FEEDBACK ONLINE - ISSUE 1
Khorus loudspeakers and Roc subwoofers
as reviewed by Clement Perry with a follow-up by Stu McCreary
Plus an interview of Tierry Budge by Clement Perry
If you've been following these pages you've seen some enthusiastic reviews of reference-quality loudspeakers, e.g., the excellent Wilson Audio WATT / Puppy Sixes (Mike Silverton), the excellent Piega P-12's (Lou Lanese), and the excellent Super Eclipse (yours truly). Each of these loudspeaker systems represents their designers' ultimate statement. Mike Silverton and Lou Lanese purchased their review pair. I, however, did not. As good as the Super Eclipse is, and it is indeed very musical, it did not beat out the VR6's with respect to overall musicality, visceral impact, and dynamics. I ultimately returned the review pair and wondered whether anything would ever unseat the VR6's as my reference. Patience is a virtue! That day has arrived! Enter the Talon Audio Khorus.
Built in Utah, the Talon Audio Khorus's design philosophy (I'm informed) is that of the infinite slope. The Khorus is shaped like an obelisk, which, according to the manufacturer, naturally time-aligns the enclosure, placing the tweeter slightly behind the midrange. The speaker's height is 46" with a width of 8" at its flat top. The base widens to 18 inches. Removing its grill permits a view of cloth-treated baffle and driver configuration. All three of the Khorus drivers stand about 24" from the floor, closely aligned near the top of the enclosure. We begin with a highly modified pair of 10" midrange/woofer drivers working in unison to cancel out exaggerated cone movement. These dual drivers are said to accurately reproduce without strain all frequencies from 17Hz to 2200Hz. The method of thislet's call it madnessdesigner Tierry Budge explains: "Midrange-based suspensions and cone-geometries can be mated to subwoofer-like motor structures and moving masses, if the resultant dynamic response displays proper execution of progressive damping principles. We designed the 10" driver we use in the Khorus with these midrange/woofer traits, along with the widest range of musically-conducive capabilities." [For more technical specifications Talon website.]
Six inches above the mid/woofer, looking more like a midrange driver, sits a 1-1/2" cloth-dome tweeter handling all frequencies from 2200Hz before rolling off at 13kHz. Picking up on this high-frequency frolic, its duties extending to 35kHz, is a 1" titanium super tweeter said to free up the compound tweeter, permitting it a more effortless extension. Dual tweeters working in such close unison yield its 2.5 designation
A first order, 6dB slope is the outcome, since the goal has always been transient purity. Normally, first-order designs are power hungry, but the Talon's inversion circuit allows great power handling as the first-order slopes keep transient purity intact. The rear sports what looks like a port but is actually what Tierry calls a "laminar flow valve," not so much an exhaust pipe as a pressure release valve. (I go deeper into this in the interview portion following this review.)
Before getting ahead of myself, let me first explain how I came across the Khorus. The story begins with an excited email from Delve Audio's Oliver Solomon: "Yo, P, you better get set to sell your speakers and buy these new speakers I just heard by a new company called Talon. Man, it's the finest speaker I've ever heard." Now, don't get me wrong, I'm the coolest of dudes. Stuff like this rarely rattles me. I hear wild claims all the time, especially from dealers. Yet I felt I'd been dissed because Oliver had listened to my system for a couple of hours only days before. Dissed, yes, but my curiosity was nevertheless aroused. I visited the website. Much to my amazement, I saw specifications that read like the back pages of Mad Magazine: "100 times quieter and 20 times faster than any loudspeaker!" Oliver, I now believed, is definitely off his meds. But, as I say, my attention was engaged. There I was again doing the Absorbine Jr. thing, taking it all in. I soon got in touch with national sales manager Mike Farnsworth and requested a review pair.
We're talking so far about what Oliver says he heard and what the website claims. I envision a dream loudspeaker encompassing the clear, see-through quality of the finest electrostatics, as in the Crosby-modified Quad I heard at HiFi '97 in San Francisco. For the very best top end extension, the very finest and most delicate treble, let's have the five-foot ribbon tweeter in the large Magnaplaners I once owned. This dream transducer should also be capable of the midrange body and ultra quick bass response of my beloved VR6's, along with the enormous stage width, depth and spaciousness I've always come to admire in the Avalon and Audio Physics. And finally, the dream transducer should disappear against a velvety black backdrop and be absolutely free of compression like the Near Field Pipe Dreams. Yes, all of this. No compromise!
I've spent three months with the Talon Khorus. Let's not mince words. I truly believe Tierry Budge has produced a near-perfect loudspeaker, and I'm saying "near" mostly to cover my butt. After long and interesting chats with Tierry and my sidekick, Stu McCreary, I've come to two conclusions: one, how very serious and experienced a speaker designer has to be in order to succeed, and two, how difficult a struggle it must have been to come up with the likes of the Talon Khorus. I'm convinced it's the best speaker I've ever heard.
Let's backtrack. The Khorus arrived in impossibly large shipping crates weighing 150 lbs. each, necessitating the help of my buddy Terry Smoak to get them up to my third-floor inner sanctum. Unpacking was relatively easy. Let's get appearances out of the way before we get down to the serious stuff: my review pair came in an appealing, high-gloss dark Rosewood finish. We set up them up in about the same spotabout four feet out and three feet from the sidewallswhere my long-time reference Von Schweikert VR-6's stood. Apart from bi-wiring capabilities, the Khorus employs a unique locking screw-on speaker terminal located underneath its belly.
The Khoruses connect to my usual array: Sony's SCD-1 DSD player feeding the Tact 2.2 Digital Room Corrector/preamplifier. The newest addition to the system is the Ortho Spectrum AR2000 which a number of us here reviewed with enthusiasm. Amplifiers, the stunningly good Bel Canto EVo 200.2 (I'm running a pair in mono configuration for the added support we all need and love). Cabling is Walter Fields NBS Monitor One and Robert Lee's new and remarkable Acoustic Zen cables. Power cords are the highly addictive Power Chords by Audience, Inc. The Sony and Bel Canto rest on the Sistrum Isolation platforms; both the Tact and AR-2000 occupy Rosinante's Dark Matter Isolation devices. Seven Richard Gray 400-S line conditioners monitor the power going to the amplifiers, while the front end benefits from the PS Audio P-300 Power Plant and Quantum Symphonies.
