Thiel Owners

We used those cables through the show and took some jabs about the $8,000 cables with the $2000 speakers. But with the master tapes, it was clear that the other cables were introducing degradation, and we wanted to wow the show. That show is obviously etched in my memory.

I failed to address power cords earlier. I don't know what happened after 1995, but in my time we simply avoided any development or serious evaluation work in daylight hours. Our factory was in an industrial park and the AC was noisy and reactive. We used a Tice PowerBlock in the listening room. I am not aware that we used any special power cords. Jim's solution was timing. In the evening, the wind usually died down for outdoor and roof-top (free field) measurements and the AC power cleaned up radically. Our listening room had dedicated power from the poles and its lighting used remote / low noise balasts. Jim worked all night in the lab, slept in the morning, worked in the "office" in the afternoon and we did our critical evaluation in the electrically isolated music room between 6 and 10:PM. That work-around persisted and worked well.

Jon - the house photo you shared is in Georgetown proper. Our farm was (and still is) halfway between Lexington and Georgetown where they subdivided the farms into 10 acre farmlets around 1900. The farm victorian was built in 1903 and was quite deteriorated when I bought it and over the years restored it to fine fettle. Good place. Horses were my first love, and I bred my daughter's salt-of-the-earth pony to a son of Secretariat for her Pony Club mount. Wildfire spent his lift there, and it spawned an upstart audio company. There's always more back story.

I have gotten the "Sorry" message a dozen times in the past few weeks when routing via google search. I reported to A'gon who says they can't replicate the problem. Sarah says to log in via the A'gon home page > explore > forums. That method has not yet produced a "sorry" or failure.

jon- in the 1980s there were some battery powered products. They were very clean and all that, but didn't deliver current spurts well enough. Once the storage caps are drained, power out depends on power in. And battery changing is worse than tube rolling - is it fresh enough? Of course today's batteries are far better . . . there is merit in the concept.

Little-known historical factoid: In the early 80s the low-output moving coil phono cartridge became the norm, along with lots of problems interfacing with phono preamps. Even when their gain was sufficient, the preamp input stage often reacted with the delicate cartridge output to cause sonic degradation and even tracking problems. Jim developed a moving coil preamp which addressed the issues. His first patent was a new kind of circuit which took advantage of the extremely low signal levels, requiring virtually no power. Its electronics were essentially a bias-buffer, selectable via (8?) front panel buttons to best match the cartridge loading particulars. A 9 volt battery supplied the biasing voltage and was sealed along with the potted circuit inside the wooden cabinet, which was made of non-magnetic, non-conductive materials (wood and plastic laminate. No AC, no stray fields, no ripple. It performed extremely well.

Noel Lee took on exclusive marketing rights and Thiel made and shipped the units to Monster dealers. If you ever see a Monster head amp, the back panel, which we silk screen printed in our shop will say "Patented and Manufactured by Thiel.

I wonder how that head amp would hold up in today's world with higher expectations and better batteries, capacitors and resistors?    

In the few minutes I have . . . Andy, good observations - the 2.4 upper coax is crossed over as a single driver - the electrical signal drives the tweeter only, and the midrange piggy-backs through a mechanical elastic surround. Indeed the CC-SAs in the 2.4SE are less than state of the art, but at the time were CC's best offering. Regarding the "glow", Thiel always avoided artifacts even if they sound beautiful. In my present upgrade work with beetlemania, we have chosen ClarityCap CSA's which are 2 generations beyond the SA and are extremely good as being extremely neutral, without artifacts. We're testing efficacy of various bypasses in parallel to the CSAs.

You are correct about the 2.7 XO midrange feed cap. It is a 400uF electrolytic, which is audio grade, but nonetheless degrades the mid signal a little, even though it is bypassed by a 15uF polypropylene and a 1uF styrene & tin foil. My upgrade strategy is to eliminate all electrolytics (somehow!) to make the speakers virtually perpetual (electrolytics drift and fail over time). As you say, great caps are very expensive. I am assembling cap bundles based on a custom Japanese best in world film, bypassed by CC CSAs, rebypassed by the custom Thiel Styrene/tin and possibly a CC-CMR - all depending on which circuits. Much comparative evaluation will continue toward finding the best performance/ cost plateaus. It is easy to spend $thousands on caps. We are likely to have at least 2 upgrade levels for each of the products we address. The 2.4 is on the list and progress is being made slowly but slowly. 

jon - those ATC measurements are commendable and likely to produce very fine results in the frequency domain. For this Thiel thread, I will add a few comments.

Loudness: 4th order or any higher than 1st order slopes allow the driver to operate in its robust range and attenuate the out of band requirements, so they can play louder cleaner. Things get so much easier in that world; that's why most designers go there. Thiel's 01 used 3rd order and the model 02 used 2nd order slopes. The change for the 03 and after to first order increased the difficulty of the design undertaking by an order of magnitude, at least.

And as I have mentioned in the past, by removing phase and time coherence, the ear-brain gives a free pass to many other anomalies; they no longer are scrutinized as real and therefore can be ignored. Examples include the edge diffraction and soft-dome break-up modes. Diffraction isn't particularly audible with high order slopes because the brain doesn't associate the source with reality, and diaphragm breakup is attenuated to lower loudness and becomes less audible. Note that the literature considers 4th order Linkwitz-Reily filters to have 0 phase shift, but that is because they pretend that 360°, which rotates phase angle a full cycle, is exempt because 360° looks like 0 on a graph. Also, the speakers described do not look time-aligned, so the transient wave-fronts will reach the ear at different times as well as phase delayed relative to the input. Many commentators say that doesn't matter, which is because the ear-brain is so good at reconstructing the probable intended sound which has been scrambled by the speakers. Our work at Thiel demonstrated to our satisfaction how that brain-work of reconstructing the probable-intentioned waveform serves to decouple the listener from the emotional experience of the music. As I have said, most commentators disagree and deem higher order filters to be OK, and first order, phase coherent wavefronts to be unhearable and meaningless.

I suspect that Thiel lovers have identified the "trueness" of phase and time coherence and are willing to put  up with the attendant compromises including less smooth frequency domain performance and higher audibility of many ancillary anomalies. Jim spent a lifetime identifying and reducing those anomalies (sonic baggage) and I am now stretching the envelope to include cleaner electronic performance which original budgets and materials science did not permit.

