Visit to listen to the LX521 on 21JUN14 - See below (at the end).
Charles F. Port, 17JAN13
The LX521 Open Baffle loudspeaker is the latest development from Siegfried Linkwitz, a retired HP/Agilent RF Engineer who has many Audio Engineering accomplishments and accolades under his belt. Siegfried published scientifically engineered Open Baffle loudspeaker designs (via his web site, www.linkwitzlab.com ), beginning (after his stint as chief engineer at Audio Artistry) with his PHOENIX project, which was soon followed by the ORION, and later the PLUTO (an omnidirectional monopole).The ORION evolved both physically (through the contributions of Don Naples of Wood Artistry) and electronically (through the contributions of Don Barringer) into its current REV 4 design. It is a majestic and musical loudspeaker. The LX521, an Open Baffle F3 FID  loudspeaker, leaves the ORION design "in the dust," even though the LX521 uses a less expensive driver complement, and costs less than ⅔ of a DIY ORION to build. More importantly, it is the most musically faithful loudspeaker that this author has had the pleasure of hearing.
ENGINEERING AND SETUP:
[New -- based on SL's feedback: 04FEB13]
Note: WATSON was an experiment that showed the effect and priority of ITD upon creating a phantom scene. It was not a driver [inspiration] for the LX521 design, other than that SL discovered the FU10 with it. See http://www.linkwitzlab.com/LX521/Description.htm , "From F3 to LX521".
Through an iterative process, SL pared and stripped away all the superfluous elements of his previous designs, with the goal of building a loudspeaker that displayed “frequency independent directivity” from < 120hz through > 7KHz. A four way dipole evolved, with a minimalistic baffle which met the requirements for uniform frequency dispersion (±60 degrees) and uniform acoustic power, while simultaneously maintaining low-distortion, and a dipolar-polar response characteristics.
One way to look at the LX521 is as a solution to the "problem" of the ORION crossover refinements: the recent shelving slopes that SL was making for the ORION were incredibly sensitive/miniscule (+/-0.25 dB changes) and were based upon data that spanned a +/-45 degree set of off-axis measurements -- it was observed that the realism of the ORION could be improved if an inverse shelving slope could be applied to a specific set of upper midrange and high frequency ranges. The difficulty was that this slope needed to start in the crossover range between the Millennium Tweeter and the Excel Woofer/Mid (around 1.4KHz) affecting both drivers in different ways, and required aforementioned 'accuracy' -- the refinements were not subtle [my opinion -- SL states they are subtle], but SL worried that variance in the manufacturing of drivers themselves could void these crossover tweaks. Between parts availability, the potential +/- 0.25dB variance in the drivers themselves, and the need for "very-great" precision in making the equalizer circuit (it is difficult to know if fellow DIY could follow along and get reliable results) the attraction for a new design is clear. The LX521's four drivers offered a larger "tool-kit" or palette to solve the problem of maintaining a uniform on-axis/off-axis power response; SL expanded his off-axis measurement data-set to span +/-60 degree's over the whole frequency range, and looked at ways to make the new loudspeaker perform more like a "true" dipole in the frequency ranges that recreate an accurate stereo sound field. The LX521, through the use of a thin, minimal baffle, coupled to smaller more "point-source like" drivers - with acoustically smaller displacement between themselves (vertically and front-to-rear) - can better recreate the acoustic clues that fool the brain into believing it is hearing a different acoustic space. I can unequivocally state that this is so.
A rather significant departure from the ORION and other projects is the inclusion of a 6dB/Octave passive crossover between the upper and lower midrange. Basically a coil and cap in series with each driver, though there is another twist: The upper midrange driver is wired in reverse phase. The passive crossover frequency is at ~ 900Hz, and divides the electronically filtered "midrange" transfer-function from the active crossover, which spans a range of 200Hz to 7KHz. It is an interesting part of the design, and leaves the door wide open to audiophile "tweakers" that want to spend $$$$$ on special caps. I think that SL's position on this is 'that is fine - just make sure you use Capcitors and Inductors that have the same uF, mH, and DCR as the perscribed components'. The author went with a bottom barrel CLARITY CAP. See the SOUND section for what I hear ....
