Thank You for the assist. Happy Listening!
There are other other threads on a 7 vs. 7.2 - e.g.
https://forum.audiogon.com/discussions/upgrade-thiel-7-s-to-7-2-s I have known people who had 7s and opted to upgrade to the 7.2s when the 7.2s were released. I've personally never heard the 7s, but I did buy my 7.2s when they were new and sold them when the 3.7s first came out. |
I've created a thread on DIYaudio website. It's basically the same but it has a few extra stuffs. https://www.diyaudio.com/forums/multi-way/345669-exercise-converting-speaker-time-phase-coherent.html#post5984990 |
On an aside note, this is why only first order is possible. A high order filter even with all positive polarity won't be able to produce a proper step response. https://www.flickr.com/photos/185616271@N05/49107462151/in/album-72157711891600612/ Also first order time coherent xover tend to be very complicated which is somewhat counter intuitive. On the other hand, a 2nd order, 12db roll off xover is fairly simple and no doubt would save a lot in component cost. I am sure that's part of the reason why most manufacturers are probably shy away from first order filter designs. https://www.flickr.com/photos/185616271@N05/49106953358/in/album-72157711891600612/ |
harrylavo I listen at moderate levels when in the sweet spot, but my listening room is a general media room that opens to the rest of the house. So I am often blasting the music loud to listen from the rest of the house. My CJ premier 12s (140w tube) had no problem driving either the 3.7s or 2.7s to house-shaking levels, while sounding clean. |
Since the issue of tubes driving Thiels has come up, I want to add a bit of experience. When I first bought my 3.5's, I used an Audio Research D90, and volume was never a problem. Later, in a much larger listening space, I used VTL ST-85s, and again volume was not a problem. I must caution, however, that when I say "not a problem" I am talking about jazz, chamber music, 60's-70's singer-songwriter, etc. I do not generally listen to hard rock, and while I play fully symphony orchestras I tend to keep the playback at comfortable levels. I also will relate that when I obtained my 2 2's, for about a year I drove them with a Fisher 202 integrated tube amp putting out 35wpc. Again in an average size condo living room and at reasonable levels. (This combo sounded fantastic, btw). Take this for what it is worth. But I guess it puts me in the camp of Thiels are okay with tubes. |
Phase Coherence is used in various ways by various people for various purposes.I understand. I am personally got lost with all the different terminologies. Very simple and very difficult!Being working on DIY, it usually takes me much more time than a typical high order speaker. But still, I hope more speaker manufacturers will do it. It may be very difficult but not impossible. I think it's just an "excuse" that most people won't try it. I was thinking about how our hearing may not be so sensitive to high frequencies and the high freq. phase shift. In our normal environment, high freq. is very reflective and when sound reflects, its phase will get change as well. Also diffraction will cause delay in high freq. and phase shift as well. If human is sensitive to these, it would drive us crazy. That's why our hearing is only sensitive to long delay, not short delay, and the long delay we hear is what we call "echo". Imagine if we listen to high order speaker and we hear all "echo", I guess that would not be very good :-) But having said all that, I still think time-phase coherent could make a difference, and if I could, my speaker would be all time coherent. |
Andy - the term of art: Phase Coherence is used in various ways by various people for various purposes. Thiel was a pioneer in Coherence along with Richard Vandersteen and John Dunlavy. We all use the term to mean Phase Coherent and Time Coincident. In other words all the elements of the signal launch and add together to produce the step response of the input signal with no negative pre-shoot at any frequency. Very simple and very difficult! |
When it comes to first-order coherent and non-coherent, there has been some misundertanding with regard to the step response. For non coherent speakers, invariably, the polarity of the different drivers will be different, that is the tweeter may be inverted polarity and the woofer will be positive polarity. Therefore in the step response, the tweeter will "APPEAR" (notice capital letter for emphasis) to go negative with respect to the woofer. But that misses one subtle but very important point that will lead to a crucial insight to the phase of coherent vs. non coherent design. Most people came familiar with step response measurements by way of Stereophile John Atkinson measurements, but his measurements only show the overall step response without the measurements of each single driver. Once each single response is shown, there is further truth to be gained. I will use one of my project to illustrate the misunderstanding. See pic of speakers here: https://www.flickr.com/photos/185616271@N05/49106259616/in/album-72157711891600612/ Below is the xover design. Notice the tweeter is inverted polarity and the woofer is positive. Also notice the step response on the lower right corner. Also notice the phase of the speaker response on the upper right corner of the plot. That is the phase starts at about 0 degree, and gradually go to -180 degree. Also notice each individual component freq. response and the cross over point. https://www.flickr.com/photos/185616271@N05/49106444352/in/album-72157711891600612/
At first glance, the tweeter seems to go completely opposite of the woofer (the initial dip of the step response). The time-coherent proponent will say – wait a minute, that’s all wrong since how can the treble be completely opposite of the woofer? But that is not quite right. The tweeter ONLY opposite of the woofer at very high frequencies, but at low frequencies, below the xover point, the tweeter and the woofer actually go up together.