The Khoruses are highly critical of location. I have them toed in about 30 degrees, where you just barely seeing their sides. My listening position is relatively close, about 7 feet from the speakers about 9 feet apart, which some listeners think too much for their tastes. I disagree. The VR6's have such wide dispersion that they perform well this far apart. It was immediately apparent that the Khoruses could do this too, though, I must admit, not to the degree that the VR6's succeed off axis, with the listener in a standing or sitting position. After many hours of extensive evaluation and nit picking, this is the only distraction I found.
Oh yes, there is one more tiny little thingiebreak-in! It's insane! These speakers won't sound anything like what they're capable of until you've put in at least 400 hard-hitting hours. No, I'm not joking. Never mind the Olympicsthis, for me, is Guinness Book of Records stuff!
Stu McCreary has the Khorus and he comments too. We both agree that the burn-in should be done patiently or else you suffer from what I like to call "decompression." I find attempting to adjust to the Khorus' too fast is akin to what deep-sea divers describe as the bends, a painful and dangerous condition. Equally, long term exposure to sizzle, hash, pop and boom can prove inadequatewhen done away with.
Just as my view of audio has been irrevocably altered by the experience of the Bel Canto EVo amplifiers doing their imitation of a fine single-ended, class A triode amp with bass handling capabilities like the finest solid-state, so have my views been changed by the Talon Khorus. More often than not, analytical listening sessions turned into pure listening pleasure. The Khorus provided utter clarity and sense of ease and resolution, regardless of volume. It's a dynamic loudspeaker that, by purposeful design, or some form of voodoo, does not sound like a dynamic loudspeaker. It comes lots closer to mimicking the speed, transparency and linear smoothness of a hugely efficient electrostatic driven by 1000-watt single ended triodes!
We all know the effects of turning up the volume. Some loudspeakers rely on high levels to achieve claimed performance. I believe that the Khorus also enjoys being played at loud levels, but that doesn't mean it won't outperform the field when played low. Unlike many a speaker system I've heard at low level, the Khorus doesn't lose its signature. When played loud, things get only clearer, more dynamic and musically expressive. I have never before witnessed such an analytical transducer sounding this musical.
The benefits of an absence of noise are enormous, especially when it comes to instrumental truth and tonality. Bass is quicker and ever so delicate, contributing to a much greater perception of individual instruments and their location relative to the microphones and each other. Amazingly, the Khorus' brings new definition to tympani, drum and kick-bass transients. Attack, presence and sense of location never sounded this good. I gain a better awareness of a recording's venue. Images stand out in stark relief in a deep space of blackness. I've never experienced this level of silence, even when playing in the middle of a hot and sunny afternoon, which we all know is hazardous to good sound regardless of A/C conditioners.
By comparison to the Khorus, every speaker I've reviewed compresses dynamic range. None, not even the VR6's, come within a country mile of reaching down into the quietest of musical passages of many CD's. I entered Miles Davis's incredibly musical phrasings, squeaking chair and all, on "Old Folks" from Someday My Prince Will Come (Columbia CK40947) as never before. Here, on this somber and slowly rhythmic recording, I can, for the very first time, feel Miles' loneliness. I can actually see him sitting, alone, desolate, blowing into his muted horn. These images, prior to the Khorus, escaped me. And to think I thought I knew that disc! My notes after this experience read only: Amen.
On the very same disc is one of my favorite minor modals, "Teo." Miles, once again, making use of choked notes, sets the stage for John Coltrane who proceeds to blow an emotion-packed solo, that to this day is still argued among jazz aficionados as being his finest. What makes this so different sounding through the Khorus is Wynton Kelly's performance on piano. It is alleviated of what I can only describe as haze. I listened in disbelief. I'm accustomed to his piano, as well as most other pianists, being usually diminished in both presence, truth of harmonic overtones, and timbre, making Wynton's performance seem apart from the main events. No longer.
Let's call this the domino effect. Consider: once Wynton's freed up, he sets up greater soundstage linearity for 'Trane, who sounds now as if he's coming from behind the left speaker, deeper in the corner instead of between the speakers. This positions Miles dead center, tight and neatly focused, against that deep-space blackness. The Khorus is not doctoring any of these recordings, making them sound better by emphasizing or de-emphasizing frequency regions. The speaker's accuracy in retrieval of detail is without peer. What I hear is a superior recreation of what is on the discnot crossover and phase anomalies occurring at the speakers.
Excellent DSD recordings, driven through the Sony SCD-1 proved a perfect match. The Khorus' responds like a high-resolution microscope, clean through the electrons, right to the original venue, once again demonstrating to this audiophile that the Khorus stands above the competition and beyond criticism.
Enter the Roc More Will Be Revealed
So colossal that its wings could eclipse the sun, so strong that it could carry off elephants, the Roc was the mythical Arabian bird in whose talons Sinbad of The Thousand and One Nights was carried off to a mountaintop. What an appropriate name for this super-duper subwoofer! The Talon Roc has not only lived up to its handle, it meshes with the Talon Khorus so musically, so seamlessly, that its very qualities are bound to become legendary.
The Talon website states that "the Roc uses a 12-inch woofer to deliver deep, tight, accurate bass without ever bottoming out. The Roc will only deliver the fundamentals and not the second harmonics (boomy bass)." Let it be known the Roc uses dual 12-inch woofers in the same fashion as the Khorus. Employed solely in conjunction with the Khorus, the Roc takes this already incredible loudspeaker to yet another level! I first placed this quite a large box in between the loudspeakers directly in front of me. That worked well enough, but my hunch was that this wasn't the ideal position. It took up too much floor space where it was, and more importantly, the Roc needs to breathe. This meant finding a place off to the side where it could dispense its low-end frequencies more evenly into the room. Placing it about six feet to the side of the left Khorus provided a better result.
In this position, and leaving the phase in the normal position, the total performance became easily the most natural sounding I've heard. In addition, when you stuff the laminar valve on the Khorus, you increase its impedance, which naturally begins to roll-off their low-end delivery beginning at about 80Hz. I repeat, merely stuffing the laminar "port" does this naturally. Setting the Roc's crossover to 60Hz results in a perfectly matched low-end.
Moreover, I didn't need the Roc for greater low-end authority. The Khorus provides this better than any speaker I've had in my listening room. What proved a revelation was that by adding the Roc I immediately alleviated two sources of distortion: intermodulation, caused by the drivers' rapid movement, and harmonic, caused by overtaxing the power requirements placed on the amplifiers. The Roc therefore contributes to better sensitivity, dynamic range, stereo focus, transient attack, decay, dynamics and definition throughout the frequency range. I take it that you think I'm hugely impressed by the Roc. You got that right!