On the setup:
The LX521 is designed to be used in rooms with a “normal” liveliness - -aka a typical living room, with a RT60 between 400-600ms. LX521 should be spaced equidistant from the users ears, and nominally should be configured in an equilateral triangle layout, where your head resides at one of the vertices. The loudspeakers benefit from having a separation of between 8-9 feet, with your head 8-9 feet from each upper baffle. The V-Woofer housing can be rotated to deal with room standing waves, and the bridge allows the upper baffle array to be tilted and rotated independently, and should be aimed at a point just behind where your seated head would reside. The upper midrange driver defines the design axis. Another caveat is that the phantom scene benefits from sufficient air around the loudspeakers -- they should be placed at least three feet (1m) from the side walls and back walls. If used in a smaller room, adding diffusive panels to the sides and rear of the loudspeaker might be helpful. The authors' experience is that the upper baffles function in a fairly wide range of rotation, while still being able to provide a solid and "centered" phantom image.
The loudspeaker requires the use (minimally) of a six channel amp, but preferably an eight channel amplifier (or eight mono-blocks/4x 2ch stereo amps) with at least 60Watts RMS per channel -- the same amplification requirements for the ORION. I use the ATI6012 amplifier, the same amplifier that Siegfried has used for all of his OPEN Baffle projects.
A very useful tool in setting up the LX521 is the above "Bosch Laser Measuring System". You can place the butt of this device right over your ear and measure (while seated) to the center of the upper midrange driver's phase plug, and get both system baffles "exactly" the same distance from your head, to within millimeters. While not exactly 'necessary' (as I mentioned above -- the upper baffles are fairly tolerant of movement within the constraints of the bridge and still provide a stable center phantom image) I enjoy the precision that this system allows me to achieve.
One other point - as the upper baffle is independent of the woofer, getting the baffle to align exactly above the acoustic center of the woofers (to get a perfect step-response) requires a MLS pulse system (like ARTA). Also probably "not necessary", but these steps appease the perfectionist (that beast within ...).
These measurements are not meant to be definitive, but are meant to provide some anecdotal evidence that the LX521 is functionally “flat” in my space (or at least as flat as a KEF105.2 ‘on-axis’ is in the same position) -- a well kept and 'up to spec' KEF105.2 was measured (2m/2.83 vRMS at the terminals) at the same local as the LX521; I then rolled out the KEF105.2 (famously flat from 38Hz-22KHz ±2db) and performed the same test with the LX521 -- here are the results (I offset the KEF graph to allow the comparison to be better seen).
Back to my premise -- the LX521 is a better loudspeaker than the ORION/PLUTO/PHEONIX -- it leaves these systems in “the dust”. While I cannot prove to you that this is so without having you visit my setup and taking a listen, I can explain why I believe my own hype.
I have built many ORION’s and PLUTO's (and one PHONEIX), and I followed all the crossover updates/evolutions [ though, in all fairness, I did not make the subtle changes to resistor values that Don Barringer recently alludes to in his 3.3.1 modifications] and I find the midrange of the LX521 much more compelling and lifelike than any of the ORIONS I built for myself or my customers. The upper and lower extremes are almost indentical to the ORION, but as "music lives" in the midrange, the difference is remarkable.
Here follows a list of recordings that I used to come to my conclusions.
I use this CD to setup all of my loudspeakers; I find that tracks 1,2,3 are very useful for determining the best position for any speakers in any given room, especially cut “3” -- an ‘out-phase’ test. A remarkable difference to my ear was how truly diffuse the out-phase voice recording was in comparison with the ORION’s, and how palatable and three-dimensional the “in-phase” voice (cut-2) was after optimizing the relative position of the upper baffles. We are not in Kansas anymore, Toto. This is a different caliber of transducer.
----------------------------------- Standards Engineer: Kent M. Fuqua Recorded direct to 2-track Stereo at The Neurosciences Institute, La Jolla, California on January 18 & 19, 2007 Produced by Peter Erskine, Alan Pasqua and Daniel Atkinson Mastered by Rich Breen A FUZZY MUSIC & KMF AUDIO PRODUCTION featuring the KMF Audio Stereo Tube Microphone Mark II CD0014 ----------------------------------- To my mind/ear, this is the definitive recording to demonstrate the LX521’s superiority over its predecessors -- This recording conveys a startling real presentation of a Jazz trio [move over “Jazz at the Pawnshop”]. The instruments are placed in a well defined space, and the timbre and “truthfulness” of each instrument exceeds anything I had ever heard from my ORION. Recorded with a tube amplified stereo microphone, the results leave you “awestruck.”