I here have a zoom in pic of the step response. You can see the tweeter and woofer go up together after the initial high frequencies. It’s subtle but it’s there and it’s very important. Green – system Red – tweeter Yellow - woofer https://www.flickr.com/photos/185616271@N05/49106444417/in/album-72157711891600612/
What does this mean? If you look at the frequency response below, you see that the phase of the system is only at -180 at 20KHz, not the entire plot. But below the xover point, the tweeter and woofer are more or less “in-phase”. For example, at 2KHz the phase is only at -60 degree, at 3KHz the phase at -80 degree. As I said before, since our perception is not very sensitive at high frequencies, most of us may not “hear the difference”. Most of the musical contents occurr below the xover point which is about 3KHz in this case and that’s where most of the phase shift has not occurred. Also the phase change is not at a constant -180 degree everywhere but only at exactly at 20KHz. For example, the phase change at 20KHz is only a few degree vs. 19KHz and likewise 19KHz is only a few degree vs. 18KHz … and so on. It’s a gradual shift in phase so our hearing may be able to adjust to it. But on the other hand, if this -180 degree occurs at 500Hz, trust me, you will definitely HEAR it! I think high order can get away with it because the phase shift occurs at high freq. where our hearing may not be so sensitive.
https://www.flickr.com/photos/185616271@N05/49106492271/in/album-72157711891600612/ So how does an ideal time-phase coherent design look like. Below is a design using ideal perfect driver. Notice how the phase of both the tweeter and woofer tracking each other at 90 degree apart. But the overall phase of the system (the green curve) is at exactly zero. https://www.flickr.com/photos/185616271@N05/49106060213/in/album-72157711891600612/ But real world system does not look that clean and the phase is not going to be exactly at 0 degree. I’ve modified the xover so the tweeter and woofer are all positive polarity, and the phase of the speaker stays more or less within 0 degree (the green curve). Notice the step response where the tweeter and woofer go up together. https://www.flickr.com/photos/185616271@N05/49106502197/in/album-72157711891600612/ |
thosb Thank You for the cable update. Good to read that Acoustic Zen (AZ) was an upgrade over Audioquest (AQ) for your system. Acoustic Zen, Audioquest, Belden, Blue Jean Cable, Cardas, Dueland, M.I.T., Synergistic Research (SR), Transparent Audio (TA), are all sonic matches for Thiel speakers. Across the various Audio forums, I am sure there are other brands represented as well. At any time, feel free to discuss cabling options, because we all hear differently. Happy Listening! |
thosb, Being an antediluvian audio nut, in 1950 I began to use DYI speaker and interconnects - - top Belden wire with the best connectors I could get. Kept this up until arthritis set in. Since, I've used Blue Jeans Cables for both Belden interconnects and Belden AWG 10 for speaker wiring. Like prof, I haven't been able to discern a significant difference between the straight Beldens and the esoteric ones. I just listened to the 2.7s, and put the $$$$ differences into a new BCD-3 CD spinner, new CDs, upgrading from a 4BSST2 to a 4B3 amplifier, and into a BP173 preamp. Just a thought |
thosb, Thanks! (Correct on cables. If you want to hear everything on the source, standard pro grade cables will do it. I used Belden for my speaker wire and there isn’t a thing I hear in other set ups using vastly more expensive cables that indicates I’m missing anything at all. Every rational neuron in my brain curdles on the mention of Synergistic Research....but I won’t go there....) My last audition of the Devore O/96 speakers left me thinking they’d likely have made me very happy. As I put it in my own thread, they were like my Spendors on steroids. The main challenges were the wider baffles (which could interfere with the projection screen image behind them), the fact they seem to require at least 8 feet listening distance to sound their best (I need a bit closer), and the question of how I’d feel about their somewhat warm/big bass voicing over time. I never got to try them