The Khorus plays louder, goes deeper, is significantly quieter, and produces greater yet subtler dynamics. It provides a greater sense of ease than my reference VR6's. The sense of soundstage scale, height and depth are state-of-art. The Khorus/Roc combination combine to create the highest degree of musicality I've yet heard from a speaker system. In other words and to repeat myself, state-of-the-art! I guess I don't need to add that I purchased them as my new reference standard.
At a combined price of $18,000, the Khorus/Roc is a steal for the audiophile considering buying a world-class speaker at any price! For me, their arrival couldn't have come at a better time. My wisest purchase, absolutely! Clement Perry
"And now for something completely different..." (Monty Python's Flying Circus)
It does get a bit tiresome after a baker's dozen or so loudspeaker have come and gone. It's hard to be original, insightful or the least bit excited when you're talking about the same old dynamic drivers in a wood box. Maybe it's got a neat sculpted baffle, trick mid/tweeter module isolation, or the largest flared ports you've ever seen, but is it really all that different in form, function and sound from all the others? All too often the answer is no. Sure, they all sound a little different, but it's a continuous scale, with very fine increments and the pendulum rarely swings too far.
It's this reviewer's rare pleasure to have in the Talon Khorus, a loudspeaker that really shakes things up, gets the juices flowing again, and reacquaints me with my passion for music.
Clement Perry did an outstanding job of describing the Khorus's unique features and technical aspects. That leaves me with the fun stuff. We agreed to this division of labors early in our Talon journey: I get "techie" with the Bel Canto EVo and Perry does the heavy lifting with the Talon Khorus. I think I got the better part of the deal, because the subjective side of the Khorus experience is extraordinary and chock full of anecdotes, and the technical side is daunting, to say the least. Let's get down to it, shall we?
The Stage is Set (and the Gauntlet Thrown)
The original claims of Talon as presented in their website and white papers are so outrageous that you might think you're reading from a Monty Python script. Ten times faster, 100 times less distortion, a ten inch woofer that handles midrange up to 2.2kHz, incredible power handling and bass extension from just over one cubic foot of air space geesh! As incredible as all this sounds, Talon has plausible engineering explanations for each claim, along with patent applications. Me, I'm from the So What School. If it doesn't sound better to some significant degree, then it's all just meaningless engineering hoohah.
This was my mindset when I un-crated the Khoruses and moved them into Stu's Place for a serious listen. Perry had started his phone campaign weeks before and I could detect these were not your ordinary run-of-the-mill-loudspeakers. He was excited by what he was hearing and couldn't help himself. We do this to each other often. It's part of the ritual and fun to call up your audio pal and let him know that your listening room ceiling just opened up and you were visited by an archangel. "OK, OK, I'll be sure to sprinkle the holy water and burn some incense," I told him with just a touch of smugness in my voice. I can't be rolled by anyone, not even my Bro' from the Big >City. I was not about to abandon my critical nature.
I'd gotten emails from several audiophile friends extolling the virtues of these speakers, with statements like, "the best I've ever heard" and "clearly superior to the XYZ's you love so dearly." This kind of thing has a negative effect. Rather then being excited to share their experience, I found myself getting more cynical and more willing to cut against the grain.
Breaking in, or Deflating the Cynical Balloon
The Khorus is not your average dynamic-driver loudspeaker and this realization arrives right out of the box in the first few hours of play. While most loudspeakers start off by sounding dry, thin and constipated, the Khorus was the complete opposite. It was immediately so full bodied and over-rich, that I was stunned. The bass was phenomenal, the midrange was a bit overblown (particularly the lower mids) and the trebleit sounded rolled off. No, I think recessed is the better word. It was there but distant, lingering more toward the back of the stage. Now, except for the bass, this wasn't promising. I thought the holy water might be needed to dispel the audio demons, rather than to invite the heavenly host.
Nevertheless, there was something else I heard that intrigued me and gave me the patience to weather the arduous break-in process.
Through that ripe, warm sound, I detected a background silence that was uncanny. I'm not talking about silence between musical passages; I'm talking about silence between and around the instruments. The pesky treble halo, haze and glare were absent, gone, adios, bye-bye.
This "haze" I used to think inherent to all loudspeakers diffuses the edges of images and fills in the gaps all around them, consequently decreasing the focus and spoiling our perception of stage depth. When that haze is removed, the solidity, precision and three-dimensionality of the soundstage stand out in striking relief. These over-ripe Khoruses removed the haze like no other loudspeaker I'd heard. It made such a strong impression that I knew in the first hour of listening that something extraordinary was taking place.
This was a déjà-vu experience. The Bel Canto EVo amplifiers had also exhibited this lack of halo and haze and in my review of them, and I commented extensively on this. Perry called the EVo the "Talon Khorus of amplifiers." With the EVo, I concluded that its incredibly low distortion gives it this unique property. So what about the Khorus?
The air was starting to leak from my cynical balloon. Could low distortion claims of Talon be true? Could this "group phase" thing and unique compound driver loading significantly lower distortion like the EVo's digital technology? Hmmmm.
So there I was on my first evening of listening with loudspeakers that arguably had the best bass I'd heard from something other than a dedicated subwoofer (much more on this later), a quiet, haze free soundfield, but with an over-ripe, almost tubby midrange and a recessed treble. Argggh! How frustrating! I was used to listening past the break-in problems, but I had serious doubts that this sound would improve over time. After all, this was not how fresh loudspeakers are supposed to sound. If they got any riper through break-in, I wouldn't be able to take it. The cynical balloon was starting to re-inflate.
Fortunately, Talon had the good sense to say something about this break-in process in the manual that came with the speakers. It warns that 50% break-in takes upwards of 250 hours of play and you're still not home after 500 hours. About the 500-hour mark the manual says, "85% of break-in: Midrange becomes more expressive, more dimensional towards the rear. Extreme highs come forward from the rear of the sound stage, creating more of a spectral match with the rest of the range." Ah-hah! That's what I was looking for! With a sigh of relief and major cynical deflation, I knew that my hearing was all right and that there would probably be light at the end of the break-in tunnel.
Another comment in the manual intrigued me. Under the heading Burn-In Note, the manual states, "In view of the burn-in time involved with the Khorus speakers, Talon has designed-in two 'elements' which minimize the actual change in sound over time as time passes, these 'elements' will diminish their overall effect, in order for the system to maintain a consistent, and correct, tonal balance." Hmmm, well, well. Could this be why these speakers have such an ass-backwards break-in progression? Are these 'elements' what make it so intensely rich until the upper-mids and treble come in? I would wager that they are.
