I don't actually intend to use these speakers in any current room, except that I might place 1 set of 2+2's (whichever I decide is least good) into the Laboratory, replacing the 1+1's already there. After all, the 2+2's are better, etc. Ultimately, the 2+2's will be the best speaker for the new Gym, after I expand my existing Gym to the full width of the garage after I build a carport. (I'm not sure I will live to see all these imagined improvements anymore, however, because I haven't done anything in more than a decade of thinking about them, and I have less money now.)
My main hope was that the new 2+2's would be better than my pre-existing set, and replace them, leaving the older pair as backup or experimentation.
I'm not at all sure that is going to be the case yet. In fact, one of the speakers has a notable rattle played full range. But the same is true of one of my pre-existing ones. The possibility exists that I will end up using one of my old ones and one of my new ones. Then it will look pretty wierd, with a white 2+2 on one side and a black 2+2 on the other.
Anyway, my first month is chalked out to be a full examination of both sets of Acoustat 2+2's. That is possibly the main reason I bought them, for testing and experimentation. Having only 1 set, I am unable to conceive of minor repair and/or modification. My system would be done for the duration. Now I have a second set I can experiment with, including taking the grill cloth off. (The grill cloths on the newer set is after-market, looser, and possibly easier to remove than on the originals.)
The newer set also has the "compact" interface unit which is far easier to remove...in fact you can normally leave it unscrewed and simply pop it off whenever. Having the compact interface also means that I could use my already Solen-cap equipped original 1+1 set, to which I added a large external capacitor (not an easy modification!) to replace the original 47uF electrolytic.
My original set is the from the original production run, with the impressive looking "large" interface unit strapped to the speaker. It was refurbished and modified to "C" mod by a famous modifier. The new ones are both Blue Medallion. They might also have been modified to C mod but I don't know yet.
Things I want to know are:
Which units are more plagued by low frequency rattles, resonance, and similar issues? How hard do they have to be driven to exhibit these flaws? (I intend to do only very safe non-destructive testing in these regards, but I already know several songs that are pretty likely to cause problems)
Are the new sets "C" mod?
How have I tuned the HF control on my original set and what difference does changing it make? What position is actually best? Is it better to achieve the HF balance I like with EQ or with treble adjustment? (I am currently using EQ, I have the control set in the middle which I think means flat though it is not marked.)
How do the frequency responses of the original compare with the new? Can they be adjusted to be the same, or whatever is best? Does the C mod vs B mod make a difference in frequency response or sound (if one unit is B mod, which I don't know).
And that's just the start. My thinking was I belabor many other mostly useless stuff and don't focus on my main midrange speaker, which is old and possibly needs repair or rethinking.
Well, with just one set it's almost untouchable. I don't even dare adjust the treble control for fear of losing my current assumed best judgement. I need to measure the control first. And with large interface and C mod that's quite difficult to do since scads of bolts need
to be removed including those on the brace.
The downside is...I've got so many other things to do these days (holidays!) AND my system was not only sounding totally wonderful and I was just getting used to the vastly improved imaging and center stability after moving the supertweeter towers out. Now I've got two sets of speakers in the room I can only put in front of each other (hardly any room for anything else) until I do hoped-for experiments as I've described above. But it's surprising how acoustically transparent Acoustats are. Having a second pair powered (!) but no signal right in front of the powered ones has surprisingly very little effect on the out-of-room sound...what I hear the most. I think the supertweeter towers s had more deleterious effect on the out-of-room sound regardless of whether the supertweeters were unpowered. (They may have contributed more to the out-of-room sound in the first place too, when powered vs not.)
One of the problems is not just that they take a lot of space to store...they are fiendishly hard to move. Since they're taller than all doorways they need to be tilted just so. It's pretty much a two-person job.
That means any moving around is going to be, by necessity, a two person operation. But I think I can assemble them mostly as one person, working on the sides... (So far, I've always assembled and disassembled 2+2's with help.)