in my home and that sure would have helped my decision.But the Joseph speakers have sounded even better than I thought they would. As for sources: A couple years ago I got heavily back in to vinyl, and took the plunge in buying a really good turntable/cartridge/phono stage (Transrotor Fat Bob turntable, Benz Micro Ebony L cartridge/JE Audio phono stage). I was pretty astounded at the sound quality coming off my records and that, combined with the fun of the physical aspects of vinyl, led me to buy ever more vinyl. It’s not that I don’t still like my digital source (Ripped CDs/Tidal streamed via Rasberry Pie to Benchmark Dac), but I have so much vinyl piled up to listen to, it’s my go-to listening experience. |
Cable land report - I asked for advice on speaker cables, andy2 recommended Acoustic Zen Hologram IIs, which I procured, and they are a nice improvement from the AQ CV-8s I had been using (thanks andy2!). I describe the improvement as adding more depth to the stage and more resolution in the mid-upper bass (male vocals, some percussion and strings). Then I came across this from millercarbon on another thread, "The AudioQuest House Sound is articulate and detailed but weak in harmonic development and tone. It emphasizes attack relative to fundamental development," and that sounds about right, talk about good ears and words! If that's accurate, seems to me AQ cables would not generally be a good match for Thiels, or those who search for tone and harmonics in their idealized listening experience. Does that conclusion ring true with Thiel users? Please be clear I am not trying to start a cable argument, just curious what others have experienced? and fyi millercarbon prefers Synergistic Research cables. |
prof - your written descriptions of what your speakers sound like is always fun and educational to read, thanks, and wish you could find a way to get a pair of devores into your rotation. I remember reading your listening/audition comments about them in the past, if I recall they were favorable? I do remember you are not a cable guy, you run CJ 140s, assume a CJ pre, but what do you prefer as a source? |
prof Always good to see you here. Thank You for the review on Joseph Audio/Spendor speakers. I concur on your assessment, impression, of the JA Perspective, having heard this model myself. While it was a pleasant experience, I chose the CS 2.4SE for imaging specificity and precision, as well. Happy Listening! |
My spidey-sense was tingling... Anecdotal observations from owning both the Thiel 3.7 and still owning the 2.7s, while also owning the Joseph Audio Perspective (Infinite Slope) speakers: I’ve mentioned it before but... The Thiels image with greater image specificity and precision, especially with a sense of sonic density to the instruments and voices. They are a bit more lush sounding from top to bottom. A bit more balanced dynamically/frequency response. They maintain imaging and tonal balance over a wider area than the Joseph Speakers (at least in my set up, and to my memory. Been a couple months since I had the Thiels set up). The Thiels are also more perfectly coherent sounding. As I’ve said, try as I might I simply can not "hear" the tweeter in the thiels. The treble area just melds seamlessly with the rest. My hunch, having heard various Thiel speakers over the years, is that this is not *entirely* due to the time/phase coherence. This is because, at least in my memory, I didn’t find the old Thiel 3.6s quite as perfectly coherent in the treble - a little bit more of a treble shine poking out with those. The CS6s that I had were smoother, but still had a tiny hollowness in the upper midrange that could take away some of the body of instruments and slightly separate highs from the rest. Subtle, but there. (I think we discussed that back then Thiel was still working out the problem of a bit of interference that could happen between the tweeter and mid - can’t remember if that was due to concentric driver design, or due to challenges in first order crossover. Now that I remember the Meadowlark speakers I had (time/phase coherent) actually had this problem to a much greater degree, I believe it’s a challenge in the time/phase coherent design). All that seems pretty much