Super tweeters. Like infra subs, they deal with the

Super tweeters. Like infra subs, they deal with the very extremes of the audible bandwidth. Basic human biology, the actual frequency response of musical instruments and Redbook's brick-wall filter
would all propose that there's not much if anything to hear with either type of device. First-hand experience suggests something quite different. Of course exotic tweeters of the diamond, beryllium or ribbon
sort already hit the—relative—bat sphere on their own. They're super as is. It's speakers with more conventional tweeters which the supers would seem to stare straight into their soft domes to, cue up the
Jack Nicholson flick As good as it gets, complete them. That movie scene concluded with the gushing
receptionist asking the Nicholson character: "How do you write women so well?" To which author Melvin Udall famously answered: "I think of a man and I take away reason and accountability." Ouch!
Reason and accountability. There's nothing beyond
20kHz particularly for aging males who are hifi's
biggest spenders. But just as true subwoofers increase audible space and scale, so do super tweeters tighten up subjective timing and can even hone
bass articulation.
This cross-coupling between where our add-ons
would seem to operate and where one might actually notice their biggest effects is a bit of a brain
teaser. Or mind fuck as crusty Udall would say. Yet
it's easily demonstrated. The UK's subwoofer specialist REL might have been first to demo their benefits with girl with guitar fare. To any reasonable
thinker, such material lacks any low-frequency content whatsoever. Yet time and again their subwoofer would improve ambient recovery and vocal lock or palpability.
When it comes to super tweeters, the personally most potent proof of their effectiveness came whilst
reviewing the EnigmAcoustics Mythology M1 2-way monitor. It was designed from the onset to be completed with their self-biased monopole electrostatic super tweeter called cleverly the Sopranino. That
speaker system had the most suave articulate gossamer illuminated treble of any box I'd heard until
then.
It was supremely spacious and the antithesis of bright, sharp, needly, annoying or metallic. Since one
can (and I did) run the Sopranino on other speakers too, it also proved how integration is key. Perhaps
not surprisingly, the team work between Sopranino and M1 eclipsed all others.
With the Albedo Audio Aptica and their ceramic Accuton drivers, I had recently acquired a compact 2way floorstander of exceptional qualities... except that it couldn't fully replicate Sopranino's treble magic. Plying some self
interest to pick a specific review assignment, I did some
online recon on current super tweeter
choices.
This soon culminated
in what on paper
looked like the most
promising candidate:
Elac's 360° dispersion
ribbon-based 4pi
Plus.2. As I've learnt
from speakers with
rear-firing so-called
ambient tweeters;
from my true omni German Physiks HRS-120 towers; and from various Gallos I've owned; omnipolar or
at least broad dispersion HF redress not only treble's power response to counteract beaming, they invariably contribute to spaciousness and air. Where true bass appeals to our gut to make music feel bigger
and more grounded, superior treble appeals to mental sight. It's easier to 'see' hifi's artifacts of imaging
and soundstaging. Those effects admittedly don't occur with live music. But they effectively fill in the
gaps left by the recording process. That shrinks a multi-sensory event down to just audible components.
We're served up pure ear fare. Our eyes are left starving.
I already was running Zu's giant Submission subwoofer. I was sold on its guttural effectiveness.
Time to handle the other extreme perhaps and
fully max out my system's aim at both heart and
head? That's feeling and mental appreciation. Why
not? Elac's Yvonne Meinhardt proved amenable to
my inquiry. She agreed to dispatch a review pair.
What else made the 4pi Plus.2 beat all comers on
paper? Big surface area again for improved power
response and dynamics; plus very flexible adaptability. The latter is served up by two chunky knob
adjusters. One handles sensitivity. This matches
the Elac to your main speakers. It covers 84dB92dB efficiency in 2dB steps. 88dB is represented
by the zero indent. That leaves two increments in
either direction. My Albedos are 85dB. My soundkaos are 92.5dB. I was covered either way. Highefficiency speakers from Lowther, Rethm, Voxativ and sundry horns aren't but with stated self interest
at play, none of those were my concern*.
The other knob inserts Elac's high pass at 10'000, 12'000 or 15'000kHz. Before another bad Nicholson
imitation has you raise your eyebrows particularly at the latter two values, do remember. No analog audio filter behaves like a true brickwall. Even set highest, there's enough leakage from a limited filter
slope to make for an audible contribution below it.
