|Response Measured May 1, Sub below 100 Hz nearly flat|
Actually the biggest change isn't even in the audio system per se, but with my new central air conditioning system, which has variable speed compressor and variable speed fan. The fan runs constantly at an inaudibly low speed while temperature and humidity are nearly perfectly controlled. (Not to mention, when the old unit kicked in--which was constantly while running the Krell, and intermittently otherwise, it made a loud buzz clearly audible inside. I have never heard the new outdoor compressor inside, nor the fan on low speed, which has all that's been necessary so far. And I could not run the fan continuously during cooling months...it would lose all humidity control. I like the constant ventilation, which includes AprilAire 2200 filtering.)
It gets high marks from friends who don't like blasting air conditioning, and I do indeed check the temperature and humidity in various rooms a lot, and this is amazingly good.
One aspect of that deserves further mention, and that is the relocating of the thermostat away from the Living Room, where it was positively interacting with the Krell Amplifier. A few minutes after turning on the Krell, the AC would start running...and never stop. Air would bounce directly on the amplifier and back to the thermostat on opposite side of the room, keeping the AC in constant operation. Even if I set the thermostat a few degrees higher, the temperature at the thermostat would quickly catch up. Meanwhile, the rest of the house was being chilled colder and colder. The Krell and Thermostat were having a one on one, even though it's actually on the opposite side of the room, but that's where the AC air is directed on high speed fan, which the old unit mostly used when it was cooling.
Now the thermostat is in the master bedroom, and I can run the Krell all day without causing the AC system to run much more than otherwise, and you never notice it turning on or off anyway because the fan just keeps on running at inaudibly low speed. The bedroom stays at a perfect 78 (the setting) while the living room gets a few degrees warmer (not bad, and remember there is continuous ventilation which is keeping things from going to the other extreme) instead of arctic blast next to a toasty furnace.
So now, I use the Krell FPB 300 all the time, and that's another huge upgrade right there. Previously I had to use the Aragon 8008 mostly, and I didn't get around to hooking up the Krell often. It's easy to turn the Krell on and off with the soft touch metal button on the front, just as easy as any kind of remote control if not moreso, so who needs remote controls? (Actually, I do have the Krell infrared.) I do turn the Krell off when I'm not playing music. It's a huge power waster otherwise, and could cause excessive wear on the output transistors. It runs up to 180 degrees on the heatsinks by design, and mine has some problem in the left channel which tends to keep slowly ramping up the bias until high temperature causes it back down to level one or two. So it will ultimately be running up to 180 degrees (F) even if just idling all day (measured the other day in the 155-160F range). The rebuilt right channel doesn't have that problem, it idles closer to 145 degrees. The left channel will ultimately need to be rebuilt. My plan it is to run it until it actually breaks. (This is basically the way it came back from Krell service in 2011, with some bias instability in the left channel.) But no reason to use up the remaining life in the left channel in idling.
I understand now how the Krell operates, and my Kill-A-Watt was sometimes overloading (it blinks and ultimately shuts off as watts go above 1400), and I did indeed worry about the previous setup which included Insteon controls for both amplifiers, the Kill-A-Watt, and lots of jumper cords and so on, all at least 14 gauge. I've seen how high current causes something almost like fire to shoot out from sockets of all kinds, expecially it seems extension cords. Best not to have them for audio reasons too. But especially with the Aragon over in the barely accessible corner with it's heavy rocker switch. The Krell soft metal touch switch is the greatest thing.
So now, the Krell plugs straight into the wall socket (the thickest gauge all brass Pass & Seymour, in a dedicated insulated ground circuit using 10 gauge wire) using only its Krell power cord, exactly as Krell instructs to do. That is certainly the safest, and maybe even the best of all things to do. Another serious upgrade compared to to how things were at the last audio party--Amp straight into wall instead of switches and meters and extension cords.
Both subs now have single power cords the entire distance. The right sub now has an audiophile power cord, 14 gauge with multiple conductors and Cardas copper. It was cheap enough and I could get exactly the right length, so I could toss the stupid 8 foot 16 gauge extension cord. Another Upgrade!
Since I only have two outlets (one duplex outlet) on the dedicated audio circuit, I must use a Y adapter somewhere, now right at the outlet itself, with both subs and the Belkin UPS power conditioner plugged into it. That's not really an upgrade just a minor reorganization to allow the Krell to be plugged straight into the wall instead of the power conditioner. This is the heaviest duty 15A Y adapter you can get. It's much safer right at the wall socket then it was before (before it was sitting on a pile of books on the left sub--don't do this).
The speakers have been angled, measured, reangled, repeatedly. My angle idea is pretty wide angle, about 15 degrees toed in being parallel to the walls, which means about 15 degrees towed away from the listener. One advantage of this width is that there is very little change in sound a few degrees in or out. It is slightly rolled off at the top, but I've decided that sounds OK for now. Much work was done on this since the party. The effect is a very relaxed listening position, yet very good imaging, yet spaciousness, everything. It almost seems like there is some magic effect in making a small angle from the wall, which is precisely what Acoustat recommended. As if the relationship to the wall matters for reflecting the backwave too. For whatever reason this angling seems best, and I'm not sure how many upgrades to count it as. Back last year I was listening the Acoustats just off axis, which was generally unpleasant, but I accepted it sometimes and got used to it others.
(15 degrees isn't the exact measurement, I've forgotten the details when I was measuring such things, and they may have changed since then anyway. Remeasurement is needed soon. Even the tape is off right now because of what I'll describe next.)
