Thiel 3.7

First of all, HELLO ZAIKESMAN! Where have you been? I'm sure I'm not the only who's missed you around here. I do hope all is well with you.
You bring up some very interesting thoughts (no wonder we've missed you). I like your thinking regarding a multi-dome MT. I suspect the biggest problem for Thiel would be maintaining correct time domain. I supposed an electrical (digital?) cross-over could compensate for that. From what I understand the drivers are corrugated to suppress resonanses. I've heard claims of 0 (thats what I heard ZERO) unwanted resonanes from both mid and tweeter to 22Khz! This may set a new standard for dynamic driver sweetness. Regarding your thoughts on the thinner baffle, many years ago I asked Jim Thiel why he didn't use a pyarmid shaped cabinet to reduce baffle width in accordance with driver size. He responded that he would prefer to use a wider baffle but was concerned that the market would object to a bigger speaker profile. He thought that having a wider baffle would offer more support for the drivers and the he could control dispersion better for the consumer, as the first reflections could be designed in rather than being dependent on the variances if consumers rooms. I also share your concern about the woofers being so far from the other drivers. I suspect this arrangement mandates further listening position from the speaker for proper driver integration and less freedom to move about during listening. Perhaps the large distance does allow the bass driver to appreciate room loading better and may offer the critical mid range and in this case in particular the tweeter some more isolation from the woofers vibrations. I understand that the price of the 3.7's may be somewhere between the 3.6's and the 6's. Probably on the higher end. Suspcions fly that the 6's will loose its place with this 3.7 offering. After price my big questions would be about frequency response and impedance. There have been rumours about a very expenisive flagship model that might be omni-directional. I can't help but wonder if the new cabinets might be an excercize towards that goal.

Hi Unsound, thanks for the greeting, nice to talk to you again too. I don't post much here anymore, except for sometimes when one of my old threads surfaces, and hardly ever look at the new threads these days, but every once in a while I do and just happened to catch yours -- lucky for me. Allow me to comment on some of your points:

"I like your thinking regarding a multi-dome MT. I suspect the biggest problem for Thiel would be maintaining correct time domain. I supposed an electrical (digital?) cross-over could compensate for that."

Actually, this is no problem at all in the analog domain if Thiel's shared voice-coil design is used. There can be no time-alignment discrepency between a single voice-coil and itself.

[This brings up a little side matter: I take exception with Thiel's terminology referring to the 2.4's M/T arrangement as a "mechanically crossed-over" multi-way driver, although I understand completely why they do so from a marketing standpoint. But the 2.4 isn't really a 3-way speaker at all -- it's a 2-way equipped with an upper driver able to shrink its radiating diameter with increasing frequency. There's only one voice-coil up there, two voice-coils in the speaker as a whole, and only one division point in the electrical crossover, ergo it can't be a 3-way speaker. (If the "upper crossover" were really a crossover, then the tweeter dome would be fed a high-pass-filtered signal.) The potential disadvantage to this arrangement (compared with real 3-ways) is that the HF driver is seeing frequencies well below what's typically fed to a dome tweeter (only about -6dB at 500Hz or so), therefore the issue of possible Doppler distortion of the higher treble may be raised. The benefit (compared with other 2-ways) is that the much lowered true crossover point means the LF driver is relieved of responsibility for the upper midrange and can therefore be made larger and go lower than is normally possible in a 2-way design. Personally, I think Thiel should have taken a stab at marketing the thing as a unique 2-way instead of a psuedo-3-way -- audiophiles like the idea of 2-ways -- but maybe they thought consumers would interpret that as being a regression carrying a higher price tag. Instead JT's talked about how the 2.4's design gives consumers a high-quality, wide-range 3-way at a price not much higher than what they might expect to pay for a good 2-way, and -- even disregarding the fact that there are $20K 2-ways and decent $2K 3-ways out there -- this tends to ring a false note with me. I think profit margin has a lot to do with the implentation of the "mechanical crossover" -- not that that's necessarily a bad thing, just something I wouldn't be loathe to admit as long as the sound quality justifies using it. But let's be honest: He managed to engineer a solution that eliminated one whole driver and half of the crossover network while maintaining high performance. It is ingenious, that's for sure.]

"From what I understand the drivers are corrugated to suppress resonances. I've heard claims of 0 (that's what I heard ZERO) unwanted resonances from both mid and tweeter to 22kHz! This may set a new standard for dynamic driver sweetness."