Armed with a little knowledge, I set upon the break-in process with a sense of mission. I played the Khoruses non-stop for three weeks with the volume cranked while the family was away during the day. I used Purist Audio disc extensively as I did my Dorian Organ recordings. When I sat down for some serious listening after two weeks, things were improved, but not to the degree I had expected.
On closer examination, I discovered that the compound loading of the ten-inch woofer yielded very little cone excursion. The accordion surround was still quite stiff and I doubted whether I had played the speakers loud enough to really give them a workout. The specs say that the Khorus will take a 1000 watts and produce a continuous 120dB. Well now, that's really loud! Much louder than I was playing them.
For the next week, I waited till the kids were off to school and the wife at work and played them at levels that shook the house. For fear of damaging my ears, I wore shooting headphones while in the room and used my Radio Shack decibel meter to check the sound pressure level. With the Bel Canto EVo monoblocks pushed near their limit, I was getting close to 120dB peaks.
After the first day of this regimen, I knew that I was hitting pay dirt. I could smell what seemed to be fresh lacquer in the room and I was finally seeing some reasonable cone excursion. Much to my delight, after a full week of this torture, the speakers settled in just the way the Talon manual said they would. The treble did in fact move forward from the recesses of the stage and the upper mids fleshed out nicely as well. The speakers still had a rich sound, but no longer over-ripe. The low bass, which I thought was already outstanding, was now incredibly goodpowerful, full and oh my God, the pitch definition!
The Talon Controversy
On various Internet chat groups, these speakers have elicited some of the most polarizing comments I have ever read. Some folks fall under their spell immediately, while others make disparaging remarks about their listening experience. Why is this? Why the love 'em or hate 'em reactions?
I have my own thoughts on why this may be happening. Let's dispense for the moment with those who may not have heard a broken in pair and those who have a vested interest in another loudspeaker and can't stand to hear praise heaped on a competitor. Even with these folks eliminated, I'm sure there is still a small number of honest, well meaning people with reasonably good hearing who just don't like the way these speakers sound. I hear the occasional comment of "it sounds rolled off," "not enough bite," or "there's something weird going on with the midrange."
Now, far be it from me to label these people as tin ears who "just don't get it." The Khoruses are not some audio philosopher's stone that separates gold from tin. There is plenty of room for personal preferences and disagreement here. However, given technology claims of Talon and the unusual properties of this speaker, I wouldn't be much of a reviewer if I didn't state my own position and vigorously defend it.
I have reached the conclusion that it is the Khorus' speed and low distortion that is messing with people's heads and ears. What may sound to some as rolled off highs is, I believe, the lack of treble halo and haze. I have confirmed this for myself by going back and forth between several other loudspeakers I have on hand. There appears to be no treble information missing from the Khorus. What is missing is the low level hash and haze that typically rides along with the upper mids and treble like a halo around the instruments.
It does take some getting used to. The initial absence of this "filler" can produce some strong cognitive dissonance. I admit that it was a bit weird at first, but in my case, the acclimation occurred quickly. I was able to identify what it was and embrace it in my first hour of listening.
There are some who say there is no such thing as speaker break-in, only listener break-in. The Khoruses make a strong case for speaker break-in. There's no mistaking the sound of the fresh-out-of-the-crate speaker with one that's been playing for 300 hard hours. But this speaker makes an equally strong case for listener break-in. Clement and I have walked several other owners through the listener-acclimation process. It was getting so commonplace that we gave it a name. We call it "the bends." Like a deep-sea diver who comes up to the surface too fast, the audiophile who experiences the Khorus after listening to conventional loudspeakers may suffer some ill effects. The recovery time is hours for some, days for others, and sadly, some will never get over it.
A less severe agent of the audio bends is the speakers' ability to deliver and instrument's bass, midrange and treble spectrum in a way that makes it appear to emit from the same point in time and space. The treble does not leap out at you, nor the bass lag behind the midrange. It comes in a very natural envelope that makes you think of real instruments instead of loudspeakers. Now, I know this is subtle. There are any number of good loudspeakers that do not have obviously disjointed treble, midrange and bass. We're talking about degrees here. The Khoruses sound just that much more holistic in the sense that it all emits from the same point in the soundstage, thus making the imaging that much more believable. Could it be because there is one compound driver handling frequencies from 20Hz to 2200Hz? Is it because there is a series crossover to the tweeter and no low pass to the super-tweeter? I don't know and I'm not writing about the technical aspects. All I know is, it works!
Midrange and Treble
With haze and glare gone, the extended treble takes on a delicacy and sweetness that one seldom, if ever, hears from a dynamic loudspeaker. The midrange melds with it very well; that is, the midrange is of the same character, cut from the same cloth, so to speak. The absence of haze and glare is also noticeable in the upper midrange. The mids are not aggressive or forward. If anything, I'd say slightly subdued, as compared to what I'm used to. Maybe it's the "holistic" thing again. The absolutely seamless bass to midrange transition makes it difficult to dissect the midrange sound. That's to be expected given the dual role of the compound mid/woofer. What I didn't expect was such a smooth transition from midrange to treble. There may be a slight dip in the frequency response (or power response, due to radiation) around the crossover point which may contribute to the subdued character, but it is slight, certainly no more than I have heard in many other top shelf speakers. My eyes see a great big 10-inch driver below a 1.5-inch dome tweeter and my brain tells me, "Nah, no way can these blend at 2200Hzway too high for a ten-inch and way too different dispersion." Again, the proof is in the pudding. It works! Talon has a technical explanation (and, as mentioned patent applications) for how this is accomplished, and it's a bit, even for me. Notwithstanding the complexity, I'm glad that there is a plausible explanation, because without it, I'd probably keep staring at those drivers and thinking my ears were playing tricks on me.
I'm a big fan of acoustic musicstrings, woodwinds and brass in the classical, baroque and jazz milieu. These instruments, especially strings, are notorious for their complex sonorities. If you look at the spectral balance of say, a cello, playing a C-flat, you will see an incredibly complex signature. There is a strong spike at the fundamental frequency, but a host of other frequency spikes representing over and under tones, resonance characteristics and miscellaneous spuriae all with time and amplitude components. Taken together these are what make the cello sound like a cello instead of a viola.
The problem with typical high-end audio systems, particularly loudspeakers, is that the spectral signature gets filtered in a way that condenses the spikes in both the amplitude and time domain. It's like looking at a MLSSA frequency response after you apply a "smoothing" algorithm. You get a bleached out, sanitized version of the cello. I think our playback systems do such a good job of thisbleaching and straining out the harmonic texture of real instrumentsthat we accept the sanitized version and underestimate how rich and sonorous these instruments actually sound.
