August 2008Teresonic Ingenium Loudspeakers
by Vade Forrester
Single-driver loudspeakers are reminders of the early days of audio reproduction. They use a single diaphragm to reproduce the entire frequency spectrum -- bass, midrange, or treble, a single driver must do it all. Thats a tall order; and, to be truthful, very few single-driver speakers come close to reproducing the entire frequency spectrum. A large driver does high frequencies poorly, while a small driver does low frequencies poorly. Thats typical of the tradeoffs a designer of single-driver speakers must face. Few designers even try to work with one driver. Stick two or three drivers in a box, add crossovers so the right parts of the frequency spectrum go to the appropriate drivers and, voilà, youve got a modern speaker.
Yet, despite the difficulties in getting full-range sound from a single driver, some flat-earthers (like me) still prize speakers built around them. The light cones and huge magnets needed to make an 8" driver reproduce 20kHz have desirable side effects: incredible speed and dynamics. Except possibly for some electrostatic speakers, nothing else Ive heard comes remotely close. And the drivers sensitivities are high, often over 100dB/w/M. That means the speakers that use them dont need lots of power to produce healthy volume levels. Also, because a single-driver speaker has but a single voice coil to produce all of its output, it is inherently time-aligned. Finally, another advantage of a single-driver design is that because everything comes from the same driver, all parts of the frequency spectrum sound alike and the speaker is intrinsically coherent.
But Ive saved the best for last. Possibly the biggest advantage of a single-driver speaker is that it doesnt need a crossover, which are so common today we take them for granted. Im convinced these filter networks, which intentionally alter frequency response, really do inflict sonic nasties on the sound. A single-driver speaker is connected directly to the amplifier, with nothing else in between, so you can hear what an amplifier really sounds like.
One company that has gone the single-driver route is Teresonic, whose $9975 USD Ingenium speaker uses a large enclosure to coax as much bass as possible from a single Lowther DX3 driver. Actually, "large" doesnt quite capture the Ingenium. Each 84-pound speaker is 73"H x 10 1/4"W x 20"D and shaped like an elongated "S." I think the cabinets are quite handsome and well finished, with a fine-furniture veneer on the front and piano black lacquer on the sides. If the speakers had strings, theyd resemble harps.
I first assumed the Ingenium enclosures were quarter-wave tubes tuned to a low frequency to boost the bass. This type of enclosure has been around since the 1920s. But the Teresonics website describes the enclosure as an "Enhanced Tapered Quarter Wave Tube" (ETQWT). I asked Teresonics president, Mike Zivkovic, to explain the enclosure design. He told me that the ETQWT has five acoustically active chambers: upper and lower, the entire enclosure itself, and two Helmholtz resonators. "All these acoustically active elements have specific roles and work together with the Lowther driver to produce full, rich, but detailed and beautifully natural Teresonic sound." The Helmholtz resonators are used to smooth out some of the Lowther driver's tendency toward shoutiness, purposely via "pure acoustical means, rather than electronics that would add coloration," according to Zivkovic. A full-width slot at the bottom of the enclosure vents the tube. Sharp brass spikes couple the enclosure firmly to the floor. The usual protective disks are available to protect finished floors.
There is a single pair of WBT binding posts on the rear of the Ingenium -- you can't biwire a single-driver speaker. When you connect spade lugs to the posts, youll understand why WBTs cost so much money -- their grip on spades is ferocious.
The Lowther DX3 driver used in the Ingenium retails for $1195 per pair, and the top-of-the-line DX4, which costs $2295 per pair, is an extra-cost option. The two drivers look much the same: an 8" cream-colored paper cone with a coaxial whizzer cone for the highs. However, the DX4 has a larger, stronger magnet and is slightly more sensitive.
A Lowther driver's featherweight cone/heavyweight magnet combination tends to make it inherently self-damped, so if you use an amplifier with a high damping factor, the bass may sound even leaner than it normally does. For that reason, Lowther-based speakers love tube amplifiers, with their typically low damping factors. The Ingeniums claimed 101.5dB sensitivity makes them a natural partner for single-ended triode (SET) amps in particular, even really low-powered ones, and almost any amp should be able to drive the speaker's 8-ohm impedance.
Setting up the Ingeniums
Not unexpectedly, bass response was dependent on placement of the Teresonic speakers. Placing them close to the front wall reinforced the bass, while soundstaging benefited when the speakers were placed farther out into the room. Mike Zivkovic said his favorite placement was just a foot from the wall, and indeed that reinforced the bass quite a bit. That placement let me hear some bass notes Ive never heard from a Lowther-based speaker before. However, because my equipment rack is centered between the speakers and a couple of feet from the wall, I thought placement that close to the wall didnt allow the soundstage to develop fully. I finally settled on a position 13 1/2" from the wall (measured to the closest rear corner of the speaker), which still produced fine bass but brought the drivers nearly even with the front of my rack, thus improving soundstaging. I suspect a location with nothing between the speakers would be ideal.
