Thinking about Lowthers: A Meditation by Max Dudious

Yo Dudes! And Dudeens! This time I'd like to share with you some thoughts about Lowther loudspeakers, how they do what they do, and why they are truly special. Lowthers are a British product that has been around for over fifty years. I've been aware of them since the '60s. I first learned of them when my college and audio buddy, Alan Shapiro, came up with a mono system made up of four long-throw Bozak 12" woofers, and a Lowther PM 6 (crossed over at around 100Hz) mounted in a braced closet door. In addition to being able to produce deep, clean bass, it was awesomely bright and clear throughout the rest of the frequency range. That was in the early 1960s. To reproduce in stereo, Alan had to build (from Lowther plans) two enclosures of the type that used the speaker's rear-waves, through a folded-exponential-horn, to augment the bass of this smallish (nominally 8") driver. That was a prototype for what later became known as a "single-driver point-source, high efficiency" system. It was exceptionally clean and clear, with the ability to produce great dynamic range, while simultaneously picking up small details that were "down in the mix." With very modest amplifiers those efficient Lowthers (rated between 96 and 102dB at one Watt/one meter), could play loudly and present a stunning image, an illusion of the spacious venue in which the music was originally played; or, the feeling that you were in the room with the musicians. That was in the early '70s.

Is Truth Beauty and Beauty Truth?

With all apologies to John Keats, I fear not. In a recent article, "Truth vs. Beauty: A Tale of Two Transports" (Stereophile, March, 2006), audio-writer colleague, Laurence Borden, gets into the old audio conundrum of "beauty vs. accuracy." In it he goes through the usual stuff:  for example, and as my literature Prof. Richard Macksey used to say: "Translations are like mistresses: if they're beautiful they're not faithful." The same might be said for sound systems: "If an audio rig sounds way gorgeous, it is most likely not true to the original." In his article Borden says, "There are logical reasons for choosing less than complete accuracy in a system." He goes on to quote a recording engineer, the venerable Steve Hoffman, as saying: "Now, I have more than one system. My mastering system is accurate, boring and very useful to me in my work. I don't listen in there [the studio] for pleasure. Not that it doesn't sound good—It does, but it's too accurate to be any fun. In some of my other systems I can spread it out a little."

Well, you might say, "A recording engineer is a special case." I think many of us have to listen to our music in rooms that are less than audio-ideal. They are too small, or have strangely configured walls and ceilings, or archways, or doors and windows that can't be moved, etc. They are far less ideal than the dedicated listening rooms that some folks are adding to their homes these days. My office/lab is like that. I'd guess audiophiles who have to listen in imperfect rooms (special cases, all), are in the majority. Other special cases are folks whose hearing is impaired due to age (like mine), or due to listening to too-loud rock 'n' roll in their early years (like me). Or people, like professional musicians, who listen so hard to performance values they are indifferent to "recording studio quality," or audio values (like I often am).

I've known a number of symphony orchestra players, and only a few are into audio. Beauty, and emotional response to it, seems to matter most to musicians, or people who share their involvement in the music as performed, and they can get off listening to an inexpensive car radio. So for the architecturally challenged, the aurally challenged, and the performance sensitive, choosing less than complete accuracy often meets their needs and suits their tastes. A large number of readers may have never thought of themselves in these more forgiving ways. But we are all special cases.

Some folks see inaccurate, overly-warm systems as "schmaltzy," or too emotional. That is a value judgment that might be made by the folks who value the "analytical" over all. That is like the difference between someone whose favorite music might be the school of composers who followed the "analytical" Igor Stravinsky with his angular presentation, as opposed to the more lyrical and "emotional" Rimsky-Korsakov (who was Stravinsky's teacher of orchestration). Both of these men's ideas are still valued by some modern composers, like David Chesky. Nonetheless, this is a dichotomy that is, after all is written and done, a matter of taste, and for whatever reason some like chocolate and some like vanilla.

