Thiel Owners

Thank you *so* much for all this great info, Tom!

I think any changes would be small enough to dismiss

OK, I'll keep this as an option depending on space.

I don't know the relative merits of CMR vs Mundorf.

Reading the anonymous writer at humblehomemadehifi I've concluded that person is a careful listener and has credible thoughts on cap performance. Reading the descriptions literally and between the lines, the CMR appears to be the near equal of the upper range of Mundorf, perhaps a tad less transparent but a scotch more neutral. I think I would be happy with either. From that website and others, it seems that going further up the Supreme line to Oil, Silver Gold, and SGO have rapidly diminishing returns with equally rapid $$$ increase! He/she is a fan of coupling SA with Supreme:

Making a capacitor using about 90% Clarity Cap SA and about 10% Mundorf Supreme works very well, this tends to open up the top end just nicely without altering anything else.

As of now, I'm leaning 20uF SA + 12 CSA + 1 Supreme on the woofer; 15 uF CSA + 12 CSA + 1 CMR and 12 CSA + 1 CSA + 1 CMR on the coax. The double bypass to replace the 28uF cap seems the most challenging to stay away from the coil. Maybe I can get the 27uF CSA from a European supplier - that would really help.

If you can make some trap doors in those corners, you will clean up bass standing waves and flutter echo enormously.

The other opening on the rear wall is a large (5'W x 10'H) walkway into the next room, conveniently in the corner! I have a bookshelf in the other corner on the rear wall. I also have cloth window shades (the front wall is almost all glass) and plants on the floor and hanging along the front wall. One-half of the floor is tile, so I also added a rug on most of that. This room was *really* bright when I moved in but I'm pretty happy with it now. Running a tone sweep fails to reveal any unacceptable room modes.

@tomthiel *Super* helpful. I owe you a beer or three. Next step is to pull a radiator and see how much room I have to work with. The solution with SA/CSA/Mundorf Supreme is the least expensive (of the options I'm considering) and with the smallest profile. I’d like to go with CSA/CMR on the coax, however, if space allows.

Something of a crap shoot in terms of ending up with similar tolerances/values for replacement parts, vs sticking with the originals that were part of the original design.

A bit of a puzzle to get the correct cap combos that match the original values but not too onerous. I suppose it’s not without risk but I’d be REALLY surprised if I end up with worse sound. Hedging against that possibility is one reason to stick with Clarity on the coax feeds. If it does end up making things worse, Rob Gillum has extras of the SAs that were the in the CS2.4SE. Having Tom Thiel guide me gives me a lot of confidence.

Eventually I hope to have upgrade paths for various legacy Thiel products that Rob can supply.

Haha, I can see it now. I'll get my pair dialed-in then you and Rob will come out with a kit for the 2.4s. There is no end to audiophile nervosa!

the buyer gets what he gets with myriad value judgements / assumptions bundled in the mix. It is not for the faint of heart; the process will lead to critical listening / comparison and then value engineering assessment to assure that the gains are solid / uncompromised and the costs are no more than necessary

Just picking the caps for the SE version probably took Jim Thiel and his team many days and weeks, never mind the initial design. Choose worthwhile candidate caps (this is what I'm doing), burn them in for a week or two, conduct careful listening tests/comparisons, probably measurements, too. Being a buyer, not a manufacturer, I don't have the time and money to try multiple combinations. Moreover, manufacturers are *highly* motivated to get the very best sound possible, albeit balanced by cost (except for Wilson and the like for which crazy prices are built into brand expectation).

In my case, my SEs sound superb but I also know there probably are gains to be had with tricked-out XOs. I paid ~$3K for my used pair and I think they sound as good as anything new up to ~15K. What if there is a relatively inexpensive way to make them sound as good as anything new up to $30K?

As I wrote elsewhere in this thread, I think Thiel made some of the best drivers in the business. IMO, the main thing that separated Thiel SQ from that of the very best was attention to the passive parts. Tom Thiel wrote that it wasn't that Jim Thiel was unaware or disbelieving of ultra caps and the like, just that he wanted to balance SQ against cost so that more people could afford his creations. And I am grateful because I am one who can afford Thiels. Not much if they were tweaked like this:
http://jeffsplace.me/wordpress/?p=5464

I suspect a CS7.2 or CS3.7 with a cost-no-object XO would sound pretty much as good as anything I've heard. But something like that Dueland-capped XO would probably add $20K retail, more than a pair of CS7.2 or CS3.7!