Reviewers often scoff at user manuals, but Teresonics manual for the Ingenium could serve as a model for other companies. Chock-full of useful information about the speakers and how to extract their maximum performance, its probably the best speaker manual Ive seen. I followed its advice on toe-in, using approximately five degrees from straight-ahead alignment. That produced a solid, dense soundstage and overall smoother sound than pointing the speakers directly at the listener.
Lowther drivers dont travel well, and to no ones surprise the Ingeniums sounded dreadful when I uncrated them and installed the DX3 drivers (the speakers don't ship with the drivers in place). But after the speakers had a couple of days recovery from jet lag, I once again heard typical Lowther sound. However, at first the sound was rather peaky and somewhat wooly, because the drivers werent totally broken in. Now, its a well-known fact that Lowthers take nearly forever to break in, and although the DX3s in the Ingeniums already had around 500 hours on them, that wasnt enough. I put over 100 hours more time on them before starting to listen critically, and they continued to improve during the review period.
After some experimentation, I had settled on my Art Audio PX-25 SET amplifier for use with the Ingeniums, along with an Audio Research LS26 line-stage preamp and Purist Audio Design Venustas speaker cables and interconnects. The Venustas had a creamy-smooth top end and deeper bass than other cables in my arsenal. But even the Venustas left a residual brightness -- that shoutiness. Then I remembered an interconnect I hadnt used in several years, the Blue Marble Blue IC. It had fantastic bass and midrange performance, but it was rolled off noticeably in the treble. In it went between the CD player and preamp and out went much of the over-exuberant treble. The Venustas power cords made a significant difference too, eliminating some roughness in female vocals. The lesson here is to avoid cables with any extra high-frequency energy with the Ingeniums; the speakers need no help in that range.
Although I have enjoyed a pair of Lowther-based speakers for several years, Im all too aware of their major drawbacks, which I've discussed already. Do the Teresonic Ingeniums overcome those issues?
First off, I wont tell you that Ingeniums turned the light-coned Lowther drivers into pants-flapping, gut-punching, wall-flexing bass engines, but these drivers surely didnt sound like typical Lowthers either. There was a surprising amount of output from the enclosure at its 30Hz resonant frequency. Im not used to hearing such deep bass from speakers with Lowther drivers, and I must say its a welcome development. Because the bass comes from the same driver as all the other frequencies, it sounds the same at all frequencies. That means its lightning fast and indistinguishable from the midbass. There was a slight dip between 50Hz and 30Hz, but it was a surprise to hear 30Hz bass from a Lowther-based speaker. In fact, Ive never heard better bass performance from a Lowther driver. The pipe organ on Liszts "Prelude on B-A-C-H" on Reference Recordings 30th Anniversary Sampler [Reference Recordings RR-908] produced a shuddering 32Hz note, which is definitely not Lowther-like!
Again, SET amps are particularly suitable matches since you dont need a lot of power to drive the highly sensitive Ingeniums, and they in turn display the rich tonal palette and palpable dimensionality for which SET amps are famous. But not just any SET amp will work; it must have deep bass response to produce the bass extension that Teresonic worked so hard to provide. Some SET amps are a bit rolled off in the frequency extremes, and you'll hear this with the Ingeniums.
So how about the other Lowther issue -- the shoutiness? Thats where the Ingeniums acoustic Helmholtz resonators kick in, attempting to eliminate the peaky treble. Did they work? Well, sort of. I doubt its possible to eliminate totally the infamous shout without resorting to extreme filtering or digital signal processing, but the Ingeniums definitely reduce it. Treble was still rather energetic -- still a bit bright in absolute terms -- but it was smoother and easier on the ears than that of a stock Lowther driver, that's for sure. The Ingeniums sustained the Lowther drivers reputation for exquisite portrayal of voices. On Songbird [Blix Street Records G2-10045], the tactile coherence of Eva Cassidys voice, replete with extraordinary detail and tonal color, made it seem as though she were right there in front of me. Some of the CD's residual brightness was still obvious, but there was none of the grating peakiness that can make listening to this CD an ordeal.
Do the Teresonics solutions to traditional Lowther weaknesses compromise areas where those drivers traditionally excel, like soundstaging and dynamic prowess? In a word, no. Like any single-driver speaker whose enclosure doesnt create multiple reflections, the Ingeniums' soundstaging was pinpoint and palpable. When I played A Sei Vocis recording of Allegris Miserere [Astrée E 8524], I heard the choral group realistically placed in a medium-sized, resonant acoustic venue. Unlike the Tallis Scholars version of this piece, which has been my benchmark for spatial definition, the room in the Vivoin Priory where this Miserere was recorded is smaller than the spacious church in which the Tallis Scholars recorded their version, and it sounds that way. It was easy to hear each voice in the four-person solo group, although unlike the Tallis Scholars recording, that group is not located a distance away from the main chorus. That was easy to discern through the Ingeniums.