The last change was to move the speakers in closer together. The wider speaker speaker angle had combined with the distance between the speakers to make the sound phasey sometimes. Moving the speakers back closer together just a few inches tightened up the image completely, side to side, nothing phasey about it now. Meanwhile the image is usually completely in front of the listener, from one speaker to the other, indicating correct focus. I could only move the speakers a few inches closer without a larger rearrangement, and that's what I did. I might even move the speakers closer if I could, just to see what that would do, but I can't. Anyway, this seems to be a good point. Once again, this is a super huge upgrade, going from a phaseyness which had been getting worse as everything else got better to tight focus.
The bass EQ is organized around a completely different ideal. I no longer accept a non-flat "room curve." Flat seems to work best, matching the electrostatic panels nicely. The bass is far more extended, but actually has a bit less boom than the Acoustats run wide open. I've tuned the bass by running Genrad oscillator over and over and over, and tweaking individual Paremetric Equalization functions (PEQ's) in the Behringer DCX 2496 crossover. The bass level was lowered there and also at the digital controls of the SVS PB13 with the new Sledge amplifier. I think I used to have that at -3dB and now it's at -9dB.
In addition to the measurement, I've included my observations both at the listening position and around the house at places where room modes seem bothersome. I tamped down all these modes whether these made much difference at the listening position or not, even accepting a slight loss in measured flatness at the listening position in order to apply cuts at the locations where the huge room modes were apparent.
Just tamping down these out-of-room resonances by 3dB seems to eliminate all the out of room issues. I haven't even noticed the room modes anymore, anywhere (though I imagine I will eventually) it's such an improvement.
And there's been endless retuning by ear, but most of the EQ adjustments come from finely turning the oscillator back and forth and now using the least amount of EQ, preferably the highest Q, to damp out model type problems without adversely affecting nearby frequencies. I've been much more systematic about canceling out problems without creating new ones.
The totally new bass ideal and achievement might even be the largest improvement of all. Everything is different now. I can organ music at 0dB and still now have the speakers and/or walls coming apart. The bass is just always there, and always seems right, often surprising with it's impact, but never too full, and not just at the listening position.
Actually it seemed (though it could be a mistake) that at high levels the Acoustats had a buzz around 85 Hz. So I moved the LR 24 crossover up to 100 Hz. BTW I no longer cheat with an LR48 rolling off the subs and an LR24 on the panels. Both crossovers are set to LR24 at 100Hz. This doesn't seem to help so much near the crossover but across the range an octave lower and higher. This also made a few bass modes around 80 Hz in the room more apparent, but they are usefully cancelled out through the DCX for the subs (while generally I have avoided non-crossover EQ for the panels). Another huge upgrade, or several!
Along with reducing the bass a lot, so there is zero rise over the midrange level, I reduced the highs so that (at one point...for some reason not in the measurement shown above in the highs because of technical issue) there was no rise in the 20kHz bar. At one point I was showing a 12dB rise at 20kHz, the highs only slightly drooping before that. That 12dB rise was entirely due to the supertweeters, which I then (and now) cross over at 20kHz. I somehow convinced myself that the measurements were wrong, this added magic something to the sound, making (as I said above) sound real everywhere in the room, and in every room.
But then one day in the past few months I did somehow hear the supertweeters more clearly. And they were adding a nasty sound. So I kept turning them down, and I basically got to flatness and they sounded OK. (I couldn't actually go lower than flatness, though it doesn't look that way in the above graph, I think I had the phone turned around).
So, much better supertweeter level, sounds cleaner and measures flat, a big upgrade there.
I've decided I like the sonic sugaring of a Gundry dip. Linkwitz has defended this on grounds related to the sensitivity of the ear at different angles, and the stereo configuration boosts the apparent highs around 6kHz, which is also a region the ear finds offensive in excess (metallic, etc). As soon as I tried it, using a very low Q PEQ around 6kHz with 3dB loss I decided it sounded correct. I haven't tuned this as much as I might, but it seems to work, and I'm counting it as another important upgrade. The Acoustats seemed to measure too high in this region especially on axis anyway. It's possible I should revisit the speaker angling because of this change, or examine the tradeoff between the too. I only started playing with the dip after I had decided on the current angling. This is almost the only non-crossover PEQ used for the Acoustats. It is dialed in through a Behringer DEQ 2496.
I discovered that my Sonos system is applying digital gain to the living room. I have reset the volume level (using Fixed doesn't help, that makes it fixed to 10dB digital gain) to -10, which cancels it out. So things that were sometimes sounding distorted no longer do. Upgrade!
I rediscovered two of my old LP-to-digital organ transfers. I hadn't much listened to the Robert Vickery recording because the huge deep bass got out of control. But now I listen to it at 0dB and higher.
Another old transfer which was one of my favorites, but strangely I never listened to it much, Magnum Opus Volume One with organist Welch. It turned out one channel was 6dB lower. I thought I had made a fixed transfer, but that was not what got ripped to my harddrive, or maybe I hadn't. It took a whole evening to figure out how to fix this with any of my digital editors. I couldn't get SOX to do it at all. Nor Audacity. None of these programs seemed to have a way of changing the gain in only one channel. Finally I figured out how to get the job done in Wave Editor. I put each channel in a separate layer by turning off a different channel in each layer. Then I could change the gain for one layer.
So now with all the upgrades I can listen to these organ recordings at digital 0dB and higher (which is approaching 90dB in my low sensitivity system, about 96dB is my max, the Tact has about 6dB of digital gain).
The third bass note in Spanish Harlem now, for the first time ever, sounds right. I think that was relating to resonance around 80 Hz.