A week after my return from my vacation in the San Diego area (notably, where much of my audio insanity derives from, where I worked at a high end store and met many high end audiophiles, though I only visited only one such audiophile on this trip, the other notably and disappointingly having given up on the habit) I noticed the super tweeter DEQ unit, which mostly operated as an RTA visual display indicator for the above 17kHz super tweeter signal, as well as an extra digital level control, had a greyed out display.
I measured the output of the supertweeters using the RTA app on my phone, and sure enough there was no output at all. When the display goes out on a DEQ, the I/O functions could still be working, but probably not. Probably there's a power supply failure that leads the entire DEQ device to be dysfunctional, not just the display. That is how it has seemed to work in every failure I've paid careful attention to so far. BTW this unit was connected with digital input and digital output, merely serving to pass (and slightly modify) digital signals from the super tweeter miniDSP which does the ultimate high pass crossover, and the Emotiva Stealth DC-1 which does the conversion to analog and final level adjustment, which I've tended to set around +7dB since the super tweeter signal is so low and also highly attenuated by the tiny capacitors I connect the physical drivers through.
Damned! (And ironically, I'd just been talking about my super tweeters in San Diego, as my still practicing audiophile friend shared his stories with Dynaudio drivers, though he used D28's and not the D21AF's I have been using as front facing supert weeters.)
I did a quick bypass of the DEQ unit. Then it was still dead in the right channel, but working in the left.
The way these are hooked in leaves me little opportunities for easy testing. I ultimately had to move the massive sand filled 40 inch high Target stands with LS3/5A boxes on top, which is not getting any easier for my 67 year old body despite the (very limited) strength training I do. Which I didn't bother to do until exhausting all other opportunities. And then it was clear on the proven good signal of the right channel which plays fine on the right super tweeters that the left super tweeters were not working at all.
This was true even bypassing the capacitors. Measurement suggests both super tweeters on the right channel, including the now unobtanium D21AF in front, now have open windings.
Double Damned!
But now perhaps is also the best opportunity to figure out what it sounds like with the super tweeters and their stands removed.
You would probably not be favorably impressed by the fact that I just hadn't done that experiment before. I'd only compared the situation with the super tweeters powered and not, and powered always seemed somehow magically better. Bass seemed clearer, and highs seemed more balanced, never harsh or closed in or honky.
Always, the difference was very slight, and possibly only sighted bias. I doubted I'd be able to pass a blind test.
But I wanted to make the supertweeters as good as they could be before trying the Acoustats 2+2's with them completely removed, which I knew was going to have a lot going for it.
When I had previously (and for over 11 years) using Acoustat 1+1, they were narrow enough that I could place the super tweeters and their stands on the outside of the Acoustats. In that position, there was very little negative effect...perhaps even a slight positive, from having the extra stuff on the outside. It seemed to make the image even wider from left to right. But because of the added width of the 2+2's, and my need for a pathway through the room from the front door to the kitchen, meant that I had to put the supertweeters on the inside, if I was to use that assemblage at all. I knew from the start it was acoustically problematic. But super tweeters are so me. I didn't want to give them up.
But now that I've done so, there's no going back. It's clear to me from 4 years of listening to the previous arrangement that taking the supertweeter "towers" out of the way opens up the center of the image. The effect sonically is much the same as it is visually. Moving the super tweeters out of the way opens up the complete image. Previously it was parcelled and often cartoonish. Now it is expansive and every little bit from left to right and front to back can be mapped out. It has more slam too.
This opening up is even audible in other rooms where the stereo image, as such, isn't.
The problem as I suspected all along was that the heavy 40 inch sand filled target stands, and LS 3/5A boxes bearing super tweeters, was just getting in the way of the natural dipole response of the Acoustats, complicating the natural 3d line source approximation with lots of spurious reflections.
So back to the drawing board on super tweeters, in more than one way. I managed to snag 3 more of the high technology Tymphany NE19VTS-04 tweeters I was using in the backs, anyways, on ebay, they were unobtainable in stock anywhere else. I bought them as a Vifa product (at Madisound, IIRC, who doesn't even list them now). Later they appear to have been also sold as Peerless. It's Tymphany either way. The Dynaudio D21AF's in front are probably too heavy to deal with in future, and about as unobtanium as it gets (but miraculously, just while writing this paragraph, I managed to snag a replacement unit on eBay, so hopefully my loss is now corrected, I will still have a pair of working D21AF's for comparison if nothing else. And, btw, in comparisons the Tymphany's seem about as good as the Dynaudio's, at about 1/20 the weight, a true engineering miracle that it seems nobody else but me has recognized (they have essentially flat on axis response to 40kHz...you want at least that or there's no hope at all. I always suspected the D21AF's would handle any power available from my 150W amp, but in this situation both D21AF and NE19VTS died in the same catastrophic situation...I'm still not sure if the amp failed or what, perhaps just a full signal digital signal combined with all that gain I was applying, was just too much, I need to be more careful about that, also thinking of using smaller amp, 50W would be sufficient).
