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September 2006

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Teresonic Ingenium
A True, Full Range, Single Driver Speaker
Article By Scott Faller
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New Adventures In High Efficiency  This stop on the high efficiency trail brings us to a true, full range, single driver speaker, the Teresonic Ingenium. Though you may be completely unfamiliar with the company Teresonic, you guys know the drivers they use, Lowtherís. When you look at the pictures of these speakers, you can tell right off the bat these speakers must be seen to fully appreciate their beauty.


Letís Dive Right in Shall We?
The Ingenium loudspeakers stand a little taller than I do at a touch over 6-feet high. They are a sleek 10-inch wide at the base and narrow ever so slightly to about 8-inch wide at the top. One of the most attractive features of these speakers is their profile. The designers have formed layers of wood to make these speakers into a very slender and elongated S shape. As I talk to the folks at Teresonic, they tell me that the person who crafts these cabinets is actually a musical instrument builder also. That goes a long way to explain the curved cabinets and the non- parallel sides. As Iím told, the designers feel that the speaker cabinets should be more like a musical instrument rather than a standard speaker cabinet to reduce the internal buildup of standing waves by eliminating parallel surfaces. That is perfect theory but quite difficult to implement in the real world especially dealing in wood.

Teresonic IngeniumThe front of these speakers have Rosewood veneer while the sides are finished in a high gloss black with the back having a textured black veneer. There is layer upon layer of lacquer applied to the cabinet and then itís polished to a mirror like finish. There is no way around it, these speakers are just plain old sexy. As many of you will recognize, the Ingeniums donít appear to be much more than a simple TQWT (tapered quarter wave tube) or a Voigt Pipe but there is more hidden beneath their gorgeous exterior. Moving onto the rest of the enclosure, the cabinet sides are constructed from 0.75-inch MDF. The front and rear of the enclosure, since they are curved, have been constructed of laminated layers of wood that are built up to 0.75-inch thick. There are several internal braces to help control cabinet resonancesí. Something of note also is the back of the Lowther driver has a brace/support which helps keep the basket and the front and rear baffles from resonating (that actually changes the frequency rather than eliminating it).

The driver that I have for this article is the Lowther DX4. Many of you are familiar with this particular driver. This is the Lowther driver that uses the Ďdoorknobí phase plug. Teresonic also offers these speakers with the DX3 and the PM2A driver. As youíve probably surmised, the Teresonic design is letting the Lowther drivers run full range. There are no crossovers, no notch filters, no baffle step compensation networks, just a pair of WBT Binding posts, some Teresonic Clarison speaker cable and the Lowther drivers. Before I go too far on their design lets do a little Lowther refresher course. The typical Lowther driver has a Qts that hovers around 0.25. For those not in the know, a Qts in this range lets you know that this driver does not work in a large bass reflex enclosure. No matter how hard you wish, it doesnít work, period, end of discussion. What happens when you try this is you get a mid-bass suck out at about 150 Hz and a rather large bass spike at about 85Hz (see graphic). As you can see by modeling a Lowther DX4 in a 2.5 cubic foot vented enclosure, the end result is none too pretty. I can attest to the way this Ďdesigní sound in real life. Been there, heard that. It pretty much mirrors the computer model.

The initial research done by Neville Theile in the early 1960ís and the further refinements made to Theileís findings by Robert Ashley and Richard Small in the early 70ís, clearly defined parameters (mechanical and electrical) in which speaker drivers could be modeled using standard test instruments and a handheld calculator to determine the proper enclosure and port size for optimum sound. The best part of their (collective) findings was that the finished speaker measures within a fraction of a db of the anticipated result. No matter how deep you might stick your head in the sand, Lowthers wonít work in a standard monkey coffin (vented enclosure). I mean, who are we to ignore science, right? Bottom line, the Lowther driver appears to be best suited for a back loaded horn due to its low Qts.