I would say that there are many ways to produce some of the aspects of coherence. Rather than massaging the various aspects, I find the way to "see" that a transducer is keeping all the temporal information straight is to feed it an impulse. If the graph of that impulse rises immediately from zero to a peak and begins a downhill decline (as no more signal is being fed to it) creating a triangle . . . then and only then is the transducer coherent. A single driver such as a headphone acts this way. When using multiple drivers, they overlap and contribute additively and/or destructively in time and frequency and directionality. When they add to act like a single driver, the term of art is "minimum phase response".

A valid test is to overlay (on an oscilloscope screen etc.) the input impulse and the resultant microphone output from the speaker. The speaker will always degrade the signal in some way due to Murphy's Law of Material Physics. If the waves look subtantively the same, then you have preserved the relevant information.

Otherwise, I would find it difficult to wade through the various claims and side-steps and judgements associated with coherence.

andy - your reservations regarding high-power output from the model 2 are valid. Small drivers with relatively low-frequency crosspoints serve to simulate a point source, with off axis / room energy being correctly associated with on-axis / direct energy. A real singer, drum, etc. in your playback room would act like a point source.

The model 2 has never been able to play as loud or deep as the model 3 and above. That's the main reasons it costs so much less. If you like Thiel and want louder, find a series 3 or higher.

jon - the ATC with a 3" midrange can play loud because it is crossed over much higher and steeper. Trade-offs. Physics rules.

Thiel's naming has been called confusing, although it is quite logical from inside the system.
There are a few different series, which developed organically over time:
O the original O series which was sequential, first product, second product, etc. without regard to what it was. That series ran through the O4a (second generation of O4) andO3b, third generation of O3. The next iteration of the O3 was dubbed Coherent Source by Peter Moncrief of International Audio Review.

That CS name stuck and all subsequent floorstanding coherent speakers fell into the CS series, with the 3 being the 10" 3-way flagship. The CS3.5 was the 5th generation of the 3 and was replaced by the 3.6 and 3.7. The CS2 appeared as a smaller, less expensive model to inherit what we learned from the 3. The O4 - 6.5" 2-way became the CS1 series which ran consecutively all the way to the 1.7. The model 2 had much longer runs without upgrades than the 1 or 3 which received the bulk of Jim's development energies. The CS2 was an 8 inch x 3" x 1" ported design which ran more than 10,000 copies before the CS2.2 in 1990. The 2.3 and 2.4 sported the coincident-coax as a proof of concept while the CS3.6 produced robust sales and received internal, non-heralded upgrades.  Note that in Thiel-land a new model designation means at least new drivers. When products received internal upgrades, they had names like 3.6.1, etc. but only dealers knew of those designations.

When home theater came along more series were added to the mix.
SCS (Small Coherent Source) the bookshelf - satellite series got the first coincident-coax 6.5x1"driver which ran to SCS4. MCS was Medium Coherent Source, often used for center channel, etc.
The Personal Coherent Source was an executive - desktop little thing of its own.
The SubWoofers were designated SW, but with upgraded room interaction software became the SmartSub or SS series.

What holds true is that each number model series remains a consistent entity such as CS3 = 10"x3 way, etc. and the post decimal number is the generation with 2 being the second, as in CS2.2 etc. Each model retains its distinct personality and attributes, but grows in quality as new technologies and solutions were developed.

The CS1 had a full series from CS1 to 1.2, 1.3, 1.4, 1.5, 1.6 and finally the 1.7. The CS2 generations always ran longer for marketplace and R&D reasons. So it topped out at 2.4. The next generation was named after Jim's death and was called the 2.7 due to the radical coax driver and asterisks woofer it shared with the 3.7. Except for that model 2 number skip, the numbering is fairly consistent. Way, way many products for a small company.

jon - I also enjoy the time I steal to write these messages.
Note that I am reconstructing history from various supplier records and so forth. What I believe is that the 3.6 was upgraded in Feb 1996 via XO component changes for smoother performance (3.6.1) and again in March 1999 to separate some film caps on the woofer/tweeter board from resistors to eliminate overheating (3.6.2). You have 3.6.1s, but may have hot caps. That upper board is behind the passive radiator. Cap damage would show as melted spots where touching white rectangular resistors. If you see no melted caps and the speakers sound good, you're OK. If there's trouble, Rob can help you.

Now for a little fun behind the curtain. My crossover modifications are specifically dealing with heat management, like in pro gear. All the layouts are modified to place all resistors along a central bar where the upgraded MRA resistors are mounted in metal clips screwed to the aluminum bar which is sunk to the input panel plus possibly a back-mounted heat sink. The result will preclude heat damage, but is also intended to introduce thermal stability to keep XO crosspoint behavior more stable during hard use. Congestion at FFF is mostly amplifier deficiency, but also includes value drift in hot components. Beetlemania's 2.4s will attach the hot bar to the SE input plate. Coils are also being elevated for 3D radiant cooling; likewise the caps are lifted from the board and the board is lifted from the cabinet wall for vibration isolation as well as thermal stability. Whew!

My 2.2s are getting real serious treatment of an additional chimney-spine: a square tube up the back and vented at the back center of the top. That chimney sucks cold air from the floor to exit at the top and sinks the XO hot bars as well as an aluminum tube from each driver to sink magnet heat plus provide additional recoil resistance for the drivers. If all unfolds as dreamt, such a modification could be available from Coherent Source Service as a Full Tilt Boogie Upgrade. My 2.2s include double bypassed caps and 4-9s foil coils in all series feed positions. The original 4-9s coils are retained in the shunts.

Good day all.
Tom

unsound - there are real advantages for outboarding, and time may lead there. I have laid out the crossovers in outboard configuration.  However, there are problems along with advantages. The separate enclosure flunked the appeal census by a wide margin. The electromagnetic field interactions of coils would require a fairly large enclosure. And the wire-cable between the XO and the drivers is a critical link that invites unknowns because an external XO might be moved, adding additional cable of unknown parameters, which could seriously impact the signal at the drivers. That cable snake requires engineering-development that I am not presently prepared to provide. Many of those disadvantages could be overcome by piggy-backing the XO on the back of the cabinet, but that reintroduces some of the problems.

All things considered, including my limited time and resources, led to starting with the XOs remaining internal, which also preserves the classic Thiel value of simplicity of use.

The 2.4 XOs are accessed from the passive radiator.

Silvano - correct. All, if you don't hear a problem, you don't have a heat / melting problem. The cap melting is caused by sustained high volume use. 

andy - your 2.4s are Lexington made with point to point wiring and 4-9s coils and domestic / european caps. I would consider them superior to later 2.4s with Chinese-made crossovers. I don't know the changeover date, but yours are Lex-made.

jay - I suppose folks know that Thiel, with its nuts and bolts x no bullshit approach, started every model with serial number 1, which was mated with number 2 ,  all matched pairs were odd-low.

