I haven't written this up yet? The Acoustat 2+2's that I set up in July have of course made the biggest difference in 11 years, since I got the Acoustat 1+1's. Speaker upgrades are big.
I had for long doubted the 2+2's were even better than 1+1's, for the reason that the 1+1's are more like a line source, or so it seems at first glance (more about that later). So, I reasoned, the 1+1's are the perfect speaker for my small space, because I don't really need more dynamic range (not really, as it turned out) just the thinner profile which works better being closer to.
So, even the likes of Mr Acoustat, a late longtime fan on DIYAudio (and no connection to the original company) preferred the 1+1's, for his mostly smallish rooms.
However, as time went on, I was beginning to think there was a certain loudness I really could not (or was never tempted to ) exceed, because the 1+1's were sounding more closed in, so I always kept the levels somewhat below the 1+1 maximum output levels, so I became more interested in what the 2+2's might actually sound like, or even thought of getting a high output level 2nd set of speakers just to hear "louder" when I really wanted to.
It was about that time, 3 years ago or so, that a friend acquired a pair of 2+2's. I heard them in his much larger room, and I was blown away. I felt there was nothing lacking at all, they were simply better in every way.
It was exactly that same pair that came up for sale, with an interface refurb and mod (because the owner feared he might have damaged them). They still seemed OK if not as glorious as I had remembered them, so I bought them.
It became clear after a day that one speaker had far less treble, and I couldn't even adjust the difference out using the level controls, nor did the "air" mod help.
Fearing the worst, I went through a process of system substitution, and narrowed the fault to one interface unit, and then to the HF transformer.
Well, as it happened, I had a spare NOS Medallion HF transformer to replace the HF transformer. The rest of the transformers in these 2+2's are NOT Medallions, as I had hoped. But actually, this makes LESS difference with the "C" mod that has been performed on them. The C mod reduces HF transformer saturation, so the enhanced anti-saturation construction of the Medallion transformers is less critical. These units ALSO got the "air" mod and switch added, but the "air" mod seems to bypass all the attenuation, possibly putting more voltage on the HF transformers, and frankly I don't like the way it sounds anyway. The C mod design, and with the variable attenuator knob type interface, seems like the best interface design to me, and can be dialed in to perfection (though I have only moved the controls a hair off center) with ease.
I had almost finished re-connecting the new transformer, I was on the last lead when I noticed the original had not been wired correctly. The - HF and - LF leads were reversed. Well, that for sure was the source of the problem! But having only one more solder connection left to finish the job, and compared with hours of work (possibly breaking something) removing the new transformer and re-installing the old transformer. So I decided to leave the new transformer in place, and now with the correct wiring too.
This restored the amazing sound I had originally heard years before. It was simply better in every way. Even the "line source" issue is not as I had imagined. And, it doesn't seem that having one Medallion HF transformer significantly unbalanced the system either.
Many things are at work here. First, having twice the membrane area means that for any SPL level, there is half as much panel movement, therefore half as much distortion from that mechanism. And there's less saturation in the transformer as well, and half the level from the Amplifier is required, meaning less distortion also. So, no matter how loudly you play, having twice as much panel area gets you half as much distortion, and this seems apparent in the effortlessness of the speakers as well as the greater information. That was the key thing I noticed from the very beginning (and in fact before I fixed the transformer: more information.
It's much like that 70's photo of the listener being blown away, as if the speakers were something like a hurricane. But in this case, there no physical force or movement of one's body or hair, it's a change in one's mind: there's more there there somehow, at every level, it's more real and satisfying.
Greater information at all levels is the biggest improvement, but there are others. Perhaps the second is that I have finally adjusted the highs correctly. With the 1+1's, with their newer style box, one can't just "turn a knob" to change the HF level. It's not that hard if you have the interfaces unscrewed, as I always did. But it was hard enough, that I never even bothered to try. I just left the HF adjustment alone, figuring it was "correct." But I have no idea if the previous owner adjusted them. It didn't look like he had, but also it seemed my resistance values were significantly lower than TheAcoustatAnswerMan at DIYAudio said was the factory default. When he said that, I didn't believe it, because my boxes looked so untampered with. But now, realizing how the 2+2's sound at about their central position, which appears to be right (for them) but midway in the HF attenuator, I realize I was playing the 1+1's too hot.
So this improvement is actually something I could have had with the 1+1's, I just never tried it. BTW, the 1+1'\s require a different attenuator setting than the 2+2's, precisely because there is also a LF transformer setting change which gives the LF transformers less "gain." So, by design, the 2+2's are set to a "central" attenuator setting, whereas the 1+1's are set much higher, according to the factor spec I have heard, just not as high as mine were set, which was about as hot as they get.
Now, I had compensated for the too-hotness of the 1+1's in a peculiar way, which negated the problem for serious listening (actually, NEGATED it too much, I always thought, but it was hard to do otherwise without creating a super tiny sweet spot, head in a vise) but meanwhile meant, for casual listening every where else, I simply got the too hot highs in even greater measure. And it turns out a lot of the listening I do is casual listening, even from other rooms, because I like the way that works out as opposed to having background music piped in to every room--because then it's too much in your face, it's actually, as I'm quite honest with myself in admitting, a form of information reduction because quite often that's better for background listening.