Tom Thiel has been very generous with his knowledge and sdecker shared his successful experience of re-capping his CS2.4s. This is a project I'm confident I can complete and with good results. I will certainly report back on this thread in hopes of helping other DIYers.

brands like Thiel that stay on top of the cost/performance tradeoff are likely to have better products than the cost no object "luxury" brands

I agree but still wish that Thiel had a full-out assault on SOTA speaker. Not that I could ever hope to afford such a product but it probably would have informed new, cost-effective ways to coax (pun intended) even more performance from the 1s, 2s, and 3s. Maybe Jim Thiel had this in mind (cs7.3?) but left this Earth far too early.

At Parts Connexion, retail pricing for a Clarity SA 15 uF is ~$20 and 33uF is ~$46. *Every* CS2.4 could have had SA caps for, maybe, an extra $200 retail (tbf, I don't know that the SAs were available when the 2.4 was developed). No doubt Jim Thiel had very good reasons for his design decisions and I shouldn't second guess those decisions. But, IMO, an extra $500-2000 retail in better passive parts for the 2s and 3s could have elevated their performance to the next tiers. I'm going to test that speculation!

BUT, where does such a move leave the line / other products, niche reputation, etc?

Yes, tough decisions and I have no business armchair quarterbacking Thiel's choices. Speaking of the CS5, I recall reading on AudioAsylum that Charles Hansen regarded the 5 as Thiel's best model with the 3.7 a "close second". I'm curious to hear a pair.

I just took a look inside my CS2.4s. It was easier than I imagined (I was worried about getting the radiator back in) although a contortion is required to remove the radiator. From Rob Gillum:

To access the crossover, you must remove the passive radiator screws and let the passive radiator drop into the cabinet. It can be rotated 90 degrees, and removed while servicing. To re-install the passive radiator, you can place your fingers at the surround, pressing outward to hold in place while re-installing the screws that hold bit in place.

I discovered that the 33uF cap on the woofer is only 100V, not 630. This opens up the 33uF CSA 250V as a direct replacement, no bypass needed to get the correct capacitance, and for only $75 for a pair. I guess I could add a 0.01 ultra if I want to go crazy.

Also, I think I have room for most of the options I'm considering on the coax board. If I wanted a 10uF Supreme to match a 18uf CSA, however, I might have to mount the board a bit lower as that cap is 4cm longer than the CSA. From the top edge of the 28uF SA as seen here: http://www.hifishock.org/gallery/speakers/thiel/cs2-4se-2-thiel/
there is about 18 cm to the cabinet wall (just past the bottom of the board as seen in the image). Most of my Clarity options should fit with a bit of stacking. Additional protrusion into the cabinet is moot given the fiberglass bat on the two boards. The extant 14uF SA abuts the 6mH coil but I imagine the coil's orientation prevents deleterious interference. In my case, I will need to place a cap even closer to the coil although probably a shorter cap that should provide a gap to the coil.

Also, the boards easily unscrew from the cabinet and there is enough slack in the wiring to provide extra room to access the leads. Finally, it doesn't seem like a huge project to take everything outboard altho' I think I can fit everything internally. Looks straight-forward. Maybe I'll do this project sooner than April?

@tomthiel PMs sent, please check spam folder?

@arvincastro  Nice system! I imagine you're very happy with your sound. I would own ARC if Ayre was not a thing. Enjoy!

I believe that some ( especially me ) 2.7 owners hope the Rob Gillum comes up with a crossover board upgrade

Make your opinions known here. Tom Thiel intends to help Rob Gillum engineer XO upgrades for multiple Thiel models . . . and he is monitoring this thread. He is working on his Power Points now, CS2.4 is probably next (actually, CS2.4 owners can get the SE version caps from Rob Gillum right now). CS3.5 is on his radar. I think the 2.3 would be easy given the similarity with the 2.4, 2.7 might not be too much more work. I suspect written requests in this thread will influence the order of model he works on.

This is an exciting development. I think these upgrades will bring Thiel SQ to a new level.

A good amp for current hungry Thiels doubles power from 8 to 4 ohms and again doubles or nearly so into 2 ohms.

Neither Ayre or Pass give a 2 Ohm rating for the amps F1 is considering. I’m not convinced, however, that matters for a CS2.4. Unless you like to listen at *really* high SPLs and/or have a large room, either amp sound be more than enough to deliver musical bliss. Interesting observation, though, that something in the, um, Ayre might have caused the blown coax. I wonder what that might be.

The CS5, though, looks to be a supremely current hungry speaker. Stereophile’s measurement shows the impedance dropping <2 Ohm in the bass! Might not want to drive those with a SET :)

The observation of congestion of orchestral climaxes at high SPLs suggests, to me, the onset of clipping. Probably need a more powerful amp if that’s how you like to listen.