Hereís where the contradiction begins (play along with me for just a while longer). When all is said and done, there isnít a tremendous amount of difference between a Voigt Pipe and a bass reflex enclosure, with a few notable exceptions. First, a quarter wave (properly designed in a true Voigt Pipe) includes a very specific amount of stuffing designed to filter out some of the back wave frequencies (mainly midrange) that resonates within the enclosure. Second, the placement of the driver on the front baffle is critical to prevent comb filtering in the bass regions, not to mention other sonic anomalies. There are a few other issues but these two are the most notable. If ever youíve listened to a quarter wave that uses a Lowther driver, youíll know first hand that they suffer from similar (not the exact) issues that a Lowther in a bass reflex enclosure does. The primary issue isnít so much the bass hump, itís the mid-bass suck out and the comb filtering of the bass. It is an issue that has been nearly insurmountable... until now.

The designers at Teresonic have come up with a rather inventive cure to the suck out and comb filtering. Their enclosures are actually a hybrid, which they refer to as an ETQWT or an Enhanced Tapered Quarter Waver Tube. They incorporate both the quarter wave design and Helmholtz resonators. I know, a vented speaker enclosure is a Helmholtz resonator in and of itself but read on. Without giving away too much proprietary information away, Teresonic has designed a number of Helmholtz resonators tuned to different frequencies and placed them within the quarter wave pipe. And guess what, it works! Honestly, when first receiving these speakers and looking inside the cabinets to see the Helmholtz resonators I thought, wellÖ wasnít sure what I thought. Simply knew it was a little weird. That said, I thought it seemed to be a pretty intelligent approach to a longstanding problem but I reserved judgment until I had a chance to listen.


The Systems & Setup
As usual, let me describe the systems that I used to drive the Ingeniums. Since these speakers are essentially a vented enclosure that is quite similar to an EBS (extended bass shelf) design, I experimented with several amplifiers including single-ended and push-pull. As you are probably aware, vented enclosures can deal tube amps a fit at times. Since SETs have damping factors (usually) less than 5, I tried a number of various tube design amplifiers to see which was the best mate to the Teresonic Ingeniums. At times also swamping resistors with the single-ended gear (more on that below).

The amps used included Welborne DRD 300B, my Handmade Audio Classic 2A3, the Audio Space 6M 300B push-pull (which are in for review), and finally for giggles a big pair of heavily modified Radii GP-75 KT-88 monoblocks putting out almost 100 watts per channel of power. Source gear was heavily modified Korato KVP-20 and digital provided via the Bolder Cable modified Squeezebox 3 using analog outputs rather than my usual MHDT DAC. The entire system gets clean power from a DeZorel Audio Reference Senior line conditioner.

Setting up the Ingeniumís was interesting to say the least. If you know Lowthers like I know Lowthers, you know I was in for some lengthy positioning issues. Decided not to tear apart my main Fleapowered reference system to test these speakers. I thought since these speakers will likely need either to be placed at the back wall or maybe even corner loaded Iíd better set them up where my old Big Fun System used to reside at that opposite end of my 40-foot long listening room. Itís a good thing I did it this way because thatís exactly how they sounded the best, backed against a wall.  Their final placement was about 30 inches from the sidewalls and the Ingenium loudspeakers backed against the wall. This gave me a nice, smooth, even bass response all the way down into the lowermost octaves (more on this in the next section). Also utilized some homemade OC-703 2x4 acoustic panels strategically placed between the speakers and at the first reflection points.

Teresonic provided their brew of speaker cables called the Clarison. These cables are copper stranded wire that is sheathed in an armor-plated shell to filter out RF and EMI and claim this wire and shielding is used in fighter jets. Canít say for sure, though can say the Clarisonís did sound better than my home brew silver plated copper cables in this system. To my ears, my silvers were just a bit too forward for the DX4 drivers where the Clarisonís sounded more natural.


Taming The Beast
As some of you are aware, certain Lowther drivers can be a bit forward sounding. This is not an issue with my Lowther PM2A. Of all the Lowthers Iíve heard, the 2A are by far the smoothest yet most detailed speaker to my ears. Am not here to tout the PM2A, though am here to tell you how the Lowther DX4 drivers sound in these most righteous cabinets. Letís talk phase plugs first. The DX4 drivers come with what I (and many people) refer to as the Ďdoorknobí phase plug. The reason itís called that is because it looks like a doorknob. On hand is also a standard pair of bullet plugs and custom made pair of what I call Ďbroomsticks.í The broomsticks are fashioned after the bullet plugs except they are a little more than an inch longer.

