Thiel Audio TT1 loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Thiel TT1's frequency response in the farfield; and, for the nearfield frequency responses, an Earthworks QTC-40, which has a ¼" capsule and thus doesn't present a significant obstacle to the sound.

My estimate of the Thiel's voltage sensitivity was 88dB(B)/2.83V/m, confirming the specified figure. The speaker's electrical impedance magnitude and phase are shown in fig.1. Like earlier Thiel models, the TT1 is a fairly demanding load for the partnering amplifier to drive, with minimum impedance magnitudes of 3.2 ohms at 140Hz and 3.1 ohms at 1.4kHz (solid trace). These values are a little lower than the specified minimum of 3.7 ohms, though the electrical phase angle (dashed trace) remains low over much of the audioband. The wrinkle in both traces at 25kHz is presumably due to the first breakup mode of the tweeter's titanium dome, but the traces are otherwise free from the small discontinuities that would suggest the presence of enclosure panel resonances. Nevertheless, when I investigated the cabinet's vibrational behavior with a plastic-tape accelerometer, I did find resonances at 309 and 344Hz that were most pronounced on the curved sidewall level with the uppermost woofer (fig.2). Neither is very high in level, however, and I doubt they will have audible effects. Thomas J. Norton did find the speaker dead to the traditional knuckle-rap test.

816Thielfig1.jpg

Fig.1 Thiel TT1, electrical impedance (solid) and phase (dashed) (5 ohms/vertical div.).

816Thielfig2.jpg

Fig.2 Thiel TT1, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of side panel level with upper woofer (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

In fig.3, the green trace above 350Hz shows the TT1's midrange and tweeter output in the farfield, and the blue trace above 350Hz the output of the woofers. Below 350Hz, the blue and green traces show the responses measured in the nearfield, as does the red trace, which shows the summed response of the ports on the rear panel. The acoustic crossover appears to be just below the specified 400Hz, and the woofers roll off smoothly above that frequency with that appears to be close to an 18dB/octave slope, suppressing any breakup modes in the aluminum cones. What would otherwise be a smooth high-pass rolloff for the midrange unit (green trace) is disturbed by a small peak at about 150Hz. The ports and the woofers behaved identically, and the well-defined notch at 34Hz in the woofers' output (blue trace) suggests that this is the ports' tuning frequency. However, the ports' output (red trace) covers a wider bandpass than usual, not rolling off until above 65Hz. Though both ports had a peak in their output at 600Hz, this is well down in level and will not affect the TT1's sound quality.

816Thielfig3.jpg

Fig.3 Thiel TT1, acoustic crossover on tweeter axis, corrected for microphone response, with summed nearfield responses of ports (red), woofers (blue), and midrange unit (green), all plotted in the ratios of their radiating diameters.

Fig.4 shows the complex sum of the TT1's port, woofer, and midrange outputs, spliced at 300Hz to the farfield response and averaged across a 30° horizontal window centered on the tweeter axis. The gentle rise in the low-frequency response is almost entirely due to the nearfield measurement technique, though the unusual tuning of the ports means that the bass rolloff doesn't extend quite as low as implied by the 34Hz port-tuning frequency. TJN did comment on the TT1's lack of low bass. Higher in frequency, the farfield response is extraordinarily flat, meeting ±1dB limits from 400Hz to 11kHz. Wow!

816Thielfig4.jpg

Fig.4 Thiel TT1, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with complex sum of nearfield responses plotted below 300Hz.

The Thiel's lateral dispersion (fig.5) is also textbook in nature: The contour lines are evenly spaced; the rolloff with increasing frequency is apparently gentle and smooth; and there are no off-axis flares or suckouts up to the cursor position at 12.25kHz. As TJN found, this behavior correlates with stable, well-defined stereo imaging. In the vertical plane (fig.6), the TT1's tonal balance is maintained over quite a wide window above and below the tweeter axis, which is 36" from the floor.

816Thielfig5.jpg

Fig.5 Thiel TT1, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90–5° off axis, reference response, differences in response 5–90° off axis.

816Thielfig6.jpg

Fig.6 Thiel TT1, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 15–5° above axis, reference response, differences in response 5–10° below axis.

In the time domain, the Thiel's step response on the tweeter axis (fig.7) reveals that the tweeter and midrange unit are connected in inverted acoustic polarity, the woofers in positive polarity. While the TT1's output is not time-coincident, which differentiates it from the late Jim Thiel's designs, it is time-coherent, in that the decay of each drive-unit's step smoothly blends into the start of the step of the unit next lower in frequency. This confirms the optimally realized, high-order crossover design. Finally, the TT1's cumulative spectral-decay plot on the tweeter axis (fig.8) reveals a superbly clean initial decay.