When you hear the Khorus reproducing that same cello note, the first response will probably be "Wow, that's rich." There is some real gristle and meat on the bones that may be hard on the audio-vegetarian's taste buds. The question then becomes, is it more accurate, or is it over-done? To answer this for myself, I performed a little experiment.
I have a sister who is a music instructor and between her and her teaching partner, they can play almost all of the wind and string instruments you find in a typical orchestra. I invited them to my listening room and asked that they bring a full complement of instruments with them. I sat right in the "sweet spot", had them play for me while standing well behind, and centered, between the loudspeakers. There is no substitute for this experience. You can claim to have heard dozens of live concerts, but until you hear the live instruments in your listening room, I don't think you can adequately judge whats real and what's just "hi-fi." I'll be blunt. The dynamic energy and richly textured sound of live instruments made a mockery of my system. Were the Khoruses too rich, too "full bodied?" Not even close! They sounded thin, compressed and sterile in comparison. I had no idea of the amount of resonant bass energy a cello can produce, or a bassoon for that matter. Although the Khoruses were a step in the right direction, they, and the rest of my system, still had a long way to go before they could substitute for live music.
I had new respect for the Talon sound after this experience and it only increased when I substituted other loudspeakers. All that I tried (and I'm not going to pick on them here by naming them) were even more efficient strainers of harmonic texture. The deficiency became obvious when playing any good recording of piano or strings. The Khorus left more of the spectral signature intact. The Khorus strainer had bigger holes and let more information through.
I have often used Carol Rosenburger's Delos recordings as an example of how much more full-bodied and bell-toned a Bosendorfer piano is compared with a Steinway. Performers often prefer a Steinway for its ability to cut through the orchestra and keep to center stage. The Bösendorfer is warmer and more powerful in the bass scales. When I heard Rosenburger's Bösendorfer on the Khorus, I just about blew a cochlea gasket. Oh my god is that ever rich and powerful! I played Horowitz, Brindel and Ashkenazy and damn, the Steinways sounded better toonot nearly as strident as I was used to. I might even learn to love Steinways the way they sound on the Khorus.
Oh, and the strings? No question there, the best massed and solo strings rendering I have heard in my room, period! I use Corelli's Concerti Grossi on Harmonia Mundi and Chesky's Chamber Orchestra performance of Vivaldi's Four Seasons as my long term strings test recordings. After reaffirming what they sound like live in my listening room, I had no doubt that Khoruses got the strings more "right" than any other loudspeaker that has visited this room.
I had a loudspeaker designer over at my place. He brought a prototype of a design he'd been working on. After listening to these recordings on his speaker, I coyly suggested, "Now, would you like to hear more of what these strings are supposed to sound like?" I disconnected his speakers, hooked up the Khoruses and cued up the Vivaldi. Oh, the look on his face! Priceless! To his credit, he admitted that he had some work to do. It was that obvious.
One thing I can state categorically: the Khorus loudspeakers have "state of the art" bass. I used to think that detail and definition were the business of midrange and treble domains. Not any more! I was blown away by the information coming through in the lower bass octaves. The pitch definition and localization of bass is, in my opinion, without peer. By pitch definition, I mean the very subtle changes in pitch that let you know that a flat or sharp has been played, or even a half step between. Perhaps as subtle a thing as a change in the tremolo frequency of a huge organ pipe would be audible. It's pretty stunning when you put on an old bass favorite and discover that there is a lot more "music" way down there. What may have sounded like an amorphous wash of droning low frequencies, now has real notes and colorations of pitch. That old war-horse "Way Down Deep" on Jennifer Warnes' "The Hunter" is a fine example. I must have heard that piece a hundred times, but until I heard it on The Khorus, I really didn't appreciate how tuneful and complex all that bass drum work is.
I had the same revelatory experience with my Dorian Organ recordings. I could hear all of the big pedal stops as clear as a bell. I could actually count the bellows cycles as the air was pumped through the big 64 footers. I measured low 20's in my room when the big pipes opened up. That, folks, is going low with authority.
Is this astounding bass performance the by-product of speed and low distortion? I don't know. Again, it just works.
Now, as for "localization," I choose this word carefully to distinguish it from "imaging." Low bass information doesn't "image" the way midrange and treble does. It doesn't carve out a fixed image in space like you hear when a saxophone is playing. It's the higher frequencies produced from the mallet striking the skin of a bass drum that fixes it in place, not the lower fundamental notes that emit immediately afterwards. However, when you have something like a bass organ pipe that is not "struck," there is very little higher frequency information to fix it in place. Oh, perhaps a faint click of a stop opening or some "chuffing" of the wind in the pipe, but if the recording is mic'd at any reasonable distance, you really aren't going to hear much. So, these low organ notes aren't going to "image" in true audiophile vernacular. But, with truly great low-end reproducers like the Khorus, these notes will "localize." You will get a very good sense of where in the hall the bass pipes are locatedare they far behind the chorus? To their left, or right? At the same height, or above? The Khoruses answer these general location questions better than any loudspeaker I've heard.
What about the congas, tympanis, and bass guitar, those instruments that are struck or plucked and produce more mid-bass frequencies? Because these do have midrange and treble components, they should be easily fixed in space. Most any good loudspeaker will do a reasonable job of placing these images on the stage. The problem is that after the strike or pluck things can go a bit awry. The midrange and bass frequencies that follow don't quite match up with each other or with the treble in terms of timing. As I've said, this timing phenomenon is a subtle thing, which the Khorus does to a degree better than what I've heard from other full range loudspeakers. The key here is "full range."
Small two-way monitors have always excelled in this as do coincident drivers. Perhaps it is because of the simplicity of their crossovers and the fact that a single driver is handling both their bass and midrange frequencies. Up till now, the only drawback to these monitors has been their limited bass response. With the Khorus's technology you get your cake and can eat it too: the holistic qualities of a two-way monitor with outrageous bass extension.
You hear this best on recordings with string bass and congas, like the outstanding Buena Vista Social Club that features righteous Cuban classics and Chesky's new recording of The Conga Kings. The Conga Kings are featured on Chesky's SACD compilation disc, and when I heard it in SACD, I suffered a traumatic case of mandible distention. It was sensory overloadimpact, texture, pitch, imaging...good Lord, this stuff is amazing!
It's one thing to say that a speaker has excellent pitch definition when playing at moderate levels. I'm sure there are a few speakers that can make that claim. It's another matter altogether to maintain that accuracy at live listening levels peaking over 100dB. This is where the Khorus really sets itself apart. These speakers maintain their purity and poise at absolutely ridiculous listening levels. I have never heard a speaker go this loud without smearing and congestion. As a result, my average listening level has gone up a few clicks, and that's a good thing.