We kept the design prototypes. My 2.2s are -3 / -4 (final, pre-production.) Early + numbers went to dealers for display. Usually reviewers got numbers in the 100s after the display and pre-buy pipeline was somewhat satisfied. The products were quite thoroughly engineered and required no changes except when production drivers drifted or shifted parameters for some reason, such as different surround, etc. viscosity etc. . . stuff happens. Eventually there might be some refinements which warranted the x.x.1 sub model changes we addressed earlier.

Usually the second generation of a product was called the x.2. But one exception was the CS6, which in the early days of Thiel in-house drivers, received some upgrades to the midrange driver and consequent changes to the crossover, and was called the CS6.1.  I estimate the date around late '96 and don't know the serial number of the change. Rob would probably know. I'm gradually collecting such information. 

Blue -  sometimes the least expensive route is to repair yours.

Rob - you have stirred the soup. It's still cooking . . .

Dan, I don't have a buy recommendation, but I might add some perspective. The 2.7 is the newest design and shares the wavy plate coax with the 3.7 - which is Jim's world-class, swan-song breakthrough. A company could be built on that driver. That said, the 2.7 will move perhaps half the air of the 6 (anyone could do the math, I have not. Calculate comparative driver areas including the passive radiators). The 2.7 also shares the curved plywood walls of the 3.7.  It operates closer to the 3 more-so than previous model 2s.

The CS6 is larger and fills a larger space. I was told at the factory that Jim considered the 6 a better speaker in some ways than the 3.7. Thiel discontinued it for a leaner product line as they struggled to contain costs. The CS6 has fewer electrolytic caps and none in the signal path, and is on our upgrade radar before the 3.7 or 2.7. Rob Gillum would know if the particular serial numbers are the original 6 or the 6.1, and what changes were made. (And you could tell us those details.)

Happy Hunting.

Prof - bummer. I am not a doctor, but I have been paying attention and know something about the territory. I suggest addressing vitamin B, which regulates and supports neurological processes. The B complex is quite complex - a practitioner may help sort out the details. Knowing your cognitive approach, a suspension of disbelief may be in order. The down-side is practically nil.
My best wishes and highest hopes for your recovery. Tom

Dan - go for the CS7.2 if you can.
Regarding your view window. Consider "Zen View" from Christopher Alexander's "A Pattern Language". The large view might be even more enjoyable as separated zen views. Put the speakers where you want them, possibly hanging a drapery behind each, or not. The view may not be harmed at all, and the overall effect might be stunningly wonderful.

Guys - I would like to provide a report of general status and recent work. As many of you know, I am deeply immersed in redevelopment work. That has led to many rabbit holes, each of those leading to its own warren. The possibilities are limitless and cannot all be addressed. I have taken cues from many of you here as well as in off forum interactions. Thank you. Although I have accumulated and surveyed many models, I am concentrating on the model CS2.2 because I have 2 pairs and know it so intimately.

This current work is informed via my role as manufacturing developer, subsequent use in recording evaluation and mastering work, reviewers comments and general feedback over the years, as well as issues and characterestics upgraded in subsequent models and my speculations on causes. In other words, I am paying attention to a broad range of inputs.

I can't go into all the details, but I can say that there are multiple, parallel performance paths, each of which seems worthwhile. These paths all lead to more clarity, harmonic rightness, spatiality and ease. It is hard to believe that so much can be made so much better in a speaker where these areas are already strengths. I tip my hat to Jim as a designer and to the human auditory processing power. We make sense, good, satisfying sense of pulsating air pressure to imagine full blown music in our minds - on pretty sketchy data streams. Amazing really. That's why MP-3 and Wave Radios can work as well as they do. But fundamentally cleaner data streams make for more thorough immersion in the imagined music.

My newly developed MO includes taking the next title off the shelf on its own terms and relating to it as the producers hoped. That provides a radically different perspective from taking a few well known tunes and perfecting their translation. Let me state that I am not seeing any meaningful changes in frequency balance while hearing significantly different musical information and involvement. I find this phenomenon fascinating.

Let's jump to a persistent, real, global problem with Thiel speakers.

yeti- I don't have torque values, but I do have some thoughts. Wood products (MDF) hold screws well against vibration; more exotic baffle materials require threaded inserts. I don't know the 1.6. Metal to metal threads are prone to vibration creep. I personally put a dab of Permatex type 2 (non-hardening) on the thread before torquing to taste. There are other brands and types of non-permanent thread goo at the auto parts store.

Add: tight driver screws make a surprising amount of difference in resolution.

Regarding "other similar speakers" - they are very few indeed. The rigors are far greater and the results far more perilous than ordinary solutions. A company seeking to "make it" financially would not go there - to phase and time coherence.

Vandersteen and Thiel started at the same time in different places but with synonymous goals, the truthful and complete replication of the musical experience. The details of startup were different, but both founders were self-educated, and used live and directly recorded music as well as thorough measurement as core tools. Both addressed diffraction from the beginning because diffraction and other errors are glaringly obvious in coherent systems. Thiel developed engineered curves to reduce diffraction effects whereas Vandersteen used minimum sized baffles for similar results. There were far more similarities than differences. And you may notice that there is surprisingly little direct comparison between the brands over the years. I attribute that separateness to market politics more than product vision and performance.

The invisible player is the retailer. The displaying retailer played a very significant role in presenting, selling and servicing new, upcoming brands like V and T. I call those dealers pioneers. Only an avid, informed and competent dealer could pull it off against well-funded advertising and promotion from the big brands. There weren't enough great retailers to support both brands. Thiel was sanguine about sharing turf with any competitor, but Vandersteen was not willing to share turf with Thiel, under threat of losing the line. We quickly learned to not approach V dealers. The exception I remember best was Dick Hardesty of the California retailer Havens and Hardesty. Dick was a consumate audiophile / educator who went on to extensively write and edit in the field.

http://www.theabsolutesound.com/articles/richard-dick-hardesty-19442014/
https://www.vandersteen.com/audio-perfectionist-journal

In product terms, Thiel developed many more products at a faster rate than Vandersteen. In market terms, Vandersteen out-sold Thiel by some significant multiple. One huge cause was cabinetry. Vandersteen had in my opinion a brilliant solution: staple particle board into functional modules and dress it in a sock. I say brilliant because their cost of enclosure was a small fraction of Thiels, which left budgets for sonic-only aspects. Thiel's early growth was production-limited due primarily to cabinet-making process development. In many ways the V speakers of the day were musically more refined than Thiel counterparts - V had the luxury of focusing more on sonics without the cabinetmaking burden. When folks visited the Thiel factory they were blown away by the scope and finesse of Thiel's cabinetmaking. Many manufacturers would plausibly claim an order of magnitude greater cost of cabinets. They were also blown away by the internal development machine with its measurements, iterative samples and records and the listening room. Thiel was extremely vertically integrated as was Vandersteen. But V didn't have to lavish attention on furniture until much later, then in products with big prices and much simpler cabinets than entry-level Thiel.

