Thiel Owners

@tomthiel, sorry I was off the forum for a week and didn't see your response about 2.7 development until recently.

I'm unclear why the 2.7 needed a HIGHER frequency woofer XO point than the 2.4's 1000Hz. The 3.7's 4.5" midrange should be able to much better handle lower frequencies than the 2.4's 2.5" midrange. Indeed, the 3.7 XO is at 300Hz, so the mid can go at least that low. So why not lower the XO point of the 2.7 woofer to say 500Hz for better power handling and even less beaming? That would stress the 2.7/3.7 midrange less than in the 3.7, and stress the 2.7/2.4 woofer less than in the 2.4, so a win/win with a lower XO point, but you state it is higher, and with 14X more capacitance, it would seem a LOT higher. Hmmm.  Please expound.

To that point, why wouldn't the 2.7 use 4x100uF film caps or even smaller to get to 416uF, rather than one massive 400uF? It would seem the slight increases in space and price 4 or more film caps would create would more than offset the potential sonic deficit of one giant electrolytic directly between the amp and wonderfully pure coax driver.

Indeed, that's the weakest link of the 2.4 for me, the excursions required of a 2.5" cone (effectively less when including the hole in the middle for a tweeter dome) to move enough air at lower frequencies at higher volumes, to below say 250Hz (2 octaves below XO point, so only -12dB; if playing 100dB, mid asked to put out 250Hz percussives at 88dB (round 'electrical' numbers, not taking acoustic roll-off contributions to the end-result 6dB/octave slopes.)).  Ask Rob how many 2.4 coaxes I've gone through, and not due to lack of clean watts and amps!

sdecker - you are asking the right questions. And I have no answers. Remember that I had no involvement or insider information from 1995 to 2012. I'll tell you what little I have pieced together. Please pardon any repetition for the long term readers.

Thiel created the CS2.7 to develop and demonstrate their ability to produce valid products without Jim. They auditioned multiple inside and outside engineering solutions and landed on Warkwyn - Toronto, a full service design development firm with full access to the Canadian Research Center which develops most of the Canadian brands' products. The concept design was developed by Home Team Thiel, and Warkwyn did the engineering and prototyping. The results were not acceptable to HTT, and that process went on for a couple of years and cost mid $six figures. I got the impression that engineering decisions, such as you iterate above, were not on the table for discussion for reasons I can only speculate.

I will say that Jim never used a cap larger than 100uF, even in parallel circuits. I will say that Jim was very cognizant of beaming and its power response implications. And it seems to me that the core personality of the 2.7 became conflated with the 3.7 to a much greater degree than previous model generations. The 3.7 was designed to play louder into larger spaces with deeper bass; whereas the 2.7 was to be more intimate in smaller spaces with less bass extension to not distress those smaller spaces, at considerably reduced cost. Such gestalt overview seems to have suffered as time went on - the 2.7 / 3.7 seem far more similar to me than the CS2 / CS3.5.

Your suggestions above seem well considered to me. I wonder with you why such basic considerations didn't make it into the product. Notice that there is a convenient slot of 2.5 - 2.6 in the line-up. Who knows what the future might bring?

Correction: In the second last paragraph I mis-typed 3.7 and 2.7 where I meant to say that the model 3 was designed to play louder . . . and the model 2 was to be more intimate . . .

if playing 100dB, mid asked to put out 250Hz percussives at 88dB (round 'electrical' numbers, not taking acoustic roll-off contributions to the end-result 6dB/octave slopes.)). Ask Rob how many 2.4 coaxes I've gone through, and not due to lack of clean watts and amps!

Interesting. If ability to play >100 dB was an important factor to me I would probably look at something like the JBL K2 S9800. Modestly efficient Thiels with their low impedance seem a, um, sub-optimal choice for those who like to listen at very high SPLs. And to still have your CS2.4s after burning multiple coaxes? You must *really* like their sound!

These numbers were chosen as an example, but isn’t as unlikely as it seems. These are peak levels taken from the listening position (9’) from a pair of speakers playing (2 speakers = +3dB) with some room boost, and C-weighting (accounting for most of the bass). That’s not filling the entire room with 100dB, those are peak readings at a semi-nearfield listening position in a near-ideal room for these speakers. And this represents probably less than 5% of my overall listening, and then for perhaps a side of an album. 95dB peaks would be a more typical *loud* listening session, still infrequent, with *no* 2.4 power handling concerns.

Even then, if that highest level is 105dB at 1m, that’s ~100 amplifier watts (if they’re 87dB@1W/1m), and my amp delivers ~500 watts per channel into 2 ohms with plenty of dynamic headroom. I now better know the limits of the limited midrange, and am comfortable with keeping volume and program material well within their comfort zone. I have never heard my amp compress, harden, and certainly not clip at any volume into any speaker load, which suggests I’m not intent on finding the limits of my amp or any guest speaker!

Rob Gillum tells me in ’destruction testing’ of the similar 2.3 coax development, they typically achieved 115dB SPL steady-state (not transients) before ’it blew apart’ (with 600W Krell monoblocks), and that 100dB peak SPLs from 2.4s should be reasonable in a 3000 cubic foot room (mine is 2500). FWIW, I have never blown a 2.3 coax, even though we have no reason to believe they are a sturdier design. Indeed, Rob says his current rebuilds of these drivers use more-modern adhesives and construction techniques that will increase the robustness of the 2.3/2.4 coax.

Half my coaxes were covered under warranty, and only one exhibited obvious signs of being driven beyond its excursion limit. More typically the lead wires fatigue from years of excursions (well within the driver's (motor + surround) excursion limits) and open the circuit.  Rebuilding a coax every couple years is a whole lot cheaper than buying a speaker today that ticks as many boxes for me as my 2.4s!