Each one of these phase plugs in the DX4 drivers produce their own unique sound. The doorknob, in my opinion, does strange things to the overall sound. It diffuses the highs a bit too much and also contributed to them rolling off just above 8k. Installing the broomsticks definitely restored the highs but found that the midrange came just a little too far forward for my tastes. They werenít bad mind you, but just not to my liking. By far the smoothest sounding to my ears was the standard bullet plug. The midrange and treble region was far smoother and more extended than the other two phase plugs. The good news is the bullet phase plugs are readily available from Lowther or one of their authorized dealers for around twenty bucks. Naturally the standard bullet plugs were employed for the remained of this review.

Knowing and living with Lowthers on a daily basis for the best part of three years, I know that although they are somewhat finicky at first. Fortunately they can (usually) be tweaked into submission. In the case of the DX4 driver, I was still experiencing a heavy amount of forwardness in the mids and treble region. Iíve played with notch filters that have worked quite well in the past and in fact used a notch filter when first braking in my PM2A drivers when they were in the Martin King MLTLís (Mass Loaded Transmission Lines). Have to admit I got some darned nice sound out of those things.

In playing with notch filters when you are running SET amplifiers, the filter tends to suck out some of the life. It is not too bad mind you though with the purity of an SET you can definitely hear the losses. Determined not to use a passive filter and set out to do some Lowther tweaking. Knowing that the some of the Lowther drivers can benefit from either the ĎCotton Ball Tweakí or the ĎFoam Tweakí, I had myself a plan. The cotton ball tweak is a relatively simple and effective way to tame the midrange and treble energy generated in part by the whizzer cone. What you do is take one pair of standard cotton balls per driver, evenly pull them apart until you have an elongated cotton ball that is about two or three inches long. Make sure they arenít lumpy! Then you roll them into a slightly tubular shape and very carefully wedge them between your whizzer cone and the main cone of the Lowther driver. This is quite effective at damping the whizzer and drastically reducing their forwardness.

The other tweak is the foam tweak. In my case I took some standard foam as used in a mattress pad and cut some small wedges out of it. The wedge is about  1-inch long, about 0.5-inch thick on one side and about  0.25-inch thick on the other. After you have these cut, you place the foam wedge between the whizzer cone and the main cone of the Lowther driver. The wedge is held in place by the rolled lip of the whizzer cone. I tried the foam wedges in differing quantities and settled on five equally spaced wedges. I tried a complete Ďring of foamí but then the DX4 drivers took on a megaphone-like quality. In the end I settled with a combination approach that worked extremely well, at least to my ears. Used five equally spaced foam wedges and between each of the wedges I pinched off a little bit of the cotton ball and stuffed it all the way down to where the whizzer attaches to the main cone. This made these drivers sound amazingly close to my PM2A!

As you are installing the tweaks please be very careful. Even though the cones are very rigid I would hate to see you poke something through them. In my case I used a pair of hemostats that were left over from the 70ís (Steven sez: Usually at this point an editor such as myself would chime in with innuendos concerning the original use of hemostats, but since my pair here are of great use for connect ing very fragile cartridge wires I shall let this moment pass without comment). Oh, and donít try this with music playing. Even better yet, turn off your amp as if you push a little too hard you wonít short out your voice coils (or scrape off the Ďhi-ferricí shellac that Lowther coats their motors with). Just in case you were wondering, Teresonic also offers the notch filter for those not interested in tweaking their new speakers. As expected, the notch filter they offer works just fine. It tames the forwardness of the DX4 without too much loss of the ĎLowther magicí.