Here's a fairly positive 2+2 review by J Gordon Holt in 1984. (Harry Pearson was far more negative, coining the term "credit card coloration.")
I dispute Holt's suggestion that the Acoustats have a less punchy sound because of an alleged high frequency suckout.
In fact, I find that with the controls set to neutral they require slightly more cut in the 2-6 kHz (and 12 kHz) regions to sound good.
This yields a fairly evenly but slowly declining response curve from 2kHz upwards. That's what seems to sound the best, possibly because of the large degree of high frequency reflected sound created with a dipole speaker.
The lack of punchiness, I believe, comes from other issues.
1. Dynamic speakers sound artificially punchy because of cone resonances, and people are used to that.
2. The Acoustats have deliberately designed broad positive resonance below 100 Hz by design to compensate for bass loss due to dipole design.
This resonance is not described in any Acoustat literature I've seen. It is rarely discussed at all. Most probably don't know about it.
Yes, the Acoustats have to have this resonance to even sound remotely like it has bass. That is the magic, right there. A tower of RTR
electrostatic tweeters would have very little bass.
While electrostatics apply force over area (fairly) evenly, that does not necessarily mean the motion directly follows that force. The motion also depends on the mass of the diaphram, it's elasticity, it's tension, and similar factors. So yes, there can be resonances.
Linkwitz added electronic bass boost to his dipole speakers. He published how he calculated how much was necessary, and everything else about building the (analog IC based) circuits required.
Acoustats have that bass boost in the panels themselves, a function of the relatively high mass of the membrane compared with other electrostats. (The Acoustat membrane is 2-3x thicker than most electrostats.)
So, I think the problem is that the needed resonance in the Acoustat bass adds time dispersion to the the bass, reducing the "punch."
I've always thought that the Acoustats were fundamentally flawed from the vision of being a "full range" speaker. They are not "full range" to the fully demanding. They need a subwoofer.
And therein is a big rub, because the subs available in the 1980's were not as good or cheap or plentiful as today.
Today we can have incredibly good subs powered by their own internal digital amps, with DSP processing to optimize them.
Now we can easily have subs that mate with electrostatic panels.
And all the better to use FIR based linear phase high order filters for the crossover.
That's how I can get a sonically wonderful 8th order phase corrected Linkwitz-Riley crossover for the subs and panels at 125 Hz, far above the resonance and wall reflection issues.
So the resonance, even rattles, doesn't matter much to me anymore. But that also means I could get by with a large 2+2 with thinner membrane and no bass resonance at all. That would be my preference, but nobody makes such a beast.
Speaker makers want to make full range 'speaker systems' not parts for audio enthusiasts to use in constructing their dream systems.
And I can simply not imagine building a electrostat speaker to my own requirments.
So I am left to working with 2+2's, and now I have two sets so I can be more fearless about experimentation.
**** Update December 8
I determined yesterday that all four new Acoustat interfaces are "B" mod Medallion. My first 2+2's had been modified to "C" mod. So I have the perfect opportunity to compare the two approaches. I can compare my old vs new 2+2's, and also swap in my earlier 1+1 interfaces (with jumper change) which are C mod plus Solen 47uF polypropylene cap.
However, the "tunings" of the interfaces may be different too.
I powered the interfaces with AC from nearly the moment they arrived, because I think that discourages cats. I have NEVER had a problem with cats clawing Acoustats (as J Gordon Holt reported). The front panel fabric is too "floppy" like a cat-proof screen door, cats recoil against things with that feeling. They could potentially claw the sides, which are hard. But I have never seen it. I think it also helps if the cats hear the new Acoustats playing music as soon as possible. Cats respect music. Things that make music are "alive" to cats, and they don't like to mess with living things bigger than they are that are. I wonder if J Gordon Holt had his cats in the room while he was playing music. Also, finally, I think the bias transformer system creates a very subtle noise we can't hear but cats can, also lending the sense that the Acoustats are alive. And I suspect might be able to "feel" the electrostatic field in front and behind the panels. Their whiskers are very very sensitive to the slightest force. I think they'd be more inclined to go after planar magnetics.