solved in the 3.7/2.7 design from what I can tell. The Joseph speakers have, as I mentioned before and to my ears, a lower level of hash (reduced driver interference?) as their main sonic virtue, which makes the sound more relaxed and un-mechanical sounding. A rare purity of tone. They seem to have a bit finer resolution, and bring out more timbral nuances, differences, in the mixes.They can sound surprisingly huge for their small size. Though I don’t think that’s anything to do with time/phase coherence vs lack of. More driver choice/voicing etc. The Thiels sound a bit more focused and dense in the bass. The Josephs are a bit more "juicy" and punchy, with a bit more "heft" lower down from the Thiels. A bit of added warmth perhaps. But it makes for exciting punchy drums and bass tracks. I can constantly "feel" the bass from the Josephs, where the Thiels would tend to produce the bass happening more holographically "in front of me" behind the speakers. The Joseph speakers are very coherent - that is one of the characteristics noted in review after review. So it seems their crossover design works to minimize driver interference. Still, it’s only having lived with the Thiels that shows up the Josephs as being slightly less coherent, both from bass to mids and mids to highs. There is a teeny bit more of the high frequencies, the tweeter, "riding on top of the sound" vs the Thiels. But again, the Josephs are more coherent than the majority of speakers I demoed. But the gorgeousness of the upper frequencies are entrancing. Last night I was listening to everything from soundtracks, to rock, to jazz, and the sense of openness, airiness, the aliveness and vividness of tone was like a sonic rainbow. Really pleasing. Finally, to throw in one more wrench: I was also listening to my little Spendor S3/5s last night, comparing with the Joseph speakers.The Spendors aren’t of course time/phase coherent, but MAN are they coherent! They also sound virtually perfect in coherence. In fact, with vocals, they are THE most coherent sound I’ve heard, even beating the Thiels. But if I’m to ponder why, it could be that the Thiels are super coherent but more revealing, so the artifice of recording technics, which will exaggerate sibilance or color voices, will be more on display.Where the Spendors have a canny balancing act of an under-damped cabinet, and a voicing that likely does a bit of BBCing, which hides a bit of the problem frequencies that tend to show up on voices. So even on sibilant recordings, for instance, the frictives on vocals "sets back" naturally in to voices instead of sounding detached. And they have a richness and roundess that recreates the organic quality of voices. They still astonish me. There you go. Too much, probably. Just don’t get me started....;-) |
Andy - you are puzzling it out. In the beginning, when we were wrestling with all these variables and making prototypes to compare A with B with C, we had some aha moments that led to the decision to tackle the 'real deal' . . . keeping the phase and time information intact - creating a coherent source. All the other approaches define ways and methods to minimize the importance of the time aspects of the hearing riddle. Addressing time/phase serves to multiply the burdens of developmen -, it all becomes enormously more complex. Previously on this thread someone (?prof?) mused whether the Thiel Rightness is actually caused by phase coherence or rather the result of all the other details that were paid attention to in the designs. I say it is both. Coherence adds its own complexities and solutions, and it also demands that other details be very right or else they sound very wrong. |
The Infinite Slope speakers are very good. His approach sequesters the phase misbehaviors to very narrow bands, so they are noticed very little, and the time misbehaviors are managed for least damage Richard Modafferi, Infinite Slope
designer, did claim that the group delay within the overlap region is
very minimum therefore, at least within this region, the transition
should not be a problem in the time domain. But as you said,
there is still a problem of phase rotation in which the signal at
20KHz will arrive at 360 degree ahead of the signal at say 300Hz.