Measure Schmeasure
This is something personally vowed I would never do, but here I am staring you guys right in the eyes about to tell you that Lowthers in the Ingenium cabinet are down 3dB at 30Hz. So before you laugh and find something else to read, thought I would break my longstanding rule. Below are published measurements on this pair of speakers. Why publish measurements? Because you wouldnít believe me if I didnít (see, I know you guys)! The measurements were taken in room and just for the record my room is 38í long, 15í wide, has 7.5í ceilings that are acoustic tiles with an NC of 52. The floors, front and back walls are concrete. OK, get over yourself already. If youíve read my previous articles you know at times I do take measurements but do not publish them. Generally keep them as a reference to help remind me of where Iíve been and listened to (of sorts). I use the Sencore SP-295c SoundPro Audio Analyzer for those of you who must know. This thing is said to be the Holy Grail of handheld audio analyzers. It does everything and then some. Bottom line is, this isnít a lowly Radio Shack sound meter. This is a finely calibrated professional-grade device that was used to measure the Ingeniumís.

As you guys know, loudspeakers are highly room dependant. The Ingeniums are no different. When I set these up on the far side of my listening room, I expected to be able get good sound by placing my listening seat about 9í away from the speakers. This has always proved to be a Ďdecentí starting place knowing the acoustics of my room. Started with the speakers towed in rather heavily (think pointing at my ears). After listening for about 30 seconds I needed to take a quick break so I could stop my ears from hemorrhaging. Needless to say, pointing these directly into the sweet spot wasnít a very good idea. I should have known better. Hereís some good advice to remember during your setup, start with your Lowthers perpendicular to the back wall. Slowly tow them in until you find that magic balance of a relatively flat frequency response. Once you do, youíll discover a rock solid center image that is of the right proportions along with smooth, well-defined highs. As it ended up, I had the Ingeniums towed in about 10 degrees from perpendicular. This took care of the last little bit of treble rise I was experiencing without rolling the highs too much. If you look at the graph again, youíll see highs started rolling at about 12kHz. If I had taken on axis measurements, the highs wouldnít have rolled off that low. Again, itís all about choices.


So How Do They Sound?
First up was the Audio Space 6M 300B push pull amps since they need to make there way back to Gini Systems. The pairing of the Teresonic Ingeniums and the 6Mís was a fabulous combination. The clarity and definition of this push pull 300B design fit these Lowthers like a glove. Amongst many, many albumís I listened to, several of them were absolute standouts. The first that comes to mind is Natalie Merchantís Ophelia. Although I was never a big 10,000 Maniacs fan, this album is particularly good. The recording quality is excellent. There is a nice mix of instruments that gives a great test for timbre and Ďpresenceí. In particular the track My Skin you can clearly hear Natalie stepping on the sustain pedal (or the sostenuto pedal, I canít tell which) of the piano and the eerie out of phase creaking sound of the pianos mechanics. If youíve not heard this before, it can be a bit unnerving as you find yourself looking around to find out who is sneaking up on you.

As I listen further, the timbre of Natalieís (or George Laks) piano is extremely good especially on this and other cuts. The gentle taps on the cymbals are extremely well defined and extended with very little hint of rolling off due to the DX4ís limited upper end. Natalieís voice on the Ingenium is something to behold. Her vocals are nice and full without any exaggeration as imparted by so many speakers. In the same vane, there is no hint of loss in midbass at all. The word that comes to mind is natural. The next cut that is truly surprising on this release is Thick as Thieves. On the chorus, the arrangement rolls in a heavily processed floor tom drum. This drum beat is centered at about 45Hz. To use an expression that the 12-Volt guys throw around, the Ingenium spoeakers hit really hard on those drum beats. Let me put it this way, Iíve never heard this kind of bass out of Lowthers before, ever, and it doesnít stop at 45Hz. It goes deeper.

Next up was some Lina from Stranger on Earth. No doubt you are asking yourself, who the heck is Lina. Well, Lina does this extremely cool cross of Hip Hop and Flapper Jazz. Needless to say, there is plenty of deep, ramped up bass on this release. Track three, It Ainít Me drops down to the low 30ís and guess what? The Ingeniumís not only keep up, but it is some of the better bass Iíve heard. Itís clean, tight and extremely well defined. Know what else? You can crank these things. I realize that Teresonic may not like reading this but I cranked the hell out of the Ingeniums on some heavy bass tracks just to see what happened. Simply needed to know if the Lowthers were going to Ďbarkí when pushed with extreme bass. Know what? They didnít flinch and just kept digging deeper as the bass stayed rock solid. Solid to the point my pants legs started shaking at about 100dB. Even at this volume, the image stayed remarkably stable. The weird thing was the soundstage actually deepened. As much as I hated to do it, had to pull the Audio Space 6Mís from the system so they could be sent back to Gini Systems. Shame too because this pairing really was stunning. It was as some of the best sound Iíve heard next to my own reference system.