If you can listen comfortably at a louder level, you will hear a lot more of what's on the recording. I have long maintained that a lot of the ambience cues and "live mojo" are at very low levels in the recording, often lingering around the noise floor. You will hear more of it if you lower the noise floor (which is preferred), or if you raise the overall sound level. The problem with the latter is that at louder constant levels, the peaks often get compressed and distorted. The wonderful thing about the Khorus is the huge amount of dynamic headroom they provide. Since the peaks are not distorted, you can comfortably listen at levels that would normally sound like fingernails on a blackboard. With higher continuous levels, those "way back there" rear soundstage cues are easy to hear, as are the plethora of human affectations, like humming, grunting, and the passing of gas.
It's the Music, Man...
At the end of the day, it all comes down to the enjoyment of music. Forget about the vivisection we reviewers are obliged to perform. The final questions we should all be asking are:
My answer to one and two is an emphatic yes. The Khoruses produce beautiful, intoxicating music. The presentation is so natural, so devoid of artificial haze, glare and congestion, that I can sit contentedly for hours, just lost in the music. This is unusual for me. In recent years I've gotten very restless and finicky, more interested in watching a DVD movie than I am in listening to complete CD. That has changed with the Khorus. They draw me in and seduce me with their sound. I'm not bored any more, because even when listening to familiar music, I'm discovering all kinds of interesting things.
As for the price? Well, it's difficult to put a price tag on this level of music enjoyment. As compared to other high priced audio products I've had, I would say that the Khorus loudspeakers yield a very high return on the investment. These are not your ordinary dynamic driver speakers in a wood box. If you are like those who recover from the bends, you will appreciate what these differences mean and will embrace them as I have.
My skeptical view of Talon Audio and my cynical attitude have been
permanently checked at my listening-room door. You can count me in as one of the
audiophiles who believes that Talon technology works. Hey, Perry, I'm a convert, and it
didn't take an
Clement Perry interviews Tierry Budge of Korus
Clement Perry: Tierry, you seem like quite the experienced type. How long have you been an audiophile and what made you want to become a speaker designer?
Teirry Budge: I was introduced to High End in1973 when I heard a Kenwood marble-bass turntable, and Crown separates driving AR3 speakers. I was struck by 2 things (that sent me on my "quest"): 1) I was pleased to hear that I could get more than I thought possible out of a stereo (I had been devouring everything that I couldreadingabout stereo since 1967), and 2) I was even more disappointed that it was still that far away from the absolute.
From 1973-1986, I heard a number of systems that seemed to do various things quite well. I won't list them all, but suffice it to say that they all did things that led me to believe that if a system did something really well, it did something else very poorlyit was all trade-offs...no clear-cut "winners." The one system that seemed to come the closest was one that I heard in 1984, I think. ARC SP10 and a D250 Mk II (I believe), driving some heavily modified Quads. The system also used a pair of Entec subwoofers which must have been judiciously and carefully integrated because I've never heard them (since) sound anywhere near as good. It was tonally balanced quite well, evenly dynamic (if a bit foreshortened), detailed, and seemed comfortable with most any kind of music. (I've heard the WAMM's sound better on a number of different pieces and styles, but never so evenly footed as this system was.) This was also, perhaps, the most transparent system that I ever heard, BUT, even the images had the see-through quality that the soundstage did. It was a fun experience, but a bit disconcerting as well. I've heard Meridians (late 70's), Celestions, Linns, Wilsons, and even some Yamaha NS1000's do a few things musically right, but always at the expense of other musical virtues. As each "reference" system did certain things well, I started to make a mental checklist of just what those things were. I found various musical strengths in specific products; However, I realized that there were a few "virtues" that I had never heard out of any speakers: 1) real-world dynamics (large AND small scale), 2) the sense of energy or "vibrance" of the real thing, and 3) timbres that bring true instrumental character and dimensionality. This, of course, was above-and-beyond the fact that no speaker had managed to assemble ALL virtues into one package. (Perhaps I should add that I feel that from about 1982 on, speakers, in generalnot specifichave been getting brighter and boomier.
It's almost as if we're saying that we can't get the excitement that we want out of our systems, so we try and liven it up a bit.) I began to feel that vibrance, dynamics and timbral control had to be the pursuit. Not because they seemed the most important, but because they seemed the most difficult to attain. So, I made it my goal...hoping that if I attained these attributes, the others would come along for the ride, as it were. Each of these elements seemed to depend, intuitively, on pistonic movement. Since it didn't seem possible to make a panel speaker perform like a perfect piston, I chose to pursue dynamic-driver-based speakers. (Yes, some panel-types have come close to pistonic movement, but they still sound a bit thin, timbrally, and dynamically compressed.) However, dynamic drivers seemed to possess a few dichotomies of their own: Soundstage width/depth, solid fundamentals, timbres, and "pace and rhythm" all seem to need large moving mass. But, to have detail, good transient definition, and transparency, you need low moving mass. Broadband agility and low bass seem to require a loose suspension; but, power-handling and absolute output require a stiff suspension. Loose suspensions seemed agile, but not "detailed"; responsive, but not vibrant. These kinds of questions and dichotomies represent some of the more challenging "troubles" and "difficulties" in getting a dynamic speaker to "get close to the music." I figured that if they seemed mutually exclusive, it was only because I hadn't found the answers yet.
CP: How long have you been tinkering at this new midrange / woofer technology?
TB: I began my own efforts in 1981, but I wasn't sure where to start. (I have lived and breathed speaker design ever since.) I suppose that, for me, dynamics came first. Since the overriding dependence on driver function was the interaction between the box and the woofer, I started with loading techniques. I tried everything: Transmission line, closed box, B4, QB3, etc. Nothing seemed to work. However, everything seemed to point, dynamically, to using stiffer suspensions and smaller boxes. While this improved dynamics to measurable degrees, I was losing my low-bass extension. (no surprise) In 1993, I designed a smallish box (1.5 cubic feet) around a high moving mass, yet relatively stiff 10" woofer. (the high mass was my attempt at bringing in low bass.) The low-frequency cut-off was around 30Hz. But, I still had a number of problems: 1) High moving mass drivers want to stay in motion, 2) the high mass of the woofer precluded any midrange responseforcing a 3-way approach (which was o.k., but it introduced a whole new set of variables), and 3) there was still entirely too much distance between the "speed" of the tweeter and that of the woofer.