The Lowther sound is not for everyone—it is for connoisseurs. Most folks love music. In a poll I read in the Sunday Magazine once a few years back, music was rated the fourth highest when it asked, "What would you least like to live without." Only food, clothing, and shelter ranked higher:  music ranked ahead of sex, and "Death by Chocolate" ice cream. [I remember such things. I can't help it. Who could make that up?] The Lowther people say, "We have an almost universal love of music through all societies because of the emotional impact it can have on our lives. It can express happiness, sorrow, joy, or a good party." Here we see Lowther's take on music. They believe its appeal is emotional, and that is where they aim their latest products.

Into the Labyrinth

Lowther has been building (or recommending) the back-wave-driven folded-exponential-horn for their 8"speakers for a half-century. They have patented numerous types of these labyrinths to augment the bass response of their drivers. They believe such speaker enclosures show their drivers at their best. The various horns are somewhat dedicated to the various drivers in their line and are a matter of taste and bank account as they become more complicated and expensive. The most elaborate are built of 1.0" or thicker Medium Density Fiberboard (MDF), have multiple drivers, with one model having a second driver facing rearwards and up on a 45 degree angle. The least elaborate are usually built out of half-inch particle board or plywood, and they have (and make use of) some box-resonances. Their new Alerion enclosure, without the 5" DX55 speaker mounted in it, when we do the knuckle rap test, resonates or makes a note that lasts longer than an instant. That note, when expressed as a frequency, is the point at which tests have shown the driver's frequency response curve starts to roll off, sharply.

The Alerion enclosure is designed to have a peak where the speaker has a dip. This peak is more of a plateau that spreads over an octave or two. If the speaker begins to roll off gradually at the top of the cello region, and falls off sharply at 90 Hz in free air, and at 70Hz in an infinite baffle (or sealed box), the designers pick a horn that will compensate for that. The Alerion box-resonance might color all the sound from 140Hz (an octave above) down. There may even be some boost from 280Hz (two octaves) down, as 140Hz and 280Hz are harmonics of 70Hz. That takes the boost nearly up to middle C (actually D above middle C). I call this range (the two octaves from 70Hz to 140Hz to 280Hz), the "cello range." Below that (the two octaves from 70 Hz to 35 Hz to 17.5Hz), I call the "deep bass." The Alerion seems to have a fullness in the cello region. But, as Lowther importer-distributor Jon ver Halen says, "Below 50Hz it sinks like a stone."

Horns, as a type of speaker enclosure, are known to behave this way. My audio colleague, Robert Harley, reminds us in a recent article in The Absolute Sound (March, 2006), "MAGICO Ultimate Loudspeaker: The Bugatti Veyron of Hi-Fi":  "Below the horn's low-frequency cutoff point (determined by the mouth size), the horn is too small to provide adequate loading and the driver begins to function as a direct radiator, losing the benefits of the horn." Here Harley is describing the front-loaded horns of the speaker he's reviewing, but the same holds true for the rear-loaded horns that the Lowthers use. The result is, near the low-frequency cutoff point, that Lowther describes as "about 70Hz," the output begins to fall off—before it sinks completely at 50Hz.

The "designed in" box resonance raises the frequency response of this 5" driver system a pretty healthy notch. When I say "designed-in" I mean that they could have engineered the cabinet out of veneered Medium Density Fiberboard, or MDF, which is denser than either plywood or particle-board, and has no voids compared with plywood, and as such has much less resonance. And they could have specified a 1" thickness rather than 0.5" they use, and doubling the front speaker baffle to 2.0". That would have made for a nearly non-resonant cabinet at only a modest increase in price, as most of the production cost is due to the labor-intensive carpentry. The designers knew what they were doing, and the cabinet responds well. Some will love the Alerion cabinet for providing bigger bass: others will find it uncontrolled.