The third horse is a little different. John Dunlavy built Duntech, a successful speaker company in Australia, largely with taxpayer support. John's inventive expertise was antenna theory and implementation. With a patent attorney for a partner, he developed much of what became wireless power transmission - the cell phone network. He moved to Colorado in the 1990s applying his funds and knowledge to building the Dunlavy brand. I saw in his work much careful attention to radiation interference and wave propagation analysis - of course. He had big computers and multiple anechoic chambers. The speaker-making was streamlined by Thiel standards: buy stuff and wire it up in a good box made elsewhere. The target is the same as T and V: cover all bases including time and phase.

The three companies didn't really pay much attention to each other. We were very busy doing out own thing.

Beyond those 3 brands, I noticed that the serious 6-figure brands, mostly in Europe, pay at least lip service to phase-time. There are some including PS and Wilson among others who give a nod to the importance of phase, but their crossovers are second order which requires each adjacent driver to be polarity reversed for smooth summersaults through the spectrum. The Thiel 02 was second order which we abandoned as "not quite real".

I hear that there were a couple of other first-order companies who came and went between 1995 and 2015 while I was away. I can see why they failed; it is very difficult. I can say without reservation that the engineering required to create a truly phase-time coherent speaker with correct tonal balance and dynamic range is a mountain of an undertaking compared to a little rough ground for higher order solutions.

Ish - TAD makes great speakers, thoroughly engineered with world-class materials, at very high prices. The have a strong following in pro and audiophile worlds. I was very impressed with the ones I heard.

However, they are neither time nor phase coherent. See Stereophile's measurements:
https://www.stereophile.com/content/tad-micro-evolution-one-loudspeaker-measurements

The verbiage surrounding tilt and assymetrical slopes is to lead one to believe that all fronts have been addressed. I do not dispute that excellent sound can be heard through non-coherent transducers. Thiel coined the Coherent Source phrase to mean "Minimum Phase - Time Coherent wavefront". TAD does not meet that definition, nor does KEF, B&W and others who suggest that they do. I would not put them on andy-2's list.

Good dealers are a treasure! That world is generally fading in the rear-view mirror of Crutchfield, Amazon, ebay and so forth. I bet you will love the 2.4SS (just playing-whatever it will be called).

Now, back to amps. As you know, my reference amps are old classic Classe. Fine amps, hotrodded, drive the Thiels fine, especially a pair of them. Etc. But I need a second amp for proof of upgrade work; I have special considerations beyond my own enjoyment.

Jim judged that the amp's limitations are the amp-maker's problems. Logical enough - except for the consumer who had to spend 5x his speaker price for the right amps, which bucks pretty much . . . everything. As you would expect, I have been surveying the amp world for some solution for driving Thiel speakers with even higher resolution than the originals. That's a double-edged sword . . . wonderful when the signal is great, and even more revealing of trouble when less than great.

I have appreciated your amp leads. I have also investigated the PS Audio BHK-300s, Ayre and other heavy hitters. I don't want to fall into Jim's trap of designing with the stellar amps, which leaves most listeners with less than best or even objectionable performance. What to do? I would like the group's feedback on the following possibility.

Benchmark straddles the fence between pro and audiophile. Their stuff is very clean, neutral, transparent and relatively affordable for its performance level. They now have a power amp, the AHB-2, a hybrid AB amp powered by a class H power supply and class A feed-forward error correction amp. Intriguing concept. The high end pros rave about it. Its measurements are stellar. I am inclined to try it for several reasons, one of which is that it is a marginal player facing the new world with a different vision. Flashing forward 20 years, I want the Thiel HotRods to be sonically viable without requiring Krell, Levinson or similar heavy iron.

The AHB-2 breaks my double-down rule, but only a little and on technicalities. Class H is a switching power supply (which break down when past their current limit). At 100 watts / channel - 8 ohms, it is only marginally adequate. It is precisely that marginality which attracts me. I want to explore that limit of great performance with shallow pockets. Benchmark engineering is analyzing the Thiel loads to make a technical assessment. I admire their approach and there are Thiel fans at Benchmark. Their vision reads like Thiel promotion of my dreams. (I feel that Thiel never promoted itself very effectively.) I am specifically investigating stereo-amp, monobloc-strapped, and vertical bi-amp configurations. The latter would assign one channel of a stereo amp to the bass and the other to everything else. So much to learn.

Anyhow, do any of you have experience with this amp? Or do any of you have thoughts or opinions about my ideas? I would appreciate your feedback.

 

Thiel is considered by many to be a small signal transducer. It works best on vocal and/or small ensemble work. I agree and chalk that up to broad range requirements for overlapping drivers. OK, fair enough.
I have been dreaming in the way-back machine. I remember product development sessions back to the beginning. Come with me to 1975 at the Georgetown Road Compound, developing the 01 and 02. For nightly listening sessions, the speaker under test was placed in mono on a stand in a lovely-sounding room previously described here. The crossover network looked like a bird's nest in free space. No board, lots of space. We hung it from a ceiling hook by twine to some fixed parts, usually the heavy inductors. Many of the parts were clipped in with roach clips. Jim knew the circuits so well that he could make flying changes during music while capsulating what the change did. In an hour session we would compare a half dozen variables for him to take back to his night-time labfest. We reviewed graphs and compared notes at breakfast.

One ever-present outcome was that the finalized product always suffered from the crossover being bedded down onto a board and put in the cabinet. We always noted it and lived with it. About a month ago, a rabbit hole led to this particular warren by way of a remembrance dream. In the early years, I reviewed and journaled all service and repairs. It was not unusual to get speakers with burned resistors and even charred masonite boards. (No fire because of limited oxygen in the sealed cabinets.) I recognize thermal distortion as an avenue for improvement, and the 10 watt vs 25 watt resistor choice discussed here led to some experiments. Under musical load, resistors get hot enough to burn, and coils can get hot enough to unwind if not mechanically bound. That's serious. Resistance and quality of conductivity change with temperature. Beware of dynamic distortion

On a different progression, I have mentioned my personal health journey that has now been greatly resolved. The root problem is neuronal overload, and the primary cause is exposure to electromagnetic fields. I now own various EMF meters and devices and have mitigated much of the EMF pollution that put me in mortal danger. I, of course, now point those meters at everything, and was amazed at the soup around the 2.2 when rocking. Serious levels.

