This is my graph:
Did I do everything right?
Are you sure you posted the right graphs? There’s virtually no difference between your “before” and “after” graphs. Your “before” graph, if it is the right one, doesn’t need any equalization at all. I don’t see anything at 1 kHz that needed adjustment, and your “before” and “after” graphs show no noticeable change after EQ.
Feel free to ignore the advice about not using any boosted EQ filters. At least as far as subwoofers are concerned, it’s a myth that just won’t die.
The situation is that you had a peak at 45 Hz that needed to be tamed. However, your subwoofer calibration (i.e. its level relevant to the main speakers) was based on that peak. Once you eliminate the peak with equalization, you will find that the sub’s level is now too low, and you have to increase it to compensate for the equalization. Well – say “goodbye” to any headroom you thought you “saved” by using only cutting filters. Gain is gain as far as the signal that passes to the amplifier is concerned. It doesn’t matter if it comes from EQ filters or the sub’s level control.
What’s apparently escaped some folks is the electrical response of the equalizer as filters are added. Let’s take your case for example, with the 45 Hz peak. If you had used a bunch of filters to boost everything above and below 45 Hz up to the level of the peak, the electrical response of the equalizer, passed to the sub’s amp, would look something like this:
However, if you had merely used a single filter to cut the peak, then re-adjusted the sub’s output to compensate, the electrical response seen by the amplifier would look like this:
For all practical purposes, what is the difference between the two? Nothing, really: In both cases, the signal passing to the amp has a big hole where 45 Hz “used” to be, and is relatively flat on either side of it (save for the natural roll-out of the filters in the first picture).
And - it should be a no-brainer that multiple cutting filters leave you with peaks between the filters!
So at the end of the day, cut-only filters accomplish nothing as far as “headroom saving” is concerned. The simple truth is, virtually any equalization taxes amplifier (and driver) headroom, so you have to have enough to spare going in.
That said, I agree with Secret Squirrel about boosting down low in the 22-28 Hz range in your case. As I noted, in order to effectively EQ you have to have a capable sub to start with. Poor extension is typically a sign of a lower-performance subwoofer, or perhaps one that’s trying to fill a room that’s way too large for it. Either way, you’re most likely going to overdrive it if you equalize, and for sure by trying to force low freq extension via EQ. The exception would be if you typically run the system at low volume levels.
Wayne A. Pflughaupt
No, I was merely making a point that there really isn’t any functional difference between EQ boosting vs. cutting, for the benefit of the people who think EQ should always be cut-only. I have no idea how your particular sub should have been equalized, since you didn’t give us a sub-specific graph.
My goof, I just noticed that you have your graphs generated with a huge 220 dB scale. That tends to make all graph traces look fairly flat. We’d have a better idea of what you had accomplished before and after EQ with a graph that’s scaled for something like 60 dB. And there's no reason to scale beyond ~15 Hz, unless you have a sub that digs lower than that.
Wayne A. Pflughaupt