parametric equalizer below.
The curve is the net response of the 12 parametric settings and the box below is for the 2nd one showing 3 db of gain at 1000hz with a very, very broad Q. With the Q set to high you can make a spike or steep dip which an old school equalizer could never do.
This is just the basic control and there is much, much more under advanced for those who want to Dr. Spock crazy doing a full range speakers and cleaning up its response with digital signal processing.
Again I like the HD unit because it takes the analog bass coming from your receiver back to a 24 bit digital signal rather than 16 bit. Despite AVSforum types recommending the cheaper one and the balanced unit they use 16 bit bass and think you're taking a quality hit doing that (taking your bass from truehd quality to DD+😮)