Of course you might throw a hissy fit if you
ran the Elac solo set to 15K. You might hear
nothing at all. Or perceive some very minor
inner-ear pressure at best. Nada might very well be the case. Explaining then how it does make a pesky
difference once you reconnect the mains now becomes a subject of endless speculation and self doubt.
Are there intermodulation effects at work just like higher amplifier bandwidth of Spectral or Goldmund
reach makes for purer treble? We certainly don't hear to 1MHz. Playing back a steady-state 15kHz tone
(if we aren't old enough to no longer hear it) won't sound any different over such an amplifier. Yet we
are sensitive to HF phase shift with complex music signal. That consists of fundamentals plus plenty of
higher harmonics all riding on steep transients. And it is phase shift or timing errors which such circuits
eliminate over say a transformer-coupled valve amp that's 3dB down at already 30kHz.
Getting embroiled in theoretical discussions on this subject unless one had the requisite know-how is, I
believe, more apt to contribute to urban audio myths, confusion and ongoing ignorance than it is to
achieve anything useful. Restricting things to personal experience on the other hand contributes to a
growing body of evidence by fellow users. Whilst none of us might be in possession of the explanation
or even a semi plausible derivative thereof, we can certainly throw our hat into the ring. We can state
that yes, for us such devices have audible merit; list their specific benefits; and trust that with enough
such feedback, fellow hobbyists might feel motivated to experiment. The rest is for psychoacousticians,
engineers and audiologists to sort out.
This conveniently returns us to the physical object at hand. Available only in gloss black—the anthracite
gray called Titan Shadow has been discontinued—this cast 4kg affair with its mushroom top is rather
more substantial and sizable than isolated photos let on. As you'll see when perusing their website, our
Germans from Kiel in the country's northern Bundesland of Schleswig-Holstein have extensive experience with exotic tweeters.
They are amongst those who early on exploited the expiration of Oskar Heil's patent for the air-motion
transformer to roll their own. That in-house development is now in its 5th generation and even includes
a wicked dual-concentric which combines a dynamic midrange with an AMT tweeter (whose positioning
in the center is adjustable in the top version).
The company's two flagship models incorporate an AMT which in Elac
speak is a JET; plus a built-in 4pi Plus.2 super tweeter on top. It's the Germanic take on the same recipe which the Mythology M1 pursues by marrying an already very capable main tweeter with a dedicated super tweeter.
Other well-known purveyors of discrete super tweeters include Tannoy and
Townshend. Similarly to how a sub can connect speaker level via a 'biwire'
cable where one half connects to the mains, the other to the subwoofer, so
super tweeters are fed the same signal as
the mains (usually by jumpering directly off
the speaker terminals for a shorter run but
possibly also by doubling up on the amp's outputs). You thus have another cable hanging off your speakers. That could become a minor eye
sore at least from the side. But as all women in pointy high heels would
tell us, beauty comes at a price. No pain, no gain.
On actual wallet cramps, here it means €2'098/pr. That's serious money
for what might seem but a tweak and nothing you'd throw at a pair of
$1'500 mini monitors. In fact the inherent see-saw principle of building
out the frequency extremes nearly demands that your main speakers
be bass complete. In most reasonable cases that should mean an actual
infrasonic subwoofer rather than attempting this feat with a passive
tower. The sub-ject for music of course is quite taboo. Most closeminded audiophiles associate subwoofers with nothing but T-Rex foot falls, submarine rocket launches
and other Hollywood excesses. It's the super tweeter which remains well beyond adolescent pursuits.
Super tweeters don't make your pants flap. They don't dislocate pictures from the wall. They don't annoy your neighbours. In fact with adolescent music replayed as compressed MP3 over inferior hardware,
they make for very poor and ineffective demonstrators indeed.
Super tweeters are for connoisseurs. They must trust their own ears since there is no truly compelling
scientific argument to rationalize the device. Perhaps that's why compared to subwoofers, super tweeters are so rare. It's nearly impossible to argue their merit successfully without having first-hand experience. Even then many you'll talk to will merely grant you a blank stare or commence a litany of arguments to prove your folly. For another commercial realization of a ribbon-based omni tweeter by the
way, there is the rarely seen Raal Requiste by Aleksandar Radisavljevic of Raal Ribbon. My photo shows
the prototype's circular ribbon array.
To complete introductions, Elac the company goes back to 1926 as Electroacoustic GmbH. After WWII, a
Siemens contract for a radio set put Elac on the audio track. By 1948 they had their first record player
with changer automatic. Production of loudspeakers began in 1984 and the first iteration of the 4pi omni tweeter occurred a year later. By 1998 Elac had its own in-house magnet manufacture. 2 years later
they began to produce their JET tweeters with SCARA robots. 2003 saw the JET in its 3rd iteration. 2005
launched the dual-concentric X-JET. In 2008 they began to supply the automotive market with OEM
drivers.