Put two and two together to equal redesigning the 2.2 crossover into a three dimensional package with more space, separation of resistors from other components, and physical separation from the drivers, in its own enclosure on a 4' umbilical. By the way, the package seems elegant to me, and in visual harmony with the cabinets. I'll post a photo when I get something presentable. For now let's talk about the woofer. It has its own board, positioned vertically with both sides exposed to air. All resistors are on the back to form an updraft cooling chimney, with the other two (midrange and tweeter) boards oriented similarly with all resistors facing inward with air inlets on the bottom and a screen on top. No metal anywhere. The rig is big enough to accommodate the largest of the CSA / MRA, etc. caps, as well as anything smaller. In the present case, I disassembled one (original prototype # -0004) cabinet, removed the crossover and wired only the woofer to the input terminal. The other (-0003) was left as a reference with the internal XO and woofer intact, but with the midrange and tweeter disconnected. I built the woofer section for -0004 by the new layout while using all the original parts in the original orientations. No upgrades, changes or replacements to confuse the issues.

Yesterday I began listening and today I continued with a long comparison followed by a set of measurements. My measurements are, sadly, still all sweep based via FuzzMeasure. Their impulse information is extrapolated mathematically, not from actual transient impulses. I'll get there eventually and get more insightful information when I do. Let's say that the two speakers via my available measuring techniques look to be virtually identical. There are no observable differences in frequency response, group delay, phase plots or waterfalls. My technique is to listen to each speaker in mono, placed beside the other; and then measure in place so that the mic hears what I hear in the same position in the same room. Then I swap right for left and listen and measure again. I am confident that I am measuring the speakers with no meaningful room noise or equipment differences.

So here goes. We have these two matched speakers with the difference being XO layout and removal from the enclosure. The test takes me back to Georgetown Road over 40 years ago to hear that delicate, lovely spatiousness before buttoning it all in the box. One recording was Pink Floyd's remastered "Take it Back" single which is both layered and detailed along with dense, dynamic and driving. #-0004 reference "A" exhibited splatting on every bass+drum hit. It would be attributed to amp clipping or passive radiator and/or woofer bottoming - overload / or just plain too loud for the material. But I didn't turn it down. On -0003 external XO "B", those same hits were audible, but not extreme, in fact they played more like "hard punch" than distortion. And all the nuance of the band and backing vocals hummed right along. Other audition material included the entire album of Patty Larkin's Stranger's World and Stereophile's Test record 3 cuts 3 and 9 - very detailed, dynamic bass-based work. Of extreme interest is that speaker A sounded like a woofer, somewhat woofy, lacking the detail one would get from the midrange and tweeter. Speaker B sounded like a full-range presentation; subjectively it was satisfying on its own terms. I had to check to make sure I hadn't somehow left the midrange or tweeter connected. I hadn't.

For me, today is a game changer. All the other upgrades have provided various levels of insight, even excitement. And their inclusion has always seemed contingent on effective budget analysis for most contribution per affordability. But this change is non-negotiable. It changes the league from small-source vocal ensemble speaker to throw anything at me.The persistent motivation had been how to shoe-horn all those large upgrade parts into very small spaces in the very well-braced 2.2; as well as how to then simultaneously address the re-bracing that would improve performance. There simply isn't room in there to do it all. I first took out the XO to install my bracing upgrade for testing. But I won't go down that rabbit hole yet. This performance upgrade is totally engaging. Next I'll implement the midrange and tweeter sections of the External XO. By the way, Resistor 1 and 2 got hot enough to burn and coil 1 got pretty warm - all mounted on stand-offs on a vertical board in open air. Imagine the environment in the sealed cabinet with a woofer within spitting distance producing its heat and EMFs.

Now it's back to the drawing board to re-orient those two resistors for better convection cooling.
Nice to visit. Thanks again for all the help and inspiration many of you have provided.

TT

Good points unsound. Amps from the same manufacturer often have differing goals and topologies and do not perform similarly. Thiel speakers got progressively more demanding - I guess the 5 bass was worst, but the earlier speakers were more benign, probably because Jim didn't yet have the Krell FPB-600 and Levinson 33Hs. Bryston amps seemed to get better and better at driving Thiels, partly because Thiel was their design-test torture load.

unsound - point taken. Sealed box bass is more phase correct. I like it too. The brutally low impedance of the CS5 deep bass might be ameliorated by a separate amp for the bottom end. Also there is the matter of those huge analog bucket brigade time delay lines for the lower and upper midrange drivers - even with very high quality caps, there is a hypothetical veil.  I wanted a geometric solution of concave driver plane mounting. But small companies can only pull so much out of their collective sleeve under real-time development budgets and schedules. Fact is: Jim was enamored with the bucket brigade delay which he had independently "invented" before learning it was already 'out there'. And he didn't accept any down-side beyond cost. CS5.2? 

Do you have an amp to drive the CS5 well?

prof - Please note that I have not heard the 7.2. I am relaying insider remarks from those who lived with the products, the process of evolution, the politics of markets and the necessary contraction of the company after Jim's death. I have also extrapolated factors regarding components and their sonic contributions. And then there is the undeniable fact that each new product stands on the shoulders of all of its predecessors, giving the x.7s a distinct advantage in many particulars.

All that said, I would choose the 7.2 as the epitome of Jim's work. He was working on a 7.3 which incorporated the 3.7 coax (or derivative) and the wavy driver geometry. Such a product could justify the cost of the quality components which beetle and I are lavishing on our upgrades. The low-level cabinet resonances could be quieted. Thermal management could be applied to the drivers and resistors, and so forth and so on, to create a next-league contender. I have little doubt that the 7.3 would be his very best work. But, I don't have a real answer to your query from personal experience. In hindsight, I wish I had stayed another day in Lexington in 2012 to absorb the upper models in the listening room. Time moves on.