Oh, wait, maybe once or twice I saw a cat clawing the side It was just like one scratch to get my attention. I haven't noticed any mark. Curiously it was when I hadn't been playing music for more than a day, so it seemed like that cat was telling me to turn the music (I normally have background music of some kind playing) back on.
Speaking of background music, I personally think it's a good idea and vastly preferable to thinks like "news" and "talk radio," which are bound to get you enraged, depressed, or something other than just bubbling along. News is more swiftly digested and understood in print.
I've always been very inconsistent about it. sometimes having background music on, other times not, it has been not most of the days of my life perhaps. That's why I automated my system in 2021 and programmed an automatic playlist generator, so I can keep the music playing.
I also worked on the sound of the FM radio so I could keep that playing the classical music radio station all the time. Previously the sound would bother me in one way or another after an hour or two and I'd have to shut it off. So now I have:
1) take the signal from the fixed output of my Pioneer F-26 (one of the greats)
2) Run it through a Musical Fidelity X-10 V3, which buffer the impedances and removes ultrasonic crap (I wonder if the V3 isn't similar to the "Noise Filter Buffer" made by audio genius Mitch Cotter. I would not be surprised if the NFB also used nuvistors as they are wonderful for this task.)
3) Sample with a dedicated ADC, I found the Black Lion Audio Sparrow works extra nice at 24/48.
4) monitor and EQ the signal a bit with Behringer DEQ 2496. I found a small bass notch below 32 Hz helps, otherwise there can be a very objectionable 20 Hz rumble.
The digital feeds into my system on coax. When I record FM, I do so with a dedicated Marantz digital recorder, but only with the preceding
digital chain, as I found the analog to digital conversion in the Marantz to be somewhat "fuzzy," and it works best with either 48kHz or 96khz digital inputs which it resamples in any case (ASRC based inputs) to 48kHz.
With those changes, FM became tolerable to listen to all day long, though I still turn it off when I'm thinking or whatever. If I selected my system wide "mute" control, it comes back on in one hour and 1 minute. If I changed the home control selector to DVD and nothing is playing on or streaming from my Oppo BDP-205, it can be sllent all day or until I remember to put something on (as I'm about to do right now).
I hooked up the speakers today. At first there was a problem with the right channel, hardly any sound, and the interface was even labeled "bad." But as I was removing it to swap with another interface, I noticed one of the wires had come loose. It doesn't hold to the screw well, since apparently the repairer/modified replaced the original wing nuts with integrated locking washers, and if you get the loop connector in between the wrong things (above the lock washer I presume) it doesn't hold.
Now they're working fine. I first noticed they were roughly the same as my originals. But then I noticed a slight increase in harshness from the FM radio signal I'm listening to. I suspect their brightness controls are turned up more than my originals, and/or it's a C mod (my originals) vs B mod difference, with the B mod sounding brighter. Since the circuits are different, they can't be compared simply by measuring the resistance setting of the HF adjustment. I'll just have to experiment with different HF adjustments to see if the new Acoustats can be tuned to match my originals more closely.
*****
When I tested the 2+2's on December 7 before buying, I played William Orbit's "You Know Too Much About Flying Saucers." Even at a fairly moderate level, this invoked rattles on one 2+2 unit but not the other.
Rattles were among the reasons I devised my 125 Hz 8th order phase corrected crossover for my original 2+2's, though not using this song, using another one by Grouse. 4th order didn't get rid of them, so I had to go to 8th order, which helped in other ways too.
I didn't really know the Orbit tune would induce rattles, I just knew it was bass heavy and I liked it.
Now I've tested the new 2+2's playing Orbit through my crossover. No rattles, even at uncomfortably high levels. (The bass from my subs sounds very clean.) I reversed the Acoustat channels and it was still free of rattles.
