I had been frustrated with the upper midrange peakiness I was hearing. Flutes, piano and 2nd harmonic overtones of lower barky instruments like baritone, cello, oboe, etc with lots of natural overtones. I attacked it will all kinds of tests on the midrange driver, but I couldn't find anything wrong at all, except for the sound. It sounded like 2nd harmonic glare around 2-3kHz and it would peak on loud passages. I call it flute stab. I remember having this problem years ago in here with different speakers.
When the Christmas tree came, I moved the stereo 90 degrees against the side wall. The acoustics are great that way, lower and mid midrange is especially muddy and imaging suffers, it has but much better livability. We can even use the fireplace!
The first night I listened to radio, it sounded good, Ididn't notice the peaks, but the radio is compressed and I wasn't playing loud or listening cricitally. Next night listening to Monk on vinyl I didn't notice any plink and plonk in the upper registers of the piano. I should have been hearing it on Monk if anything. So I start thinking shit, maybe it's my new DAC doing it?
Tonight listening to DAC, I gave the speakers a workout with some of my "big system" tracks. Kalevi Aho Symphonic Dances is loaded with bells and brass, flutes and loudness, modern dissonant harmonies, huge dynamic crescendos with piccolos leading the way. I was surprised to hear the speakers sound much more relaxed and listenable now. So the peaks must have been worse in the other orientation due to the room acoustics. I'm wondering if I am getting slap echo in the space between the walls and the 6" thick ceiling acoustic treatments which have wooden sidewalls. The gap is only about 2-3 feet, but it is very long and goes all around the room. But the wavelength for 2-3 feet is 450-700Hz, too low. I'll have to stick a mic up there and run the sweep, and look for other ways that 3k stuff could form. Maybe it's just too much glass windows, or corner echos?
In a related story... Yesterday I gave the midrange cones a good fondling. The paper is extremely stiff and the cone is actually a curved wall which prevents bending. There is no give at all in the cone wall. Pressing very hard I was surprised that I couldn't make it bend at all. As the cone goes down into the voice coil, the angle gets much steeper than at the outer edges. This further reduces flex because the steep angle of the cone makes a stronger cone. All this should help reduce cone cry, screaming, breakup distortion, whatever you want to call it. And I couldn't find any evidence of that with measurements. That's good because I want to build some other boxes for these drivers but I was worried a little about the midrange if it was screaming. Zaph just published his tests of this JA8008 midrange driver on his blog. Passed with flying colors! But those drivers T/S specs look like they aren't broken in yet.
http://www.zaphaudio.com/blog.htmlScroll to December 4, 2012 entry.
I still intend to do some torture test multitone distortion tests on the midrange with ARTA to make sure it is behaving in the upper midrange frequencies. But for now it seems to be mostly gone. But the other acoustic problems of this orientation are a bigger problem, which is why I choose the less feng shui orientation most of the time. Sounds better except for the flutes.
I remember having this problem a few years ago in this room, but it seemed lower in freq. But for some reason it really came back strong with these speakers in that orientation. A sine sweep at the listening position showed nothing. A puzzle.