But the other problem with steep slope is the rapid change in phase
which will be addressed below. I have
designed speakers that is first order time-coherent (no phase shift)
and first order NON time-phase coherent. The common denominator here is first order - but one is time coherent but the other in NOT time coherent. The non coherent version has 180 degree phase shift at 20KHz. BUT I had a hard time telling
the difference in the sound quality or the intrinsic type of sound between the two xover types. Although I do prefer the
time-coherent version, but the frequency response and oxver point
between the mid and tweeter are all different between these two
version so I don't if most of the differences come from the
time-coherence or because of different types of voicing. So where do I think the differences come from? I
think most of the differences that we have talked about will be
because of #2 below. And of course solid state amplifier does not have any xover that can explain the differences. |
Andy - The Infinite Slope speakers are very good. His approach sequesters the phase misbehaviors to very narrow bands, so they are noticed very little, and the time misbehaviors are managed for least damage. Previously you noted " how high frequency affects our hearing". The Infinite Slope treble reaches the ear ahead of the rest of the signal, and even though it does so in a well engineered fashion, that pre-arrival is radically different from natural sounds, in which the wavefront arrives simultaneously. The ear-brain is very good at reconstructing those elements into the alleged sound, but that takes work to do. Some folks prefer the wavefront to arrive intact. I am one of those folks, as are most of you on this thread. Thiel took the philosophical position that waveform integrity was important, regardless of whether the majority of listeners assigned importance to it. By the way, source material, amps and ancillaries that work best with Thiel also keep those relationships straight. The low to no negative feedback designs such as Ayre, address the same goals with the same priorities as Thiel. |
There is a real limitation to dynamics in first order filters. On the one hand, there is no time smear or phase rotation in the crossover range for very realistic immediacy, but on the other hand, the drivers, especially the tweeter, do more work, generate more heat, and experience anomalies coupling to the air beyond their 'natural range'. Thiels are actually small-signal machines which do pretty well in normal rooms at normal volumes. But they are not and were not intended to be screamers.In interesting with respect to two different design philosophies. After a short exchange with the designer of the "Infinite Slope" of Joseph Audio in another thread, which optimized for frequency domain whereas time-phase optimized for time domain, and "Prof" has listened to both Thiel and Joseph Audio, and he said he like them both. I personally think there is a unique sound with first order that cannot be found in the higher order design. Maybe "Prof" can further describe if there is any intrinsic difference between these two type of speakers. |
Figured that was the reason for you asking. In my old house, before I had 3.7s, I had Thiel 7.2s. The room was huge. It was about 16x20 with a 19 foot ceiling that opened into other spaces. Easily the equivalent of over 7,000 cubic feet. The 7.2s were rated at 86db (tested by one magazine I believe at 85.5) and the 3.7s at 90 (tested by one magazine at 90.7). At one point I was driving the 7.2s with a Bryston 4BST and it was more than once where the amp went into momentary (literally a second) clipping (I have an integrated AV system so used it for both movies and music). When I went to the Proceed HPA amp, it had plenty of juice to drive the 7,2s, which, are noted, were a much more difficult load than the 3.7s (subsequent to that I got a 15 amp version of a Bryston 14BSST to drive the 7.2s, which it could not and I ended up with 3.7s, which the 14BSST handled better as far as the impedance but not as well as a Modwright KWA150SE). It's not your place with the potential buyer, but, with the changes in ownership over time with Madrigal Labs/Levinson some of the older amplifiers may not be supported by the factory for repairs. I would think unless the person has a huge room and plays them insanely loud, it would not be a problem with the 3.7s. |
Not seen a Levinson 27.5 in recent times but can tell you I help deliver many moons ago Levinson amps with Thiels. Should have no trouble driving them. If one is in a large room and listens very loudly that is not to say that something that delivers more power can be more appropriate for them (but don't be fooled by the conservative power ratings. Old Levinson 33Hs (helped deliver a pair of those - came with a free hernia - 220 lbs. each shipped with the crate), could drive just about anything (at least what I've seen and they didn't have excessive power ratings vs. many other things - very conservative). With my old Thiel 7.2s (which are a harder load that the 3.7s), I did own Proceed amps (which were basically Levinson budget amps). and they drove them no problem. |