@f1wheels That should be a really nice sounding system, unless the Ayre kills another coax :o

Please let us know how changing the caps goes for you. I will be making a more comprehensive change to my XOs, maybe next month. I imagine Rob Gillum has supplied good instructions for you to follow but we can all learn from your experience.

Had the house to myself tonight and not only played the SEs loudly but played with listening position. Soundstage's measurements were at a manufacturer's recommended 30":
https://www.soundstage.com/measurements/thiel_cs24/

With the spikes and outriggers this lifts the speaker another 2". So, I tried a lower chair and was able to get my ears 32-36" off the floor using different combinations of pillows (my ears are probably more like 38-40" off the floor in my usual seat). But I also sat closer, so I was changing vertical *and* horizontal off-axis angles. Additionally, it put my ears further from the back wall and couch I usually sit on. So, I was changing at least 3 variables at once.

Anyhow, I was able to get the best sound yet. Image density remains less good than the best I've heard but the sound seemed to open up a bit with a notably more immersive soundstage. I'm slowly getting the position dialed in - can't wait to hear what the XO upgrade does!

At that point the sound changes a bit from the reflections from the pillow around my ears, similar to when I introduce some more room reflection by moving my curtains off the side walls near the speakers.

I am certain that my ears relative to the high couch back is a big part of the differences in sound I heard. In my case, I think that and listening height are more important than differences between, say, 8 and 9' distance.

my ears are about 7'10" from the coaxes

My ears were just a hair closer than 8' when I was on the lower chair. Previously I tried the couch closer, also with my ears about 8' away from the coaxes, but this was the first time I really experimented with a *lower* position. Next, I will try removing the couch cushion and try various pillows to lower my ears. This would have my ears about 9' away. That might not be the answer tho' as I *did* try a couple of songs with risers under the front spikes to tilt them up (this is how Vandersteen does it for differing listening distances albeit with changing screw settings rather than adding risers).

Interesting to me as I've mostly experimented with speaker position rather than listening position. I know Jim Smith recommends starting with listening position before starting on speaker positioning.

Lafuma - I have two of those, mesh versions, that I use in the yard during summer. Fantastic for taking a nap in the shade!

Last night I was using a wooden low-rider style. I kept adding padding until my ears were in the range 32-36. I thought that ~35-36" sounded best-ish. I intend to dial that in more then return to speaker placement.

Here’s an update on my CS2.4SE crossover upgrade project, including an update on Tom Thiel’s hot-rodding intentions. I’ve been PMing Tom for the past several weeks. He is directing most of my decisions and I’m providing him feedback as a beta-tester.

So far, I have ordered and received Mills MRA-12 resistors from Sonic Craft (the only vendor that had all the correct values). Mills should be a step up from the ERSE resistors used in many Thiel models. All but one of the resistors on my SE boards were not labeled with manufacturer but they are probably ERSE (or Xicon). I considered every resistor I could find that met Thiel’s spec. Dueland and Path Audio are widely regarded as the best resistors available but these are crazy expensive (~$30 each compared to ~$5 for Mills) and subjective reviews suggest their sonic performance is not commensurate with their price (hey, that sounds like a LOT of things in audio!). Mills MRA, I think, represents a clear upgrade over Thiel’s OEM resistors while also representing good value. Tom agrees and these will probably be included in the forthcoming kits.

I have these installed only on one channel so far. It took me about 3 hours and a second pair of hands but the second speaker should go faster with my experience other than there’s no help for my soldering gun which is less than professional grade (Tom Thiel recommended at least 140 W for the lead-free solder on Thiel boards; my gun is 180 W). I did this just yesterday, so no burn in time tho’ Tom thinks this is not necessary for resistors. My initial impression is that lower-level “grunge” has been removed, ie, the noise floor seems lowered. This is subtle but is quite worthwhile for the sound I seek! I will listen/compare more before I upgrade the other speaker, including in mono one speaker at a time. Look for further updates in the coming days and weeks.

Tom has been researching the many options among capacitors, including bypasses. He is very close to a final parts list for his Power Points and CS2.2 as well as my CS2.4, and has the layouts worked out (apparently, the CS3.6 will also be among his first “hot-rods”). He is planning point-to-point connections. My SEs, built in 2012 around the time Kathy Gornik sold Thiel, have printed circuit boards so Tom thinks I will hear an improvement just from that simple change. Only the coils and styrene bypass caps will be salvaged from the original boards. Most of the new caps will be sourced from Clarity and are custom sizes so it will be a few more weeks before he has these (and another delay before the kits become available).