If true, the 22kHz figure would be quite a high first resonance point for a midrange diaphragm, but nothing at all to write home about for a tweeter, just the minimum allowable to my mind (many aluminum dome tweeters go a few thousand Hz higher before breakup -- in fact I'd be mildly surprised if this one didn't as well -- and some of the newer exotic domes are supposed to go twice that high). Anyway, in this case of the corrugated diaphragms, talking about reducing resonance and increasing stiffness are really two ways of talking about the same thing (as opposed to talking about reducing resonance through application of increased damping).

"Regarding your thoughts on the thinner baffle, many years ago I asked Jim Thiel why he didn't use a pyarmid shaped cabinet to reduce baffle width in accordance with driver size. He responded that he would prefer to use a wider baffle but was concerned that the market would object to a bigger speaker profile. He thought that having a wider baffle would offer more support for the drivers and the he could control dispersion better for the consumer, as the first reflections could be designed in rather than being dependent on the variances in consumers' rooms."

Here I think we're getting confused between what I was talking about, which was baffle thickness, and what you're talking about, baffle width. A 3" thick baffle restricts what kind of environment you can present to the rear of drivers mounted on it, and affects midrange drivers most. Speaking of baffles, I'd also like to see Thiel take a shot at covering theirs in a sound-absorbing material, at least in the vicinity of the upper drivers.

"I also share your concern about the woofers being so far from the other drivers. I suspect this arrangement mandates a farther listening position from the speaker for proper driver integration and less freedom to move about during listening. Perhaps the large distance does allow the bass driver to appreciate room loading better and may offer the critical mid range and in this case in particular the tweeter some more isolation from the woofers vibrations."

I doubt that the height the woofer is mounted at was influenced by, or has much effect upon, how its vibrations transmit to the other drivers. Of course being mounted closer to the floor could have advantages for the bass, but unfortunately that's not the only frequency range handled by the LF drivers in Thiel's 3-way designs. The listening distance is dictated not just by the driver spacing, but also the baffle angle, and the greater spacing allows the angle to be closer to vertical. One way around this to use stepped, rather than angled baffles and drivers. Personally, I have found the angled drivers on Thiels to contribute, along with the low positioning of the drivers in general, to a kind of "looking down into the soundstage" perspective unless you sit well away from the speakers.

"There have been rumours about a very expenisive flagship model that might be omni-directional."

It seems JT has been torn about whether to build a $$$ flagship for years. I think he'd like to try and see what he can do, and knows what kind of cache these things carry in high-end circles for better or worse, but I also get the feeling he's philosophically sort of against cost-no-object extravagance at the same time, both as an image thing and also from an engineering standpoint. Besides, it would divert resources from building products that more people could buy and own. But that such a speaker coming from Thiel could ever be omnidirectional is indeed news, even if it never gets made -- I thought he was dedicated to monopolar radiation in principle, at least as a practical matter. I wonder if he's considering use of horizontally-mounted drivers and acoustic "lens" reflectors a la that B&O speaker (not truly "omnidirectional" in the vertical component, but capable of being made time and phase coherent).

Zaikesman, I really do miss your contributions! Thank you for providing me with a clearer undertanding of how your multidome might work. Jim Thiel did something like this years ago when he reversed the driver to baffle relationship (e.g. CS 2 vs. CS 3.5). You provide and intersting perspective on the 2 way vs. 3 way marketing. I suppose one could argue that different frequencies are being provided by differernt drivers that just happen to share a voice coil. As for me, it really doesn't matter much one way or the other. I think it interesting that Thiel can accomplish this resonace control from the "midrange" driver through the treble region because they are one and the same. I suppose your right, in that the "tweeter" segment may show control even further out. Yes, I think we were talking about different perspectives regarding baffles. I do see your point. From what I understand Thiel suffered from expensive failure in their attempts at cast baffles during shipping. I guess its hard to heal from such a burn. Perhaps he'll develop one using aluminum? We have often shared ideas independently developed. I too have desired some sort of soft baffle covering for some time now. The only other reason I can think of for placing the woofers so low would be to lower the center of gravity for better balance. I too was surprised by the omni concept considering Thiels consistent stance on radiation principles. Perhaps now that Thiel designs and manufactures all of his own drivers, he may feel free to pursue this with better footing? Jim Thiel despite his reputation for specific types of speakers, really has ventured in different directions. Thiel has used various ports, sealed boxes, equalizers, passive radiators, TMW arrays, MTM arrays, passive cross-overs, active cross-overs, mulit-drivers w/ different ranges, single voice coil mutli drivers, self powered speakers, etc.. Why not an omni? Omni's migt be especially attractive to the home theatre crowd.

Zaikesman, BTW Gary is the new Shari.

Zaikesman,
I enjoyed reading and learning from your posts. Very informative and your point is stated clearly. Thanks.