Next up was my Handmade 2A3 Classic. At 2.5 watts, it qualifies as a true fleapowered amplifier. Iím using the Sophia Meshplates and the Mullard GZ-34 rectifier tube. This amp is a real honey. As many of you know, a 2A3 is a bit more tonally Ďrichí sounding amplifier. My Handmade Classic is no different. Since I tweaked the DX4s, thought it would only be fitting to toss the single most sibilant recording I know of, Eva Cassidyís Songbird. If any songs are going to show warts in the mid to treble region, this collection will. After letting the Lowthers warm up for a while I have to say that the treble region was extremely smooth without showing harshness. As you would expect, detail was delivered by the truckload. As I walk down the frequency scale into the midrange, there are still huge amounts of detail that youíll seldom hear on a standard pair of multi-way speakers. Since the texture of the 2A3 is richer than the 300B I was a little worried that the midrange and vocals might be a little too Ďthick.í As I found, the vocals were nice and full without being overblown in the least. There wasnít a hint of the midbass polluting the vocals at all. As we work our way down to the lowest octaves, the bass stayed extremely good which I still find quite amazing. Granted, the enclosure causes a few weird harmonics at in the lowest octave, which made those final 20Hz of sound a little Ďpookieí (thatís a technical term) at times, it wasnít too distracting. In fact, I was able to tighten the bass up even more by adding a swamping resistor (10 watt, 35 ohm) in parallel across the driver.


A Quick Sidebar
OK, swamping resistors. For those of you that arenít intimately familiar with single-ended triodes and Lowthers in particular, at about 40Hz the Lowther driver begins to resonate at its Fs (free air resonance). This can cause issues with your chosen output transformers on your amp. Certain (but not all) transformers see their peak reactance at or near this same frequency. The combination of the two, the high resistance of the Lowther and the high reactance of the transformers can cause a distinct loss of bass. In turn, the addition of a Ďswamping resistorí lowers the impedance at the Speakers Fs. If you remember, when you place resistors in parallel, the formula reads 1/R1 + 1/R2 = Rt. The net result is an overall lowering of the resistance. The other thing to keep in mind is that a speaker shows a reactive load to an amplifier. In other words the speakersí resistance of (say) a nominally rated 8 ohm speaker can drop to 3 ohms and also rise to over well 50 ohms at different points across the frequency spectrum. The swamping resistor should be at least a 10 watt, non-inductive resistor of high quality. In my case, I would have liked to use a 50 ohm but all I had was a 35 ohm Mills in my parts bins. Not optimal but it works just fine to lower the overall resistance seen by the speakers. The sound of the swamping resistor is transparent. The addition of the resistor tightened and restored much of the low bass (in the bottom two octaves). Science, itís an amazing thing.

Ok, back to the Handmade 2A3. With its puny 2.5 watts of output power, the Teresonic Ingeniums just plain sang with this amp. Granted, you arenít going to reach concert level volumes out of them but you can hit the mid 90ís in SPL at about 10 feet, which leaves plenty of headroom for the amp (relatively speaking). There is no doubt in my mind that if my Handmade Classics had a little better output iron, Iíd be getting even tighter and deeper bass from them. Though the bass coming from this amp equipped with standard Hammond output transformers is quite good, quality iron would sound even better. Where the Handmade 2A3 really excelled was on acoustic music, jazz in particular. Her rich harmonic overtones and wide open sound was a marvelous match with the Ingeniums. If I had to describe this sound in two words it would be absolutely lovely. This combination really reminds me why I love a good 2A3 amp. Donít get me wrong, heavier music sounded just find too, itís just that the full-bodied texture of the 2A3 sound is especially inviting in this combo.