Mr. Thiel’s goal is to maintain Thiel Audio’s adherence to neutrality, high resolution and fidelity to the input signal while improving the overall sonics via superior passive parts. But he also is balancing value, so e$$$oteric parts may not be on his list. Instead, I expect to see/hear a well-considered crossover upgrade that should be a readily audible sonic improvement - even compared to my SEs - yet in line with Thiel Audio’s value-oriented approach.

Tom is still in the “hot-rod kit” development process but I want to get this out now because he is wondering about the demand for taking the new crossovers outboard, ie, the new boards would be in their own cabinet just behind each speaker. The advantage of outboard is maximized sonic performance via isolation from physical and microphonic resonances. This would also allow substantially better cooling which is important for those who listen loudly! I think this would also be easier to install for DIYers (I’m guessing the eventual kits will be DIY or send your speakers to Coherent Source for Rob Gillum to do the work). Tom has the shop to potentially match our cabinets (altho’ black would be easier and matches the front baffle of most Thiels). I imagine a XO cabinet would be the same width as our main cabinets, maybe a foot or so tall. Finally, an outboard solution would increase the options for new bracing to further reduce main cabinet resonances. The main (only?) downside of an outboard crossover is reduced WAF.

Tom would like input from the larger community as he finalizes his plans. So, please respond “yea” or “nay” regarding outboard crossovers so that he can gauge interest.

Here is an example of an outboard crossover (Avalon Ascent): https://usato.audiograffiti.com/annunci/diffusori-acustici/167157/

and: http://www.hifido.co.jp/KWB/G0201/E/400-10/C15-87521-47650-00/

Put me down for “yea”.

@tomthiel Right, I switched back to the “normal” configuration one week ago Tuesday and listened over the weekend. It sounded similar: open, clear and relaxed. One conclusion is that my DAC must have needed >500 hours to fully break in. But I do think the parallel configuration sounds just a bit more more relaxed and open. I had the thought to compare side by side in mono like I did during the XO work but haven’t been motivated enough to do that. One issue with the parallel configuration is that the cables are more elevated off the floor and for more of their run. My right channel is near the back door and house guests occasionally kick the cables off their risers even in the normal configuration. 

But, hey, no house guests during a pandemic! I’ll probably try the parallel configuration one more time. It did seem magical even if I’m now uncertain it made more than a small difference.

Danged tricky to respond to negative reviews if you're a manufacturer. Best just to cut your losses especially with someone like JGH. IIRC, Holt gave a tepid review to one of John Curl's designs (which was other wise widely praised) and it pretty much took the legs out from his company.

That said, Atkinson gave a rave review of the CS 2 2, so that might have canceled the negative press by Holt.

For myself, I use the magazines to help form a short list then rely my ears thereafter. The reviewers are wrong too often! And they rarely have much to say about value. There are many "mid-priced" (it's all relative in this hobby!) products that sound nearly as good, if not outright better, than the $$$ designs. Too many reviewers (Fremer and everyone at TAS) start with the price tag . . .

I need to turn up the volume to get a decent ‘clarity’ from them.

Could be many things including your listening preferences. Could be that is the sweet spot for your gear. I’m running an Ayre AX-5 which has the same signal/noise ratio regardless of volume setting. But most preamps have a "best" sounding volume. Regardless, I’m reluctant to ascribe the effect to the Thiels.

BTW, stay tuned to this thread over the coming months. Tom Thiel is working on upgrades for legacy Thiel crossovers. The cs2.4 will be among the first tackled. The idea is to have DIY kits and/or upgrade service available through Coherent Source Service (Rob Gillum’s Theil service company). I expect these will bring sonic performance to a new level.

I would be interested in upgrading the newer speaker.

Mr. Thiel is targeting the older models first partly because he thinks the X.7s are starting with better technology. Just guessing here but it will probably be late summer or fall before the first round of kits are available from Coherent Source. Anything for the X.7s will be beyond that timeline.

posts are on the back

Same with my SEs. Not an issue as the external cabinet is attached via cable or umbilical cord. Probably an inch or three between the cabinets. Actually, that brings up another disadvantage of the outboard solution: cost. In addition to the extra cabinet, cabling between the two is needed.

Thiels rule!

I’m optimistic that the new boards will elevate them to the next tier. As I wrote elsewhere, probably my last speaker.

Those cross-overs do look cool. Put me down for yea.

Woo-hoo, let's twist Tom's arm!

those outboard crossovers are HUGE on the Avalons!

Those were arguably the best speaker on the planet when new, certainly on the short list. A three-way with high-order filters takes a lot of parts.

For my CS2.4s,  I imagine a XO cabinet would be speaker width, maybe 10" deep and about 1' tall. The cabinet would be vented/screened top and bottom for maximal air flow.

Thanks for posting, Tom!