----------------------------------- Policromo Heinz Karl Schwebel -- Trumpet Engineer: Flavio de Souza Recorded at Teatro Castro Alves, Salvador, Bahia, Brazil 28th July - 02 August 2003 MICROSERVICE TECHNOLOGIA AMAZIONIA LTDA ----------------------------------- I have long enjoyed the Trumpet, possibly my favorite brass instrument (though I also love the French Horn) -- this is one of the few recordings that captures the “raw brutality” and beauty of the instrument. Face it -- a trumpet in close quarters is an instrument to be treated with respect: It has so much power, with distinct metallic overtones/harmonics, that it can overpower the auditory system and create inner ear cavity “resonances.” I deem it one of the best instruments to use to determine how ‘real’ the system is that is reproducing the sound -- it is one of the best tests to determine the veracity of your system. It is not often that I hear a believable trumpet emanating from a loudspeaker -- even very expensive ones. The LX521 crosses the threshold -- it brings you to the hall where this was recorded, and there is a live trumpet "playing right there". Listen to cut “5” titled “Rustiques” -- it is to die for, on a well set up LX521 ….
----------------------------------- JAZZ GROOVES The Best of Mapleshade, VOL.3 Engineer: Pierre Sprey Compilation MAPLESHADE PRODUCTIONS 2010 ----------------------------------- I enjoy CUT 6 -- "Sir Phyllis Blues" by Hamiet Bluiett Sextet (#02932) Once again, I am able discern things that are masked by my ORIONS, and the presentation of the recording venue is both realistic and dynamic as in a live performance (more so than I have heard before.)
Bolero & Others
Conductor: Adrian Leaper
Recording Engineer: Antino Miranda Rorded June 18-21 1996 La Nave
ARTE NOVA CLASSICS
Asuming for a second that you are like me, each of us has a recording that -- while nothing special -- is one that we have listened to "a lot", and know initmately. It is not the best recording you have, but somehow it ends up on your player often, so you are able to discern differences pretty readiliy, especially if/when you change things around a bit.
This ARTE NOVA recording is like that for me -- nothing really special ( I have better performances of each peice, and better recordings) but I know it well, and (perversly) I enjoy listening to it. My pet poison on this CD is the Daphnis et Chole' [Tracks 1-3]. When you hear "new" things in something that you have listened to a hundred times, that gives you pause. I was hearing all sorts of nioses (people talking offstage?) and clarity to some instruments that had not been there before -- I don't listen too loud, so this is a good indication that there is more low level resoltion going on with the LX521 than I normally get.
Recording Engineer: Martin Sauer -- Recorded 11-14 December 1988 Tonstudio van Geest, Germany
I love guitar music, but I consider it 'cheating' to use it as a reference, as many loudspeakers are very good at creating a believable guitar [ The Maganeplannar SMG, for instance]. But here is another CD that I listen to often, and there is a wealth of detail that I am now hearing for the first time. Things such as Gerald Garcia humming (ever SO softly) while he plays the beautiful Brazilian music I know so well, and a better sense of the acoustic environment that he is playing in (what sounds like cars in the street, passing by the studio).
This recording is a revelation on the LX521 -- the sound-stage is a mile wide! Whew -- you really hear the stage where this was recorded, and the quality of the recording comes out in spades: I am not exactly sure how "Classics Today" assigned this a value of 9/7 (a 7 "sonic" performance out of 10), as it is a 10/10 all the way -- at least on the LX521. I sat back and enjoyed one of the great pieces of American music written this century. Another "must" on the LX521 -- just beautiful.
4 WAY STREET (CD) David Crosby, Stephen Stills, Graham Nash & Neil Young Engineer: Bill Halverson Recorded live at the Fillmore East, New York. June 2nd-June 7th 1970/ The Chicago Auditorium, Chicago, Ill., July 5th, 1970 / The Forum, Los Angeles, Calif. June 26th-28th, 1970 ATLANTIC RECORDS
Shock -- Gasp! When you hear "Triad" ( the most beautiful and heartfelt ode to polygamy/polyamory that I have ever heard) played on a well setup LX521, I guarantee that your mouth will drop open in shock and wonder as you ponder "how did I get teleported back to a 1970's Auditorium?" This is now my reference for demonstrating the LX521. Scary real!
A dozen ways to evaluate a loudspeaker:
Here follows a comparative graph of my subjective evaluation of the systems, as described by SL here [URL]
Just a quick note to state that this is a far simpler system to build than the ORION -- it took me a week to complete the chassis. If you are an impatient fellow (as my wife often accuses me of being) then your road to audio nirvana is much shorter via the LX521.
It also lends itself to modification -- I plan to out 'Magico' Magico with a 6061-T Aluminum/brass LX521 upper baffle -- it will be interesting to see if a further level of resolution can be gleaned from an already hyper-resolving system, if all the drivers are mounted in a rigid 18mm 6061-T Aluminum alloy baffle, one that (hopefully) allows every single quanta of motion to be converted into acoustic energy -- I repeat: that would be a very interesting modification to hear.