Next Up Are The Welborne DRD 300Bís and this was a pretty amazing transformation in and of itself. Within the first three notes you could hear that the DRDís took command of the lower octaves. The iron from Electra Print made all the difference, Iím convinced of it. Since the bass got so much better I thought I throw on something a bit more upbeat. Blue Sixís first release Beautiful Tomorrow is a trance-like blend of House and Ambient Chill music. This album is heavily laden with deep bass grooves that sound fantastic on the Teresonic Ingeniums. With the Welborne DRDís, the image got much, much sharper. This isnít unexpected, as the DRDís donít use coupling caps in their design. As they warmed up, the DRDís started really throwing their weight around showing the other amps just how they are supposed to sound. The soundstage deepened and then the DRDís started showing off by tossing images three or four feet outside of the speakers.

Since I was on the Chill Out kick, I decided to toss on some Zero 7, When It Falls. The speaker did a marvelous job handling the well-recorded bass on this CD. All too often the bass on this CD muddies the midrange when played on less than accurate speakers. The Ingeniumís gave me a clean, clear accurate midrange while allowing the firmly recorded bass to come to the forefront. The DRDís proved that a quality 300B amp is really hard to beat when it comes to precision and clarity. The Ingeniumís responded accordingly. They promptly disappeared on most music and projected a superb center image that never wavered. The performers proportions and locations were first-rate while never projecting the pretense of many multi-way speakers.

Next up are my Radii monoblocks, which use KT-88 tubes putting out about 100 wpc in total. Iíve ripped into these things and pretty much tossed most of the stock parts that were in the signal path in favor of expensive cottage industry parts. Iíve also done a few aftermarket tweaks like power supply bypass caps and switchable negative feedback. Though not nearly as clean sounding as my SETís, these do a darned fine job. Was a little hesitant when first putting these in front of the speakers. Iíve never plugged these into anything as efficient as Lowthers before as they have always been relegated to driving speakers with a much lower sensitivity, namely my Odyssey Audio Epiphanyís. After messing about with the multi-taps and finding out which sounded the best, I settled on the 4 ohm taps. Though the 16 ohm taps gave me the most bass, the 4 ohm taps sounded the cleanest. Once these amps got warm and opened up, things got even more interesting.

With the endless power and significantly improved bass, there was some serious fun factor in this combination. One of the first pieces I played was Peter Gabrielís Up. This particular release has some significant bass on numerous tracks. At first was a little worried that the Ingeniums wouldnít be able to keep up. Boy was I wrong. The opening refrain to the song Sky Blue has some killer bass licks. The speaker performed fabulously on the bass reproduction. They handled the deepest bass notes as quick and nimble as editor Steveís Ferrari. Best part, they stopped on a dime with very little overhang. Just for grins I tossed on some Bela Fleck (actually Victor Wooten) just to see how theyíd do. On Left Of Cool there are several tracks that give me an overall idea of how bass will be handled and at the same time how stable of an image the speakers will maintain. The first cut Throwdown at the Hoedown, towards the end of the song we find the guy at the mixing board panning Bela and Victor back and forth between opposite channels. As I play this even at unreasonable volume levels (well over 100dB peaks, mainly cause its cool) the constantly shifting image stays extremely well focused even with all of that bass energy going on within a single driver speaker. I really thought that Belaís banjo would start to smear when the Lowthers started to compress, but it didnít. I for one am damned impressed at this feat. I could go on and on about the bass but Iíll spare you. For some time now Iíve heard that lots of people really like their Lowthers served up with lots of watts. Now I understand why. The big push pull amps in front of Lowthers have this Fun Quotient that is tough to match with the accuracy and delicacy of a single-ended triode.