I hope to learn enough and find the time to soup up the 7.2s. Notice that they don't show up on the used market. Rob says that the large majority of CS7 owners upgraded to 7.2s and are happy as clams with few reported problems. Plus, I find them beautiful in a way that reflects my design sense.

prof -  Our 'other' listening room was my victorian farmhouse living room, where the company began. That room was 10' high x 15' deep x 17' wide plus a bay wall adding another 3' depth with 45° clipped corners. It also had a door in each wall except behind the speakers. I never heard the room overpowered, mostly because of the doors to relieve standing wave buildup and the non-resonant plaster on wood lath walls and ceiling. Good rooms are at the heart of good playback.

unsound - I love that amp. We met Nelson Pass early-on and had the Stasis 500 for all our development work from about 1980 (pre-production). That amp was still there when New Thiel bought the company. I don't know the Series II, but the basic architecture was state of the art at the time, plus it had gone back to Threshold for service. The Stasis variable bias was brilliant and effective. I would consider using that amp today.

Time for a story? OK.
Nelson developed Statis, and patented the technology. Nakamichi who dominated the car-audio / cassette player market at the time, wanted in to the emerging high end market. They contracted Nelson to develop two Stasis amps for them. He did so for the then princely sum of $quarter-mil. Nakamichi took it home and in true Japanese-culture fashion proceeded to remove any and all traces of the novel Stasis technology. Those of you who Japan - 1985 know that signing off on anything not in the textbooks might require ceremonial death. Forward 1.5 years. CES introduction of the Nakamichi Stasis. No one cares; it doesn't sound exciting. Nakamichi challenges Nelson. Nelson buys some amps on the market and evaluates them to contain NO Stasis stuff. Nelson objects that his reputation is being impinged. Nak doesn't get it. Nelson sues in international court that his reputation is being damaged via the failure of his Stasis technology in the Nak amps which contain no whif of Stasis. Nelson looses. Court says that Nak paid for and is free to use any of the assets, even if just the Stasis name. Nelson has bigger fish to fry and goes on to his brilliant career.

andy - I don't see any claims for the Meadowlark, nor technical specs or lab reviews. Good reputation, but I can't comment on their coherence.

Green Mountain has tons of claims and an approach that seeks coherence. There is a Stereophile review that demonstrates not really achieving what they claim. The impulse response is clearly not time-aligned and not integrated with best tonal response listening height. The designer's review reply side-steps the issues. I would call it a technically deficient attempt. I haven't heard them.

Back to Green Mountain - it seems I read a review of a fairly early model. Later 6moons reviews of their further work sounds very impressive. I still hesitate to comment without measurement verification of success.

Sorry for my first response based on 1 review of the Diamante.

All - lots of good information. Bottom line is that most of those who try are prone to fail. An underlying cause is that coherent transducers are roughly an order of magnitude more difficult.

Andy asks why more manufacturers don't "do it". Short answer is because they can't afford to solve all the problems for the very limited market to pay for the development costs.

Case in point - Thiel Audio. We began with customized drivers from the usual manufacturers: Seas, ScanSpeak, Dynaudio, Vifa and others. Early on we forged a relationship with Vifa where Thiel developed what it wanted / needed and Vifa prototyped and eventually produced it. We got favored customer status and they got to put it in their catalog for anyone to buy.  The other manufacturers were not as adventuresome, preferring to make their own designs with less expense for larger market share. Our drivers were inherently expensive with bigger magnets, tighter specs, more critical surrounds and spiders, etc. It worked for both of us. Good partnership.

Except that we wanted to go beyond their comfort zone for some of the reasons Andy mentions. So by the 1990s we were deep into prototyping our own drivers and sourcing parts from speaker manufacturers and other industrial sources. By the mid 90s we had to make our own drivers from scratch to get what we needed.

There are no "good" concentric drivers on the market because most of them end up in car or home cinema uses with lower budgets and expectations. It would be hard for you to imagine the effort that went into Thiel developing its own driver-making capability, not because we wanted to, but because we wanted to build speakers beyond what the supply market could deliver to a demand market which doesn't require the rigors of broad bandwidth, high-performance drivers.

Regarding the prior thread of other coherent manufacturers, and why there aren't more. A case study that applies broadly is the "New Thiel". Ownership hired folks who cared about preserving whatever Thiel was doing, who hired among others Mark Mason formerly of PSB - smart and talented design engineer. It fell to him to prove to ownership and management why coherence matters. Fact is, that task is nearly impossible. They collectively decided to put their eggs in the same basket as everyone else and make very good "normal" speakers. 5 stars from Stereophile, etc. But, who cared? There are myriad good normal speakers. Unique vision lost. Company failed.

So why did Thiel take on the awesome task of making coherent speakers? Why do very few others succeed at it? I've said that it is hard and expensive - so why do it? I have previously shared how we looked at many topologies and possibilities of where to spend our efforts. Here are a couple examples of how we landed on coherence as a requirement.

The cats.
The farm / commune always had animals. The cats ruled the interior space. The living room was the test room. One of our test sources was a simple (no effects) recording I made of nature sounds, including wind in the bushes . . . and birds. The cats never cared much what we were doing. But during a session of 1st vs 2nd vs 3rd order slopes - Precious, the energetic black cat, scrambled up the speaker and took out the tweeter while it played twittering birds in the bushes. Hmmm. The 'cat effect' joined with the 'leaf effect' as unique signposts along the road to coherence.

The leaf effect occurred when we hauled the experimental 03 about 20' high into the Walnut tree in the side yard for outdoor anechoic-free-field measurements. (Poor man's anechoic chamber) We got differing measurements for unexplained reasons that turned out to be summer leaves vs autumn leaves vs bare winter branches. Score one for my daughter to decipher the cause! But, another thing became evident. The sound of the wind in the leaves and branches made sonic sense with a coherent transducer whereas we dismissed it as noise with higher order slopes. Very, very interesting.

There are other examples. I may have mentioned the teenage girl effect and the passerby-neighbor effect. We became convinced enough to surmount our skepticism and challenges of courage. We knew it would be intensely difficult to pull off coherence, but we chose to do it because we believed it mattered.

Notice that in the general industry narrative, they conclude that it doesn't matter enough to pay for the troubles. That opinion dominates. From 1978 onward, we never lost faith, and that term is what the skeptical scientist would apply to it. The Canadian Research Council proved to the New Thiel owners that coherence could not be heard. Most manufacturers believe it can't be heard. Thiel's dedication to the aspect of coherence is a matter of belief when viewed from a scientific perspective. And it isn't like Thiel's dogged pursuit proved anything. The world still says it doesn't matter.

But some folks, from previously unexposed novices to high-end recordists, "get it". Once they do, they generally don't let go, even though some aspects of smoothness and dynamic range are inherently compromised by the factors required for coherence. Nothing is free. Thiel chose to chip away at all the aspects and continually develop solutions to all the elements brought to bear by opening Pandora's Box.