All throughout, the base of operations was always Kiel where I grew up and went to school. It's a harbour town on Germany's East coast. It not only serves as a very busy ferry terminal to Scandinavia but
also hosts the annual Kieler Woche. That's a world-famous sailing regatta in the Baltic Sea that's grown
into one of the globe's biggest events of its kind.
For final tech inquiries, Yvonne Meinhardt connected me with Rolf Janke. I wanted to know whether the
4pi Plus.2 was a circular AMT derivative or actual ribbon (their drawing suggested the latter); whether
its sensitivity adjustments were basic voltage dividers or a multi-tapped transformer; and how steep or
shallow the hi-pass filter slopes were. Obviously adding a parallel nominal 6Ω load increases amplifier
demands even if tweeter bandwidth isn't current hungry. Still, your amp should be stable into 4Ω even if
your speakers are of the 8Ω type. Depending on adjustment, the 4pi Plus.2 can present a minimum 3.5Ω
load.
For wiring up the 4pi, Elac don't recommend anything above 2 x 1.5mm² for up to 4-meter runs unless
the main speakers are low-impedance types. That might warrant 2 x 4mm² conductors for the super
tweeter. Obviously one shuns highly resistive cabling due to its counterproductive HF roll-off. The 4pi
diaphragm is a 5µm
aluminium foil embossed with a wave
pattern driven from a
custom transformer to
guarantee 53'000Hz
bandwidth. Because
this transformer's
quality and stability
are critical, the efficiency adjustments are
made with resistors,
not secondary windings. The filter slope is
a 2ndorder function
both acoustical and electrical. At the maximally 1cm wavelengths involved, Rolf Janke opinined that
phase wasn't that interesting. The high-pass frequency is adjusted with capacitor changes. The enclosure and wave guides are diecast aluminium. Rolf was quick to stress the vital importance of their nonlossy switches which must operate with very low voltages. "These switches are silly expensive" he
laughed on the phone, "but essential to the peformance."
Finally and as you may have figured out already, the 4pi Plus.2's circular dispersion implies that it will at
the very least restore full-space HF radiation to correct in-room power response for the treble which
always falls off seriously above 7kHz. That's true even if its 3'500 to 53'000Hz coverage won't add actual
bandwidth beyond an advanced main tweeter (Elac's own JET makes 50kHz). That's where the Elac goes
beyond competing super tweeters to propose that its primary benefit isn't bandwidth at all. It's its
unique 4pi dispersion. It's precisely why this Elac had my attention over a revisit with the monopole planar Sopranino. Gallo's 180° CDTIII tweeter does wonders for soundstaging. Didn't it stand to reason that
the 360° 4pi Plus.2 might graft a satisfying echo thereof—or even more than an echo—onto normal
speakers?
Playing the room. Like LF which ride room modes for boom
nodes, the 4pi Plus.2 plays the room with its deliberate reflections in all directions. But unlike LF, it cannot cause resonant problems which would impinge into and muddy up
the vocal range. Its wavelengths are far too short. The only
issues are fixing the high-pass and output level relative to
the mains with the precision switch controls. Here the Elac
is rather less fussy to get right than a subwoofer; or integrating a passive 'full-range' speaker into a setup for most
linear powerful bass without hot spots.
Conceptually Mark & Daniel tread the same path with their
upfiring ambient AMT dubbed Omni Harmonizer. The obvious difference? Theirs must first reflect off its 45°-scattering dispersion lens. The 4pi Plus.2 achieves its
radiation pattern with direct output and far lower moving mass. Technically it would appear to be the
more sophisticated and advanced solution to go after the same effect.
The 4pi Plus.2 is intended to broaden the dispersion of your main tweeter above 7kHz where the latter
collapses. That's exactly how Rolf Janke explained they do it for their two flagship models. Since the
mushroom's output is too attenuated in the presence region to interfere, the main tweeter still locks in
all the usual directivity and image localization cues it usually does vis-à-vis the midrange. A bit flippantly,
you might say that the 4pi Plus.2 is a saint maker. It's in the popish business of adding ethereal space
halos around our virtual performers. Now some final tidbits.
By 1998 all but one vendor they'd
sourced magnets from had
moved to China. So Elac took on
magnet production to control this
vital part of driver manufacture.