The Alerion enclosure makes female voices sound very full and luscious, dare I say voluptuously beautiful. If you like female voice—singing anything from bluegrass to blues, from intimate cabaret singing to grand opera—you might love this loudspeaker. It has a similar effect on male voices, making rich baritones sound even more testicular. If you listen to a lot of late night string quartets, solo cello or other chamber music—you might love this loudspeaker for making string tone rich and full. If you have difficult neighbors who dislike pounding bass in your apartment building—you might love this loudspeaker, for it makes little deep bass. If you need bass, you can get yourself a self-powered sub-woofer and get the full bloom of the bass viol and the organ's pedal tones. As is, this is a li'l darlin' of a speaker, even though it adds romantic colorations and it lacks deep bass. It is not faithful, but it is ravishingly beautiful. It is the kind of speaker people either fall in love with, or hate. It reminds me of the woman prizefighter (Hilary Swank) the aging fight manager (Clint Eastwood) takes on in Million Dollar Baby:  you can't help but love her. She's too old and too small, but Clint's character dubs her "Mo Quishla," Gaelic for "my darling."

Single Point Source

What recommends the Alerion are three characteristics that are the signature of the Lowther line: "clarity, presence, and sheer musical dynamism," as Art Dudley opines in another Stereophile article, "Buying Off the Rack" (Feb. 2006). These qualities originate in a very fast single-point-source full-range driver. A single-point-source driver is typically free of crossovers with all their phase and gain problems. Multi-driver speakers, even relatively simple two-way designs, often have to deal with the difficulties of phase and gain matching, because anything less than perfectionistic matching causes sonic blurring. Most manufacturers do this as best they can with crossovers that have numerous parts. The signal passes through all of these parts and can't help but endure some deterioration. The solder joints alone, small ones with anything less than proper soldering, can cause some veiling. A single-point-source full-range driver preempts all crossover problems by having no electrical crossover. I agree with Harley when he opines, relative to the MAGICO Ultimate, but equally true concerning the Lowther: "Directly connecting the power amplifier to the drivers' voice coils, with no intervening capacitors and inductors, confers a huge advantage in sound quality." (Op. cit. March 2006) Nearly all Lowther drivers have a mechanical crossover at about 2100Hz, where the high frequencies enter the whizzer, with its lower mechanical impedance. More about Mr. Whizzer later.

A single-point-source has all the sound originating from one point in space, so all the frequencies arrive at the ear from the same distance. There are no milliseconds differences, as the sound from each driver arrives sequentially at the ear, that make for subtle time-smearing and less clarity. More clarity makes for better differentiation of spatial cues, and in turn better sound-staging; or the illusion of greater sound stage width and depth. This creates the possibility of following a single voice or instrument in the mind's ear as it pleases the listener. So not only is the sound cleaner and more coherent, it has greater presence with better spatial perception and instrument differentiation. The Lowthers' difference in clarity is often described as the removal of veils when compared to most other speakers.

Another feature Lowthers provide (which most other speakers don't do as well) is the ability to reproduce large dynamic contrasts, the ability to go suddenly from very soft to very loud and back again, without congestion (or failure to offer clear differentiation of instrumental timbres). Even at low-levels, Lowthers can startle you. People who live with Lowthers for a while often come to be life-time Lowther owners due to their ability to excel at clarity, dynamic range, spaciousness, and their ability to pick up low-level details "down in the mix." If you've been reading my stuff, you'll remember that these are characteristics I value in headphones, in cables, amplifiers, speakers, etc. And if you've been paying attention, you'll find we just went from three to four desirable characteristics. Just keepin' you on your toes.

World War II Technology?

How does Lowther achieve these characteristics? In another Stereophile article (Jan 2006), my audio-colleague Art Dudley, writing about the Hartley company history in a footnote, says:

"Then came one of Luth's [the engineer and eventual partner] finest inventions of all: a magnetic driver suspension that may have been an outgrowth of the work he did with underwater mines during World War II. Magnetic suspension transformed the driver's voice-coil into a sort of part-time electromagnet: In the presence of an AC signal, the coil and cone could move quite freely; but in the absence of a signal, a strong restorative force pulled the coil back to its starting position—and in doing so created a damping effect that was almost five times faster than the best that could be achieved mechanically." (It's interesting to compare the magnetic suspension Luth invented for Hartley with Lowther's own Hi-Ferric technology. Both seem to involve coating the voice-coil and/or former [the thin, light, hollow tube around which the voice coil is wrapped] with a magnetically permeable substance.)

