Revdoc

That's a good idea. I done tons of dual 12 ported systems, so I've been changing it up with the 18 recently. Last setup was an old Obsidian Audio 18 in the same 4.5 cubes, a little less port area and only 1200 watts. It worked really well, even though the box and port were on the small side. But, with 2 M12s I could use twice the power and make up for the small surface area loss vs. an 18. It will just be way more expensive lol.

Looking for opinions on a 15" mega platform (X or M series) Sundown sub vs. an 18" "normal" sub like the U series. I have about 4.5 cubic feet net to work with, about 64 square inches of port area, and 2800 watts RMS. I would love to run a mega platform 18", but they require about 7 cubes and 100+ inches of port area. Is the extra excursion of the mega 15" enough to make up for the cone area disadvantage vs. an 18"? Modeling them in WinISD, the mega 15" is louder from 29 hz to 36 hz, and the 18" is louder everywhere else. I know that's not always accurate in real life. Does anyone have experience going from a larger sub to a smaller sub with more throw and finding the smaller sub is actually louder? Also open to suggestions on another 15" or 18" sub that would work better with this particular box/port/power setup. I have had several Sundown subs in the past and liked them, but I'm not dead-set on them.

Hi, I am having trouble finding the Fc of a sealed enclosure using the IM-SG. I have followed the instructions in the manual: connect the leads to the speakers, turn on unit, start at lowest frequency and increase until you find peak impedance. The problem is it tells me peak impedance is 8.4 ohms at 30.X hz, fluctuates around 30.1-30.3. It drops to 5-6 ohms as you keep increasing frequency, then goes up to 7.6-7.7 at around 65 hz. The setup is two Elemental Design's EHQS 12s in a truck box, less than 2.0 cubes sealed. These subs never had much output below about 50-60 hz, in fact they are inaudible using the IM-SG at the 30-40 hz range. I am more curious than anything, am I seeing a second resonance a full octave below the "real" Fc, and that's what the IM-SG is reading at 30 hz? Or is it possible for the Fc of a box to be much much lower than the usable output bandwidth?