What Am I Missing - Help With Sub Graph

[Kevin R. Anderson]

I've spent a lot of time reading this forum and experimenting using REW with an M-Audio MobilePre and Behringer mic. I've read Wayne's house-curve thread and used the following settings that seemed to fit my situation:

30 6.0
35 4.4
40 3.1
45 2.0
50 1.1
60 -0.1
70 -0.6
80 -0.5
90 0.0

In testing my MFW-15 sub (using the default target settings for a subwoofer), I obtained the following graph (1/12 octave smoothing) with 4 EQ settings on the BFD .

I thought I was close to being right on, but am I really out in left field?

I would appreciate any constructive criticism on my settings, house curve, cross-over, EQ settings, etc.

mfw.jpg

[Wayne A. Pflughaupt]

Welcome to the Forum, Kevin!

Your graph looks fine. What is it that makes you think something is wrong? Can't comment on your EQ settings, since we don't know what they are, or have a pre-EQ graph to look at...

Regards,
Wayne

[Kevin R. Anderson]

Hey Wayne: Thanks for your response and your great posts which make a complicated subject more understandable.

I posted my EQ'd graph on AVSForum and got comments that the graph looked as if the sound was thick and lacking in mid-bass punch and that a 15dB rise was problematic.

If I understand your posts on the house curve, I thought this is what I was shooting for. When I get the chance in the next few days, I'm going to experiment with some other curves, but I wanted to make sure I wasn't misunderstanding some basic concepts.

I attached the pre-EQ graph, with the most audibly noticeable feature being a 38Hz hump. I'm using 4 settings on the BFD and could probably get by with 3.

mfw no eq.jpg

[Wayne A. Pflughaupt]

Thanks for the kind words, Kevin.

I posted my EQ'd graph on AVSForum and got comments that the graph looked as if the sound was thick and lacking in mid-bass punch and that a 15dB rise was problematic.

If I understand your posts on the house curve, I thought this is what I was shooting for.

Yes, you're doing it correctly if you followed the Hard Knee and House Curve articles. Personally I'd try to get that 58-65 Hz range down another couple dB, but it'll also increase the 55 dB dip, so it might not be worth the fight.

I suppose one man's "punch" is another's "bloat" - to each his own - but excessive mid-bass is indeed what the hard knee approach addresses. Please feel free to try a "regular" house curve and see what works for you. Any "gospel" you see on subwoofers should be taken with a healthy skepticism - including mine. Every room and sub is different, as well as the user's personal tastes, so you should experiment for yourself. You might also want to consider Ayeronaut's curve that shelves below 30 Hz. It's easy to experiment with different house curves with the BFD's memory function.

As far as the "problematic 15dB rise," your commentator at AVS is somewhat misinformed. Apparently he was looking at the Target line between the 64 dB and 80 dB markers (your first graph). It appears that your crossover setting is 90 Hz, which the Target hits 2-3 dB above the 100 dB marker. That accounts for at least a few dB of the "15 dB rise."

With no house curve in place, there is going to be a 6 dB drop at the crossover frequency, as you can see in this picture that depicts the slope of an 80-Hz, 24 dB/octave crossover:

REW LP fliter slope.JPG

In addition, the 6 dB house curve file you loaded into REW accounts for (obviously) another 6 dB of the "15 dB rise." So, 6 dB from the crossover, 6 dB from the house curve, and 3 dB from poor chart-reading technique - that accounts for the "15 dB rise." Which of course in reality is only a 6 dB rise.

Regards,
Wayne