Lowther's Hi-Ferric technology is often mentioned, and is explained in much detail on their web-site. It sounds a lot like Dudley's description of the Hartley system to me. It may be the reason the Lowther drivers can sound so much faster and cleaner, more able to pick up low-level details than conventional drivers: they are faster, cleaner, and more able. Hi-Ferric technology may be the reason that the Lowthers are often mentioned as having a similar sonic thumbprint as the Quad electrostatic speakers. It may be the reason that I bought a pair of Hartley 18" woofers in 1969 that I own and use to this day; and the reason I've gotten extremely well-blended sound between the fast Lowther Alerions (albeit not recording-studio accurate) and my quick Hartley-Klipsch horns.

Big Magnetic Field; Small, Light Cone

In addition to their Hi-Ferric technology Lowther employs a magnetic field several times as strong as most contemporary loudspeakers, especially for the size of its drivers (5" and 8" nominal). The Lowther drivers are designed to have a throw of one millimeter. I infer this kind of driver is better suited to being horn loaded (as opposed to being a direct radiator in a sealed box), especially at high volume, for reasons Harley mentions above. Moreover, the magnetic field is coupled to a nearly-infinitesimally-light, treated-paper cone that can start and accelerate with extraordinarily short rise-time in response to an electrical pulse. The voice-coil gap is also built to very close tolerances, measured in thousands of an inch. The voice coil itself is wrapped and adhered to the former-tube on both the inside and the outside, which makes for a larger electromagnetic force (EMF) to drive and brake. With so much electromagnetic flux in the gap, the coil/cone has little problem centering. Braking on this vibrating coil/cone construction makes good use of the EMF for fast settling, and like the Hartley, it goes to the neutral position in the absence of signal. The high damping of the design allows some designers to use it as an open-back, bi-planar driver simply mounted on a board above a woofer. This driver offered excellent overall performance that was extraordinary in the days soon after WW II, when low power amplifiers were the only amps available.

We can infer how well this works, especially if the voice-coil is treated as Dudley suggests, and which Lowther says it is:  a large magnet creating a lot of Gauss, a voice-coil itself sometimes acting as an electromagnet, all driving a very light (treated to avoid picking up moisture) paper cone. This system gives the Lowther its extreme detail and delicacy, its startling dynamics when playing softly or loudly, all the while remaining a very flat, neutral sounding transducer. It is remarkable how well this family of speakers picks up low-level details and nuances of performance. Even grace notes so far "down in the mix" they are barely noticeable on other systems become an integral part of the whole on Lowthers. Some other speakers can do this (notably the electrostatics), but few dynamic drivers with the ease and "correctness" of the Lowther.

Harley waxes poetic, if a bit purple, about the "wildly expensive" at "a hair under a quarter of a million dollars," MAGICO Ultimate's sound quality, saying; "This system did many things well, but in two qualities, it was revelatory. These two qualities, which were related and reinforced each other, also carried with them many tertiary effects that contributed to the stunning overall presentation.... The most striking aspect of the Ultimate's sound was a palpability and immediacy that went far beyond anything I've previously heard in reproduced music. The illusion of the instrument actually in the listening room.... The second quality of the Ultimate that is unprecedented in my experience, and one that no doubt contributed greatly to the stunning sense of realism, was the reproduction of exceedingly fine detail.... The Ultimate's uniqueness is its ability to reach way down [into the mix] and present the finest, lowest-level aspects of instrumental timbre and microdynamics."

These are the same qualities that I believe make the entire Lowther 8" speaker line high performers in their size and price class, and the Alerion speaker terrific (if uneven) in its price-class, at one percent (1%) of the price of the MAGICO Ultimate. I think the Alerion already comes close to the sound of the Lowther's better 8" drivers now, and with further refinement will be even better. I haven't spoken to Lowther about this, but I expect they will have some program for upgrading the Alerion's little EQ network at little or no cost as the solutions work themselves out.   