The method was this: I was listening far off of the central axis of the speakers. On the speaker axis, the sound is way too hot and even slightly brittle, and very much head in a vice. Of axis a little, it gets a little better, but the head in a vice got better and worse. Finally, between 18-28 degrees off axis, there's a range where the high attenuation seemed about right, but all the venetian blind effect was gone, all of it. So it seemed the best positioning was about 23 degrees off axis, giving full relief on either side from that pesky vice. That position was also, a bit too much attenuated at the listening position, but it was OK, especially with my super tweeters crossed in at 20kHz but contributing lower. It was often unnerving, however, to have the highs bright (and sometimes uplifiting because of that) and then sit down and have the highs greatly collapse, even if actually being somewhat more natural but from the other side.
Well, now, I have none of those issues. The 2+2's are just fine head on, and may be optimal at a more useful angle of 12 degrees or so off of the speaker axis. The brightness with the level control centered is just about perfect at the listening sweet spot and everywhere else. This is big, very big, for my casual lifestyle.
So part of this was my previous ill-adjustment, and the other part was something I'd never even imagined before. The 2+2's are two vertical columns of electrostatic elements, and those two vertical columns are in fact themselves angled slightly from one another and from the central speaker axis. That slight angling has many useful effects.
For one thing, when one is right on the 2+2 speaker axis, neither element is facing you directly. As before, I believe these Acoustat electrostatic drivers seem to have a slight issue exactly head on, by themselves, but here they have no issue on the speaker axis because then you are off axis by small amounts (5-10 degrees I figure) which is right where the Acoustat panels my themselves sound best. But then, as you move off the center of the 2+2's, you get more on-axis with one panel, and less on-axis with the other panel. The blending effect of that eliminates the worse beamy qualities at every angle, at least in the range of plus and minus 25 degrees. So now, I can pick whatever angle works best for other reasons, and not be constrained by a horrible venetian blind effect right at or nearly at the center of the speaker.
Other speakers do similar things. The top Martin Logan models have for many decades used a horizontally curved membrane. In my opinion, that introduces many technical issues. It was amazing that they got it to work at all, but the earliest models weren't very good sounding IMO. Now I think the latest ones may be fine, but it's still complicated thing to do, as the mebrane must stretch and relax far more as it goes in and out.
The Sound Labs use lots of little speakers arranged in a cylinder. That has advantages, but disadvantages also. To get the same amount of radiating area, you need a substantially bigger speaker, and it's far more expensive to make.
Given such possibilities, the Acoustat way of simply angling the two columns a speaker is amazingly elegant and works amazingly well, IMO. Perhaps, overall, it's the best approach. It can't be done for more than two columns of panels, and work equally well. Two vertical columns is the optimal number, as each can be only a few degrees off the central axis.
And that applies to the third improvement. It could even be that the two angled columns actually produce a narrower effective "line source." It does require a slightly greater distance from the speaker for full coherency, perhaps 4-5 feet (the 1+1's are coherent at 3-4 feet). But at that slightly greater distance, the imaging is even better, along with more depth, etc. The greater information also contributes to this, so the quality of the line source itself may not be much better, but it is far from being worse. The 2+2's routinely have the spacious depth which I called layered depth that I first heard when I started using the Krell FPB 300 on the 1+1's eleven years ago.
I've continued keeping the minimum (in the back inside) distance from wall at 3 feet, actually 39 inches on the inside to the front wall and 47 inches from the outside to the front wall. The factory spec of 3 feet in my experience is an absolute minimum you must exceed. The distances I've listed are the greatest my living room can sustain and still be good for other purposes, as I discovered at my last party. To make the current speaker arrangement work at all, I had to put the supertweeters on the inside, which is not the best location for them, but works well enough, and allows the 2+2's to be as far apart as possible, which is helpful in my relatively narrow room, and allows for the slightly greater distance from the speaker to the sweet spot, which is now just behind the room center (as I had discovered this year, works perfectly fine with the EQ I had been using, and even better when fully dialed in). It took a month to find this new slightly further back sweet spot and angle the speakers just right, and then some more time to reset the midrange EQ's to notch out the slightly different LF resonances and the make the usual 2-8kHz slight softening for best sound.
And any amplifier has to work half as hard into the punishing 2-ohm minimum load, which is another big win. Now I no longer need a 1200W into 2 ohms amp like the FPB 300 (which has now been retired, after one too many failures after professional repairs, when I have time perhaps I'll learn to fix it myself). The Hafler 9300 sounds equally fabulous without any strain at any useable level. The Hafler is somewhat power supply limited (compared with the Krell) but with the 2+2's it's become a non-issue.
So, it's a win-win-win-win!!!! And now I have the incredible 1+1's to use as my Laboratory speaker (though that took clearing out all the junk, which could not have been done in months had I not already been retired).