CP: Can you tell me how you got the "20 times faster" and "100 times quieter"?
TB: I have always used tweeters that have "rise-times" (measured with a "step" or impulse response) between 6-12 uS. The 6.5" "midrange" that I used for the 3-way that I designed in 1993 had an out-of-box rise-time of about 70 uS. But, when this woofer was dropped into the box, the rise-time was close to 1500 uSmore than 20 times slower!! The 10" woofer that I described had a rise-time of about 150 uS, free-air; but, it was closer to 2500 uS in my "small box," QB3. This kind of disparity (12->1500->2500 uS) was actually quite good, by market comparisons, and the whole 3-way did quite well in it's day. But I couldn't help but think that since the voice-coil of each driver sees signals which travel ator nearthe speed of light, there had to be more information "in between" this great disparity in speed. I have since learned that both a) musical "energy" and, b) dynamic gradations, are lost when the differences in speed are so great.
You asked how I came up with the numbers "20 times faster, and 100 times lower in distortion." Well, the answers are, perhaps, a bit more practical than technical. The 10" woofer that I designed for the Khorus has a free-air rise-time of about 130 uS. In a 1 cubic foot box (like the Khorus'), QB3 loading, the 3dB down point would be around 60 Hz (not good), but the woofer/box combo. would have a dynamic rise-time of about 1500 uS. (Progress, compared to my system of 1993.) HOWEVER, in the "Group Phase" loading (explained in the attached technical paper) the rise time is less than 50 uS, and the 3dB down-point is 17 Hz! So, as far as the "gain in speed" goes, you divide 1500 uS ("old" QB3 loading) by 50 uS (Group Phase Coupling), and you find that GPC brings a gain of 30 times, for this particular woofer.
As for the "100 times lower distortion," we took a low-frequency organ note (around 28Hz), IN A MUSICAL PIECE, and turned up the volume until we got to the point of hearing a "tremolo" kind of a sound. (the point at which intermodulation begins to dominate) With the QB3 loading, this occurs at a continuous sine-wave output of about 105dB. (1M) Under the same conditions, the Group Phase loading showed no signs of this sound...even at 126dB, where the amplifier gave out. Here's where the numbers get a bit tricky: 126-105= 21. We're getting at least 21 extra decibels out of this loading. If you add 21 dB onto 10 Watts, you end up with close to 1300 Watts. Since every 10 dB greater is a multiplication factor of 10, we figured that there wasn't much difference between saying that we're getting 100 times the output wattage, or saying 100 times lower distortion, since it's all measured logarithmically. I suppose that it's more of a marketing thing, but we couldn't think of how else to describe it.
Group Phase became a perfect solution since it overcame a number of different issues: 1) "speed" disparity, 2) the apparent dichotomy of the virtues of low/high moving mass, and 3) suspension control vs. low-frequency extension. One of the unforeseen strengths turned out to be that the overall speed allowed us to have much better integration with a tweeter than using a low-mass 6.5" or 5.25" woofer. (the latter two, at best, are 900 and 1300 uS rise-time-performers, whereas the Group Phase 10" is down below 50 uS...as fast as a dome-mid.)
As the system got faster and faster, we began to notice something: Yes, the system had more detail, more transparency, more "blackness between the notes," but it was SO clean that it almost sounded like it was "missing some highs." In fact, we can't tell you the number of times we've had audiophiles say, "I don't get your speaker...I only hear the highs when there's high-frequencies in the music." Perhaps it's just me, but this statement seems to involve a bit of pretzel logic. Nonetheless, we use a couple of tests to confirm the existence of the highs: 1) a 1500-2500Hz square-wave, and 2) live musictypically massed violins. We use square waves because the leading edge will demonstrate both high-frequency extension AND high-frequency control. The "control"lack of ringingis important to rich and delicate harmonics in the same way a linear damping factor is for an amplifier. The rest of the square wave demonstrates how coherent the system is...timbrally, dynamically, harmonically. As for the massed violinsit is extremely difficult to produce their unique set of fundamentals + harmonics; due, in part, to the fact that there are lower-frequency-based "beat frequencies" as a result of the various playing styles of the individual violinists. Having the group sound large AND "sweet" is a horrific challenge for tweeters to negotiate.
CP: Please explain why this speaker sounds rolled off until well broken in?
TB: If we listen to harmonics alone, the system isn't "rolled-off" at all, but if we listen for the "air" that we're used to hearing, then I would have to say that all 3 speakers sound rolled-off. Of course, Talon would like to believe that what's missing is all the modulation caused by the (uncorrected) beat frequencies of the various phase shifts, which exist naturally in dynamic drivers. (see "inversion circuits" in the Technical Paper.) We also feel that there are several arguments supporting this: 1) no instrument produces its own air. Such "air" only exists through the interaction of the room/microphone/mic-preamp with the instrument itself. In other words, this is the province of the recording engineer, not the speaker designer. (just think about how a given speaker's presentation of "air" is superimposed on every piece that is passed through it. It tells youeven if you're blindfolded"oh yeah, I recognize this speaker...it's______." Live music has no omnipresent "air.") 2) Listening to a good set of headphones. (I use this example because with headphones, the "mechanical" problems are on a much smaller, and more manageable, scale.) The better, and faster, the headphones get, the more you are aware of the harmonic richness of the music, not the grainy/shushy sound of the "air." They get cleaner, and more controlled, and LESS hissy.
In the end, it's hard to make excuses for the high-frequency balance, because the speaker meets the design criteria. Basically, we feel that we have to have the discipline to leave it alone and trust that the future will bear it out. It may sound "softer," but only by direct comparison. If we turn the whole "problem" around, we realize that we can get far greater (and cleaner!) dynamic output this way. In any case...So far, this presentation of "air" seems to be the closest thing to an identifiable "weakness." And yet, it's probably closer to a "flavor" choice, than an absolute weakness.
The Khorus DOES measure like it's about 3-5dB down in level compared to the midrange (2KHz on up), but there reasons for this: Mostly, it's because the Khorus has two tweeters which overlap, electrically, from 3-20KHz. Placing a microphone at a "listening distance" helps show the true in-room output, but now the distance from the microphone demonstrates all kinds of room cancellations. Actually listening to something like warble tones, or 1/3 octave bands (like on the MF Sound Check 2 disc) will demonstrate,empirically, that there isn't any terrible disparity.
CP: How did you meet sales and marketing president Mike Farnsworth?