I doubt that Thiel, as a fledgling, internally capitalized company, would have continued just making 'normal' speakers. It didn't matter enough in a marketplace inundated with companies already doing that. But there was something about the truth of the musical experience that fanned our flames, that kept us going for what turned out to be 35 years and would have been as long as Jim was able to keep making progress toward his vision of the complete loudspeaker. Thank you all on this forum for 'getting it', for honoring the decades of work that went into augmenting this obscure corner of the playback experience . . . 'for the Love of Music'

jon - regarding bright 2 2s. You are correct that there is a slight propensity toward warmth. The mid-bass centered at 100Hz is almost full when the speaker is optimized 5' from walls. When moved closer to walls, that zone and below gets stronger. There is also some roughness in the low treble, from 5 to 10K which can be problematic.

A huge source of the "bright" complaint is that most recordings are made to emphasize the brightness range for air-play appeal. Also, that range is where microphones and recording gear are likely to misbehave and recording effects such as the Aphex Oral Exciter do their job of adding tooth and sizzle to recordings. And playback systems also contribute anomalies, and all signal including compromises is under a microscope with a coherent transducer. A big part of the problem is cat and mouse and whom to blame.

It is impolite for a manufacturer to point fingers elsewhere, but those times are past with us here. You all have done the homework to find good associated gear and choose well-made recordings. You are in the 1%. In my 2 2 upgrade work I am looking at tweaking the series resistor feeding the midrange to add up to a half dB between the woofer and tweeter. Too early to know how it will work out, I'm still developing my measurement tools.

unsound - you are right. Measurement distance of 50" and closer earlier in time, does not allow the proper triangulation for the drivers' travel path. 8' was Thiel's stated minimum. The limit was Stereophile's set up, but the results looks like speaker design failures. The closer the drivers to each other and the lower the crosspoints, the less the incorrect distance matters. But it does mislead the reading public. Andy makes a proper point that lower crosspoints give the upper driver a much harder time, requiring long excursions and sophisticated cooling.
To the point of Seas, Vifa etc. could do "it". We tried for years without success working with the best. It's not so easy as it might appear. And if someone did, the wire routing factors, etc. are so precise that high failure rates can occur and then who points fingers at whom. Taking it in-house was a huge challenge for us, but it was the only way we could get what we decided we needed.

Coincident drivers solve the lobing problem between the upper concentric drivers and the woofer crossover is at such long wavelengths that its lobing is not very consequental. Sit with your ears at 3' and back at least 8' and you are in the design target.

Beetle - problem is I don’t drink coffee. Proper number is -0003 is the reference A. Good catch. How’s the coffee?
There are plenty of good reasons for an external XO. But it is tweaky, difficult and would put off many people. In the case of the 2.2, there isn’t a good option to squeeze best parts into the interior spaces. And the merits are likely to be substantial.

But to your Oy! issue, this problem might be peculiar to this model. The general opinion seems to be that the 2.2 is more mellow, easy, forgiving, and with a bigger bass than other Thiel speakers. Some people say it’s the only Thiel they can tolerate. I had speculated that we thought our first passive radiator somehow coupled with rooms "better" than anticipated, giving that full-bottom presentation. But it doesn’t measure "full"; it stacks up quite nicely with the 3.5 and 3.6 that I have here - matching the specified target roll off point without any bloat or other measured anomalies.

John Atkinson used the 2.2 for years as his own system reference. He commented in his Stereophile review how the passive radiator produced a "hard bottoming" relative to the CS2 port’s "soft chuffing" at volume. He said he eventually gave them up because they just wouldn’t produce loud enough bass for him. I can’t visualize how the passive would hit hard - it is made of 2 large, soft surrounds on the back and front of a semi-soft foam plug. ??? So maybe this "splatting", "generalized low end" and "easy mellowness" of the 2.2 are all attributable to these layout and overload characteristics which I am addressing with the EXO.

So, just sit tight regarding your potential need to tweak this problem on your 2.4s; by the time I get to working on the 2.4, we’ll know a lot more. I’m looking forward to picking up the pair I scored on Long Island - when it gets safer.

ish - I know those Hales speakers very well. I consulted for Hales during their development and compared 1st vs 4th order XOs. Paul is very bright and competent and pragmatic. The development time / cost / benefit and all adds up to 4th being "good enough because people can't hear the difference". Note from these impulse responses that the speaker is neither time nor phase correct. Paul didn't think it necessary. https://www.stereophile.com/content/hales-design-group-transcendence-five-loudspeaker-measurements

The sealed bass is awesome and Paul thought it embarrassed Thiel's reflex bass. OK. The sloped baffle was for the purpose of what your salesman executed in the store. The German who had resurrected Hales Design Group from the ashes of Hales Audio wanted SALES. By the way, the baffle was not concrete, but Hydrostone a fiber reinforced combination of portland and gypsum cements which I had developed for the CS6, but Jim substituted concrete after I left. Jim thought of "concrete" as the optimum enclosure material and Walter Kling who replaced me had an architectural/ builder background. Concrete lasted a very short time because it shrinks for 7 years and cracked at stress points. I doubt that Hales baffles ever cracked. Nevermind.

Hales frequency response is exceedingly flat and its component and build quality is very good. But it is a horse of a different color.

jon - the fiber is to increase impact and stress resistance and add some damping. It does not reduce shrinkage. Concrete is Portland Cement based, which shrinks. Gypsum cements expand. USG Hydrostone is a combination of the two and can be admixed with acrylic, etc. plasticizers to increase damping at the expense of lowering resonance frequency. Paul added some plasticizer. I chose to run straight but added two different fibers which serves to suppress resonance & increase stiffness. I like grown solutions, and used hemp and rice awn fibers, but most folks would choose polypropylene or glass, etc. USG has zero, expansive and contractive products. I suggest you look there. I investigated air entrainment in the baffle core for lower mass & higher resonance frequency. These were follow-on developments after the CS5 cast marble baffle, which worked well, but cost and weighed a lot.

All, is anyone here bidding on that 3.5 EQ? If not, I'll try to snag it for the lab. (Remember the idea of fully balanced EQ with better caps and resistors?)

One interesting aspect of external crossovers, is that so many aspects in the cabinet are devoted to vibration management. Gluing the parts to the board impinges on thermal stability, but if left unglued, they rattle and buzz and introduce microphonics. Out of the box, that aspect is not a problem. Also, a major limit to directionality of coils is their position in the driver magnetic fields. That goes away too. And the heat thing is big; the enclosure keeps getting hotter, whereas the EXO self-cools. And two-sided boards become practical for isolation of resistors from caps. You get the picture.