That's true vertical integration.
Why Elac's 4pi hasn't more press
particularly online will be due to
its 30-year run next year. It's ancient news. But nobody really has
come up with anything better since. It's still fresh as dew and arguably more relevant now with the
raised HF ceiling of high-resolution music files. Nobody dreamt of those five decades ago when Elac still
built cartridges.
For that we look at October
29th, 1957. This date marks the
day by which Elac had sold an
astonishing 3 million KST103
phono cartridges. The display at
left memorizes that achievement. Elac's auto changer from
1948 at right reaches even farther back.
Such roots show commercial
resilience. Now we have a fuller picture against which to assess their long-lived super tweeter.
Sœur Marie Keyrouz's Psalms for the 3rd Millennium were recorded in a
church. They not only feature her Oriental Ensemble de la Paix but also the
Ensemble Orchestral de Paris with chorus. The 4pi Plus.2 accomplished a few
things. It increased depth of field. There clearly was more spatial grandeur.
Without dissecting the choral voices into cutouts, it cast a more persuasive
sense of multiplicity, of many different voices singing in unison. And it better
differentiated the solo vocals from them whilst also bestowing a quasi halo
of recorded reflections around the sister to illuminate her against space. Saint maker indeed.
On Aytaç Doğan's glorious Deva album of popular Turkish songs instrumentalized for qanun and accompaniment, the "Khallık Fernını" opener sports
very wispy cymbal and brush work across a widely spaced drum set. Some
of it is so fine as to nearly fall below the treshold of audibility. The 4pi Plus.2
lowered that threshold and with it lifted a small damper on decay lengths.
Then it physically raised these sound makers up a bit for increased height. That's because the ribbons
sat a hand's width above the main tweeters.
As had the choral heads on the otherworldly Keyrouz album, the massed strings
on Omar Faruk Tekbilek's riveting desert soundtrack for Kebelek|The Butterfly showed rather more individuated 'white caps'. The illusion of paralleled performers playing the same notes was heightened. The breathiness of the solo bass
ney was enhanced as well. Close-mic'd piano had clearly more overtone action,
more energy spray off the strings. With Javier Perianes' inspired reading of Blasco
de Nebra's Piano Sonatas [Harmonia Mundi], this effect was much subdued due
to more farfield microphones. Now I had enhanced depth of field again.
Nagra's HD DAC treats all signal as DSD. Here the Elac omni restored treble liveliness. Compared with
standard PCM converters but also Lindemann's musicbook:15 whose AKM 4490 silicon treats DSD with
its own circuitry, '1-bit' has its own softer more mellifluous flavour. If you miss PCM's shinier top which
polishes more gloss on tone textures, the 4pi Plus.2 is that Carnauba wax. Don't mistake this for brightness. It's not. This Elac action occurs above the region where a misjudged response telegraphs as bright.
It's not about the Lowther shout domain. It's the realm of air.
Another fringe benefit was better distinctiveness at lower levels. No matter what, reducing SPL fogs
over the hifi window. It's not a matter of if but of when. This top-end loss and its various consequences
are the things which classic tone controls—more or less crudely perhaps—compensated for. With the
4pi Plus.2 in the mix, the onset of this clouding over was delayed. Given that we do a lot of listening at
lower levels, this was most welcome.
Besides enhanced spaciousness, air and slightly glossier tone colours—plus all the obvious isolated stuff
of better visibility for steeper more brilliant triangle hits and fierier violin flageolet—the perhaps primary
benefit for visually oriented listeners should be a keener sense of 'holography'. That is about a level
of distinctiveness and how individuated sounds peel out of their surroundings and against silence. Clearer separation is one aspect of it and as such most apparent on dense material. It's like turning up overhead lights to increase contrast. It's the inverse of what happens at a symphony concert. Before the
conductor flicks his skinny baton for the first mark, the lights gradually dim. With it visible contrast diminishes as does separation. We're supposed to rely less on eye sight and make our ears the primary
participants.
With playback, actual sight doesn't factor one iota.
Turning some virtual overheads up by a few dB
compensates. It makes things more specific. That's
not a poetic term. It reads quite dry in fact. Yet the
actual effect isn't dry but fluid. So let's return to
something seemingly basic but well recorded. Even
more importantly, it's played brilliantly. With the
long solo opener of Rafael Cortéz's Cagiñi [Herzog
Records] and the omni tweeters in play, it became
easier to appreciate the many fine nuances of tone
modulations which this amazing guitarist coaxes
from his red instrument.