TB: Mike and I met because he had spent a few years building speakers, and he was convinced that no 10" woofer could ever do what I claimed it could. (sound familiar?) He had to come and hear for himself. (This was almost 2 years ago.) After hearing, he called me every day for two weeks. His first comment in each conversation was, "that speaker has thrown me for a loop." He was actually only looking for a subwoofer, but ended up saying, "this is what I've wanted to do all of my life." He has become the driving force behind refining, and getting all of this to market. I have always wanted the Technology to be "complete" (meaning, an assembly of ALL musical virtues and/or minimum of weaknesses), and Mike has wanted to make the COMPANY "complete." (i.e. finished look and feel, brochures, ads, reviews, manufacturing, everything.) I couldn't have met Mike at a more perfect time. Any sooner, and some of the Technology would have been set aside for manufacturing concerns. As it is, he took no convincing...he knew it instantly, as if he had been doing this for years.
CP: So how did you come up with all the names at Talon?
TB: For about 6 years, we've gravitated towards raptor names. (Khite is actually Kite with the Khorus' "h" in it...we also have a product by the name of "Khestrel," in the works. "Roc" is the name of a mythical raptor that could hold an elephant in its claws.) It took a bit of time and effort to come up with a name that was fairly simple, strong, and represented our tendency to raptor names. For us, "Talon" works. (The logo was another struggle altogether, but we feel even better about its "look and feel.")
CP: This sounds all too easy, which I know it couldnt have been. Were there trails and tribulations?
TB: "Trials" are a bit more difficult to enumerate, both because a) they bring up difficult memories, and b) we feel so fortunate to be a part of a technology that is more than the sum of its parts. Sure, we've been through debilitating lies and rumors. (sometimes at the hands of those we were only trying to help.) We've had more than two dozen potential associates who have either graciously offered to separate us from our best ideas, or run off with cabinet plans, take us to court over their own mistakes, take our services but not pay, steal and copy crossover designs, or try to beat us to market with our own product. But, through all of this, the biggest challenge has always been the following: Locating an answer that you KNOW is there, but has never seen the light of day...then moving to the next "answer, "...and the next one...and the next one...not knowing when you'll feel it's "complete."
CP: What challenges do you see in your bright future and what type have you encountered thus far?
TB: Over the last two years, the biggest challenge that we've anticipated has been that of finding a way to express the reality of the technology, and our excitement over its introduction, in such a way that people know that we take the technologynot ourselves!seriously. When you think about a marketing-hardened industry, it takes as much creativity to genuinely provide a new technology as it did to "invent" the stuff in the first place. Along these lines, one of the biggest struggles has been to present a market-accepted line of speakers. This Technology is more expensive than most, to implement. At one point, we discussed the possibility of diluting the technology, in order to make a more affordable product. But, it was decided that a) those who would criticize the higher price would likely find something else to criticize if it were less expensive, and b) those who could afford, or stretch to, what we had to present, would greatly appreciate the "no compromise" approach. Obviously, we opted for those who would both support and appreciate our efforts. As it is, because of the total lack of compromises, each one of the speakers belies its sizeeven the Khite. This is a hallmark of "Group Phase Coupling." The Khite, properly demonstrated, can portray the full size and weight of the Symphonic Double-bass Drum...in a way that most $20,000 speakers can't.
Through all of this, there have been a number of staunch supporters...some, of whom, have been responsible for my not giving up, through the hard times. Now, just the promise of the technology is enough to keep us going for years.
CP: Okay, so whats in the future for Talon Audio?
TB: The plans for our future might border on the "overwhelming" to go into. Suffice it to say that we have at least 5 products planned, above the Khorus, and 2 products "below" the Khite. As for those "above," the idea is to make them bigger, more efficient, and more tailored to an individual's home...not sonically better, per se. (This is not an attempt to minimize these products, but an admission that the scope of the Khorus is truly SOTA.) Those "below" the Khite would be the first Talon products to experience judiciously chosen compromises. In all actuality, we would love to license out Technology to some of the bigger companies so that the compromises are limited, and the technology is more accessible. We hope to meet, and become involved with every aspect that will better the "experience." We don't wish to be anything but speaker designers, but we'd like to "lend a hand" wherever possible. We have patentable applications for Sound Reinforcement, and multi-media presentation. In either case, we believe that we can provide something that has far greater performance out of much smaller and more manageable packages. We have a patentable idea for a speaker with a boom-microphone-like reproduction of sound. (for exhibits and displays) We even hope to take the time-related reconstruction concepts to a University, and spend the time developing the associated equations. We hope to leave no stone unturned.
In the short term, the "products" that we have coming up are 1) some seriously cool retrofittable spikes that make use of correct mechanical-grounding principles (dare I say...more openness on top?), 2) visually matching stands for the Peregrines, 3) a more "exotic," "export" Khorus enclosure (readexpensive), and 4) visually sprucing up the Peregrines and the Khites, while increasing their own ability to dissipate mechanical energy. In the long term...while we have already received the initial prototype drivers for the more expensive systems, we have decided to hold off, in an effort to provide the best product line that we can right now.
CP: Can you provide a cutaway photo of the Khorus?
TB: Although I don't have a cut-away of the cabinet, there is a reasonable description of the loading technique in the Technical Paper that I'm sending you. (We won't mind providing a cut-away, once the patents have been granted.) As for the Roc, it uses all the principles outlined in the "Group Phase Coupling" section of the Technical Paper. But, in its case, I designed a 12" woofer with a 4" voice-coil, almost 2" of "throw," and the suspension/motor-structure of a high-powered 18" pro-sound woofer. It's a beast. (For whatever it's worth, the Roc has enough "speed" to successfully negotiate a 900 Hz crossover point, but this probably doesn't surprise you, by now.)
CP: Explain what occurs when I stuffed the ports on the Khorus?
TB: The Khorus' impedance looks like a classic QB3 design, with two separate peaks in the low end. (one at approx. 50 Hz, and one at 17Hz.) But, unlike the QB3, the Group Phase loading doesn't set the low-frequency cut-off at the trough between the peaks. Rather, it is at the center of the lower peak. With the port plug in, the system has only one low-frequency peak, coinciding with the upper of the two peaks. In other words, it now has the impedance structure of a closed-box. The low-frequency cut-off, under these conditions, is about 50 Hz. But the plug causes the appropriate phase shift to begin around 80 Hz. Having removed the "duty" of the bottom 2 octaves, the Khorus plays with even lower distortion, and actually sounds more efficient. Of course, the performance of the Roc helps elevate the response of the entire system. You almost have to think of it as bi wiring from the preamp-out, instead of the normal amp->out.
Well, I just estimated that you're getting about 10-12 pages worth of information...but then...dare I say it?.."you asked for it."