Some General Observations
One thing that you should realize is that the combination of the Lowther driver with itís super high Gaussian strength magnet and its limited Xmax coupled with the cabinet design is going to limit the bass output at low listening levels (read = < 65dB) . Donít get me wrong here, there is bass output at low listening levels but it is slightly subdued. The bass really starts to bloom above about 75dB. This is speculation but I suspect that that the Ingeniums due to their ETQWT design donít begin to properly back load the driver and enclosure until they reach certain SPL or pressure within the cabinet. In turn, once that pressure is satisfied the speakerís bass really kicks into high gear. It then is delivered in spades. This shouldnít be an issue for most people since most people listen to music at SPLs higher than conversation level. On the other hand, some live in apartments with thin walls and are forced to keep to a very low listening level. In your case, you should be aware of my impressions. Again, what Iím finding here is likely highly room dependent. In a smaller room, you likely wonít experience this.

When it comes to all of the tweaks I performed, some reading this might ask themselves why I went to all this trouble when I should have simply written about this speaker as is was supplied. I honestly donít feel that the phase plug, cotton ball and foam tweaks are really any different than swapping the preamp or speaker cables until I found the pairing that made these speakers sound their best. I just happen to know Lowthers a little better than most people. Like to think that I know how to set them up so they perform at their best. Was changing the phase plug going over the top? Not in my mind. The phase plug was just another wrench I pulled from my audio toolbox used to tighten a loose nut. Besides, I may have just helped somebody out there make their personal pair of Lowthers sound better by giving them a handful of tweaks to try.

As some of you are aware, Lowthers are extremely difficult to make completely  Ďdisappearí in your room and the Ingeniums are no different. If I have fussed about with them some more I could have gotten there but as it was I got pretty close. On the vast majority of the music the DX4ís didnít call attention to themselves. But at certain frequencies they uncloaked themselves. With each of the amplifiers I chose, I got a rock solid image from the music regardless of volume levels. All of the performers appeared right where they should have on the virtual stage. The nature of most Lowther drivers is to bring the soundstage forward. The Ingeniums with the DX4 driver is no different, although I achieved a reasonable soundstage depth of a handful of feet, I likely could have gotten it a bit deeper if the speakers were pulled out from the back wall a bit more. In turn I chose to dampen the back wall with OC703 panels. Itís just the choice I made.

When it comes to the Teresonic Ingeniumís dynamics, something Lowthers are so noted for, they are obviously a bit curtailed due to the particular enclosure the designer has chosen. The upper register dynamics are still there but the lower octaves sound more like the typical box speaker but better. Unfortunately we canít have our cake and eat it too. This is one of the benefits of rear horn loading these drivers, the dynamics. When it comes to overall dynamics, my Medallions still stand head and shoulders above the Ingeniums, but there is one crucial limitation that the Medallions have and that is bass in the lower three octaves. This is exactly where the Teresonic Ingeniums absolutely excel. Again, audio is all about compromise.

And before we get out of this article, let me encapsulate the bass produced by the Teresonic Ingeniums just a little more. Throughout this entire article Iíve been blathering on about their bass and want to make this crystal clear. The bass produced by these speakers is most excellent but bass from an 8-inch driver is not the same as that from a 15 inch driver. The Ingeniumís bass is deep, tight and very accurate compared to your typical low efficiency speakers, though doesnít hold the same quantity of  room-filling bass of a larger high efficiency 15 inch driver (or the like). That said, I am wholly impressed with the depths this cabinet design takes the Lowthers to... depths that the Lowther drivers have never seen before.


Happy Trails
In the end I am completely dumbfounded by these speakers. Using current modeling techniques, these speakers shouldnít be able to reproduce bass like Iím hearing and measuring. Granted, the computer program that I use is for vented enclosures rather than TQWTís but Iíve heard enough quarter waves to know that they donít typically hit 30Hz. Sure enough though, the Teresonic Ingenium hybrid ETQWTís deliver extremely deep bass by the truckload. It isnít wimpy bass either. Itís rock solid. Though the bass is very even for well-recorded music, if you were hoping that you can plug in some head-banging music and rock out Iím afraid thatís likely not going to work without augmenting with a sub. Unfortunately most rock music is mixed too bass-lite for these speakers and this is nothing new. Nor should it be considered a deficiency of the speakers. Remember, since we eliminated tone controls on preamps, we just limited our choices in music based upon our tastes in speakers.