816Thielfig7.jpg

Fig.7 Thiel TT1, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

816Thielfig8.jpg

Fig.8 Thiel TT1, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

I was impressed by the Thiel TT1's measured performance. In most ways it resembles what I would expect from a speaker designed by Mark Mason, an engineer who worked with Paul Barton at PSB. It is a shame that Mason is no longer with Thiel, but his legacy remains in the sound and the measured performance of this excellent speaker.—John Atkinson

COMPANY INFO
Thiel Audio Products Co.
566 Mainstream Drive, Suite 500
Nashville, TN 37228
(615) 913-8532
ARTICLE CONTENTS

COMMENTS
DaveinSM's picture

hmmm, it sure seems to me that Thiel is banking on its high end reputation to charge a premium for speakers that look like PSBs with fancy wood veneers. Jim Thiel's designs may have been "idiosyncratic", but they sure sounded good to me. Besides, I just couldn't bring myself to spend seven grand on a small floorstander that seems to need a good sub or two to be gratifyingly full range.

findcount's picture

LOL.......you're right about the PSBs.......the drivers look cheap to me.......

Anton's picture

So, they ditched Thiel's designs, brought in Mark Mason and then parted ways with him...and have a 'name' with no continuity of design philosophy or driver manufacturing infrastructure.

Basically, the have paid for brand name nostalgia at this point.

Venere's picture

Clearly banking on brand recognition. Happens all the time in other industries. In the high-end automotive world look no further than Bugatti, Bentley, and Lamborghini, now all owned by VW Group and designed and built by various international teams. Thiel probably aren't setting any sales records (in fact I would be very surprised if they survive in this ultra-competitive market), but I bet they're doing better than if they were marketing the new "Mason TT1".

mallred's picture

Great headline Anton! In the 90's, I owned 4 different models from CS-6's to 1's. I enjoyed them all at the time and think they tried hard to advance the hobby. The new version of the company needs to hurry up and go out of business...

mikerr's picture

I don't know how I ever came upon Thiel speakers but I just love them.
I started out with the 04a's back in the olden days ( I still have them)...I also have and have had several sets of other model Thiels.
Not too long ago I scored a pair of 1.7's (which to me are more related to the 3.7's than even the 2.7 due to it's folded piston driver). The 1.7 I believe was an affordable ($4000) mishmash of the 3.7 and 2.7 that was put together right after Jim Thiel passed-away.
I feel that my 1.7's are 'the' Last TRUE Thiel speaker and Wow do they sound AMAZING !!!
The new Thiels seem so disappointing, of course the Legacy was broken when the blueprints were thrown out. If I were in the market for a High end speaker I would seek out one of the 3 Thiels I've mentioned here. buy according to how much you can spend. I bought my 1.7's on ebay for 1/3rd of the original cost and I guarantee you these guys are "Special".
I've been watching several sets of the NEW Thiel company's speakers on ebay and none of them are even getting a minimum bid at auction end, while Jim Thiel designs are selling well ...for good reason.
My 1.7's have 'life' and 'focus'. It is a thrill to come home to these every night.

Coalpedlar's picture

I still have an old pair od CS-2's.
They still sound great with the proper equipment driving them...

DanGB's picture

Imagine if someone bought out Martin-Logan, and immediately phased out the electrostatic speakers from the range, or if Tannoy had new owners who ditched the dual-concentric drivers.

These speakers may be good, they may be not, but one thing they aren't is Thiels.

DaveinSM's picture

The Thiel website has been static for quite some time now, and even their facebook presence has been pretty much silent lately. It's like nothing is happening over there in those fancy new Tennessee offices. It's sad, really. I think that the same thing has happened to a lesser degree over at Krell. Cheaper designs at higher prices to cash in on the name recognition. Except for the super high end, it seems like high end audio is declining.

Allen Fant's picture

Another happy Thiel owner here (CS2.4 SE).
Excellent overview- TJN.

Allen Fant's picture

Wise man- DaveinSM.
Krell is in the same boat, so to speak.

John Atkinson's picture
Allen Fant wrote:
Krell is in the same boat, so to speak.

I understand that Rondi D'Agostino, one of Krell's founders and Dan's ex-wife, has bought out the owners and is now running the company again. www.stereophile.com/content/sisters-sound-rondi-dagostino.

John Atkinson
Editor, Stereophile

findcount's picture

in terms of sound quality, Krell has been surpassed by many other brands even from the 90's.......their new amps look cheap on the outside and inside.......

Sfdoddsy's picture

Whilst the review is competent, and the measurement are as always enlightening, surely this is a missed opportunity.