There is a real limitation to dynamics in first order filters. On the one hand, there is no time smear or phase rotation in the crossover range for very realistic immediacy, but on the other hand, the drivers, especially the tweeter, do more work, generate more heat, and experience anomalies coupling to the air beyond their 'natural range'. Thiels are actually small-signal machines which do pretty well in normal rooms at normal volumes. But they are not and were not intended to be screamers. You are on to something. I always notice more edge on higher order filters, which can be perceived as greater snap and slam. We had a drum kit and xylophone in the listening room at the original farm house. I vote that the first order filters sound much more like real drums and percussion. That direct comparison helped form our decision to go first order. |
Note that the 1.5 drivers were entirely developed by Thiel in-houseOK, I see. I just thought they did look similar to some of the Vifa drivers. I have an eccentric theory about why phase-coherent x time coincident speakers are "harder" to driveI also notice that if I disconnect the tweeter, the sound becomes subjective less "dynamic". I also notice that higher order filter speakers do have more perceived "slam" vs. first order filter speakers as if the drums become more "dynamic". It may have to do with how high frequency affects our listening. But then beyond this, I am just guessing ... |
Andy - a couple of points in a very complicated maze. Choice of impedance indirectly includes slopes because slow slopes require less moving mass to avoid self-attenuation on the treble roll-out, and lower inductance for the same reason, and therefore fewer coil winds. Note that the 1.5 drivers were entirely developed by Thiel in-house; they include under-hung coils, copper shunts, focusing pole and plate geometries, etc. Thiel had a complete driver development lab that was fairly robust by the late 1980s. We developed our drivers and turned the designs over to Vifa for production engineering and supply. We were too small to "own" those designs, so we allowed Vifa to put them in their catalog to recoup their tooling expenses. So, they could be considered "off the shelf", but they got on the shelf by our putting them there. I have an eccentric theory about why phase-coherent x time coincident speakers are "harder" to drive. I believe that coherence allows our auditory perception to be accepted as "real" and not "reporduced". We take that "real" input much more seriously, and many aspects become sonically important, whereas they were not even heard in the incoherent speaker. I have previously described how I came to form this theory - it is an important leg of my sonic understanding stool. That phase-related amp misbehavior from the amp driving the Thiel low impedance load is obvious, but if driving a high-order low impedance load, I believe it might not be obvious. |
With respect to "ease of drive", I looked at the CS1.5 which I believe do not use "Thiel designed" drivers but more or less "off the shelf". Based on Stereophile measurements, the impedance minimum is about ~3.7 Ohm at around 200Hz. Based on that, I assume the drivers used in the CS1.5 are 4 Ohm design. The overall impedance of the CS1.5 is not that different from most 4Ohm speakers using conventional design approach. For comparison, I ran a quick simulation on my time-phase coherent design, all using 4Ohm drivers: 1. For a 2-way design, minimum impedance is 3.6 Ohm at also 200Hz. 2. For a 3-way design, minimum impedance is 3.3 Ohm at around 160Hz. But using a more conventional NON time phase coherent methods, the impedance is about the same, therefore my guess is time-phase coherent is not the real reason for being "difficult to drive". |
As for some of the comments with regard to tubes driving Thiel speakers, well I have a pair of Cary Six Pacs Monoblocks rated at 50W in triode mode. I tried them to drive the CS2.4, but they just do no have any dynamic and the music lacked any life and vitality. My conclusion is that the Six Pacs do not have enough power to match well with the CS2.4. On a larger issue, I am not sure why Thiel in general are a bit difficult to drive. In my experience, time-phase coherent speaker designs tend to be a bit less efficient than other more conventional designs but it shouldn't be difficult to drive. Is it because the Thiel driver themselves have very low impedance? I myself designed a few time-phase coherent speakers (which I hope to share soon), but the impedance curve or the overall efficiency are not that different if I were the do the same but with using more conventional approach. I supposed it's not because of time-phase coherent but something more intrinsic to Thiel specific driver specs. |
bighempin 2nd Note- while you were pulling vinyl, I did peruse the tweeter in question. At no time during out session did I detect any abnormal frequency response(s) nor degradation in sound quality via DAC, turntable (TT). I venture to report that it is operational from a performance stand. Cosmetically, it could be viewed otherwise. The dent is not overt, in appearance, to my eyes. Happy Listening! |
bighempin Thank You for the day of listening to your system. Weather-wise, cool and damp outside, it was the perfect time to enjoy fellowship, music and talking Audio shop. This was my first audition of PS Audio gear and can honestly report that it is a sonic match for Thiel loudspeakers. Plenty of detail, dynamics and speed via tubes, was appreciated. Happy Listening! |
thielliste, Yeah, the Thiels seem to perform well with tubes IMO. As to SS, from my experience I can only say that 250W of Bryston power drove some Thiel CS6s that I had very easily. The 3.7s should be even easier to drive. If one has a really big room and listens really loud, that could change. But then, moving between 250 W to 300, or even 140w to 300, is a very modest increase in actual available loudness potential. |