To assess the Teresonic speakers' dynamics, I played Eric Mongrains Fates [Prophase Music MVDA4585] for solo guitar and synthesizer. In the first cut "PercusienFa," Mongrain uses his guitar as a percussion instrument, and the jagged dynamics can be downright scary, so great is their power. Notes flew out of the speakers as though propelled by a cannon. Thats what happens when you combine a very light cone with a very powerful magnet, and it comes along with the coherence and purity that have caused people like me to buy such unconventional speakers. Unfortunately, until I inserted the Blue Marble Audio Blue IC into the system, it was difficult to tell I was listening to a guitar; the sound was all string and no body. Fortunately, with that interconnect in place, guitar sound returned.
Be warned, therefore: Like any high-resolution speakers, the Teresonic Ingeniums will tell you in no uncertain terms how the other components in your system sound, whether thats good or bad. I initially thought the speakers had a really nasty high-frequency peak, but I later discovered the problem was an unfortunate selection of exotic driver tubes in my power amp. Switching to the standard set of tubes smoothed out the peak completely. Youll also hear exactly how different cables sound in your system, not to mention the differences between analog and digital. But feed these speakers right and your appreciation for them will grow.
My Second ReTHM speakers ($7500 when last manufactured) also attempt to tame the Lowther shout. ReTHMs Jacob George takes a different approach than Teresonic's Mike Zivkovic, however. Instead of using the enclosure to tame the peakiness, he modifies the whizzer cone in front of the Lowther DX4 driver, adding an elongated wooden phase plug with several additional perforated paper parasitic cones. To my ears, the modification definitely helps; the shout is reduced considerably, but like the Ingeniums, the ReTHM speakers still sound somewhat bright. ReTHM's approach seems more listenable, or perhaps its just that Ive listened to my speakers for so many years that I have become accustomed to their sonic personality.
George also tried to enhance bass response by placing the drivers in an unusual enclosure. His rear-loaded horn-like enclosure is much shorter and deeper than that of the Ingenium. Unfortunately, the ReTHM speakers bass is more typical of a Lowther-based speaker: not much output below 50Hz. Why not, in that case, add a subwoofer? Ive tried several subs, but I have encountered two problems. First, its really hard to find a subwoofer that can keep up with the Lowthers speed. Many wind up sounding like amorphous mush next to the fleetness of the speaker. Second, because the Lowther driver is so sensitive, many subwoofer amplifiers dont have enough gain to match the speaker's output level.
Elsewhere, the ReTHMs are pure Lowther: super fast and spookily dynamic, highly sensitive, and offering world-class soundstaging. With the shout diminished, they're pretty easy to listen to. Of course, all of this applies to the Teresonic speakers as well. On Songbird, Eva Cassidys voice sounded equally captivating with both speakers, but it was perhaps just a little bit strident with the ReTHMs, indicating the peakiness was not totally controlled. Neither speaker is what youd call smooth in the treble range.
If I could trade my ReTHM speakers even up for the Teresonic Ingeniums, I'd do it, even with their increased visual footprint. Their bass response and abundant Lowtherness were music to my ears.
Properly set up, the Teresonic Ingeniums provide a high-resolution view of the music and the rest of the audio system of which they are part. Their speed reveals a huge amount of information that many speakers smear, and youll probably hear details that youve never heard before with them, unless youve been using another single-driver speaker. Youll also get a solid, panoramic soundstage and staggering dynamics. Im hugely impressed at the engineering ingenuity Teresonic applied to the Ingenium enclosure, which attacks the problems of Lowther drivers on multiple fronts.
However, if the mere thought of six-foot speaker enclosures in your listening room creeps you out, the Ingeniums wont be your cup of tea. But if large fine-furniture-grade enclosures appeal to you (as they do to me), you should definitely check out these speakers. Theyre not big just for the sake of being imposing but as a means of achieving deep bass response.
If youre ready for some high-sensitivity speakers with reasonably wide frequency response, excellent soundstaging, dazzling dynamics, intrinsic coherency, and an arresting appearance, find a way to audition the Teresonic Ingeniums. And if youre already a fan of Lowther-based speakers, you absolutely have to hear the Ingeniums. Ive never heard Lowther drivers sound so complete. Well done, Teresonic, well done!
Copyright © 2008 SoundStage!
All Rights Reserved