As the comments above indicate, there is a lot of love for Thiel speakers. To not compare the new Gainst the old, given the vast differences in design philosphy, seems like a real letdown.

The design and measurements do seem closer to a traditional Toole PSB/Revel/Paradigm speaker than previous Thiel first order concentric iterations.

So give us that comparison rather than an anodyne set of MAs

yuckysamson's picture

I apologize in advance if this comes off as some kind of hi-fi snobbery or the like, but that being said, I'm confused about a few details of the system and set-up used to evaluate the speakers.

Obviously Mr. Norton is a professional and a great reviewer, but it strikes me as a bit odd to use the Integra surround piece as the 2-channel pre-amp, as well as the DAC (a giveaway that it's not up to the task is that when using the Marantz' built in dac the Rowland pre-amp was better suited). Also just the digital front end in general, you'd kind of expect some higher-end digital source (even streaming roon to a Hugo or something of that nature, take your pick, benchmark, Auralic, Ayre, etc.) to a proper two channel pre-amp, and I'll leave the proceed out of this because it's capable, (although to some a solid two 5-10k, 2-channel power amp would be more appropriate) but suffice it to say it's also not a piece that a lot of people considering these speakers would be using similar electronics. Basically is this the "right road for the rubber"?

It also smacks a bit that Mr. Norton chose to use neither the spikes nor the feet. Excuse my raised-in-a-british-hi-fi-store-mentality, but this can make a significant difference to the entirely of the loudspeaker's output.

On the other hand it is comforting to see someone reviewing these Thiels with 'down to earth' mentality and products, but if we're talking dollars-for-dollars, there are better front and middle ends up to the task.

It's tough to discern from this review how the speaker really stands up to anything, I'm not surprised that it faired 6one/half-dozen-other against the Montior Audios. If, however, the same A/B demo was done in a more modest room, with a (and I'm just riffing here) Rega RP6 TT, a viable tube integrated (take your pick) and some select cabling, AND the spikes and set-up done perhaps more carefully, AND the other HT elements removed from the room, I'd suspect that the differences, regardless of which was better or worse, to the monitor audios, would have been significantly more pronounced, more defineable.

I'm just surprised as this isn't the typical associated equipment from a STEREOPHILE review list.

findcount's picture

they used an AV amp so the speakers won't look too bad to readers........whenever a review only has 2-3 pages and only 1/4 of it is on the sound quality......you know the product is a bomb

virgum's picture

The mediocre wallmart world emblem product-TT1, the run for almighty profit for the share holder even if you throw away genius.
Happy owner of CS 2.3 driven by a Halo a 21.Nothing ever auditioned,including speakers with the price of a car a piece compares in naturalness,accuracy and imaging.Advice for owners to get all these wonders can do;change the electrolytic caps,(there are 3 in crossover,each-100uf,I changed them with mundorf electrolytics +-5% for 3$ each),the surround rubber and the composite used in between the mids and highs as crossover,visible as aluminium dome surround tend to get dry and lose the properties over time(all of them by now) so to fix this use a fine brush and something to revive the rubber and plastics like product for auto dashboard once a month.You wont believe your ears!

eriks's picture

JTN,

There's absolutely nothing wrong with your measurements, or your microphone. :) JA I'm sure will jump in, but he's going for quasi-anechoic, while OmniMic is gated, far field.

The OmniMic plots are great, and show overall very neutral speakers devoid of gimmicks. My experience with Monitor Audio is similar lately. Never done this with Thiel. Look up the Bruel & Kjaer recommended curves, and you'll notice the measurements you took are fairly well aligned.

Best,

Erik

Sea Otter's picture

...And look at the measured performance of the loudspeaker. The data here shows performance in fundamental design parameters far beyond that shown by any Wilson, Magico, Marten, or YG, at any price point, that has been tested by Stereophile (or any other independent third party that I am aware of.)

It appears that Mr. Mason is no longer with Thiel, which seems a shame, as they have definitely lost one of the most talented loudspeaker designers out there.

While I sympathize with the posters who seem dissapointed about the departure from thiels legacy by the new management team (Teams?) And share their reservations about the future of the brand, I would like to raise a glass in respect to the excellence of Mason's design.

Well done, sir.

eriks's picture

If you are experimenting with OmniMic, take some compression measurements as well. Those will really start to open up your eyes and ears.

Seriously, I think you'll find compression, or lack of it, to correlate very well with relaxed and open sounding. Compression often explains why you may hear a speaker not match the measured FR.

Best,

Erik

findcount's picture

a 2-page review for such a famous brand's USD7K speakers.....and only 1/4 of the review on the sound quality itself speak volumes for the new Thiel.......just looking at the speakers' drivers, you can tell it's the beginning of the end........

X