With the same set of strings, there is a surprising
breadth of timbre variations on hand. These elements are easier to appreciate and fall into as a
natural byproduct of attentive listening. One can
simply follow the melody and leave it at that. Or one can listen more inclusively and pay attention to
these tonal shadings as well. It's up to the listener. With the Elac, it is a bit easier to get into harmonic
shifts and admire this element of artistic self expression.
Wrap. Once you really think about its tech, the
resultant dispersion pattern, its operational bandwidth and what elements of playback it addresses,
the 4pi's effectiveness comes as no surprise. It is
perfectly logical and predictable. The real surprise
is twofold. One: why haven't we heard more about
this brilliant invention? That'll be due to its first
iteration having launched in 1985. Two: Since Gallo
discontinued their top-mounted spherical tweeter
which sat as a mohawk atop a spun aluminium
sphere, only mbl have anything like it. Being trade show regulars
which many folks have heard and many commented upon, associating Elac's 4pi Plus.2 super tweeter
with that type of presentation seems most à propos and intuitive.
Naturally it only factors for the very top. mbl's omni approach extends far lower in frequency. But as a pointer on what to expect, it
seems fair to say that with the 4pi Plus.2, you'll have some of that
air/space thing going on with your far more conventional speakers
too. Hopefully this report has made Elac's omnipolar super tweeter
newsworthy, again. Relative to my Aptica, it did add the Mythology
M1 treble magic I thought it might. In closing, I'm no expert on this
breed of device. I've for example not heard the AudioSmile, muRata,
Tannoy, Tonian or Townshend though some of these were written
up in our pages. What I do know is that all standard tweeters are
good to the limits of my hearing. Adding another beaming direct-radiating tweeter doesn't add much.
It's Elac's 4pi radiation which makes the decisive difference. Because mbl's driver tech isn't available as
an add-on and would likely be very inefficient and even costlier if it were, the 4pi Plus.2 occupies a
league of its own. In my book, that makes it an especially super tweeter indeed.
Reviewer: Srajan Ebaen
Source: 2TB iMac 27" quad-core with 16GB of RAM (AIFF) running OSX 10.8.2 and PureMusic 2.02 in hybrid memory play with pre-allocated RAM, Audirvana 1.5.10 in direct/integer mode 1, Metrum Hex,
SOtM dX-USB HD with Super-clock upgrade & mBPS-d2s, AURALiC Vega, Aqua Hifi La Voce S2, Apple
iPod Classic 160 AIFF-loaded, Cambridge Audio iD100, Pure i20, Pro-Ject Dock Box S Digital, RWAmodifed Astell&Kern AK100, Nagra HD DAC with MPS [on review]
Preamplifier: Nagra Jazz, Bent, Audio Tap-X, Esoteric C-03
Power & integrated amplifiers: FirstWatt S1 monos, SIT2, F6; Crayon Audio CFA-1.2, Bakoon AMP-12R,
Goldmund/Job 225, Gato DIA-250, Aura Note Premier, AURALiC Merak [on loan]
Loudspeakers: Albedo Audio Aptica, soundkaos Wave 40, Boenicke Audio W5se, German Physiks HRS120, Zu Audio Submission
Cables: Complete Zu Event loom; KingRex uArt, Zu Event and Light Harmonic LightSpeed split USB cables; Tombo Trøn S/PDIF; Van den Hul AES/EBU; AudioQuest Diamond glass-fiber Toslink, Arkana Research XLR/RCA and speaker cables [on loan]
Powerline conditioning: GigaWatt PF-2 on amps, Vibex Granada on all components
Equipment rack: Artesania Exoteryc double-wide three tier with optional glass shelf, Rajasthani hardwood rack for amps
Sundry accessories: Extensive use of Acoustic System Resonators, noise filters and phase inverters
Desktop system: iPod/AK100 digital transports, Wyred4Sound minT, Aura Vita, Gallo Strada II + TR-3D
Room size: Irregularly shaped 9.5 x 10m open floor plan combines the living/listening room, kitchen and
office. Added to this space the speakers see the air volume of the entry hall and a long corridor plus the
2nd-storey 6 x 9.5m loft. Wood-panel ceiling slopes up to the loft. Parquet flooring. Lots of non-parallel
surfaces ('vertical gable' windows, twin-angle ceiling, spiral staircase enclosure, fireplace enclosure). For
a pictorial tour, see here.
http://www.6moons.com/audioreviews2/elac2/1.html