SDL - I love the basement idea. But also, these EXOs will be in presentable cabinets of their own. I can’t help it, I was born that way.
Tomic - I have reverted to point to point on masonite - no printed circuits. When rebuilding Beetle’s 2.4s (late / Chinese, on PCBs) we noted coils with up to (perhaps) 20% variation from spec. Those changes were required to re-balance considering the capacitive coupling to the PCB traces. I prefer to keep the coupled capacitance separate from the inductance. I am also at greater liberty to manage the layout to avoid parallel leads and/or bring them to contact and twist to virtually eliminate self-capacitance.
I am loving the audition material selection. By randomizing it via the next album alphabetically, I have reduced the tendency to design for only the best audiophile material. I learn as much from ordinary or substandard cuts as I do from great cuts. However, anyone is welcome to send the Chesky catalog or other great stuff.
Eric - you are most welcome to share your turbulent / laminar flow ideas if you wish, either here or via PM. I have a setup that works, but might be significantly improved. I cover the baffle with F11 pure wool felt at 1/8 or 1/4", covered with the finest Ultrasuede Fine fabric. The drivers and bezels are covered with a stretchy version of USF. The US surface fibers are so fine as to be moved by the pressure - shear waves. The effect is lovely. I am now working with an aerospace engineer with a technology patent for surface flow dynamics management for spacecraft re-entry.
No end to the fun.

prof - I have not heard the Alexandra. I moved to New Hampshire and by the late 90s I was focused on things other than audio.

pw - The room is so often the major culprit in the mix. Thiels are point source emulation and therefore wide dispersion, so room reflections matter more. Also the coherent wavefront tends to stimulate room modes more readily than the slurred wavefronts of higher order speakers. I am a fan of physical room treatment as much as possible. Tell us about REW.

All - Are any of you proficient in patent and trademark law? If so I would like to confer about Thiel intellectual property. Send PM or email tomthiel@worldpath.net

jasx - your other speaker is 1785, always odd low as in 1,2. They were made approximately late 90s, model was introduced in 1992.

I just bought a pair of 3.6s for our upgrade project. Soon I will document the XO revision status / serial numbers for our benchmark timeline. 

harry - I can address part of your query. The 2.2s were very well developed / mature and had a long run. Lots of fans. The 2.3s were the first application of the mechanical / crossover-less coax concept. I hear that there were improvements on the table pretty early, and not many 2.3s were sold, perhaps the shortest run ever. The 2.4 was a big uptick in performance and sales and has been an audiophile darling, possibly more so than any other Thiel product. That's some market mechanics.

Some folks here can address the sonic differences. I have and love my 2.2s and am working on a hotrod kit for them.

PS: I am calling the 2.2s by their proper name. The decimal was dropped under threat of lawsuit by Bose. But the product has been out of manufacture for way long, Mr. Bose is no longer with us, his legal staff was embarrassed . . . so let's pretend they don't care anymore.

Guys - Ted Green / strata-gee.com has published his article on Thiel,LLC recent bankruptcy filing. https://www.strata-gee.com/

jon - all the Thiel aluminum drivers are annodized which deposits a coating which is often marketed as "ceramic". Your 2.3 driver is an early example of Thiel aluminum diaphragms. When gotten right, those metal drivers have far better resolution than paper, but paper can be pretty good and is very forgiving. I think the 2.2 midrange was Thiel's last paper cone, which was actually augmented with polypropylene fibers for greater stiffness and consistency than plain paper.

prof - Ted Green runs a technology consulting company. His interest in Thiel is as a former performing musician / bandleader with an inherent interest in David rather than Goliath. He seems to know brands and nuances very well, but has never said he was an audiophile or Thiel owner. He does admire what we did.

I am in direct contact with the bankruptcy court as well as some recommendations from this forum. It seems there is a streamlined process whereby an "affinity group" can form an expedited company to purchase assets such as the intellectual property of the bankrupted Thiel LLC. Hmmm

beetle - I moved to New Hampshire in 1996 and have been active in the New England Luthiers Group - serious guitar-makers. A few of them have worked for Bose, with stories to tell! One story of interest is that their lab/listening reference monitor was the Thiel CS3.5. Now, isn't that special?

Well guys, I have been doing homework on the (new) Thiel, LLC bankruptcy as well as making slow progress on classic hot-rods. First project will be beetlemania's CS2.4s - pretty full-blown in scope.

What has been getting clearer is that the low-impedance problem rests at the root of much of the system limit. We can't change the low impedance load. I also want to avoid dodging the issue by requiring heavy iron amplifiers, which are few and expensive and, of course, can work very well, but the matching problem persists. I am exploring a different way to address the issues while avoiding the pitfalls of bi-amping with different amps and different cables. Here goes.

Most amps behave better into low impedance (heavy) loads in their normal 8-ohm / stereo (or 4 ohm if tubes) configuration rather than strapped to mono. I will be testing amps in a vertical bi-amp configuration, where one channel drives the woofer and the other the uppers, however that breaks out depending on model. We sequester various load and performance problems into the respective ranges. We can also internally hard-jumper for single input operation. We specify short runs of specialty cables - same lengths, same configuration, preferably 4 runs in same loom for even-handed capacitance and inductive cable reactances. I have ordered Morrow SP-4 bi-amp in this configuration. We will need special splitter interconnects with single source and double load (at power amp end) terminations. We add potential solutions without limiting our operating options.

I will be using my workhorse Classé DR-6 pre and DR-9 poweramps. Old, but decent and well known to me. I also hope to gain use of an older Ayre amp of suitable capability. Again, not the giant super studs, but something more affordable which many users could obtain. I have ruled out many amps as very good, but . . . somehow not neutral or transparent. For my learning and proving the designs, I need neutral, uncolored signal. I have about decided on the Benchmark AHB-2. It is a new hybrid configuration and loved in pro circles as a very great truth-teller (that I can afford). Two of them will allow trials in single amp stereo, strapped mono and vertical bi-amp as described above. John Siau (its designer) has endorsed its ability to support our heavy loads.

I am accustomed to working in mono with one speaker. So I will keep an original reference for comparison as I iterate the mate. Things are coming together to actually get to work. I am both excited and apprehensive. The apprehension centers on the nature of proposed improvements. Resolution / detail / articulation is the strong suit of Thiel designs. Most of our projected improvements will be in that same arena. We will be lavishing costs on an area of performance which is already first-rate and therefore not functionally a system limit. But, I for one and possibly some of you might find meaningful improvement in what we are undertaking. May it be so. That's the exciting part.