There are two drivers available for the Alerion enclosure: the DX55 (left) and the C45. According to Lowther's literature, "The DX55 is a speed demon, very fast and extended. The C45 has slightly less resolution and speed, and sounds a little more relaxed. Price [per pair] is $2750 with the DX55, $2350 with the C45. Maple [blond] is the standard finish, but cherry [reddish brown] can be ordered for an extra $500." I guess the price is somewhat on the high side, but so is the performance. I've seen and heard small two-way "mini-monitor" sized speakers that are priced at the same level. As none of these top-of-the-line two-ways make "deep bass" either, I'd say it amounts to a reasonable comparison. So, you pays your nickel and you takes your choice.

How Does It Sound?

It sounds much (but not quite as much as it could) like the larger Lowthers, the PM5A's (left) for example, in regard to clarity, presence, dynamics, and low-level detail retrieval except it has little or none of the "whizzer problem." In the larger 8" (nominal) Lowthers, the high frequency whizzer cone is about 3.5" in diameter, while in the 5" (nominal) models it is 2.5". It is said the whizzer interferes with the larger cone. One way to reduce this interference is to reduce the size of the whizzer. After doing the math I am pretty certain the 5" model represents about a 40% reduction in radiating whizzer surface. Furthermore, the edge of the smaller whizzer is not rolled up like a pie plate as it is in the larger models, nor is it angled forward as much. It lies flatter to the larger cone, blocking rather than doubling the loudness of the inner part of the larger cone. There is also less chance of the rear waves from the whizzer interacting with forward waves of the larger cone. The manufacturer of the Hørning Perikles speaker dislikes the 2100 Hz peak so much he chooses to remove the whizzer cone entirely and add a tweeter (Dudley, Feb op cit). That model also employs two 9" woofers, turning the nominally 8" DX2 into a wide-band mid-range.

In his work with single-point-source full-range drivers, Nelson Pass has developed for over a dozen of them a "notch filter," which is comprised of an impedance/capacitance/inductance network in parallel (not series) with the drivers. I've experimented with various values and I've found a set that I feel reduces most of the problematic peak at 2100Hz, the infamous Lowther "shout," quite satisfactorily for me. That is to say, why should we surgically excise the whizzer like a cancer when we can damp the problem area electronically with a few inexpensive parts (connected in series with each other but) in parallel with the driver?  

Nelson Pass, on his website, reports the DX55 measures pretty well through the midrange and trebles with some equalization. To me it sounds like it has a noticeably less up-front presence. Kudos to Nelson's gang for working that out. Interestingly, Pass comments in his articles on the KleinHorn, (go to www.passlabs.com and surf to "articles") the best sound he was able to come up with was using a pair of pipes (Helmholtz resonators) with 21" woofers beneath the KleinHorn (crossed over at 100 Hz), and a tweeter on top of the DX55 (crossed over at 10kHz). That also made of the DX55 a wide-band mid-range. See store.hifiauthority.com/olsherkits.html  for photos and plans of Dick Olsher's BassZilla, which uses the Lowther in a similar way. Can we infer that Robert Harley, Art Dudley, Nelson Pass, and Dick Olsher all value those characteristics of speaker performance that to a great extent define the Lowther? From their activities and opinions expressed in their writing, I think so. And we might gather that each of these august audio dudes is somewhat fascinated with Lowthers and the Lowther Sound.