The external XO in an ~8" cube would be unobtrusive to include in a living space. I am even more interested now that I know the dimension. Given that my goal is to optimize the SQ, adding this small cabinet behind the speakers is a no-brainer. I'll await the report of your trials.

I need to correct the record. Above I wrote:

no burn in time tho’ Tom thinks this is not necessary for resistors

But here are his words to me in a PM:

All components benefit from burn-in, including resistors, but ESPECIALLY solder joints. The metallurgic structure has been disturbed and somehow heals in use. I expect your job will sound better over the coming weeks.

Apologies for misinterpreting an earlier message. I'll let the speakers run at least 100 hours before I do any serious comparisons.

boxes strewn on the floor?

Voting options should include "It depends"?
:^)

No manufacturer can be all things to all people but there could be more DIY options given that these will be "kits". If Mr. Thiel does go outboard it would probably not be too onerous for a DIYer to modify these with binding posts and simply run a speaker cable from the XO on your rack to the speaker.

For myself, I prefer a solution of a high-quality strap from the external to the speaker cabinet (XO cabinet on the floor directly behind the speaker) and then cabling to the amp as normal.

more urgent for older models as their cross-overs are likely to be needed (due to age)

Good point! I see that as a secondary benefit. The intention of the upgrades is to notably increase the quality of the passive parts and, thereby, the SQ. As Tom Thiel wrote earlier in this thread:

Thiel was always about finding the optimum point on the cost-performance slope so that real music lovers could afford our products.

Speaking for myself (and not Mr. Thiel), the upgrades seek to maximize SQ beyond what was possible at the price points of the original products. IMO, a cost-no-object approach to the XOs for the CS7.2 or CS3.7 would have likely have placed those speakers on par with the best available. The upgrades intend to seek to squeeze the ultimate SQ from the designs.

I am still burning in my new resistors, so don’t yet have a final verdict but my initial impression is that the Mills MRAs are a worthwhile, yet subtle, improvement over the ERSE resistors originally installed. This change in parts would have added $200-300 retail to the CS2.4 and represents, I think, the kind of decision Jim Thiel would have made when optimizing the “cost-performance slope”.

In my case, I recognize the drivers in my CS2.4s are really frackin’ good. IMO, I would have to move up to something like the Vandersteen carbon or TAD beryllium drivers to find something clearly better. Speakers with these drivers are an order of magnitude more expensive than my Thiels! But I think I can get really close to their level of performance by optimizing the XOs. In other words, it's a solution that gets me close to the very best but at a price I can afford.

Also, keep in mind that the technology has advanced since Jim Thiel designed the original XOs. Even the relatively recent Clarity SA coax feeds in my CS2.4SEs have been notably surpassed by Clarity CSA.

@unsound Glad you find my updates informative. Your CS3.5s must be close to 30 years old - I understand your concern re: cap life. That should further incentivize you to seek Tom Thiel's upgrades as they become available.

Actually, yea or nay *might* well work for everybody :)

In the case of the CS2.4, Tom Thiel has worked up a one-sided layout for internal installation and a two-sided layout for outboard installation, the latter to save space and enhance the chimney effect for better cooling. As these will be DIY kits (or, I imagine, send your speaker to Coherent Source for the work) there is a good chance we can each go with our preferred installation. The XO parts list will be identical, it’s just a matter of layout and extra connections in the case of outboard. Tom wondered how the community would react to outboard as an option and I think he now has an idea.

Again, the advantages of outboard are isolation from physical and microphonic resonances, improved cooling, and increased options for further cabinet bracing. The advantages of internal installation are reduced upgrade cost (no extra cabinet and connections) and no added box to reduce WAF.

Note that I am aware that some might want to go farther afield with cost no object components and others may balk at the significant cost of my choices. My vision is to find affordable solutions that reach the next performance / cost plateau.

I will add that I think Tom Thiel’s choices are *very* sensible. The upgrades will almost certainly (can’t say for certain ‘til we listen!) yield a significant SQ improvement but without going beyond the budget of most serious listeners.

Left to my own devices, my choices would have been similar to Tom’s in some ways. I was honing in on a solution that would have added a substantial (30%) Clarity CMR bypass to CSA coax feeds. This would have been more expensive and not necessarily overall better than what Tom outlined. In his research, Tom has learned that certain bypass practices can have detrimental effects! Elsewhere, I was going to add small polypropylene bypasses to the extant caps. Tom’s solution is far better, replacing the electrolytics in the shunts with the custom 160V PPs. We are fortunate that Tom is able to work with Clarity to have this cap made to spec. An off-the-shelf solution would be very expensive and with ginormous caps that would be very difficult to fit.