On the other hand, if you have a well-balanced recording these speakers will absolutely sing. The Teresonic Ingeniums deliver every ounce of the single driver magic without any of the limitations of the other single drivers on the market. They have that  Ďpresenceí that Lowthers are famous for. Their bass reaches down to 30Hz (near flat) and their highs go well above 12k and for many, they canít hear much above that anyway. As it is with most speakers, the Ingeniums were a little finicky to set up but once you have them dialed in, they sound simply marvelous. I can say this without any reservation, if I had heard these before I had my reference system completed, I would have likely bitten the bullet and bought this pair of speakers, they are that good.

I donít gush much anymore. Iíve found that nothing much gets me overly excited except my reference system, which is one of the pitfalls of writing about audio gear. One thing I can say is the Teresonic Ingeniums have got me really pumped. I never thought Iíd hear this kind of bass out of a Lowther driver regardless of the enclosure type. Sure, I see some of those rear loaded horn on the Internet that has those five-foot mouths, but those almost come from the land of make-believe. There canít be two or three pairs of those in the world. On the other hand, the Ingeniums are real. You can touch them, caress them, and in my case salivate on them, as they are some of the sexiest speakers Iíve had in my house in a long time. Be forewarned though, the price of admission is damned steep. At $10,000 the Teresonic Ingeniums are well beyond many peoples reach. So it goes with much of high-end audio, though if you are willing to pay the price for almost two decades of testing, research and design, and then are also willing to take the time to properly set the Teresonic Ingeniums up and get them dialed in you are in for one heck of a ride!

Whether you are into single-ended triode, lesser wattage push-pulls like the EL-84 (which sounds quite lovely in front of them by the way) or monster multi-tube behemothís like my Radiiís or a pair of Extreme modified ASL Hurricanes that Response Audio sells, these speakers are a top performer. If you keep in mind that they respond best to evenly mixed music, you wonít be disappointed in the least. As I sit here typing the closing remarks to this article I am utterly amazed that the Teresonic Ingeniums can deliver bass in the magnitudes that they are. That and the fact that is so even. Science and creativity can be marvelous things when you combine the two. It is more than obvious that the fine folks at Teresonic have poured their hearts and minds into these speakers, and it has paid off. Not only are these speakers a Ďstatement,í they have a coherency of sound that is nearly unrivaled in the industry because of the Lowther driver plus they do bass. Am sorry, still canít get over this amazing fact.

If you couldnít tell by now, I sorta like these speakersÖ a lot.


My Ratings
Please keep in mind this rating system is used to compare the Teresonic Ingeniums against absolute perfection, or a money no object speaker design. If you see what you think may be a low(ish) score, it's because there are speaker designs that are even more refined but consequently cost considerably more. To top that off, if I assign 5's across the board then I have just painted myself into a corner leaving no room for that 'ultimate' speaker. You won't see me handing out many 5's. In turn, I feel I need to leave room in the ratings system to accommodate those speakers. 



Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High-frequencies (3,000Hz on up)



Inner Resolution

Soundscape width front

Soundscape width rear  
Soundscape depth behind speakers

Soundscape extension into the room


Fit and Finish

Self Noise


Value for the Money


Type: Full range, high sensitive Lowther driver loudspeaker

Enclosure Type: ETQWT transmission line with Helmholtz resonators

Drive Unit: 8-inch Lowther DX3 driver

Crossover/Filter - None

Frequency Response: 30Hz to 22kHz ( Ī 3dB)

Sensitivity: 101.5 dB/W/m

Impedance: 8 Ohms

Power Handling: 4 to 100 Watts into 8 Ohms

Connections: WBT gold plated terminals

Internal Wiring: Zero-interference Clarison cables

Dimensions: 73 x 10.3 x 20 H x W x D in inches)

Net Weight: 84 lbs.

Accessories Supplied: Spikes & floor discs - gold finish, adjustable

Cabinet Finish: Real wood finishes include Rosewood/Black (other colors available as special order)

Price as reviewed: $10,000


Company Information
Teresonic LLC
6017 Wellfleet Way
San Jose, California 95129

Voice: (408) 973-8813
E-mail: info@teresonic.com
Website: www.teresonic.com













































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