So perhaps my motto ought to be, "Bring me your old, tired, rattling Acoustats, and they will sound perfect in my system."
The new ones in fact sound great as I used them. They seem to have more "slam," maybe it is the boosted highs after all, or it could be the medallion bass transformers my older system doesn't have.
Still seems to support my belief that these are really best used above 125 Hz, as you might expect with electrostatics. But possibly they both Acoustats handled the bass better when they were new, and their mechanical structures more solid, and perhaps membranes tighter as well.
So maybe the correct understanding is that you want these crossed over at 125 Hz for the long run. Initially you may enjoy the full (even if somewhat fake...boosted with membrane resonance) electrostatic bass, but eventually looseness and rattles will set it. It's above 125 Hz that it's really indestructible, above that pesky resonance.
It's so ironic that an old friend was an Acoustat Monitor (with tube amps) lover who used the Acoustat monitors on the bass. His system in 1981 had Hill Plasmatronics on the highs, sometimes Magnepans in the mids, and Acoustat 4's for the bass. "There's nothing like Acoustat bass," he said.
Well, dipolar electrostatic bass is fine in principle, but you'd need still larger panels to get real bass out of a dipole without any boost or resonance in the membrane structure itself. And in fact electronic boost might not be bad in such a system, best all digital with soft limiting and phase correction.
Or perhaps dipolar bass is not so fine in principle. It doesn't activate room modes nearly as much, but perhaps it also has less "impact." Another friend was always complaining about electrostatic bass, he regards it as fundamentally wrong, but some people get "imprinted" (his word) on it.
In a way, I think he's right. You don't get adequate bass from Quads or Acoustats or many other "full range" electrostatics. I haven't heard the highest end Sound Labs. I only think he's wrong in dismissing electrostatics (not to mention crossovers) altogether. Electrostatics are great used in the middle, between subs and supertweeters. In that range there is no single driver that works as well as a point or line source electrostatic. They just don't do the very extremes very well, most audibly in the bass. And I think it is wrong to expect them too. You just need an adequate digital crossover system like mine to get them to mesh well with subs.
For background music standing up and penetrating the house, nothing works as well as a tall line source electrostatic. Every other room seems adjacent to the concert hall, which is all the more pleasant in background as "not in your face."
***** Update December 9
There is little doubt in my mind now (ie, there is still some doubt) that these new-to-me 2+2's have more dynamic punch. As much as 300% more punch. But, along with this, there is also little doubt (though perhaps a bit more doubt) that over time, they sound more fatiguing. Perhaps I just got tired of examining the 'punchy' sound with relevant recordings at high level. Or perhaps the two observations are part of the same coin. As I previously reported, Stereophile complained of lack of punch and specifically blamed a softness in the highs around 2-4kHz (which is exactly what is required for good sound with most speakers--the Linkwitz/Gundry dip). I wasn't buying their analysis, but perhaps they were right.
There's little question at all that the highs are set to a higher level, though it might be the factory selected level in both cases. The new B mod 2+2's have the big power resistor with a strap, which has a clear marking for the "0dB" position. The older 2+2's have a knob which has no marking, but turned right in the middle (straight up) would seem to be the suggested position (though, since it was modified from A mod to C mod, who knows).
Possibly Acoustat decided to crank up the default level for the tweeters after the Stereophile review (they reviewed an A mod version) so the B mod has a higher default tweeter setting.
Or possibly part of this is due to the B mod vs C mod. The C mod might be less fatiguing as it reduces primary current in the HF transformer. OTOH, the C mod might be less punchy, as it also introduces a second highpass cutoff in the HF circuit response. With B mod the HF transformer primary is direct coupled, with C mod it is not.
If I am lucky, the punchiness will not go away when and if I turn down the highs enough to cure the fatiguing problem.