To see a superlative LX521 build being documented, look at Bill Schneider's [LX521 Build] (Wow!)
The LX521 is a better loudspeaker than the ORION/PLUTO/PHEONIX -- it leaves these systems in “the dust”. It is the best loudspaker that I have built, here-to-date. Instead of hearing "less" of something-or-other (some reports of moving from the ORION to the LX521 are that "something is missing", but that 'less is more'...) I hear more -- more detail, more musicality, more spacial-resolution, and more "life-like" sound. The LX521 is a winner.
I have made a "non-professional" video of the LX521 (you have been warned) -- you can see it here [URL] -- it meanders a bit (it is my first video ever posted) -- I will clean it up someday, or shoot another one -- but for now, it serves to show what the LX521 looks like. I can assure all interested parties that no alcohol was involved in the filming of this video, though I might have been running a slight fever from the pervalent "flu" that is making the rounds.
Email from Philip Lande -- received 16MAR13, 5:18 PM
"Charles, It’s been one week since we visited your home to listen to the LX521 Monitors that you built. I know it was presumptuous of me to email you asking for an audition. Omar and I were complete strangers and yet you welcomed us into your beautiful home and gave us a full evening to listen to truly reference sounding reproduction.
I came to your home of two minds. As a music and sound reproduction junkie, I was hoping that Siegfried Linkwitz’s latest design was every bit as good as I had read about but, I was hoping that it wouldn’t completely trash my gear at home. One thing is a night out. Another is returning home to my wife and informing her that my never to be replaced and just purchased Anthony Gallo Reference 3.5’s are old news.
Well, your Magic LX521 Monitors emasculated my rig. Once I returned home and played the exact music that we listened to I had to admit that while I have great in-home stereo reproduction, your new system exceeds mine in almost every parameter that I consider important. Dynamics, cohesiveness from lows through the midbase to an unbelievably beautiful midrange to airy though never too bright highs were evident from the very first track that we played. I never felt that any single part of the audio signal was overblown or recessed. These are complete full range speakers.
We listened to Bill Frissell’s I heard it through the Grapevine and it was just more involving than my reference. (I chose it because the recording has spectacular sound staging.) Arvo Paart’s Da Pacem Domine is a beautiful choral piece and we were just there. We were listening to a live performance. It was perfect.
What doesn’t the LX521 play well? We listened to Organ music-Great! We checked out Electronic Music- Massive Attack, Zero 7- Awesome. We also auditioned a number of Classical tracks, Old man rock (Dire Straits)- it all came through as world class sound. We listened to digital media and records. In fact, Omar brought Cat Power’s Jukebox album that probably was the best sound of the evening.
I am just an Audiophile with very limited understanding of electronics and you were so helpful in explaining how I could assemble this speaker. I am pretty sure Omar will have to tackle the ASP’s. We enjoyed viewing your workshop and the various projects that you have completed or are planning to build.
Once again, thanks so much for your time. You are certainly welcome to visit me anytime. Of course, I’ll have to build the LX521’s before you come. I can make a mean steak though.
Regards PJL "
Phil LandeVP SalesCounter Intelligence, Inc.9015 Brookville RoadSilver Spring, Maryland
Email from Willie Simpson -- received 02JUL14, 12:51 PM Saturday, 21JUN14
Over the weekend I visited Charles Port's home to listen to his amazing Siegfried Linkwitz designed, Open Baffle loudspeaker system, the LX521. I have to admit it was one of the best speaker systems I have ever heard. The realism was amazing; I could pinpoint the positioning of the voices and instruments on the sound stage. I could not believe I was not in a live setting. What made this experience even more amazing was the fact that Mr. Port built this Pair of LX521 speakers himself. After listening, I may just commission my friend Mr. Port to build me a pair.
Note: Willie has an excellant on-line store to purchase LP and CD's -- check it out.
Email from Deryl Benson [firstname.lastname@example.org] 11FEB15
Here is the report:
The sound staging and imaging qualities were outstanding. In addition, the system had the proper mid-bass and lower midrange weight that is lacking in a lot of high performance audio systems. The bass was a bit overpowering and didn't stop quickly enough at times which would lead one to question if there were cabinet resonances and/or lack of mechanical grounding of the woofer cabinet.
