Another late night with good listening and important audio discoveries.
1. Midbass better with Butterworth 24 than Linkwitz-Riley 48. Even with the room curve(s), which currently boost deepest bass below 35 Hz and highest highs above 18kHz, there seems to be a broad depression in the bass using the LR48 crossover for the Acoustat high pass. BU24 gives much nicer midbass sound. By mistake (probably) I had originally done this series of room curves (from Sunday February 6th) using the BU24. Based on the impulse response mainly, I had decided that LR48 was acceptible (and preferable for getting the buzz causing bass out of the speaker). But then I went ahead and ran the RCS measurements with the BU24 selected anyway, because that was what I had just finished testing.
I had determined by Monday that I had made this mistake, but decided to switch back to LR48 for speaker protection and (thinking Acoustat response below 104Hz crossover is nothing much to speak of anyway) thinking it wouldn't make much difference. But all along I have been noticing weak midbass around 100 Hz and just below (which is party by design...underlapping to crossover to minimize the effect of bad resonances around 100Hz).
But until I installed the notch filters on Tuesday, I really did want to keep the buzzes out, and the weak midbass was a small price to pay.
But now I am using notch filters to get around the buzzing (and it continues to work great), I shouldn't have to compromise the rest of the midbass as much. So I went back and tried the BU24. BU24 brings back much of the missing midbass. And actually it does this regardless of whether room correction is used.
This many not be an inherent property of BU24, but a set of circumstances in my system and listening room.
#2 Currently, the uncorrected sound is better ??? Well now that I have decent sounding system without correction, I can run system either way. There is a huge difference with my current correction curve #2 (which actually had its room curve tweaked on Tuesday) and bypass. #2 reduces the highs (which are generally too hot, I admit) and brings up the midbass (only slightly). It clearly reduces resonances, you can hear much more detail in the music because of the reduction of spurious resonances. But by comparison with bypass, the corrected sound is flat, undynamic, and boring. (You don't notice this until you actually compare the two.)
I don't think this is entirely a situation of preferring the euphonic colorations of my system. I think it mainly stems from the fact the the frequency response of the Acoustat, with its tilted up high end in axial response, is a deliberate design choice to make up for the relative beaming of higher frequencies. And I may have to do the correction of bass and midbass better with a better chosen room curve. I will try something closer to actual measured response.
I may be able to make the correction sound better than bypass with addition changes to the room curve or multiple measurements. But for now, I like bypass better.
#3 I can now play Supernatural by Santana (SACD) without unpleasantly strong bass shaking the room apart. Big improvement! It sounds like an entirely different and much better recording now. It was a big disappointment last year how badly this recording sounded without an extra bass cut. Now I can listen to the record without even engaging my "boom correction" filter.
#4 Best to shut humidifier off when playing. My noisy humidifier is about 10 feet from the listening position. I run it all winter to keep my throat from drying out. But when I was playing Dark Side of the Moon tonight (in great contrast with last night) I found the side slightly on the harsh side. The sound generally seemed to improve (though I didn't go back to DSOM) when I turned off the humidifier. Duh! But the big problem in situations like this is how to remember to turn humidifier back on. (It was even worse when I was shutting off refrigerator.) But now I have a trick. I turned off the light in the kitchen where the humidifier is, and shone a tensor light on the humidifier. This trick almost didn't work, as I first went to bed without looking at the kitchen, but I caught it on my first trip to the kitchen a few minutes later.
#5 Supertweeter back to +15. It certainly doesn't seem to add to harshness, not sure if it can actually reduce apparent harshness, but it's usually more fun to have supertweeter at higher level, and with 20kHz level, I think it has lower output than last month (when I was using 15.5kHz LR48 higpass, now I am using 20kHz BU24 highpass, higher but less steep crossover). Not sure yet if I want to keep it like this. I also seem to like room corrections where I leave supertweeter off for measurement, then add it back in for measurement, as I do with correction #3, but #3 currently doesn't enjoy the additional room curve tweaks I put into #2.
#6 One usually thinks that the panels are producing great bass. But just turn the subwoofer off, and it's clear that the panels are mid-tweet drivers. With my crossover anyway.