I plan a new supertweeter perhaps mounted only in the back of the Acoustats, possibly firing backwards only (and timed to arrive with the front) or both ways, on a strap of metal bent to fit under the Acoustat base board to the middle of the transformers.
I honestly believe the supertweeter effect is greatest in the reverberant field anyway, and not in the audiophile obsession--leading edge transients. Otherwise there would be almost universal discontent with super tweeters. Many of the leading edge tweeters (Scanspeak comes to mind) have pronounced peaks above 20kHz, which presumably extends the ultrasonic response much as I was doing. Now if this were all about the leading edge, it would be almost impossible to get it exactly right. I tried very hard (using ARTA program measurments) to get it as exact as possible, and most supertweeter users have never done anything like that. And move your head 1mm and it's different, the supposed leading edge may start out inverted, etc. Anyway, I think it's much more about the reverberant field reflected sound that leaks into your ears from the side. It's not that critical, down to the 0.1mm and so on, to get the supertweeters exactly coincident, and impossible in most cases anyway.
In actual soundfields, leading edge transients are rare. All is buried in the jiggling ambient noise.
What adding a super tweeter does is make this ambient noise sharper. That actually makes it sound softer because it's simpler.
Anyway, what counts is getting the supertweeter added sharpness within a few ms of the actual signal. Probably even 7ms (about 7 feet in distance) or so from back reflections is fine, but I could also try compensating it for simultaneous first arrival at the listening position. I could also try a separate front firing unit, with a different delay...
Anyway, for now I'm enjoying a more wholesome sound, full size players, wholistic, musical, etc., from not having any super tweeter stuff in the critical area in between the speakers.
You might say, I should have tried this before.
Update on Friday.
I haven't yet moved the LS 3/5A's based supertweeter assemblages completely out of the living room, which I presume, following ancient Linn advice (yes, no kidding, I first heard this in the day from the Linn Rep where I worked in 1977, though I honor it roughly in the breach) will make it just that much better still. Also, I need to get it out of the way for appearances sake. And it will take some doing because every place where equipment of this value could be put is already filled up. Especially inside the house, I need to carve out junk of lesser value and do something with it. Another thing I observed on my trip is that it's critically important to get on with the transfer or disposal of junk equipment or you'll still be stuck with it when you're too old to move it very easily. So I've got years of work cut out for me here, it looks like. And perhaps it's a good excuse, just about as good an excuse as owning cats, to be getting up and moving around now and then. So I've moved all the new odds and ends to be investigated onto the Coffee Table in the living room, and now I can move the LS 3/5 A's (which are so heavily modified as to be not really that anymore, they combine D21 with B110 and external driver connections and internal magnet shielding...because I was previously using in proximity to a CRT TV in Kitchen. But they originated as now extremely valuable LS 3/5As, and I believe I still have enough parts to make them all whole again and like original except a capacitor or two which might have been lost from the crossovers. Which I probably still have, if I could only find it within dozens of potential boxes, often hard to get to. So that's how things go. This time around, I thought they made a dandy acoustically solid base for the supertweeters, and they did, except too large and massive and complicated when positioned in between the speakers combined with the similarly large Target 40 inch stands. I'm now convinced the best supertweeter arrangement is on axis in back of the Acoustats, and possibly back firing alone is sufficient combined with compensating anti-delay (delay for midrange and bass only) for the first bounce (to and from the back wall). That, combined with a new lower powered amp and/or protection/monitoring system, etc, will be the NEXT GENERATION supertweeter arrangement. AND, I should probably wait about another year or so before deploying, so as to have the current sound firmly set in my mind. AND I've needed a pause in supertweeter deployment anyway (and bear in mind my supertweeters are truly super...I hear nothing coming out of them as such...I only believe they have a beneficial effect on how other things sound) so I can optimize the actual audible part of the HF spectrum. Back in 2021 I deployed a chairside EQ and began experimenting with midrange EQ's (which are now dialed into my midrange unit) that went up to a cut around 12kHz. The measured effect in pink noise was a 3dB/octave rolloff which became noticeable around 2kHz, but instead of just being a limited Linkwitz/Gundry "dip" it was a slice, basically continuing to 17kHz (at which point the Acoustats swiftly drop off).