Email from Elliott Starin < email@example.com> VISITED 26MAR15
As long as I can remember, I've had an interest in and a zeal for high fidelity audiophile sound systems. I had a rare opportunity last week to meet up with a fellow audiophile/DIY'er builder, Charles Port, who has been an open baffle evangelist for many years. He auditioned a pair of handcrafted LX521's for me for the better part of three hours and I came away at a loss for words to describe the experience. Though the concept of uncolored and unadulterated sound reproduction is not new to me, I gained a renewed appreciation for it as he served up a series of CD's and LP's that showcased the detailed clarity and imaging capabilities of the LX521 speaker design.
Though we listened to a variety of vocal and instrumental (classical, jazz) pieces, my favorite was a Martin Grubinger piece "Drums and Chants" that placed me squarely on the percussionist's stage with antiphonal chanting layered on top and below, left and right, all around.
The realism and emotive draw of Marta Gomez' "Cielito Lindo" was equally impressive. Stunning "uncolored" vocals.
I came away convinced that I need to build a set of open baffle speakers and am currently researching it to finalize a system level design.
Charles was a great host, equally generous with his time and his considerable knowledge of equipment and all things musical.
Elliott Starin Rocky Ridge, MD
Email from Ray & Alicia Kanth -- Visited Saturday, 16JAN16
Thank you for hosting us recently to listen to your LX521 based audio system.
When you first played several of your music selections - CD and vinyl - it was immediately clear to us that we were listening to an exceptionally fine audio system, even though we were largely unfamiliar with the music you introduced to us.
Then you played CDs we had brought along. Our music selection included Western classical music (symphony, chamber music, and piano), Chesky Records' collection of reference recordings (vocals, small and large ensembles, brass, drum solo, etc.), and some Indian classical music selections. This was music with which my wife and I are intimately familiar from having listened to live performances (many but not all) as well as the CDs played countless times at home. Our current audio system comprises KEF reference speakers driven by NAD pre and power amps, fed by Oppo 105 with CDs and TIDAL streaming.
Two words that best describe our experience listening to your LX521 speakers were natural and realistic auditory illusion. Whether listening to stringed instruments, male and female voices, bamboo flute, or drums, the tone and timbre were such that the sounds reproduced were just like the real thing - very believable. And the imaging was such we could imagine being in the presence of the music performers. The third most important attribute we can add is the lack of listening fatigue after hours! After having attended Rocky Mountain Audio Festival in Denver a couple of years ago (the largest audio festival in the U.S.) and other audio shows in New York city and elsewhere, we have listened to audio systems that can cost as much as a mortgage! While some of these systems have very impressive sound, some were tiresome even after only after a short duration. We have to admit we don’t know whether the fatigue was caused by speakers or if it had to do with the very high sound levels and electronic artifacts.
There was nothing in the audio system we heard that was objectionable or of any concern. The one small concern we have is that these LX521s were driven by Pass Labs power amps! As fine as these amps are, they are well out of our price range, and therefore we don’t know how these speakers might sound with more moderately-priced amps, such as, ATI or Emotiva. Having said this, our long quest to replace our current speakers has been fulfilled. LX521 will be our next speakers!
Charles: we can’t thank you enough for readily inviting us to your home, for your incredible hospitality, and for creating the perfect atmosphere for us to become acquainted with LX521s to the extent we could arrive at our decision to acquire a pair for ourselves! We look forward to consulting you on our plans.
Sincerely, Ray & Alicia
SYSTEM BLOCK DIAGRAM
 F3 is Form-Follows-Function and FID is Frequency-Independent-Directivity I base this on the current cost at Madisound for the driver complement -- an ORION 3.4 - 4.0 driver set costs $2,335.14 -- an LX521 $1,479.15 -- 63% of the ORION -- The ASP construction cost are roughly equal, but the physical chassis is considerably less complex (and thus cheaper) to build than an ORIONSee http://www.linkwitzlab.com/Watson/watson.htm In other words, The precedence effect - where directional cues that are due to the direct sound (the ‘first-wave-front’) are given a higher perceptual weight than those due to reflected sound - is more related to ITD than to amplitude. The WATSON improved voice intelligibility, even though the it was down only 2dB in amplitude from the main signal, illustrating that the “mind” can sort through the perceptual clues to synthesize a believable auditory scene (AS).Proceedings of the Institute of Acoustics, “The Beneficial Coupling of Cardioid Low Frequency Sources to the Acoustics of Small Rooms” L Ferekidis, wvier, Lemgo, Germany Email: firstname.lastname@example.org 31OCT03RT60 = http://www.linkwitzlab.com/rooms.htm#CA Standard reverberation decay time defined as the time for the sound to die away to a level 60 decibels below its original level.