These upgrades will not be inexpensive ($TBD). All XO parts are replaced - most caps are custom - except for Thiel’s custom 1 uF bypasses and the coils. As I wrote earlier, if I were to replace my CS2.4SE with something new I would start at something like a Vandy Quatro or Vivid B1; $15K speakers! After these upgrades, I suspect such a search would have to reach to something like the Vandy 5 Carbon, a $30K speaker. In other words, the CS2.4 is a seriously good speaker in stock form and optimizing its crossover should elevate its performance to the next tier (or beyond). Do I want to live with a speaker whose neutrality, transparency, and resolution exceed or rival anything up to $30K? And for the “only” cost of the upgrade? Hmmm, decisions, decisions ;^)

As Tom wrote, some owners may want to go even further. Earlier I linked to Jim Smith’s outboard XO for his Avantgardes featuring a rack of Dueland caps and resistors. Would that approach outperform what Tom Thiel has outlined? I hope so – that’s at least $20K in parts! But we’d have to listen to know for sure. To my thinking (and budget) that is not sensible for a CS2.4. Maybe you CS3.7 and 7.2 owners will choose to push the limits? But remember that Tom Thiel’s “base” upgrade is a notable upgrade even for those models.

later production 3.7s have Chinese made crossovers which seem to have some polyester caps where polypropylenes are specified. And those are built on printed circuit boards

My SEs also are on PCBs and with some MKT caps where Jim Thiel’s schematic specified PP. My pair was built in 2012 (the year Kathy Gornik sold Thiel Audio) and are among the last SEs built. @jafant I suspect your pair are similarly equipped. For us, Tom Thiel’s upgrade will probably be an even bigger jump in SQ than for owners of earlier SEs.

I would consider keeping your CS 2.7 loudspeakers as is, experimental/unique

Swapping that multistrand for Cardas would also be unique, no? 

I’ve never heard ATC. Maybe they’re onto something? But I’m skeptical. As Tom Thiel wrote, the steep filter lets you operate a driver in the range of pistonic behavior. This is *highly* desirable (and also requires diaphragm material up to the task). But this throws off phase coherence. There is no free lunch. If there were, all designers would hone in on the same design.

Thiel Audio placed phase and time coherence as a top priority. The downside is that the slow rolloff may not sufficiently suppress the inevitable break up modes. As I’ve written in this thread, I think Jim Thiel made some of the best drivers around. The diaphragms are light and rigid and the break up modes are out of the "main" region covered by each driver. Even at that, some may consider the break up modes insufficiently suppressed by a 6dB filter. Richard Vandersteen seems to have taken this even farther with his carbon/balsa drivers but you need some serious coin to move up to those. The carbon midrange is available only in the 5 Carbon ($30+K) and 7 models ($60+K).

IMO, most of the newer Thiels get it right in terms of balancing phase alignment and pistonic behavior (I’ve heard CS2.4, 3.7 and 7.2 but not earlier models). My ears tell me so, and Soundstage’s measurements of the CS2.4 confirm "very low" distortion despite the 1st order filters. Nothing is perfect but I think Thiel gets you most of the way there and at an affordable price.

That said, if ATC or others have figured out how to maintain phase alignment while also optimizing pistonic behavior I’m happy to learn! I'm not an audio engineer, either. More of a dork with a soldering gun :)

Past the 100 hour mark on my Mills MRA-12 resistors and it was time to evaluate the sonic difference. I had to do this in mono, comparing the upgraded speaker to the OEM version. Not ideal but the only other choice was to upgrade both speakers and rely on sonic memory. I used Roon DSP to mix the signal into mono. This allowed me to use my “reference” recordings rather than rely on rarely listened-to mono originals (which I also tried). To minimize room effects, I put the speakers close together in the middle of my room, about one foot apart (ie, each speaker had the “same” room interaction). In this position, I simply shifted a couple of feet one way or the other on my couch so that I was directly on-axis. The on-axis energy shifted the balance from what I’m used to (my normal arrangement has the speakers just under 8’ apart with no toe-in) but both speakers were equally handicapped.

Anyhow, I’ve now done two comparative sessions. My impression from both sessions is that the Mills has a fuller, richer sound although my perception of this varied from song to song. I heard little, if any, difference on solo trumpet but a pronounced difference on the well-recorded 2L Mozart violin concerto. Guitars and voices were more "full-bodied" on folk-rock, blues, and bluegrass. More “tonally-rich” might be another way to describe it. On a Chesky test recording, percussions were more emotionally engaging, toe-tapping. The Mills also seems to have a bit more texture or, at least, it was easier to hear into the microdynamics. I think this is related to my initial impression of a "lower noise floor".