The DX55 Alerion (right) shares family resemblances with the larger Lowthers, only with less bass, and without the in-your-face presence quality of old (without the notch-filter), which, at 40% of the size, it should. It has similar clarity, presence, dynamics, and low-level resolution (but not as much) as the rest of the 8" Lowther family through the mid-range and highs. I think it is a work in progress. It is warmed up a notch or two in the "cello region" by the Alerion horn cabinet, giving it a suave and romantic foundation beneath the rest of its characteristics. It sounds pretty good on its own with both a Single Ended Triode (SET) deHavilland Ios 845 stereo amp, and a pair of heavily Pooged Marantz 8Bs, wired in triode (push-pull), and bridged to mono. I found it sounded best crossed over at 100 Hz to a pair of my 18" Hartley/Klipsch woofers, but it may not be fair to mention those because I built them (in 1969) one-off from plans for the Electro-Voice Patrician I found in a 1955 issue of what was then called Audio Engineering, subsequently known simply as Audio. There is a D.I.Y. project for the ambitious—building corner horns for subwoofers, but what kind of a nut would do that?? Oooops.

The Alerions sounded nearly as good with my Renaissance Phantom self-powered (300 W) sub-woofer. This is a nice unit with a 12" active driver coupled to a 15" passive radiator. It has the radiating area of an 18" woofer with the speed of a 12", which approaches the speed of a Hartley. It's a pretty slick design with many features (line level or speaker level inputs, signal turn on, 180° reversible phase, with both knee and gain settings). It is tuned to 17Hz (lowest D, or two octaves below the cutoff of the Alerion) on the low end, and it is continuously variable up to 150Hz on the high end. You can see the Phantom at the Renaissance web-site http://www.renaudio.com under "home theater". Mikhael Shabani can make one customized for either rock or classical music by increasing or decreasing the mass of the passive resonator to taste. In my humble opinion (IMHO), this is one of the truly outstanding subwoofers in performance and value at about $1400. And it just happens to blend wonderfully with the Alerions. Together with a pair of Alerions, the Phantom might resurrect Jimi Hendrix.

To Review and Sum Up

I've tried to demonstrate that there are certain qualities of reproduced sound that are noticeably different from speaker brand to brand. I've tried to show how four well known and respected members of the audio community (TAS editor Robert Harley, Stereophile columnist Art Dudley, and equipment designers Nelson Pass and Dick Olsher) seem to be converging towards an agreement that really good loudspeaker systems have these traits in common to a high degree:  clarity, dynamic range, spacious sound-staging, and the ability to pick up details down in the mix. A fortuitous mixture of these qualities will make for greater illusion of "musicians in the room," which seems to be the highest goal to which a first-class system can aspire. I also tried to explain, though I am not an engineer, the how and why of Lowthers' performance:  how they get big sound from small drivers with such short throw of the cone; some of the tricks they have used to improve the speakers incrementally over the past fifty years; and how the back-wave folded-exponential-horn makes good use of the back wave energy, tuning it to augment the speakers' bass response.

The Alerion is a good example of a new product that has incorporated some incremental design changes for the better: smaller size, reduction of the "Lowther shout," and a new folded horn developed by Lowther engineers that adds a warmer, more romantic "cello region" to its clarity, dynamic range, spacious sound-staging, and retrieval of low-level details. This is not a perfect loudspeaker; its size required some trade-offs, and I have a feeling it is a work in progress that will benefit from outside interest, but this interest will, I think, result in changes. Still, it offers a rapturous quality to human voice, and if you value the characteristic strengths of the Lowther family of speakers, and you listen in a small-to-medium sized room, the Lowther Alerion is a speaker to consider.

For more information, visit the Lowther website, www.Lowther-America.com. The system designs of David Dicks, who has been experimenting with alternatives to folded horns, can be found at http://www.commonsenseaudio.com. The website of the mother corporation in England, can be reached at http://www.lowtherspeakers.co.uk, where you can see many sets of plans for the larger Lowthers' enclosures.

If you are moved to order any of these drivers, or complete systems, just grab your Grand Dame and do a "Pomp and Circumstance" around the room to your phone or computer, and when you get hooked up with Jon ver Halen at Lowther-America, tell 'im Max sent ya'. I really feel the entire Lowther line of speakers does a terrific job at creating the illusion of musicians in the room. They do so many things "just right," you can't help but be intrigued—just right for people like me and Jimi Hendrix.

Ciao Bambini,

Max Dudious