In the last post, I purported to show how removing most of the boost I had given the Acoustats a few years ago, +3dB and 1/3 octave at 1013 and 853 Hz, fixed the balance problem between new and old speakers. It seems like the newer speaker doesn't need that boost, perhaps because of tighter diaphragm. My initial approach was to cut those two boosts by 1-2dB to +1.5dB at 1013 and +2 at 853. But there was still a troubling difference around 500Hz, the newer speaker having a suck out at that point. At first I thought it was because the 853 Hz boost wasn't wide enough.
Fixing that was very problematical. Boosting 500 Hz, with +3dB in a 1/6 octave GEQ boost, produces a peak around 600Hz that's even more alarming than the depression it replaced.
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So the issue is we need to push 500 Hz up, but 600 Hz down. It looked to me like the down part was actually the most important, and I found a 1/6 octave cut at 563 Hz worked pretty well. After doing that, the peak seemed to move up to 800 Hz so it was clear I needed to remove any boosting from 853 Hz at all, so that as of January 13 at 4am the newer speaker EQ now looks like this:
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Which measures (with the iPhone 8s held about 1 foot from the back of the chair, something I'm now trying to be more consistent with)
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| New Left 2+2 with EQ updates above |
I'd still be interested in pushing down the region from about 600 to 800 Hz slightly, I don't believe that should be louder than 1kHz. And possibly broadening the EQ right around 1kHz which is slightly depressed. But I've already gone beyond the level of fine tuning which should be done with RTA. I need to switch over to doing oscillator sweeps so I nail the critical frequencies where change is actually needed. RTA is simply too approximate, you can't really see what is going on, though it's useful for getting the big picture.
But I think this is already pretty darn good and far better matching the right speaker than when I started.
I also took a brief look at the funky dips at 40 and 70 Hz. Those are because I have been using the "Background listening" Bass (subwoofer) EQ for these measurements which has a suck-out at the listening position but sounds better (less boomy) everywhere else in the house.
Measurements roughly confirmed this. I decided for now upon two different places to measure the background EQ, the doorway to the kitchen (which is about equivalent to the couch) and the kitchen table.
At the doorway, the response rises with decreasing frequency below 180 Hz, peaking around 38 Hz. I've needed to roll off 20 Hz in the background response to prevent the whole house mode that occurs around 20 Hz, which I can feel, for example, at the sliding glass door (which perhaps I should also measure...).
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| Kitchen Doorway with pre-existing 25-31.5 Hz boost |
This is pleasant actually, gives a kind of loudness compensation for background listening, and requires little change from the 'flat' response at the listing position with the Listening Position EQ setting.
But I felt the rise including 31.5 Hz was just too much.
It was pointless to boost 31.5 and 25 Hz at all, since that boosting was actually causing them to stand above everything else so much. So I dialed those boost back to zero in the right channel of the Background EQ. Even with 0dB boost at 31.5kHz, there is still a bulge there, dropping lower (by design) at 25 and 20 Hz.
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| Kitchen Doorway with no boost 21-31.5 Hz |
That was fine at the dining room table position too, showing the slightest peaking around 31.5 Hz even with no boosting. But the dining room table shows a huge notch at 56 Hz, a peak at 125, and another smaller notch around 180 Hz which need further exploration.
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| Dining Room Table |
I do most background listening from here, so it should be better than this. And certainly the recent removal of boosting 31.5 Hz is only to the good as well. 20 Hz is doing fine suggesting the cut there is of no harm here. Save for 56, 125, 180, and 720 or so other, Background EQ'ing looks all to the good.
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