This is dialed in as a set of 3 PEQ's actually, each one of which was tweaked by ear. But such tunings are never certain. I've long wanted to re-analyze the possibilities. I may be rolling off too much of the audible highs, long before it even gets to for-me inaudible highs above 16kHz. So you would think I should optimize what I can hear before bothering with what I can't, but my practice of audio, which presumes the possibilities of apparent subliminal effects (there has been controversial and unreplicated research showing brain wave changes when the bandwidth is increased from 20 to 40 kHz). But then perhaps too much I waste my time on things which might actually be of little value compared to the things that may well (and objectivists would believe) have important value.
So much as I keep wanting like a junkie to get the supertweeters back up again somehow, with some combination of bubble gum or something, I should resist that temptation, and even set make a rule that I won't again try super-tweetering for about a year, both to get an all new better and safer approach up and running, and to familiarize myself with the sound without it, and to get the audible parts of the Acoustat EQ understood if not dialed in better.
So I think I'll choose Halloween 2024 as the first date I will permit myself to run the supertweeters again, in some new setup, hopefully a much perfected one, with no extra stuff in between the speakers, and just a little bump above the back transformer, and a working power limiting system to prevent future burnouts, and probably a different amplifier (in my own collection I might try the 60 watt Marantz 15b which has 'just enough' bandwidth and presumably Sid Smith got the internal slewing and limiting right, this amp is legendary for good sound. I've always wanted an excuse to use them. But I also keep lusting after the few $200-300 Chifi Class A amps still available on ebay.
Whatever amp will probably be right out front and center where the Aragon 8008 BB is now. I've done enough A/B'ing to say there's no audible difference between the Aragon, as currently biased (on the high Class AB side: about 28mV instead of Klipsch specified 12mV across the collector resistors) and the Hafler 9300's. And under no situation is the Hafler underpowered. The speakers begin to sound dynamically limited at exactly the same point with either amp. So I don't need the greater (measured) 600W (spec 400W) into 4 ohms that the Aragon provides, the 350W (spec 250W) that the Hafler provides is sufficient. And the Hafler 9300 is better in every measured way, 0.002% THD instead of 0.02% for example, and even better HF damping factor (it was even better than the Krell FPB 300). The Trans Nova circuit in the 9300 is about as simple and fast as it gets. However, Parasound HCA-1500A is almost identical, and slightly superior in near clipping distortion levels. With the relays and stuff it's just less of a 'perfectionist' amplifier IMO than the 9300. But winning amplifier of earlier epochs basically need not apply. Before 1982 or so it was impossible to make amplifiers this good, then better parts made it easy.
The problem is, I'm not sure I want to sell the 8008 BB, and I've got no other place to put it, certainly not without removing the 2" spiked Mapleshade carpet feet.
I'll keep the A/B setup, but only temporarily put other amps to the side during A/B testing, rather than in front, which will be dedicated to the supertweeter amp in future setups starting next Halloween. (I also have parts to build a Pass Class A...an effort which now seems unimaginable. The whole purpose of the Pass amp was for the super tweeters in the first place. I have years worth of repair work to catch up on first. And at the current rate, they will be many years more before much is done.)
I've got plenty to do until then to give the supertweeters very much priority. I've now got 3 essential but dead DEQ's, all needed a power supply refurb. I should get the first one going to get back to having the chairside EQ which was so helpful to EQ experimentation.
I need to get things moving through "the laboratory" again and back working again. There's an incredible pile of to-be-fixed stuff in there now.
An alternative to the Chifi class A amplifier would be Schiit Aegir. The power is just right. I'm not going to consider such a thing until I've sold an equivalent amount of stuff on eBay, starting right now. But it looks pretty cool. The design goal is correct, there is really no need for a class A transistor amplifier. But high bias is generally good (this amp is quite high bias for the power, and features their special circuit which sounds good in the description and the Amp scores well at Audio Science Review...in fact about the best thing I can see for the price, as it is surrounded by $5k amplifiers in the upper end of the ratings). The upper bandwidth is huge and there are no coupling capacitors or servoes. The one non-purist thing is a relay, but those are fairly ubiquitous, and this one is CPU controlled.
