This is cross-posted to AV123 here: http://forum.av123.com/showthread.php?s=&threadid=8129

I got around to doing FR measurements of my sub (Hsu VTF-2) this weekend. I posted some thoughts in another thread that I will copy-paste here to keep things together.

First, I charted my sub using my RS analog SPL meter in a few situations (180 phase port A plugged, 180 phase port B plugged, 0 phase port B plugged, 0 phase port B 1' from corner, 0 phase port B 2' from corner) and then I measured it using a Behringer ECM8000 mic, M-Audio MobilePro and ETF 5.x software (0 phase port B in corner and 180 phase port B in corner).

I'll copy and paste my prior post about the impact of phase and position, but for now, here's a pic of the different measurements:



The ECM8000 line is somewhat arbitrarily placed in relation to the two RS lines - I placed it close to the other two for easiest comparison.

What do I take from this comparison? That the RS values are pretty good for general EQ work and that the corrections are probably not that critical.

For my personal use, I will probably need to do a significant wide cut centered around 30Hz and a narrow boost around 60Hz.


Quoting my earlier post in another thread:

I just did some measurements with jimsfield's 1/12 octave tones (big thanks for those) and my RadioShack SPL meter, and found a couple of interesting items.

First was the phase. I have a Hsu VTF-2 which has a 0/180 phase switch instead of a variable phase knob. I noticed that when set to 0 I had pretty seemless transition to my mains, but when set to 180, the transition turned into a massive hole (as to be expected). I didn't expect the hole to be down 20db at 100Hz (my receiver is set to an 80Hz x-over)! Make sure you all check your x-over range. The phase switch had no impact below ~63Hz in my testing.

Second was placement. I have my sub in the front left corner of the room. I tried moving it forward along the wall and found that the drop in response was more pronounced at higher frequencies (almost no effect below 40Hz). In the end, the corner was much more even than one or two feet into the room along the wall (I only charted these two additional positions).

Lastly, I tried applying the correction factors (interpolating for 1/12 octave) and I don't think I really find them that important. I'll know more once I run tests with my nicer equipment. But, now it's time for weekend chores.

Here are the two raw ETF graphs for 0 phase and 180 phase. Note that the absolute values (e.g. 90db) are not valid since this system is not calibrated, but the relative values (one point is 5db higher than another) are valid. Also note the different scales from the graph in the first post. ETF limits the options on the X axis scale and 20-200Hz is the best option.

0 Phase:



180 Phase:



It's crazy what a little phase does.