All-in-all a worthwhile upgrade - audible benefits and at a reasonable price. I think Tom Thiel’s upgrade path is off to a good start.

@prof My pleasure. I *am* doing this mostly for selfish reasons (I want to have killer speakers at a price I can afford). But am glad to help Tom Thiel and Rob Gillum develop an upgrade that will benefit many more.

I'm pretty excited about it and think the "final" product will be a substantial improvement for our already excellent speakers. Tom continues to refine the parts list. One of the last pieces of the puzzle regards the paired 100 uF caps that are common in many models. Jim Thiel chose electrolytics for these because film caps in this value are quite bulky and *very* expensive. Also, to his ears these were less important sonically (they are in the shunt position so do not directly carry the signal). Others disagree, however, so we're going to compare a couple of film cap choices as replacements. One is a custom cap from Clarity so it will probably be at least another month before Tom can begin his evaluation.

If Rob Gillum has the kit to fabricate drivers, it wouldn’t be a huge stretch to make new, improved versions of the cs2.4 with Tom’s XO design. Jim Thiel’s last drivers (x.7) were the best but I think those had to be outsourced. But the Lexington made coax and woofer in the 2.4 aint too shabby 😀

Prof, . . . you can keep your 3.7s and join the upgrade brigade for even more musical satisfaction.

@prof Tom Thiel is learning much about the late model Thiel crossovers as well as how to improve parts quality for all the models he is now working on. You might hold onto those CS3.7s another year or so and try his upgrade when it becomes available. 

Ayre and ARC would be on my short list. Also, Pass, Aesthetix, and Classe. Heed the power ratings per Tom Thiel. You very much want an amp with a decent 4 Ohm rating and 2 Ohm is not overkill.  Maybe take a look at Wes Phillips’ review in Stereophile. I recall he tried two or three amps (but I could be thinking of his cs2.4 review).

@vair68robert 
Interesting idea about rewiring the binding plates. I’ll consider that if I decide I prefer your parallel configuration. Still running the standard. I want to have one more critical session with this configuration. 
Right, I have no intention of modding my Ayre. That volume control is mounted on the back plate for a reason :)

Update on Mills MRA-12 resistors: I replaced the other channel a couple of weeks ago. I hear more bass impact, a more spacious soundstage, and, especially, an ease of presentation. The MRAs even seem to have partially mitigated a somewhat “glassy” quality in the midrange. I can’t wait to hear the full upgrade!

Tom Thiel has placed an order for the custom caps but they won’t arrive until late June or thereabouts. The parts list is nearly finalized for CS2.4s. There are a couple of caps that merit A-Bing to determine which to use in the final design. So, probably late summer or later before the CS2.4 kits are available. 

@ronkent Thanks for the report. I'm not surprised. I don't consider Thiels the best available but I do consider them the best at their price points. They "punch well above their weight class". IMO, models like the CS3.7 and 7.2 just miss the ultimate tier of performance. If Tom Thiel is able to design hot rod kits for the CS3.7 (it's on his radar but he is working on older models first) I expect the performance to rise to that next tier. I suspect a 3.7 with an upgraded crossover will be sonically competitive with models costing ~$50+K (I'm thinking stuff like the Vandersteen 7 and Vivid Giya).

The Thiels i am thinking, have more cabinet resonances and nothing will change that. Changing speakers is such a pain (selling and shipping the old ones for example) that i probably will be keeping these for many years. the crossover upgrade sounds awesome but i for one am not qualified to go in and change everything so i guess that it is not in my future.

Tom Thiel has an idea for identifying cabinet resonances and, possibly, addressing them. Stay tuned. In the meantime, the CS3.7 is not too bad in that regard:https://www.stereophile.com/content/thiel-cs37-loudspeaker-measurements
For comparison, here is a $50K Wilson (Wilson makes some of the very best cabinets in the business): https://www.stereophile.com/content/wilson-audio-specialties-alexia-loudspeaker-measurements

If you are not comfortable building new crossovers, I imagine there will be a couple of options depending your confidence level with a soldering gun: 1) Rob Gillum can build and install these, altho' that means shipping or personally transporting your speakers to Lexington; or 2) the CS3.7 boards appear easily accessible: http://www.theaudiobeat.com/visits/thiel_audio_carries_on.htm
(assuming that panel isn't glued on), so you might have Rob Gillum build the new boards, ship them to you, and you would only need to replace the boards. Alternatively, you could have someone local do this last bit (friend or technician at a local shop). But temper any excitement you might have - Tom is unlikely to have a solution for the CS3.7 until next year.

