New to all of this - my first measurement

[jhuang]

I finally got REW set-up on a laptop, using a Behringer ECM8000 (didn't use Sonnie's calibration file) with a Behringer Xenyx 802. On the Xenyx, I set EQ for high, mid, and low to be zero (at the 12 o'clock position), the FX to negative infinity, and level at zero. Is this correct?

I used the RCA outs, connected to the SB Live External box (line inputs), with the outputs going to my Pioneer receiver (with MCACC turned on). I've attached both the 20-263 plot, and the all freq. Any comments? Also, any suggestions on the huge dip at around 106 Hz? The crossover is set to 80 Hz in the receiver. My speakers at Axiom M80Ti and the sub is an HSU VTF-2 set to max extension. NOTE, I did run the measurements with the output of the SB directly to my external amp (thus bypassing my AV receiver) and I see this 106 Hz vacuum as well in both L and R speaker.

Any help would be greatly appreciated!

low freq.jpg

all freq.jpg

[Snatcher]

I am a newbie just as you, but maybe I can help a bit meanwhile. I have the same mic and mixer, and I used them exactly as you describe. As far as I know, that is OK.

I believe that you will be asked to plot just the sub to check. I had a similar problem at around the same frequencies, and it was because the mains were out of phase with the sub. Anyway, I believe it is best to check the sub first and later do the integration with the mains.

[jhuang]

Excellent point. Luckily, I didn't move anything (my mic was still in exact same position), so I connected the SB directly to my sub, recalibrated the SPL meter, and took a measurement. Here it is:

sub.jpg

[Snatcher]

I had misread one part of your original post, but I believe that you need to make this measurement passing through the receiver, just in order to have the crossover settings affect the graph.

I take from your last post that you bypasses the receiver for that graph. If that is not the case, sorry for misunderstanding.

The graph does change a lot, and to my untrained eye it looks like it can be worked very nicely though.

[jhuang]

Okay, one more measurement. I don't know if this is as meaning full, since the sub is crossed out at 80 Hz (and the dip is at ~106 Hz). As a summary, here are the above graphs:

1 and 2: Output to AV, with MCACC turned on, then to external amp, then to mains + sub
3: Direct connection to sub (bypass AV)

I took the final measurement, output to AV like in 1 and 2, but I disconnected the mains, so only the sub is activated. I put all of the plots onto one graph:

total.jpg

The weirdest thing is the DIRECT TO SUB output has a very strange behavior. Note that my AV has the mains set to "small" so it shouldn't be adding significant to the <80 Hz. Plus on the AV TO SUB ONLY graph, the mains are disconnected. Note that all of the 3 curves below were taken with a new "calibrate SPL", so any difference in db between them can be due to calibration error (my RS old analog is really screwy, maybe time for a new RS SPL).

[jhuang]

Okay. Final measurements. I went ahead and hooked everything up to the AV, output to main speakers and sub. However, I disabled the MCACC (fyi, that's Pioneer's version of auto-calibration). Note, I do not have BFD yet, nor do I have any real acoustic treatment in my room. Here are the plots before and after MCACC (I trimmed the graphs to try to line up the "mean" SPL levels between the two)

compare1.jpg

compare2.jpg

[brucek]

I went ahead and hooked everything up to the AV,

The correct way to do it.

It does look like you have a dip at ~100Hz.

It would be nice to see a sub only (always through the AV - leave the EQ auto off) with no mains turned on (simply remove the speaker cables (with the power off of course).

Then a measure of the mains only with no sub turned on.

Use a horizontal axis of 20Hz to 200Hz for both.....

brucek