So here are some possibilities:
1. Punchiness and fatiguing are opposite sides of the same coin. Once the highs are adjusted the same, both speakers will be identical in both parameters.
2. Punchiness is caused by one factor, and fatiguing is caused by another. Some guesses are:
a) punchiness is caused by B mod vs C mod, fatiguing is caused by level of highs
b) punchiness is caused by medallion transformers (B mod unit) , fatiguing by level of highs
c) punchiness is caused by medallions with C mod, etc
I need to assess the level of highs in new vs old Acoustats.
**** Saturday Afternoon
I now have the measurements. As expected, the new 2+2's have significantly extended highs, which only begin to turn downwards from a 4kHz shelf around 14kHz, whereas the old ones begin turning down around 8kHz, mind you this is with the same eq notches I applied for better sound for the first pair, notches at 3kHz and 12kHz. If I continue to use new pair, I might just readjust the notches rather than the speaker HF level. But I do plan to see how HF level works, for the first time, that at least might be what makes this whole exercise worthwhile.
Also, the new 2+2's have significantly larger level, at least 2dB higher measured right in front of the speaker in the same relative place.
It looks to me like the new ones have either a rebuilt or a less deteriorated HV level. Possibly it was modified/repaired with slightly higher voltage level than stock. But it could all be a matter of relative deterioration.
My older pair was worked on by a famous Acoustat modifier around 1998 or so, I think. It seems he would have repalced the HV diodes or other parts if they were deteriorated then. So this makes the difference look more like the new ones having higher-voltage-than-stock.
But even that 2dB level can hardly describe the difference in impact the speaker have, listening to pink noise. The new 2+2's sound 10dB louder. At the same level where the old 2+2 sound as smooth as riding way above Cloud 9, the new ones sound like you're riding just below the peaks of Cloud 9, riding through one mountain of cloud after another. The dynamic contrasts are frightening. Just listening to pink noise. Yet it measures about equally flat, just needs a small bit of EQ readjustment perhaps, and/or lower HF level.
So I think it's the effect of a higher bias voltage, getting more of that "real electrostatic" sound. Maybe it was more like they were new too, but I think also it's a kind of nitro upgrade done by the same guy (also an Acoustat modifier, if less renowned) who put on new socks and may have done other upgrades, including Cardas jacks and new possibly more acoustically transparent socks. I think the upgrade in
bias voltage is minor compared with new, but large compared to elderly bias supply. Possibly the diodes were 5-10% higher voltage than new, is my guess, but 30% higher than old.
I have, never used, a suitable HV 15kV probe. I burned out one of my meters years ago using a 5kV probe in my first attempt to measure Acoustat bias voltage.
Along with it, there's a slight tick about every 20 seconds in one of the new speakers. It takes ear nearly to speaker to hear it. It's quite tolerable like that, though since I bet it results from a tiny bit of arcing it generates ozone and it might get worse, or even self-heal. I smell no ozone and I doubt it's a serious generator.
While the highs do need re-EQ if not HF adjustment, I'm liking the more dynamic sound. My old 2+2's were just too laid back. That was their problem.
Perhaps that difference will survive HF level, EQ, and speaker level adjustments. Or perhaps not.
*****
Just turning down the panel level by 2dB relative to the bass (unchanged) seems to have eliminated the "listening fatigue" problem. Somehow, the new panels play louder. I've also noticed that the upper panels on my older 2+2's seem to have diminished level compared to the bottom panels. A more systematic examination should be done.
I've also noticed that the manual for the A version of the 2+2's says the "flat" position is 3 o'clock, not the 12 o'clock I had been presuming. So it looks like I've had the HF level too low. Which seemed unintuitive to me because I had to add some EQ notches in the treble anyway. But it seems the new speaker has more extended response, and perhaps that's what the HF control being higher does. The combination of my existing HF notches and the more extended response sounds about right, more transparent and punchy than before.
This may just be about the adjustment, and not the many other differences between my two pairs of 2+2's.
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