I have the CS2.4SE, now with Mills MRA-12 resistors over the OEM sandcast resistors. This was a worthwhile upgrade! I have ordered new bypass caps and will build entirely new boards later this year.

I recently purchased a pair of CS 2.7 that I am running with a peachtree nova 300 and accessing Tidal as a source. I found the highs a little bright and the lows so so.

I've not heard this amp but class D amps are reported to be generally less musical (albeit gobs of power for a low price). You might try a solid state design from ARC, Ayre, Classe', or Pass (among others). In the meantime, make sure your placement and room are optimized. Jim Smith's "Get Better Sound" is a good place to start without spending a bunch of money.

I'm a bit gun-shy about messing with the tone of my 2.7s

The upgrade circuit is nearly identical to OEM. “Nearly” in that bypass caps will alter capacitance by about 1%. Otherwise all cap, inductor, and resistor values are unchanged from Jim Thiel’s circuit. The difference is a substantial upgrade in parts quality. Tom Thiel posted earlier that Jim was well aware of the benefits of higher quality parts but made his choices to optimize the performance/price curve and keep his speakers attainable for regular working folks.

But there are audible improvements for those willing to open their wallets some more, especially given the increased performance with time. Many of the parts Tom is planning for the upgrades were simply not available 10-20 years ago. I consider my CS2.4s to have excellent cabinets and, especially, drivers. But there is ample opportunity to upgrade the crossovers and get notably better SQ.

That said, Tom Thiel will be measuring the results of the upgrades to ensure that the balance is not upset in some unpredictable way. 

@prof I should add that the layouts will be different, especially for the outboard solution. This, more than the change in parts quality, is why Tom wants to ensure that the new orientation is not deleterious.

i asked my distributor if he could order the lastest crossovers in 2015 he told me Thiel didn't have them available anymore.

Well, the only person to ask now is Rob Gillum at Coherent Source Service. He has an easy inquiry form on his website and he has replied to my multiple queries within a few hours if it’s a business day.

I prefer the sound *with* the outriggers. Not sure how much is due to better floor coupling versus the added 2” higher axis.

Has anyone tried comparing the sound with and without the outriggers that Thiel provided?

I forgot that the new crossovers would be outboard. That would almost certainly rule them out for me.

Tom Thiel is planning both as options. The outboard versions are likely to be more tricked out. Internal mounting is space limited and reduces the options for big capacitors and so forth. From the pics I’ve seen, the CS3.7 has one or two 100 uF electrolytic caps and something like four 75 uF ’lytic caps. Upgrading all of these to film caps (probably Clarity CSA) will need a lot more space and it seems unlikely that you could simply replace the ELs with film without also changing the layout . . . and taking a bite out of the cabinet space. Still, Tom is planning an upgrade path for those who don’t want to go outboard.

I really think these will be the speakers they bury me with

Yes! I was already happy with my CS2.4SEs and the resistor upgrade has been *very* satisfying (I think the new resistors are still breaking in, they keep sounding better and better). Other than the physical limitations of an 8" woofer and passive radiator, I think Tom Thiel's crossover upgrade will make my 2.4s sonically competitive with all but the very be$t design$. And I imagine these could be my last speakers.

you should buy my 2.7's :)

LOL! Actually, there was a pair of white CS2.7s on A'gon just after I bought my SEs and for <$500 more. That had me second guessing. The 2.7 coax is almost certainly better than that on my SEs. But I'm committed to these SEs now as I've modded the XOs. That probably damaged the resale value even while notably improving the SQ. I need to see this project thru' to the end. And when I get there, they will almost certainly sound better than stock 2.7s (tbh, never auditioned the 2.7).

upgrade the equalizer, which would be required for system synergy

I might not even be able to *spell* "equalizer" . . . Is there potential harm to the balance by simply upgrading the caps and resistors on the XOs, keeping the layout as is? Keeping the same layout might preclude replacing the electrolytics with film caps but I imagine 30 year old 'lytics should be replaced if only with another 'lytic. I guess I'm wondering if there is a "partial" upgrade route for 3.5 owners that would replace aging caps and increase SQ at least a bit but without risking the balance with the bass equalizer.

 I haven't yet looked at the 3.5, but will look into it. The equalizer could indeed be ignored in an upgrade. 

Sounds good, Tom. Seems to be some demand for that model! And maybe someone will step up to address the equalizer?

Not much musical content below 35 Hz: 

http://www.sineworld.com/html/basic_knowledge/freqchart.html

I can never again live with a speaker that isn’t robust down to 40 but I’d rather have a killer speaker that stopped at 40 than a mediocre one with full output below 30.

8 v 10” woofer. Prof and ronkent can probably describe the difference.